chapter 6 ecosystems

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6Agriculture, water, andecosystems: avoiding thecosts o going too ar

Fuelwood

Recreation

Pestcontrol

Soilformation

Regulationof waterbalance

Nutrientcycling

Cropproduction

Climateregulation

Provisioning services Regulating services

Supporting services Cultural services

Natural ecosystem

Coordinating lead authors: Malin Falkenmark, C. Max Finlayson, and Line J. Gordon

Contributing authors: Elena M. Bennett, Tabeth Matiza Chiuta, David Coates,Nilanjan Ghosh, M. Gopalakrishnan, Rudol S. de Groot, Gunnar Jacks, Eloise Kendy,Lekan Oyebande, Michael Moore, Garry D. Peterson, Jorge Mora Portuguez,Kemi Seesink, Rebecca Tharme, and Robert Wasson

Overview

Agricultural systems depend undamentally on ecological processes and on the services provided

by many ecosystems. Tese ecological processes and services are crucial or supporting and

enhancing human well-being. Ecosystems support agriculture, produce ber and uel,

regulate reshwater, puriy wastewater and detoxiy wastes, regulate climate, provide pro-

tection rom storms, mitigate erosion, and oer cultural benets, including signicant

aesthetic, educational, and spiritual benets.

Agricultural management during the last century has caused widescale changes in land

cover, watercourses, and aquiers, contributing to ecosystem degradation and undermining the

processes that support ecosystems and the provision o a wide range o ecosystem services. Many

agroecosystems have been managed as though they were disconnected rom the widerlandscape, with scant regard or maintaining the ecological components and processes that

underpinned their sustainability. Irrigation, drainage, extensive clearing o vegetation, and

addition o agrochemicals (ertilizers and pesticides) have oten altered the quantity and

quality o water in the agricultural landscape. Te resultant modications o water ows

and water quality have had major ecological, economic, and social consequences, includ-

ing eects on human health [well established]. Among them are the loss o provisioning

services such as sheries, loss o regulating services such as storm protection and nutrient

retention, and loss o cultural services such as biodiversity and recreational values. Adverse

ecological change, including land degradation through pollution, erosion, and saliniza-

tion, and the loss o pollinators and animals that prey on pest species, can have negative

Natural ecosystem services

Artist: Peter Grundy, United Kingdom

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eedback eects on ood and ber production [well established]. In extreme cases human

health can also suer, or example, through insect-borne disease or through changes in diet

and nutrition. All too oten the consequences o modiying agroecosystems have not been

ully considered nor adequately monitored.

It has been increasingly recognized that agricultural management has caused some ecosystems

to pass ecological thresholds (tipping points), leading to a regime change in the ecosystem and loss

o ecosystem services. Ecosystem rehabilitation is likely to be costly, i possible at all. Some

changes can be nearly irreversible (or example, the establishment o anoxic areas in marine

water bodies). Tese changes can occur suddenly, although they oten represent the cumula-

tive outcome o a slow decline in biodiversity and reduced ecological resilience (the ability

to undergo change and retain the same unction, structure, identity, and eedbacks).Te poor people in rural areas who use a variety o ecosystem services directly or their

livelihoods are likely to be the most vulnerable to changes in ecosystems. Tereore, ailure to

tackle the loss and degradation o ecosystems, such as that caused by the development and

management o agriculture-related water resources, will ultimately undermine progress

toward achieving the Millennium Development Goals o reducing poverty, combating

hunger, and increasing environmental sustainability.

An integrated approach is needed or managing land and water resources and ecosystems

that acknowledges the multiunctionality o agroecosystems in supporting ood production and

ecosystem resilience. Tat requires a better understanding o how agroecosystems generate

multiple ecosystem services and o the value o maintaining biodiversity, habitat hetero-

geneity, and landscape connectivity in agricultural landscapes. Social issues, such as theimportance o the role o gender in management decisions, also require more emphasis.

Attention should be directed toward minimizing the loss o ecosystem resilience and build-

ing awareness o the importance o cumulative changes and o extreme events or generat-

ing ecosystem change. It is also necessary to meet the water requirements or sustaining

ecosystem health and biodiversity in rivers and other aquatic ecosystems (marshes, lakes,

estuaries) and to demonstrate the benets o these services to society as a whole.

It has been estimated that by 2050 ood demand will roughly double. As populations and

incomes increase, demand or water allocations or agriculture will rise. Simplied, there are

three main ways in which this increased water requirement can be met: through increased

water use on current agricultural lands, through expansion o agricultural lands, and through

increased water productivity. While all are plausible and a mix o solutions is likely, each hasvastly dierent implications or nonagricultural ecosystems and the services they generate.

With the current high levels o land conversion and river regulation globally, greater con-

sideration should be given to improving management o water demand within existing agri-

cultural systems, rather than seeking urther expansion o agriculture. Dependent on local

conditions, technologies and management practices need to be substantially improved,

and ecologically sound techniques implemented more widely to reduce the impacts rom

agriculture, whether extensive or intensive. Further intensication will require careul

management to prevent urther degradation and loss o ecosystem services through in-

creased external eects and downstream water pollution. With the basis o many essen-

tial ecosystem services already seriously undermined, there is an urgent need not only to

An integrated

approach isneeded or

managing land,

water, and eco-

systems thatacknowledges

the multi-

unctionality o

agroecosystems

in supportingood production

and ecosystem

resilience



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6Agriculture, water, and

ecosystems: avoiding thecosts o going too ar

minimize uture impacts, but also to reverse loss and degradation through rehabilitation

and, in some cases, ull restoration.

An integrated approach to land, water, and ecosystems at basin or catchment scale is urgently

needed to increase multiple benefts and to mitigate detrimental impacts among ecosystem services.

Tis involves assessing the costs and benets as well as all known risks to society as a whole

and to individual stakeholders. Societally accepted tradeos are unlikely without wide stake-

holder discussion o consequences, distribution o costs and benets, and possible compensa-

tion. It is also important that the results eed into processes o social learning about ecosystem

behavior and management. A ew tools are available to assist in striking tradeos (including

economic valuation and desktop procedures or establishing environmental ows), but more

ecient and less sectorally specic tools are needed. Most o the tools were developed toenable better decisionmaking on well known problems and benets. Needed are tools to ad-

dress the lesser known problems and benets and to prepare or surprises.

Decisions on tradeos under uncertain conditions should be based on a set o alternative

scientifcally inormed arguments, with an understanding o the uncertainties that exist when

dealing with ecological orecasting. o minimize the sometimes very high uture costs o

unexpected social and ecological impacts, it will be necessary to conceptualize uncertainty

in decisionmaking. Adaptive management and scenario planning that improve assessment,

monitoring, and learning are two components o this conceptualization.

Ongoing attention is required to communicate ecological messages across disciplinary and

sectoral boundaries and to relevant policy and decisionmaking levels. Te challenge is to pro-

duce simple messages about the multiple benets o an ecosystem and about how eco-systems generate serviceswithout oversimpliying the complexity o ecosystems.

In view o the huge scale o uture demands on agriculture to eed humanity and eradicate

hunger, and the past undermining o the ecological unctions on which agriculture depends, it is

essential that we change the way we have been doing business. o do this, we need to:

Address social and environmental inequities and ailures in governance and policy as

well as on-ground management.

Rehabilitate degraded ecosystems and, where possible, restore lost ecosystems.

Develop institutional and economic measures to prevent urther loss and to encour-

age urther changes in the way we do business.

Increase transparency in decisionmaking about agriculture-related water management

and increase the exchange o knowledge about the consequences o these decisions. Inthe past many changes in ecosystem services have been unintended consequences o

decisions taken or other purposes, oten because the tradeos implicit in the decision-

making were not transparent or were not known [well established].

Water and agriculturea challengeor ecosystem management

Changes in agriculture over the last century have led to substantial increases in ood security

through higher and more stable ood production. However, the way that water has been man-

aged in agriculture has caused widescale changes in land cover and watercourses, contributed

There is a need

not only to

minimize uture

ecosystemimpacts, but

also to reverse

loss and

degradationthrough

rehabilitation

and, in some

cases, ull

restoration



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to ecosystem degradation, and undermined the processes that support ecosystems and the

provision o a wide range o ecosystem services essential or human well-being.

Te Millennium Ecosystem Assessment, an international assessment by more than

1,300 scientists o the state o the worlds ecosystems and their capacity to support hu-

man well-being, identied agricultural expansion and management as major drivers o eco-

system loss and degradation and the consequent decline in many ecosystem services and

human well-being (www.maweb.org). Analyses illustrated that by 2000 almost a quarter o

the global land cover had been converted or cultivation (map 6.1), with cropland cover-

ing more than 50% o the land area in many river basins in Europe and India and more

than 30% in the Americas, Europe, and Asia. Te Millennium Ecosystem Assessment also

showed that the development o water inrastructure and the regulation o rivers or manypurposes, including agricultural production, oten resulted in the ragmentation o rivers

(map 6.2) and the impoundment o large amounts o water (gure 6.1; Revenga and oth-

ers 2000; Vrsmarty, Lvque, and Revenga 2005).

Many scientists argue that as a society we are becoming more vulnerable to environ-

mental change (Steen and others 2004; Holling 1986), reducing our natural capital and

degrading options or our current and uture well-being (Jansson and others 1994; Arrow

and others 1995; MEA 2005c). Natural and human-induced disasters, such as droughts

and amine, are also likely to increase the pressure on vulnerable people, such as the rural

poor, who depend most directly on their surrounding ecosystems (Silvius, Oneka, and

Verhagen 2000; WRI and others 2005; Zwarts and others 2006).

Furthermore, as populations and incomes grow, it has been estimated that ood de-mand will roughly double by 2050 and shit toward more varied and water-demanding

diets, increasing water requirements or ood production (see chapter 3 on scenarios).

map6.1 Extent o cultivated systems in 2000

Note: Cultivated systems are defned as areas where at least 30% o the landscape is in croplands, shiting cultivation, confnedlivestock production, or reshwater aquaculture.

Source: MEA 2005c.



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map6.2 River channel ragmentation and ow regulation o global rivers

Source: Revenga and others 2000.

Unragmented Moderately ragmented Highly ragmented No data Unassessed

Sumo

fdischarge(cubickilometersperyear)

Sumo

fcapacity(cubickilometers)

16,000 5,000

4,000

3,000

2,000

1,000

0

14,000

12,000

10,000

8,000

6,000

4,000

2,000

019201900 1940 1960 1980 2000 19201900 1940 1960 1980 2000

Intercepted continental runoff Reservoir storage

Note: The time series data are taken from a subset of large reservoirs (0.5 cubic kilometers maximum storage each),

geographically referenced to global river networks and discharge.

Source: Millennium Ecosystem Assessment.

fgure6.1 Development o water inrastructure and regulation o riversresulted in the impoundment o large amounts o water



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Simplied, there are three main ways to meet this water requirement: increasing water

use on current agricultural lands through intensication o production (see chapters 8 on

rained agriculture and 9 on irrigation), expanding agricultural lands, and increasing water

productivity (see chapters 7 on water productivity and 15 on land).

Tese options have vastly dierent implications or ecosystems and the services they

generate. Increased water use on agricultural lands through irrigation will reduce the avail-

ability o blue water resources (surace water and groundwater), especially or downstream

aquatic systems, and can contribute to waterscape alterations, or example, through the

introduction o dams or irrigation. Increased green water ows (soil moisture generated

rom rainall that inltrates the soil) through higher consumptive water use in rained

agriculture (as a result o increased crop productivity) will also reduce the availability owater downstream, although the extent to which this could occur varies [established but

incomplete]. Expanding agricultural land can alter the water ow in the landscape, with

impacts on terrestrial and aquatic ecosystems. Finally, while increased water productivity is

intended to produce more ood without using more water, it can lead to deterioration in

water quality through increased use o agrochemicals.

Humanity is acing an enormous challenge in managing water to secure adequate ood

production without undermining the lie support systems on which society dependsand

in some instances while simultaneously rehabilitating or restoring those systems. Research on

ecosystems has generally been separate rom research on water in agriculture, leading to a seg-

regated view o humans and ood security on one side and nature conservation on the other. In

this chapter we challenge this view by describing recent understanding o how all ecosystemssupport human well-being, including ensuring ood security and redressing social inequities.

We ocus on the links between ecosystems and management o water in agriculture.

Water unctions as the bloodstream o the biosphere (Falkenmark 2003). It is vital or

the generation o many ecosystem services in both terrestrial and aquatic ecosystems and

provides a link between ecosystems, including agroecosystems. As or agricultural produc-

tion, we consider the importance o both blue and green water (see chapter 1 on setting the

scene) or ecosystems, both those characterized by the presence o blue water, such as marsh-

es, rivers, and lakes, and terrestrial ecosystems that depend on and modiy green water.

We rst assess the ecosystem eects o past water-related management in agriculture,

highlighting some o the oten unintentional tradeos between water or ood production

and water or other ecosystem services. We then outline response options or improvingwater management. We emphasize the need to intentionally deal with the unavoidable and

oten surprising tradeos that arise when making decisions to increase ood production,

noting that these are oten embedded within complex social situations where dierent

stakeholders have highly diverse interests, skills, and inuence (see, or example, chapters

5 on policies and institutions, 15 on land, and 17 on river basins).

Agriculture and ecosystems

While agricultural production is driven by human management (soil tillage, irrigation, nu-

trient additions), it is still inuenced by the same ecological processes that shape and drive

nonagricultural ecosystems, particularly those that support biomass production and others

Humanity

is acing anenormous

challenge in

managing

water to secure

adequate oodproduction

without

undermining

the lie supportsystems on

which society

depends



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such as nitrogen uptake rom the atmosphere and pollination o crops. Agricultural systems

are thus viewed as ecosystems that are modied, at times highly, by activities designed to en-

sure or increase ood production (box 6.1). Tese ecosystems are oten reerred to as agroeco-

systems; the dierence between an agroecosystem and other ecosystems is considered to be

largely conceptual, related to the extent o human intervention or management.

Disruption o the processes that maintain the structure and unctioning o an eco-

system, such as water ow, energy transer, and growth and production, can have dire con-

sequences, including soil erosion and loss o soil structure and ertility. Severe disruption

can result in the degradation or loss o the agroecosystem itsel or other linked ecosystems

and the ecosystem services that it supplies (see chapter 15 on land). Te degradation o the

Aral Sea is a dramatic example o human intervention having gone too ar (box 6.2).

There are many land and water manipulations that can increase the productivity o agricultural land

in order to meet increasing demands or more ood. All have consequences or ecosystems. The key

message is that agriculture makes landscape modifcation unavoidable, although smarter application

o technology and more emphasis on ecosystemwide sustainability could reduce adverse impacts.

These land and water manipulations include:

Shifting the distribution of plants and animals. Most apparent are the clearing o native vegetation

and its replacement with seasonally or annually sown crops, and the replacement o wild animals

with domestic livestock.Coping with climate variability to secure water for crops. As water is a key material or photo-

synthesis, crop productivity depends intimately on securing water to ensure growth. Three dier-

ent time scales need to be taken into account when considering water security: seasonal shortalls

in water availability that can be met by irrigation so that the growing season is extended and extra

crops can be added; dry spells during the wet season that can be met by specifc watering that can

be secured, even in small-scale arming, i based on locally harvested rain; and recurrent drought

that has traditionally been met by saving grain rom good years to rely on during dry years.

Maintaining soil fertility. The conventional way to secure enough air in the root zone is by drainage

and ditching through plowing to ensure that rain water can infltrate. However, this also leads to

erosion and the removal o ertile soil by strong winds and heavy rain. These side eects can be

limited by ocusing on soil conservation actions, such as minimum tillage practices.

Coping with crop nutrient needs. The nutrient supply o agricultural soils is oten replenished

through the application o manure or chemical ertilizers. Ideally, the amount added should bal-

ance the amount consumed by the crop, to limit the water-soluble surplus in the ground that may

be carried to rivers and lakes.

Maintaining landscape-scale interactions. When natural ecosystems are converted to agricultural

systems, some ecological processes (such as species mobility and subsurace water ows) that

connect parts o the landscape can be interrupted. This can have implications or agricultural

systems as it can aect pest cycles, pollination, nutrient cycling, and water logging and saliniza-

tion. Managing landscapes across larger scales thus becomes important; an increasing number

o studies illustrate how to design landscapes to increase the productivity o agriculture while

also generating other ecosystem services (Lansing 1991; Cumming and Spiesman 2006; Anderies

2005; McNeely and Scherr 2003).

box 6.1 Agriculture makes landscape modifcations unavoidable



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It is thus important to adapt agricultural management (including crop types) to the

ecological conditions. Growing crops unsuited to the climate conditions, or example,

could have harmul consequences. When agricultural techniques that had been developed

in the temperate climate o Europe were introduced in late 18th century Australia, the

result was vast areas o salinized lands (Folke and others 2002). rying to grow lucrative

oil palms on saline soils in the Indus Delta and Pakistan and the acid sulphate soils o

Southeast Asia is another example o a severe mismatch between agricultural activity and

ecological conditions. In the 1970s it was argued that there was a climate biaswater

blindnessthat led to eorts to transer inappropriate agricultural technology rom de-

veloped to developing countries (Falkenmark 1979).

Human well-being and ecosystem services

Te Millennium Ecosystem Assessment (MEA 2005c) showed that the well-being o hu-

man society was intimately linked to the capacity o ecosystems to provide ecosystem

services and that securing multiple ecosystem services depended on healthy ecosystems.

The Aral Sea is probably the most prominent example o how unsustainable water management or

agriculture has led to a large-scale and possibly irreversible ecological and human disaster. Reduced

water ow in the rivers supplying the sea has resulted in outcomes that have impaired human liveli-hoods and health, aected the local climate, and reduced biodiversity. Since 1960 the volume o wa-

ter in the Aral Sea Basin has been reduced by 75%, due mainly to reduced inows as a consequence

o irrigation o close to 7 million hectares o land (UNESCO 2000; Postel 1999). This has led to the

loss o 20 o 24 fsh species and collapse o the fshing industry; the fsh catch ell rom 44,000 tons

annually in the 1950s to zero, with the loss o 60,000 jobs (Postel 1996). Species diversity and wildlie

habitat have also declined, particularly in the wetlands associated with the sea (Postel 1999). The

water diversions together with polluted runo rom agricultural land have had serious human health

eects, including an increase in pulmonary diseases as winds whipped up dust and toxins rom the

exposed sea bed (WMO 1997).

Wind storms pick up some 100 million tons o dust containing a mix o toxic chemicals and salt

rom the dry sea bed and dump them on the surrounding armland, harming and killing crops as well

as people (Postel 1996). The low ows into the sea have concentrated salts and toxic chemicals,

making water supplies hazardous to drink (Postel 1996). In the Amu Darya River Basin chemicals

such as dichlorodiphenyl-trichloroethane (DDT), lindane, and dioxin have been carried by agricultural

runo and spread through the aquatic ecosystems and into the human ood chain. Secondary salini-

zation is also occurring (Williams 2002).

Attempts to rehabilitate the Northern Sea are under way through the Syr Darya and Northern Aral

Sea Project (www.worldbank.org.kz); initial results are seen as positive (Pala 2006). A dam has been

constructed between the two parts o the sea to allow the accumulation o water and to help reha-

bilitate parts o the delta. While the project aims to reestablish and sustain fshery and agricultural

activities and to reduce the harmul eects on the drinking water, the extent o past changes makes

restoration highly unlikely. The ecological and social changes in the Aral Sea ecosystem are consid-

ered largely irreversible.

box 6.2 The Aral Seaan ecological catastrophe



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Whether an ecosystem is managed primarily or ood production, water regulation, or or

other services (gure 6.2), it is possible to secure these or the long term only i basic eco-system unctioning is maintained. In many agroecosystems considerable eort goes into

ensuring crop production, but oten at the expense o other important services, such as

sheries (Kura and others 2004), reshwater supply (Vrsmarty, Lvque, and Revenga

2005), and regulation o oods (Daily and others 1997; Bravo de Guenni 2005).

Biodiversityvariability and diversity within and among species, habitats, and eco-

system servicesis important or supporting ecosystem services and has value in its own

right. Further, biodiversity can act as an insurance mechanism by increasing ecosystem

resilience (box 6.3). Some species that do not seem to have an important role in ecosystems

under stable conditions may be crucial in the recovery o an ecosystem ater a disturbance.

Similarly, i one species is lost, another with similar characteristics may be able to replace it.

While the concept o biodiversity comprises ecosystems, species, and genetic components,most o the discussion in this chapter ocuses on the unctional role o ecosystems and spe-

cies (or taxa) in terms o the ecosystem services that they provide.

Tere is increasing evidence that ecosystems play an important role in poverty reduction

(Silvius, Onela, and Verhagen 2000; WRI and others 2005). Many rural poor people rely on

a variety o sources o income and subsistence activities that are based on ecosystems and are

thus most directly vulnerable to the loss o ecosystem services [established]. Tese sources o

income, oten generated by women and children, include small-scale arming and livestock

rearing, shing, hunting, and collecting rewood and other ecosystem products that may be

sold or cash or used directly by households. Floodplain wetlands, or example, support many

human activities, including sheries, cropping, and gardening (photos 6.16.3).

Provisioning services

Goods produced or providedby ecosystems

Food Fuel wood

Fiber Timber

Regulating services

Benefits from regulation ofecosystem processes

Water partitioning Pest regulation

Climate regulation Pollination

Cultural services

Nonmaterial benefits fromecosystems

Spiritual Recreational

Aesthetic Educational

Support services

Factors necessary forproducing ecosystem services

Hydrological cycle Soil formation

Nutrient cycling Primary production

Source: Adapted from MEA 2003.

fgure6.2 Types o ecosystem services



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The decline o biodiversity globally, most severely maniested in reshwater systems (MEA 2005b),

has renewed interest in ecosystem conservation and management and in the links between bio-

diversity and ecosystem unctioning (Holling and others 1995; Tilman and others 1997), including

the role in human well-being (MEA 2005c) and the links to poverty (Adams and others 2004; WRI

and others 2005). Many people highlight the ethical argument or conserving biodiversity or its own

intrinsic value, and projects aimed at conserving endangered species (establishment o protected

areas, changed land-use practices) have been common investment strategies, with dierent social

outcomes (Adams and others 2004).

Research in recent decades has illustrated the importance o species diversity or ecosystemunctioning (see photos o wetland biodiversity). The general theory is that a more diverse system

contributes to more stable productivity by providing a means o coping with variation.

However, it has recently been argued that it is not the richness o species that contributes to eco-

system unctioning, but rather the existence o unctional groups (predators, pollinators, herbivores,

decomposers) with dierent and sometimes overlapping unctions in relation to ecosystem process-

es (Holling and others 1995). To understand the role o diversity or ecosystem unctioning, it is

necessary to analyze the identities, densities, biomasses, and interactions o populations o species

in the ecosystem, as well as their temporal and spatial variations (Kremen 2005). Diversity o organ-

isms within and between unctional groups can be critical or maintaining resistance to change.

Species that may seem redundant during some stages o ecosystem development may be criti-

cal or ecosystem reorganization ater disturbance (Folke and others 2004). Response diversity (the

dierential responses o species to disturbance) helps to stabilize ecosystem services in the ace o

shocks (Elmqvist and others 2003).

box 6.3 Biodiversity and ecosystem resilience

PhotobyC.

MaxFinlayson

PhotobyKarenConnif

PhotobyC.

MaxFinlayson

PhotobyC.

MaxFinlayson

Pelicans Dragony

ElephantsCrocodile



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Te Millennium Ecosystem Assessment concluded that a ailure to tackle the decline in

ecosystem services will seriously erode eorts to reduce rural poverty and social inequity and

eradicate hunger; this is a critical issue in many regions, particularly in Sub-Saharan Arica

(WRI and others 2005). It is also true that continued and increasing poverty can intensiy

pressure on ecosystems as many o the rural poor and other vulnerable people are let with no

options but to overexploit the remaining natural resource base. Te result is oten a vicious

cycle in which environmental degradation and increased poverty are mutually reinorcing

orces (Silvius and others 2003). Te Millennium Ecosystem Assessment (MEA 2005c) con-

cluded that interventions that led to the loss and degradation o wetlands and water resources

would ultimately undermine progress toward achieving the Millennium Development Goals

o reducing poverty and hunger and ensuring environmental sustainability.

Consequences and ecosystem impacts

Modications o the landscape to increase global ood production have resulted in in-

creased provisioning services, but also in adverse ecological changes in many ecosystems,

with concomitant loss and degradation o services (MEA 2005c). Water management has

caused changes in the physical and chemical characteristics o inland and coastal aquatic

ecosystems and in the quality and quantity o water, as well as direct and indirect biological

changes (Finlayson and DCruz 2005; Agardy and Alder 2005; Vrsmarty, Lvque, and

Revenga 2005). It has also caused changes in terrestrial ecosystems through the expansion

o agricultural lands and changes in water balances (Foley and others 2005).Tese changes have had negative eedback on the ood and ber production activities o

agroecosystems, or example through reductions in pollinators (Kremen, Williams, and Torp

2002) and degradation o land (see chapter 15 on land) [established but incomplete]. Adverse

changes have varied in intensity, and some are seemingly irreversible, or at least dicult or

expensive to reverse, such as the extensive dead zones in the Gul o Mexico and the Baltic

Sea (Dybas 2005). Te catastrophic collapse o coastal sheries as a consequence o environ-

mental change is another example (see chapter 12 on inland sheries). Tis chapter ocuses

on the consequences or ecosystems o green and blue water management in agriculture while

acknowledging that many other human activities also play a role. Synergistic and cumulative

eects can make it extremely dicult to attribute change to a single cause (box 6.4).

PhotosbyC.

MaxFinlayson

Fisheries, cropping, and gardening are among the many human activities supported by oodplain wetlands.Photo

6.1

Photo

6.2

Photo

6.3



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Aquatic ecosystems

Water-related agricultural modications have had major ecological, economic, and social

consequences, including eects on human health, through changes in the key ecological

components and processes o rivers, lakes, oodplains, and groundwater-ed wetlands [well

established]. Tese changes include alterations to the quantity, timing, and natural vari-ability o ow regimes; alterations to the waterscape through the drainage o wetlands and

the construction o irrigation storages; and increased concentrations o nutrients, trace

elements, sediments, and agrochemicals.

Aquatic ecosystems provide a wide array o ecosystem services [well established].

Teir nature and value are not consistent, however, and our understanding o how eco-

system processes support many o these services is inadequate (Finlayson and DCruz

2005; Baron and others 2002; Postel and Carpenter 1997). In several areas around the

world changes have contributed to a loss o provisioning services such as sheries, regu-

lating services such as storm protection and nutrient retention, and cultural services

such as recreational and aesthetic uses. In some cases ecosystems have passed thresholds

New challenges are emerging or water managers in agriculture as a consequence o the cumulative

and sometimes synergistic eects o multiple drivers, including climate change and invasive spe-

cies.

Global climate change is expected to directly and indirectly alter and degrade many ecosystems

(Gitay and others 2002). For example, it will exacerbate problems associated with already expanding

demand or water where it leads to decreased precipitation, while in limited cases, where precipita-

tion increases, it could lessen pressure on available water. There are also major expected conse-

quences or wetland ecosystems and species, although the extent o change is not well established

(Gitay and others 2002; van Dam and others 2002; Finlayson and others orthcoming).There is growing recognition o the important role that invasive species can play in degradation o

ecosystems and ecosystem services (MEA 2005c). Invasive species, spread through water regula-

tion or transport and water transer and through trade, have altered the character o many aquatic

ecosystems (see photo). Once established, invasive plants can block channels and irrigation canals

and decrease connectivity within and between rivers and wetlands, replace valuable species, and

damage inrastructure (Finlayson and DCruz 2005).

Invasive species rom orest plantations are also

threatening water supply or downstream users, as

shown in South Arica where cities such as Cape

Town and Port Elisabeth depend on runo rom the

natural low biomass vegetation in the catchment

(Le Maitre and others 1996). Invasive species in ri-parian areas are a problem or water resources in

several other parts o the world. The annual losses

due to the invasive woody species tamarisk in the

semiarid western United States reach $280$450

a hectare, with restoration costs o approximately

$7,400 a hectare (Zavaleta 2000).

box 6.4Cumulative changesnew challenges or

water management in agriculture

PhotobyC.

MaxFinlayson

Water hyacinth, a rapidly growing, ree-oatinginvasive plant, has degraded many ecosystems



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or gone through regime shits leading to a collapse o ecosystem services, making the

costs o restoration (i possible at all) very high. Tese losses have adverse eects on

livelihoods and economic production [well established]. Tere is ongoing debate whether

the positive outcomes in terms o increased upstream production o ood outweigh the

negative consequences or people dependent on downstream ecosystem services. While

most cost-benet studies show that the costs o the losses have been higher than the

gains, other scientists argue that these studies have many weaknesses (Balmord and

others 2002).

Although agriculture, especially water management in agriculture, is a major driver

behind the loss o downstream ecosystem services [well established], there are competing

explanations or the manner and importance o individual processes and events and theultimate role o agriculture as a triggering orce or degradation is in many situations un-

known. Dams, overshing, urban water withdrawals, and natural and anthropogenic cli-

mate variation can contribute to cumulative and synergistic eects, reduced resilience, and

increased degradation o downstream ecosystems (photo 6.4). Uncertainty is oten high

when it comes to the exact location or timing o the response o downstream ecosystems to

upstream water alterations. Tis does not mean that we can ignore the role o agriculture.

But we need to address the problems as complex and interacting, and to consider a systems

perspective or analyzing multiple drivers o change.

Te next two sections oer examples o how water-related management in agriculture

has changed the capacity o downstream ecosystems to generate ecosystem services and a

brie discussion o the consequences o some o these changes.

Water quantity and waterscape alterations. Increased cultivation in recent decades has

resulted in increased diversion o reshwater, with some 70% o water now being used or

agriculture and reaching as high as 85%90% in parts o Arica, Asia, and the Middle

PhotobyC.

MaxFinlayson

Photo 6.4 Dams provide many benefts or people, but also aect ecosystems by changing thehydrology and ragmenting rivers

Long-term trend

analysis o 145major world

rivers indicates

that discharge

has declinedin one-th o

cases



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East (Shiklomanov and Rodda 2003) [well established]. Regulation o the worlds rivers

has altered water regimes, with substantial declines in discharges to the ocean (Meybeck

and Ragu 1997). Long-term trend analysis (more than 25 years) o 145 major world riv-

ers indicates that discharge has declined in one-th o cases (Walling and Fang 2003).

Worldwide, large articial impoundments hold vast quantities o water and cause signi-

cant distortion o ow regimes (Vrsmarty and others 2003), oten with harmul eects

on human health (box 6.5).

Water diversion and the construction o hydraulic inrastructure (reservoirs, physical

barriers) have altered downstream ecosystems through changes in the quantity and pattern

o water ows and the seasonal inows o reshwater (see global summaries in Vrsmarty,

Lvque, and Revenga 2005 and Finlayson and DCruz 2005). Negative eects includethe loss o local livelihood options, ragmentation and destruction o aquatic habitats,

changes in the composition o aquatic communities, loss o species, and health problems

resulting rom stagnant water. Less ooding means less sedimentation and deposition o

nutrients on oodplains and reduced ows and nutrient deposition in parts o the coastal

zone (Finlayson and DCruz 2005).

Many water-related diseases have been successully controlled through water management (or ex-

ample, malaria in some places), but others have been exacerbated by the degradation o inlandwaters through water pollution and changes in ow regimes (the spread o schistosomiasis). Where

diseases have spread, the adverse eects on human health are due to a complex mix o environmen-

tal and social causes. The Millennium Ecosystem Assessment reported many instances where water

management practices contributed to a decline in well-being and health (MEA 2005a; Finlayson and

DCruz 2005). This includes diseases caused by the ingestion o water contaminated by human or

animal eces; diseases caused by contact with contaminated water, such as scabies, trachoma, and

typhus; diseases passed on by intermediate hosts such as aquatic snails or insects that breed in

aquatic ecosystems, such as dracunculiasis and schistosomiasis, as well as dengue ever, flariasis,

malaria, onchocerciasis, trypanosomiasis, and yellow ever; and diseases that occur when there is

insufcient clean water or basic hygiene.

In addition to disease rom inland waters, waterborne pollutants have a major eect on human

health, oten through their accumulation in the ood chain. Many countries now experience problems

with elevated levels o nitrates in groundwater rom the large-scale use o organic and inorganic ertil-

izers. Excess nitrate in drinking water has been linked to methemoglobin anemia in inants.

There is increasing evidence rom wildlie studies that humans are at risk rom a number o chemi-

cals that mimic or block the natural unctioning o hormones, interering with natural bodily processes,

including normal sexual development. Chemicals such as DDT, dioxins, and those in many pesticides

are endocrine disruptors, which may interere with human hormone unctions, undermining disease

resistance and reproductive health.

The draining and burning o orested peat swamps in Southeast Asia have had devastating health

eects (see box 6.6 later in this chapter) that extend across many countries and that may be long-

lasting. The investigation o environment-related health eects linked with the ongoing degradation

o the orested peat swamps is a major issue or health services in the region.

box 6.5 Water management and human health



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Interbasin transers o water, particularly large transers between major river systems

as are being planned in India, or example, are expected to be particularly harmul to

downstream ecosystems (Gupta and Deshpande 2004; Alam and Kabir 2004) and to ex-

acerbate pressures rom hydrological regulation (Snaddon, Davies, and Wishart 1999).

Where these are being considered, scientic and transparent assessments o the benets

and problems are strongly encouraged. Junk (2002) has highlighted the similar adverse

consequences on water regimes expected rom the construction o industrial waterways

(hidrovias) through large wetlands, such as the Pantanal o Maso Grosso, Brazil. Te na-

ture o expected changes depends on the amount and timing o water being transerred

and so needs to be assessed case by case.

Shrinking lakes. Tere are many instances where consumptive water use and waterdiversions have contributed to severe degradation o downstream ecosystem services. Te

degradation o the Aral Sea in Central Asia represents one o the most extreme cases (see

box 6.2).

Te desiccation o Lake Chad in West Arica is another example. It shrank rom

25,000 square kilometers in surace area to one-twentieth that size over a 35-year period.

However, there are competing explanations or this reduction. Natural rainall variability

is an important driver. Te lake is very shallow, and at various times in its history it has

assumed dierent states, with changes triggered by climate variability (Lemoalle 2003). It

is unclear what role human-induced change has played, but dierent drivers include the

withdrawal o irrigation water, land-use changes reducing precipitation through changes

in albedo (the energy that is reected by the earth and that varies with land surace charac-teristics), and reduced moisture recycling (Coe and Foley 2001).

Lake Chapala, the worlds largest shallow lake, situated in the Lerma-Chapala Basin

in central Mexico, is another example o consumptive water use upstream aecting the

size o a lake. During 19792001 water volume in the lake dropped substantially to about

20% o capacity due to excessive water extraction or agricultural and municipal needs.

Average annual rainall rom 1993 to 2003 was only 5% below the historical average and

eorts were made to reduce water use in irrigation, but still the amount o surace and

groundwater used in the basin exceeded supply by 9% on average (Wester, Scott, and

Burton 2005). Above average rains in 2003 and 2004 increased the water volume to about

6,000 million cubic meters. Tere is still intense competition over water allocation, and

environmental water requirements have yet to be determined, leaving the uture o the lakeand the allocation o water or urban and agricultural purposes under threat.

Te high variability in lake volume in both Lake Chad and Lake Chapala means that

the people depending on ecosystem services rom these basins need to have a high adaptive

capacity to cope with the rapidly changing circumstances, whether induced by people or

nature.

Shrinking rivers. Consumptive use and interbasin transers have transormed sev-

eral o the worlds largest rivers into highly stabilized and, in some cases, seasonally non-

discharging, channels (Meybeck and Ragu 1997; Snaddon, Davies, and Wishart 1999;

Cohen 2002). Streamow depletion is a widespread phenomenon in tropical and sub-

tropical regions in rivers with large-scale irrigation, including the Pangani (IUCN 2003),

Worldwide,

large articial

impoundments

hold vastquantities o

water and cause

signicant

distortion o fowregimes, oten

with harmul

eects on

human health



16/45


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249



2003). Indeed, there are instances where the opposite occurs: where wetlands reduce low

ows, increase oods, or act as a barrier to groundwater recharge. Given the wide range o

wetlands, rom entirely groundwater-ed springs and mountain bogs to large inland river

oodplains, such variation should not be surprising.

Changes in water quality. Many actors contribute to changes in water quality. Tis sec-

tion looks at nutrient loads, agrochemicals, and siltation.

Nutrient loading. Te use o ertilizers has brought major benets to agriculture, but

has also led to widespread contamination o surace water and groundwater through run-

o. Over the past our decades excessive nutrient loading has emerged as one o the most

important direct drivers o ecosystem change in inland and coastal wetlands, with the ux

o reactive nitrogen to the oceans having increased by nearly 80% rom 1860 to 1990

(MEA 2005c). Phosphorus applications have also increased, rising threeold since 1960,

with a steady increase until 1990 ollowed by a leveling o at approximately the applica-

tion rates o the 1980s (Bennett, Carpenter, and Caraco 2001). Tese changes are mirrored

Large parts o the tropical peat swamp orests in Southeast Asia have been seriously degraded,

largely due to logging or timber and pulp (Wsten and others 2006; Page and others 2002). The

process has been accelerated over the last two decades by the conversion o orests to agriculture,

particularly oil palm plantations. Drainage and orest clearing threaten the stability o large tracts o

orests in Indonesia and Malaysia and make them susceptible to fre.

Attempts to clear and drain the orests and establish agriculture have high rates o ailure. Under

the Mega Rice Project in Kalimantan, Indonesia, large areas o orest were cleared and some 4,600

kilometers o drainage canals were constructed in an attempt to grow rice on a grand scale using

emigrant workers rom the heavily populated neighboring island o Java. The cleared land was un-suited to rice production, and the scheme was abandoned. In 1997 land clearing and subsequent

uncontrolled fres severely burned about 5 million hectares o orest and agricultural land in Kaliman-

tan, releasing an estimated 0.82.6 billion tons o carbon dioxide into the atmosphere (Glover and

Jessup 1999; Page and others 2002; Wooster and Strub 2002). The fres created a major atmospheric

haze, with severe impacts on the health o 70 million people in six countries. In addition, there have

been economic eects on timber and agricultural activities, with the fres compounding the loss o

peatlands through clearing and ailed attempts to cultivate large areas or rice.

Rehabilitation o some degraded areas is under way, but it is a slow and difcult process trying

to reestablish the hydrology and vegetation (Wsten and others 2006). At a regional level the Asso-

ciation o Southeast Asian Nations (ASEAN) has taken an active interest in the problem through the

ASEAN Peatland Management Initiative, acilitating the sharing o expertise and resources among the

aected countries to prevent peatland fres and manage peatlands wisely. The regional initiatives arelinked with national action plans. Monitoring mechanisms are in place, and a policy o zero burning

or urther land clearing has also been established, in particular or oil palm plantations.

Despite these steps, the problem o peatland degradation continues. The expansion o oil palm

plantations is a major driver. The peat swamps are still being cleared and burned, undermining eorts

to conserve and use the peatlands o Southeast Asia wisely and threatening the health o people lo-

cally and regionally.

box 6.6The widespread impacts o draining and

burning in Southeast Asian peatlands



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by phosphorus accumulation in soils, with high levels o phosphorus runo. In developed

countries annual storage peaked around 1975 and is now at about the same annual rate as

in 1961. In developing countries, however, storage went rom negative values in 1961 to

about 5 teragrams per year in 1996.

Excessive nutrient loading can cause algal blooms, decreased drinking water quality,

eutrophication o reshwater ecosystems and coastal zones, and hypoxia in coastal waters.

In Lake Chivero, Zimbabwe, agricultural runo is seen as responsible or algal blooms,

inestations o water hyacinth, and sh declines as a result o high levels o ammonia and

low oxygen levels (UNEP 2002). In Australia extensive algal blooms in coastal inlets and

estuaries, inland lakes, and rivers have been attributed to increased nutrient runo rom

agricultural elds (Lukatelich and McComb 1986; Falconer 2001). Diuse runo o nu-trients rom agricultural land is held to be largely responsible or increased eutrophication

o coastal waters in the United States as well as or the periodic development, oten varying

rom year to year, o anoxic conditions in coastal water in many parts o the world, such as

the Baltic and Adriatic Seas and the Gul o Mexico (Hall 2002).

Nutrient management can be undermined by the loss o wetlands that assimilate

nutrients (nitrogen, phosphorous, organic material) and some pollutants. Extensive evi-

dence shows that up to 80% o the global incident nitrogen loading can be retained within

wetlands (Green and others 2004; Galloway and others 2004). However, the ability o

such ecosystems to cleanse nutrient-enriched water varies and is not unlimited (Alexander,

Smith, and Schwarz 2000; Wollheim and others 2001). Verhoeven and others (2006)

point out that many wetlands in agricultural catchments receive excessively high loadingso nutrients, with detrimental eects on biodiversity. Wetlands and lakes risk switching

rom a state in which they retain nutrients to one in which they release nutrients or emit

There are reported cases o regime shits occurring in lakes because o increased nutrient loading,

resulting in the loss o ecosystem services such as fsheries and tourism (Folke and others 2004).

Some temperate lakes have experienced shits between a turbid water and a clear water state, with

the shit oten attributed to an increase in phosphorous loading (Carpenter and others 2001). Some

tropical lakes have shited rom a dominance o ree-oating plants to submerged plants, with nutrient

enrichment seemingly reducing the resilience o the submerged plants, possibly through shading and

changes in underwater light (Scheer and others 2001). Other wetlands and coastal habitats have

also experienced similar shits. In the United States nutrient enrichment caused a shit in emergent

vegetation in the Everglades and a shit rom clear water to murky water with algal blooms in Florida

Bay (Gunderson 2001).

Other evidence comes rom lakes subject to inflling and nutrient enrichment. In Lake Hornborga

in Sweden emergent macrophytic vegetation prolierated ater initial inflling o the lake margins and

increased runo o nutrients. The situation was reversed only ater massive mechanical intervention

and investment (Hertzman and Larsson 1999). In Australia agricultural runo has resulted in shits in

vegetation dominance as a consequence o nutrient enrichment, increased inundation and saliniza-

tion (Davis and others 2003; Strehlow and others 2005).

box 6.7 Regime shits rom excessive nutrient loads

Nutrient

managementcan be

undermined

by the loss

o wetlands

that assimilatenutrients and

some pollutants



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the greenhouse gas nitrous oxide. Regime shits are oten rapid, but they have likely ol-

lowed a slower and dicult to detect change in ecosystem resilience. It is generally dicult

to monitor changes in resilience beore a system hits the threshold and changes rom one

state to another (box 6.7; Carpenter, Westley, and urner 2005).

Agrochemical contamination. Pollution and contamination rom agricultural chemi-

cals have been well documented since the publication o the seminal book Silent Spring

(Carson 1962). Bioaccumulation as a consequence o the wide use o agrochemicals has

had dire outcomes or many species that reside in or eed predominantly in wetlands or

lakes that have accumulated residues rom pesticides [well established]. Te decline in the

breeding success o raptors was a turning point in developing awareness about the dangers

o using pesticides (Carson 1962).An increasing amount o analytical and ecotoxicological data has become available or

aquatic communities, and more recent research has also ocused on risk assessments and

the development o diagnostic tests that can guide management decisions about the use

o such chemicals (van den Brink and others 2003). aylor, Baird, and Soares (2002) have

highlighted the high levels o pesticide use and low levels o environmental risk assessment

in developing countries. Tey have promoted an integrated approach to evaluating envi-

ronmental risks rom pesticides that incorporates stakeholder consultation, chemical risk

assessment, and ecotoxicological testing or ecological eects, also taking into account the

potential eects on human health.

Vrsmarty, Lvque, and Revenga (2005) report that water contamination by pes-

ticides has increased rapidly since the 1970s despite increased regulation o the use oxenobiotic substances, especially in developed countries. However, bans on the use o these

chemicals have generally been imposed only two to three decades ater their rst commer-

cial use, as with DD and atrazine. Many o these substances are highly persistent in the

environment, but because o the generally poor monitoring o their long-term eects the

global and long-term implications o their use cannot be ully assessed. Policy responses

to contamination may lag ar behind the event, as shown in the well documented case o

agricultural pesticide bioaccumulation o DD in the Zambezi Basin (Berg, Kilbus, and

Kautsky 1992).

Siltation o rivers. In many parts o the world extensive sheet wash and gully erosion

due to land management practices have devastated large areas, reduced the productivity o

wide tracts o land, led to rapid siltation o reservoirs and threatened their longevity, andincreased sediment loads in many rivers (see chapter 15 on land). On a regional scale some

reservoirs in Southern Arica are at risk o losing more than a quarter o their storage capac-

ity within 2025 years (Magadza 1995). While many Australian and Southern Arican wa-

ters are naturally silty, many have experienced increased silt loads as a result o agricultural

practices (Davies and Day 1998). Zimbabwes more than 8,000 small to medium-size dams,

or example, are threatened by sedimentation rom soil erosion, while the Save River, an in-

ternational river shared with Mozambique, has been reduced rom a perennial to a seasonal

river system due in large part to increased siltation as a result o soil erosion.

Globally, rivers discharge nearly 38,000 cubic kilometers o reshwater to the oceans

and carry roughly 70% o the sediment input, though rivers draining only 10% o the

Water

contaminationby pesticides

has increased

rapidly since the

1970s despite

increasedregulation,

especially in

developed

countries



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252

land area contribute 60% o the total sediment discharge (Milliman 1991). Te high sedi-

ment loads carried by Asian rivers are a consequence o land-use practices, particularly

land-clearing practices or agriculture that lead to erosion, a situation likely to continue

as a consequence o the expansion o agriculture in Arica, Asia, and Latin America (Hall

2002). A notable outcome o the supply o sediment and associated nutrients to the oceans

is the increased requency and intensity o anoxic conditions in recent years (Hall 2002).

Tere are also situations where river regulation has caused a decline in silt transport to

downstream habitats, with reduced siltation along oodplains and in deltas and other down-

stream ecosystems. Tis has occurred in the Mesopotamian Marshes, where large-scale drain-

age is a bigger problem than silt-related changes in the downstream ecosystems (box 6.8).

Terrestrial ecosystems

Hydrological changes that occur as a result o agricultural expansion, particularly into

orests, are seldom thought o in terms o water management in agriculture, although such

changes are o at least the same magnitude as those resulting rom irrigation (Gordon and

others 2005). Tis is an area in need o urther research, especially as biouels and tree

The Mesopotamian wetlands, one o the cradles o civilization and a biodiversity center o global

importance, used to cover more than 15,000 square kilometers in the lower Euphrates and TigrisBasins. Agricultural development and other drainage activities over the past 30 years have reduced

them to 14% o their original size, and vast areas have been turned into bare land and salt crusts

(Richardson and others 2005). The ecological implications have been severe, with drastic land deg-

radation and impacts on wildlie, including bird migration and the extinction o endemic species, and

on the ecology o the downstream Shatt el Arab and coastal fsheries in the Persian Gul. The local

population o hal a million Marsh Arabs have become environmental reugees.

The causes o this severe ecological degradation are complex. Some o the causes were inten-

tional, the results o drainage eorts to reclaim marshland, deal with soil salinization, improve agri-

cultural productivity, and strengthen military security in southern Iraq in the 1980s and 1990s. Other

causes were unintentional and included both the large-scale consumptive water use in irrigation

systems and the return o saline drainage, agricultural and industrial chemical pollution, and the loss

o ood ow, with its load o silt and nutrients, linked to recent large-scale streamow regulation inupstream Turkey.

With the extent o existing regulation and degradation, the proposed rehabilitation o 30% o the

Central Marshes upstream o the conuence o the Euphrates and Tigris could generate its own

adverse impacts on aquatic ecosystems urther downstream. The additional evaporation rom just

1,000 square kilometers o restored open-water suraces would consume an average ow o 67 cubic

meters per second, or 25% o the original (pre-regulation) dry season ow, and reduce downstream

streamow even urther. Without an increase in the amount o water available, simply returning the

water to upstream areas may not be enough to restore the marshes and could urther reduce the ow

o water to downstream areas.

Source: Partow 2001; Italy, Ministry or the Environment and Territory, and Free Iraq Foundation 2004.

box 6.8 Desiccation o the Mesopotamian wetlands



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cover and its management (McCulloch and Robinson 1993; Bosch and Hewlett 1982;

Bruijnzeel 1990).

General work on the inuence o vegetation, climate, and land cover on the water

balance o a system has shown that there are vegetation-specic changes (Lvovich 1979;

Calder 2005). Management o plant production that redirects blue water to green water

can reduce the amount o water to downstream systems (Falkenmark 1999). For example,

replacing crop or grasslands with orest plantations can decrease runo and streamow

(Jewitt 2002). Te South Arican Water Act classies orest plantations as a streamow

reduction activity, and orestry companies have to pay or their water use since less o the

precipitation reaches the river.

Moisture recycling. Clearing land or agriculture and increasing use o irrigation have modi-

ed green water ows globally, reducing them by 3,000 cubic kilometers through orest clear-

ing and increasing them by 1,0002,600 cubic kilometers in irrigated areas (Dll and Siebert

2002; Gordon and others 2005). Te ability o changes in land cover to inuence climate

through changes in green water ow has been increasingly recognized. It has been suggested

that large-scale deorestation can reduce moisture recycling, aect precipitation (Savenije 1995,

1996; renberth 1999), and alter regional climate, with indications o global impacts (Kabat

and others 2004; Nemani and others 1996; Marland and others 2003; Savenije 1995).

Pielke and others (1998) conclude that the evidence is convincing that land cover

changes can signicantly inuence weather and climate and are as important as other hu-

man-induced changes or the Earths climate. However, the models employed do not dealexplicitly with green water ows, but rather with the compounded eects o changes in al-

bedo, surace wind, lea area index, and other indicators. Nevertheless, regional studies in West

Arica (Savenije 1996; Zheng and Eltathir 1998), the United States (Baron and others 1998;

Pielke and others 1999), and East Asia (Fu 2003) have illustrated that changes in land cover

aect green water ows, with impacts on local and regional climates. Likewise, biome-specic

models o land cover conversions rom rainorest to grasslands have shown a decrease in vapor

ows and precipitation as well as eects on circulation patterns (Salati and Nobre 1991) and

savannahs (Homan and Jackson 2000). Tere are also indications that increased vapor ows

through irrigation can alter local and regional climates (Pielke and others 1997; Chase and

others 1999). Te conversion o steppe to irrigated croplands in Colorado resulted in a 120%

increase in vapor ows (Baron and others 1998), contributing to higher precipitation, lowertemperatures, and an increase in thunderstorm activity (Pielke and others 1997).

Whether these changes can trigger rapid regime shits (box 6.9), which in many cases

may be irreversible, and changes to which armers need to adapt is still speculative. In the Am-

azon the clearing o land has reduced moisture recycling, resulting in prolonged dry seasons

and increased burning, and may have triggered an irreversible regime shit rom rainorest veg-

etation to savannah (Oyama and Nobre 2003). Tere is also increasing concern about changes

in the Arican and Asian monsoons, including weakening o the East Asian summer monsoon

low-pressure system and an increase in irregular northerly ows (Fu 2003). Likewise, modeled

vegetation changes or agricultural expansion in West Arica have shown potentially dramatic

impacts on rainall in the Arican monsoon circulation (Zheng and Eltathir 1998).

There are

indications thatincreased vapor

fows through

irrigation can

alter local

and regionalclimates



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Societal responses and opportunities

Te negative eects o past agricultural management on ecosystem services and the need

to produce more ood or growing populations provide an unparalleled challenge. Meet-

ing this challenge requires large-scale investments to improve agricultural management

practices, increase the availability o techniques to minimize adverse ecological impacts,

enhance our understanding o ecosystem-agriculture interactions, and reduce poverty and

social inequities, including issues o gender, health, and education that aect ecosystem

management decisions.In presenting possible responses or meeting this challenge, we emphasize several

ecological outcomes that we consider to be critical in this eort: maintenance or rehabili-

tation o the ecological connectivity, heterogeneity, and resilience in the landscape, which

in turn implies maintenance or rehabilitation o the biodiversity that characterizes the

landscape. We ocus on integration and awareness o the negative consequences o choices

in terms o the tradeos between ood production and other ecosystem services. We do

not propose specic responses or specic ecosystems or locations, although we aim to

help national and local decisionmaking with a ramework or addressing some o these

issues. Many o the responses outlined are dependent on eective governance measures

and policies that support sustainable development with a balance o ecological and social

Ecosystems change and evolve, with disturbance now seen as an inherent component o ecosystem

processes [well established]. The speed o change in many ecosystems has, however, increased

rapidly, and there is now concern that large-scale changes will increase the vulnerability o some

ecosystems to water-related agricultural activities. Ecosystems are complex adaptive systems (Levin

1999), with nonlinear dynamics and thresholds between dierent stable states. Nonlinear changes

are sometimes abrupt and large, and they may be difcult, expensive, or impossible to reverse. The

increased likelihood o nonlinear changes stems rom drivers o ecosystem change that adversely

aect the resilience o an ecosystem, its capacity to absorb disturbance, undergo change, and still

retain essentially the same unction, structure, identity, and eedbacks (Gunderson and Holling 2002;Carpenter and others 2001) and provide components or renewal and reorganization (Gunderson and

Holling 2002).

Variability and exibility are needed to maintain ecosystem resilience. Attempts to stabilize sys-

tems in some perceived optimal state, whether or conservation or production, have oten reduced

long-term resilience, making the system more vulnerable to change (Holling and Mee 1996). While

todays agricultural systems are able to better deal with local and small-scale variability, the simpli-

fcations o landscapes and reduction o other ecosystem services have decreased the capacity o

agricultural systems and other ecosystems to cope with larger scale and more complex dynamics

through reduced ecosystem resilience locally and across scales (Gunderson and Holling 2002).

Little is yet known about how to estimate resilience and detect thresholds beore regime shits

occur (Fernandez and others 2002). Better mechanisms to monitor regime shits include the iden-

tifcation and monitoring o slowly changing variables (Carpenter and Turner 2000) and measurablesurrogates o resilience (Bennett, Cumming, and Peterson 2005; Cumming and others 2005).

box 6.9Resilience and the increased risk o rapid

regime shits in ecosystems



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outcomes, issues covered in detail in chapters 5 on policies and institutions and 16 on

river basins.

Improving agricultural technology and management practices

Te Millennium Ecosystem Assessment (MEA 2005c) supports the view that intensica-

tion o agricultural systems will create ewer tradeos with ecosystem services than will

expansion. Intensication will require improvements in agricultural productivity, espe-

cially in water productivity (see chapter 7 on water productivity) in water-scarce envi-

ronments. However, because intensication can bring its own ecological problems, or

example, through pollution or the introduction o invasive species, command and control

approaches to management should be avoided (Holling and Mee 1996). Te potentialproblems o intensication could be lessened or avoided through the adoption o a systems

approach to agriculture and integrated approaches to landscape management (see below).

Many o the chapters in this volume address agricultural techniques and improved

management practices. Chapters 14 on rice and 15 on land highlight the need to consider

techniques and practices that may not increase the production o one or a ew specic

crops but that support the provision o multiple benets. Unless responses that restrict

the potential adverse impacts o intensication are applied, intensication will not be any

more environmentally and socially benign than many past agricultural practices.

Applying integrated approaches to water, agriculture, and other

ecosystemsIntegrated policy and management approaches are increasingly seen as crucial in acilitat-

ing decisionmaking and making tradeos between ood and other ecosystem services. In-

tegrated approaches have taken many orms, including integrated river basin management,

PhotobyC.

MaxFinlayson

Photo 6.5 This use o wetlands in Malawi attempts to integrate multiple benefts and costs

The potential

problems ointensication

could be

lessened

through the

adoption oa systems

approach to

agriculture

and integratedapproaches

to landscape

management



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integrated land and water management, ecosystem approaches, integrated coastal zone

management, and integrated natural resources management. Teir general aim is oten the

same. Tey actively seek to address integration o all the benets and costs associated with

land-use and water decisions, including eects on ecosystem services, ood production,

and social equity, in a transparent manner; to involve key stakeholders and cross-institu-

tional levels; and to cross relevant biophysical scales, addressing interconnectedness across

subbasin, river basin, and landscape scales (photo 6.5).

While integrated approaches or environmental management are seen as an impor-

tant eort and have long been promoted, there are ew successul examples. Te gover-

nance systems required to support the appropriate institutional and managerial arrange-

ments, particularly or the allocation o resources and planning authority concomitantwith responsibility at a local level, seem dicult to achieve (see, or example, chapter 16 on

river basins). One complaint is that most o these approaches are based on a technocratic

view o decisionmaking, whereas real lie is ar messier, with power struggles, lack o trust

between and within stakeholder groups, and complex and evolutionary behavior o eco-

systems that make it dicult to assess total benets and impacts. Folke and others (2005)

see a need or more emphasis on building, managing, and maintaining collaborative social

relationships or river basin governance, which is in line with current thinking about eco-

system management.

Where river basin organizations have succeeded, that has oten been because o their

ability to deliver on the common aims o jurisdictions (such as coordinated water man-

agement to supply irrigation). Te situation is more complex when dealing with inter-national transboundary rivers, such as the Nile and the Mekong. An alternative to river

basin processes may be to explore more regional guidance or common policies, as is being

developed in Southern Arica (box 6.10).

Te complexity o the social policy and institutional links that govern ecosystem

management and inuence necessary tradeos is shown or wetlands in gure 6.3. Dier-

ences in local contexts may aect the manner in which relationships between individuals

While integrated

approaches orenvironmental

management

have long been

promoted,

there are ewsuccessul

examples

The South Arican National Water Act o 1998 protects the water requirements or ecosystems and

supports them through an ongoing scientifc eort. This is in line with the principles contained in

the Southern Arican Development Commission (SADC) regional water policy o May 2004, which

recognizes the environment as a legitimate user o water and calls on SADC members to adopt all

necessary strategies and actions to sustain the environment. At the national level water reorms in

South Arica and Zimbabwe have successully mainstreamed environmental water requirements in

water resources policy and legislation. Namibia is similarly considering policy that stresses sectoral

coordination, integrated planning and management, and resource management aimed at coping with

ecological and associated environmental risks.

Mexicos 1992 Law o National Waters is another example o national water reorms that consider

ecosystem needs. It empowers the ederal government to declare as disaster areas watersheds or

hydrological regions that represent or may represent irreversible risks to an ecosystem.

box 6.10 National and regional policy initiatives on water and ecosystems



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and institutions are built and maintained. High levels o knowledge and human capacity

are considered critical to crating the institutions and policies required or successul in-

tegrated water management (see chapter 5 on policies and institutions). Tis chapter em-

phasizes the need to raise awareness o the role o ecosystem services in societal well-being

in both multiunctional agricultural systems and across landscapes and on the importance

o maintaining the ecological and social processes that support these.

Assessing and nurturing multiple benefts

Improving awareness and understanding. Integrated approaches help to deal with the

competing interests in water resources Tey make it possible to share the multiple benetsand costs that are generated across a river basin and that are improved or degraded through

agricultural interventions in the landscape.

Assessment o the multiple ecosystem services and the processes that support them is

a key component o these approaches. Historically, decisions concerning ecosystem man-

agement have tended to avor either conversion o ecosystems or management or a single

ecosystem service, such as water supply or ood production, oten without consideration o

the eects on such groups as the rural poor, women, and children (MEA 2005c). Many eco-

system services do not have a price on the market and are oten neglected in policymaking

and decisionmaking. As we better understand the benets provided by the entire array

o ecosystem services, we also realize that some o the best response options will involve

managing landscapes, including agriculture, or a broader array o services. Tat will entailtaking greater account o social issues, such as gender-based roles and poverty, when mak-

ing decisions about agriculture and water management (WRI and others 2005).

Te Millennium Ecosystem Assessment has provided a major advance in under-

standing the links between the provision o ecosystem services and human well-being

(www.maweb.org). Increased awareness is still needed on several dierent levels. Te

scientic knowledge o how ecosystem services contribute to human well-being within

and between dierent sectors o society, and the role o water in sustaining these ser-

vices, need to be improved. Dissemination o inormation on these issues and dialogue

with stakeholders should be enhanced. Civil society organizations can help to ensure

that appropriate consideration is given to the voices o individuals and social groups and

to nonutilitarian values in decisionmaking. Minority groups and disadvantaged groups,such as indigenous people and women, in particular, need to be heard. Women play a

critical and increasing role in agriculture in many parts o the developing world (Elder

and Schmidt 2004).

Urbanization provides new challenges. For the rst time in human history more

people live in cities than in the rural areas. It has been estimated that the urban areas in

the Baltic Sea region in northern Europe need an area o unctioning ecosystems some 500

times the size o the cities themselves to generate the ecosystem services they depend on

(Folke and others 1997). Te green water needs or ecosystem services that support these

cities are roughly 54 times larger than the blue water needs o households and industry

(Jansson and others 1999). However, people who live in cities oten become mentally

Historically,

decisionsconcerning

ecosystem

management

have tended to

avor conversiono ecosystems

or management

or a single eco-

system service,such as ood

production



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260

disconnected rom the ecological and hydrological processes that sustain their well-being.

In this perspective armers are the stewards o the landscape in which cities lie. Tis pro-

vides a new challenge or water and ecosystem management.

One o the main gaps in our scientic understanding o ecosystems and ecosystem

services is where the thresholds lie and how ar a system can be changed beore it loses too

many essential unctions and totally changes its behavior (Gunderson and Holling 2002).

Without this knowledge the early warning indicators required to provide advance warn-

ing o anticipated adverse change or o when a threshold is being approached cannot be

developed.

Source: Adapted from Foley and others 2005; chapters 14 and 15 in this volume.

Fuelwood

Recreation

Pestcontrol

Soilformation

Regulation

of waterbalance

Nutrient

cycling

Cropproduction

Climateregulation

Fuelwood

Recreation

Pestcontrol

Soilformation

Regulation

of waterbalance

Nutrient

cycling

Cropproduction

Climateregulation

Provisioning services Regulating services Supporting services Cultural services

Cardamomseed

Fertility transferto other systems

Soil fertilityimprovement

Watershedconservation

Fodder forlivestock

Soilconservation

Commercial timberand fuel wood

Nitrogenxation

Natural ecosystem Intensive cropland

Multifunctionality in rice elds Alder-cardamom system

FishReligious land-scape values

Water storage,lowering ofpeak oods,groundwaterrecharge

Climateair temperature

Ducks,frogs,snails

Biodiversityenhancement

in human-dominatedlandscapes

Riceproduction

Prevention ofsoil erosion

fgure6.4 Comparison o intensive agricultural systemsmanaged or the generation o one ecosystem serviceand multiunctionality in agroecosystems



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Managing agriculture or multiple outputs. Increasing attention to ecosystem services

provides an opportunity to emphasize multiunctionality within agroecosystems and the

connectivity between and within agroecosystems and other ecosystems. It is oten assumed

that agricultural systems are managed only or optimal (or maximum) production o one

ecosystem service, ood, or ber (gure 6.4). But agricultural systems can generate other

ecosystem services, and we need to improve our capacity to assess, quantiy, and value

these as well. Encouraging multiple benets rom these systems can generate synergies

that result in the wider distribution o benets across more people and sectors. Ecosystem-

based approaches to water management need not constrain agricultural development but

can be points o convergence or social equity, poverty reduction, resource conservation,

and international concerns or global ood security, biodiversity conservation, and carbonsequestration (see chapter 15 on land). Ecosystem-based approaches aim to maintain and

where possible enhance diversity and to build the ecological resilience o the agricultural

landscape as well as o ecosystems altered by agriculture (box 6.11).

Te concept o multiunctional agriculture is not new; it has long been practiced in

many orms and combinations. Integrated pest management is one way to manage a whole

landscape in order to sustain an ecosystem service (pest control) that enhances agricultural

production. Tis type o regional management requires integrated approaches based on an

ecological understanding o ragmentation and landscape heterogeneity (Cumming and

Spiesman 2006). Hydrological understanding is also important. Studies have shown that it

is possible to control insect outbreaks by timing irrigation events (Lansing 1991) and that

The resilience perspective shits rom policies that aspire to control change in systems assumed to

be stable to policies to manage the capacity o social-ecological systems to cope with, adapt to, and

shape change (Berkes, Colding, and Folke 2003). Managing or resilience enhances the likelihood o

sustaining development in changing environments where the uture is unpredictable.

Variability, disturbance, and change are important components o an ecosystem. For example,

when variability in river ows is altered, marked changes in ecosystem unctions can be expected

(Richter and others 2003). Wetting and drying o soils can be important or the resilience o ecosystem

unctions, such as pest control and nutrient retention in wetlands. Exactly what level o variability to

maintain and when variability is site specifc are areas o intense research (Richter and others 2003).

Maintaining diversity has been shown to be important or bui

chapter 6 ecosystems

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