2022-15 workshop on theoretical ecology and global...

2022-15

Workshop on Theoretical Ecology and Global Change

Andrew Dobson

2 - 18 March 2009

Princeton UniversityUSA

Food Web Collapse and the decline of ecosystem services

Food web collapse and the decline of ecosystem services

Andy Dobson

Principal collaborators

• David Wilcove• Will Turner• Walter Jetz• Jon-Paul Rodriguez• Mark Roberts• MA Scenarios Team

Brief Outline

• Population Viability Analysis• Future threats to birds• Identifying sites to protect• Ecosystem Services & habitat loss• Dynamics of habitat loss• Trophic collapse and ecosystem services

Global Nature Reserves

Do these parks protect biodiversity?

PVA’s for Yellowstone Grizzly’s

Year

1960 1965 1970 1975 1980 1985 1990 1995 2000

Annu

al ra

te o

f inc

reas

e,

0.5

0.6

0.7

0.8

0.9

1.0

1.1

PVA for Yellowstone grizzly bears

Year

1960 1965 1970 1975 1980 1985 1990 1995 2000

Annu

al ra

te o

f inc

reas

e,

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Probability of extinction in next 25 years > 1.0

Observed females with cubs

Year

1960 1970 1980 1990 2000 2010

Num

bers

0

20

40

60

80

100

120

Year vs Females Year vs COY

Resources for grizzliesSpring Trout Abundance

Year

1975 1980 1985 1990 1995 2000 2005

Num

bers

0

10000

20000

30000

40000

50000

60000

Clear Creek Trout Run

Future PVA : Detailed stochastic demographic model..with “peer-reviewed” data ?

Or : More phenomological bear / habitat / resource model ?

What determines where we put new nature reserves?

Criteria for establishing and expanding reserve systems

• Spatial distribution of species that need to be conserved

• Cost and availability of land• Present and future threats• Selection algorithms focus on different criteria –

can we develop ones that ‘optimize’ across present and future threats?

Geographical distributionof Endangered species in the US

Mammals

Birds

Fish

Molluscs

What is minimal area required to protect at least one population of all currently listed

US Endangered Species?

Florida scrub jay

Geography

Ancient Sand Dune• Deposited >1 mya ago• now 100-300 feet above

sea level Lake Wales Ridge

Threat

© R. Bowman

©ABS

1,380 km2

habitat

178 km2

habitat

Species

©S

. Tel

ford

Quantifying future threats: The MA Scenarios

• Use a range of climate and human population growth projections to examine possible futures

• Climate change is based on the IGPCC projections

• Human population based on a range of economic projections that assume different responses to environment

Future land-use and climate change andextinction risk in birds

Walter JetzBiological Sciences

University of California San Diego

David S. WilcoveAndy P. Dobson

Ecology, Evolutionary BiologyPrinceton Univeristy

Observed change in annual mean temperature

Observed climate change

The impact on species?

The impact on species?

(following Thomas et al., Nature 2004)

The Millennium Ecosystem Assessment

– Not predictions – scenarios are plausible futures

– Both quantitative models and qualitative analysis used in scenario development

4 Scenarios about the future of the world

Source: Millennium Ecosystem Assessment

Changes in indirect drivers

• In MA Scenarios:– Population projected

to grow to 8–10 billion in 2050

– Per capita income projected to increase two- to fourfold


Changes in indirect drivers


Crop Land Forest Area

Changes in direct drivers

Adapting Mosaic 2100

Landuse ChangeClimate Change

Model: Image 2.2 (Strengers et al 2005)

Climate and Land-use Change: The Global Patttern

Order from Strength, 2100

Landuse ChangeClimate Change

Model: Image 2.2 (Strengers et al 2005)

Climate and Land-use Change: The Global Patttern

A global distribution database

• Distribution ranges of all 9,754 species, geo-registered to known projection

• Following analysis: • polygon ranges resampled to 0.5° grid (259,200 quadrats)• 11,418,435 quadrat records• Excluded 838 freshwater, marine and pelagic species• Breeding ranges only

The geographic patternAll Aves

Families with over 50% pelagic or freshwater species excluded1-523 species per 5km pixel

From extent of occurrence to estimate of area of occupancy …

Chestnut Wattle-eye (Platysteira castanea)

Habitat: Humid Forest

Global Land Cover Classification (IGBP)

(1 km2 resolution)


Cells with forest



0.5° quadrats of range that contain forest

TG Scenariopresent to 2050

From estimate of area of occupancy to estimate of area lost …

Predicted Land Transformations

IPCC Year

2050 4.7 1.6 ° 11% 8%2100 1.9° 15% 10%

2050 13 1.9° 11% 7%2100 3.0° 16% 9%

2050 20 2.1° 11% 9%2100 3.4° 17% 13%

2050 15 1.8° 10% 10%2100 3.2° 14% 14%

Clim. Hab.TCO2

Order from Strength

TechnoGarden

Adapting Mosaic

A2

B1

B2

LandCoverClimate

Global Orchestration A1

Environmental Change: The Pattern

Madonna’s World

Marley’s World

MaNonna’s World

Maradona’s World

Predicted Proportional Loss in Range SizeAll the World’s Land Birds


0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Spe

cies

Percent Range Transformed

0

400

800

1200

Jetz, Wilcove & Dobson(2007)

AgricultureClimate ChangeLand-use change

Predicted Proportional Loss in Range Size

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Spe

cies


1,000

10,000

100,000

1,000,000

Geographic range size

0

400

800

1200


AgricultureClimate ChangeLand-use change

Predicted Proportional Loss in Range SizeAdapting Mosaic

Global Orchestration Order from Strength

TechnoGarden

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Spe

cies


1,000

10,000

100,000

1,000,000

Geographic range size

1,000

10,000

100,000

1,000,000

0

400

800

1200

0

400

800

1200

IPCC Year

2050 448 43%2100 988 45%

2050 398 39%2100 952 48%

2050 540 70%2100 1,767 72%

2050 906 79%2100 1,804 84%

Range lost to Hab.

Order from Strength

TechnoGarden

Adapting Mosaic

A2

B1

B2

50% Range Lost

Species

Global Orchestration A1

Environmental Change: The Impact on Biodiversity I

Latitude, Range Size and Type of Change

Red: Land-use changeBlue: Climate Change

Latitude and Proportional Range Loss


Latitude and Proportional Range Loss


Bird Species Diversity

Adapting mosaic

Adapting Mosaic, 2100

The geographic pattern

Order from Strength, 2100

The geographic pattern

• Assumption “total loss”. To which degree may species survive / adapt to changed habitats?

• Assumption “range stationarity”. To which degree may species be able to shift their ranges in response to climate change?

• Assumption “minimum area requirement > ½ 0.5°quadrat”. To which degree will species be still represented and thus covered by sub-pixel habitat availability?

• Assumption “area of occupancy”: To which degree is the area of occupancy overestimated, i.e. proportional range loss underestimated?

• How well does the current reserve system buffer species from projected land use changes, but not from effects of climate change?

Additional Questions

Conclusions• Land-use change will dominate range contractions, particularly in

the tropics, while climate change will dominate in higher latitudes

• The species that are most vulnerable to these changes are only poorly identified by the current threat categorizations.

• The causes, magnitude and geographic patterns of potential rangeloss vary across socioeconomic scenarios

• While climate change will severely impact biodiversity, in the near future land-use change is is likely to lead to greater species loss.

• Habitat preservation should be a main priority of decision-makers and conservation practitioners

Green, Cornell, Scharlemann & Balmford, Science, 28 January 2005

Developed

Developing

CR

OP

LAN

D

PA

STU

RE

CR

OP

YIE

LD

ME

AT

PR

OD

UC

TIO

N

Green, Cornell, Scharlemann & Balmford, Science, 28 January 2005

Developed – OpenDeveloping - Filled

GlobalRed ListFor Birds

Assessing the Condition and Multi-scale Impacts of

Cultivated SystemsStanley Wood1, Ken Cassman2 & Joanne Gaskell11International Food Policy Research Institute2Department of Agronomy and Horticulture, University of Nebraska

2005 AAAS Annual Meeting17-21 February 2005Washington, DC.

Millennium Ecosystem Assessment: New Approaches to Multi-Scale Analyses

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

World Asia

Bill

ion

Hec

tare

s1961 c2004 c2004 cTotal L

1961 cropland (1961 yields)2004 cropland (2004 yields)2004 cropland (1961 yields)Total Land Suitable for Cultivation

Land “Spared” By Intensification (1961-2004)(Cereals, Roots/Tubers, Oils, Pulses, Sugar, Fiber Crops)

1.4BHa(126%)

0.9BHa(178%)

Ecosystem services

• Services supplied by natural ecosystems to the human economy.

• How do we classify these?– MA Classification – resilient or brittle?– Or – a more biological/mechanistic classification

• Can we predict how they will collapse?– How do we map services onto biological diversity?

Classifying Ecosystem Services• Provisioning,

– include food, such as fish, game-meat, fruit and berries from wild trees, fire wood, and fresh water. Have to be harvested!

• Regulating, – ultimately make life possible for humans and other non-voting

species.– include climate and air quality control, detoxification, storm

protection and regulation of disease and pest outbreaks. • Supporting,

– include primary production and the oxygen it generates, pollination of wild and domestic plants, soil formation and nutrient cycling.

• Cultural – includes recreation and ecotourism – create revenue and jobs

• Preserving – provide unknown future benefits to humans: new drugs and

foods

Do Ecosystem Services map onto Trophic level?

• Top trophic levels – aesthetic goods and services, some food – marine fish– Brittle, quickly lost as habitat lost

• Plants – oxygen production and CO2removal, fibers, forestry- More resilient, vary linearly with area?

• Basal trophic levels – soil retention, nutrient cycling, removal of toxins– Most resilient, persist in modified habitat?

Eco

syst

em F

unct

ion

Biodiversity (Number of species x abundance)

(a)

(b)(c)

(e)

(a) -> (e) decreasing resilience

(d)

Possible functional forms(Salas et al in Mooney, 1996)

Resilience of ecosystem services

Purification of air

Purification of water

Carbon sink

Water source

Local harvest of food

Pollination of local agriculture

Buffering invasive species and pathogens

Recreational and spiritual value

Ecosystem service ‘Resilience’ function

a

a/b

a

b/d

b/c

b/c

c/d

c/d

Strong tendency to move up trophic level, down resilience scale.

Less resilient, more brittle ->>

Curve that fits change in function with biodiversity lossAndy's a through e a indicates low sensitivity of ecosystem service to biodiv loss0 indicates irrelevant

Ecosystem typeEcosystem service Cultivated Drylands Forests anUrban syst Inland wateCoastal Marine Polar Mountain IslandProvisioningfood ebiochem and pharm c?genetic cfuel afibre aornamental efresh water aminerals, sand 0Regulatingair quality aclimate regulation awater regulation aerosion control awater purification and waste treatment bregulation of human diseases cbiological control ddetoxification cstorm protection cCultural ccultural diversity and identityspiritual and religiousknowledge systemseducational valuesinspirationaesthetic valuessocial relationssense of placecultural heritagerecreation and ecotourismSupportingprimary production aO2 production apollination invasives issuesoil formation asoil retention anutrient cycling cprovision of habitat c

Ecosystem type

Ecos

yste

m f

unct

ion

Classify as a -> ea = most resiliente = least resilient

Services performed bySpecies low in trophic level tend to be ‘a’, etc

Table 1Ecosystem type

Ecosystem service Urban systCultivated Drylands Forests anCoastal Inland wateIsland Mountain Polar MarineProvisioningFresh Water a e a a 0 c a a a 0Fiber a a a a a e a a e aFuel wood a e a a e 0 a a e eFood a a a e a e a a e eGenetic resources 0 e c c e c c c c cBiochem and pharmaceuticals 0 a c c e c c c e eOrnamental Resources 0 a e e e e e e c eRegulatingAir quality b a a a a a a a a aClimate regulation c a a a a a a a a aErosion control c a a a e e a a a 0Storm protection a a a c e c a a a 0Water purification and waste treatment c a b b e a c c a aRegulation of human diseases e e b c ? d c c a aDetoxification c a c c e a c c e aBiological control d e d d e e c c a eCulturalcultural diversity and identity c a d d c e e e c crecreation and ecotourism d a d d c e e e c cSupportingPrimary production a a a a a a a a a aO2 production a a a a a a a a a aSoil formation & retention a a a a e a a a a 0Pollination c e c c a 0 c c e 0Nutrient cycling c e c c c a c c e aProvision of habitat d e c c e d c c a e

Ecosystem typeEcosystem service

Anthropogenic Terrestrial……….-> Aquatic, Marine

“What did you do in the M.A. Dad?

Mean Value of Ecosystem Servicesby Trophic Level

(data from Costanza et al)

Mean Value ($/ha)

0 200 400 600 800 1000 1200 1400

Trop

hic

leve

l

0

1

2

3

4

5

WHAT IS THE ECONOMIC VALUE OF EACH TROPHIC LEVEL?

Value of Ecosystem Services x Trophic Level(data from Costanza et al)

Proportional Economic Value (Min : Mean : Max)

0.0 0.1 0.2 0.3 0.4 0.5

Trop

hic

Leve

l

0

1

2

3

4

5

PROPORTIONAL VALUE OF ECONOMIC SERVICES BY TROPHIC LEVEL

NOTE : This may mean that ALL species are of equal economic value!

The edge of the Serengeti……

Val

ue o

f Eco

syst

em S

ervi

ces

Val

ue o

f Ser

vice

s in

Mod

ified

Hab

itat

0% Proportion of habitat converted 100%

Decline in value of ecosystem services as land is converted from pristine to human-modified

Val

ue o

f Eco

syst

em S

ervi

ces

Val

ue o

f Ser

vice

s in

Mod

ified

Hab

itat


Land conversion creates a different, new source of revenue


Net value at any time is sum of ecosystem servicesand services provided by converted land

Val

ue o

f Eco

syst

em S

ervi

ces

Val

ue o

f Ser

vice

s in

Mod

ified

Hab

itat

Net value in mixed habitat


Val

ue o

f Eco

syst

em S

ervi

ces

Val

ue o

f Ser

vice

s in

Mod

ified

Hab

itat

ThresholdNo detectable

If Value ES >> Value S in MH

But the world may be asymmetrical…

Conversion alwaysReduces economic

value


Val

ue o

f Eco

syst

em S

ervi

ces

Val

ue o

f Ser

vice

s in

Mod

ified

Hab

itatIf Value ES << Value S in MH

LowerThreshold

Or we may underestimate the value of ecosystem services

Conversionalways increaseseconomic value

-80

-60

-40

-20

0

20

40

1985 1986 1987 1988 1989 1990 1991

primary producers

secondary consumers

primary consumers

tertiary consumers

A

-120

-100

-80

-60

-40

-20

0

20

1976 1977 1978 1979 1980 1981 1982 1983 1984

quaternary consumers

B

Spe

cies

loss

(%) p

ost-a

cidi

ficat

ion

Annual species loss (as % of pre-acidification species number) in response to gradual experimental acidification in two north temperate lakes. A) Four lower trophic levels in Little Rock Lake, WI, USA: primary producers (initial N = 51 phytoplankton species); primary consumers (initial N = 36 primarily herbivorous zooplankton species); secondary consumers (initial N = 9 omnivorous zooplankton species); and tertiary consumers (initial N = 9 primarily carnivorous zooplankton species); and B) quaternary consumers in Lake 223, Ontario, Canada: (initial N = 7 fish species). For A), initial pH = 5.59, final pH = 4.75; for B) initial pH = 6.49, final pH = 5.13.

Increasing acidification ----

Little Rock Lake Food Web – Trophic change through time

0 1p

Eco

syst

em s

ervi

ce

50% of maximum rate

Proportion of species pool that persists

How could we quantify the relationship between species diversity

and the supply of ecosystem services?

Note for Nerds – Essentially a Michaelis-Menton function or Type II Functional Response

Proportion of species pool that persists

0 1p

Eco

syst

em s

ervi

ce

50% of maximum rate

p2

More Brittle

More Resilient

Shape of the relationship should change as we move between ‘more resilient’ and ‘more brittle’ services

Which suggests the slopes might change for species on different trophic levels

Dependence on ‘pristine’ habitat

Assume ES = MS

0 0.2 0.4 0.6 0.80

0.5

1Services provided by total habi

Proportion converted

0.952

0

Ni

Pi

Ci

10.01 pi

0 0.2 0.4 0.6 0.80

0.5

1Services provided by total habi


0.952

0

Ni

Pi

Ci

10.01 pi

• High (90%) <- Dependence -> Low (10%)

Type II threshold at 10% conversion

Assume ES = MS


Type III threshold at 10% conversion

0 0.2 0.4 0.6 0.80

0.5

1Services provided by total ha


0.999

0

Ni

Pi

Ci

10.01 pi

0 0.2 0.4 0.6 0.80

0.5



0.999

0

Ni

Pi

Ci

10.01 pi

Assume ES = MS


Type II threshold at 80% conversion

0 0.2 0.4 0.6 0.80

0.5



0.992

0

Ni

Pi

Ci

10.01 pi0 0.2 0.4 0.6 0.8

0

0.5



0.992

0

Ni

Pi

Ci

10.01 pi

Assume ES = MS


Type III threshold at 90% conversion

0 0.2 0.4 0.6 0.80

0.5

1Services provided by total h


1

0

Ni

Pi

Ci

10.01 pi

0 0.2 0.4 0.6 0.80

0.5

1Services provided by total h


1

0

Ni

Pi

Ci

10.01 pi

weak dependence strong dependence

Lower trophiclevels

Upper trophiclevels

"Trophic Pyramid"

3/4 ratio

p=ES50

Trophic diversity and ecosystem function


"Trophic Pyramid"

p=ES50

-------> Total Species Diversity

Total species diversity --------

Re-arrange as a ‘interval’ community ordered by trophic position

(sensu Joel Cohen’s ‘Cascade Model’ and Martinez & Williams ‘Niche Model’)


"Trophic Pyramid"

p=ES50

-------> Total Species Diversity

Eco

syst

em s

ervi

ce

Most Resilient


"Trophic Pyramid" -------> Total Species Diversity

Eco

syst

em s

ervi

ce

Most Resilient

More Brittle

Proportion of maximum ecosystem service supplied as net

biodiversity declines

.11

1

pST

S = number of species left in community

T= 50% Efficiency Threshold

Tau = trophic level

Assume thresholds occur at N+0.1Stau : N is number spp at lower tau

Species Composition

0.0 0.2 0.4 0.6 0.8 1.0

Effic

ienc

y

0.0

0.2

0.4

0.6

0.8

1.0

DecomposersPlantsHerbivoresPredators

Loss of service x trophic level

Then use species-area curves to convert this to loss of service as area eroded

Species x Area x Trophic Level

Area (proportion)

0.0001 0.001 0.01 0.1 1

Spec

ies

(pro

port

ion)

0.2

0.4

0.6

0.8

1.0

All SpeciesDecomposersPlantsHerbivores Predators

Global Change

'Pristine Habitat'

Global Change

'Pristine Habitat' 'Agriculture'

Global Change

'Pristine Habitat' 'Agriculture' Degraded Land

Global Change


Urban Areas

Humanpopulation

Human population

Humanpopulation

Natural history of measles infection

SusceptibleBirths

Birth rate

Infected Recovered

Vaccination

Essentially a similar processto land use change!! ?

----------------------- Reserve Establishment ->

Pristine Agriculture Abandoned

-----------------Succesion/---------->Restoration

Basic land use change modeldF sU dPFdt

dA dPF bU aAdt

( )dU aA b s Udt

dP A hPrPdt A

0*

1

ah sFd s b

Pah

s b

* ah sFd s b

**

( )aAUs b

* *A hP

Forest

Agriculture

‘Degraded’

Human Population

Settles monotonically to equilibrium

Simple logistic as a functionof land currently under agriculture

Land use change in the Phillipines and Pacific coast US

Forest

Urban

Agricultural

Abandoned / degraded

Forest

Agricultural

‘Recovering’

Land use change in New England and the Lake States (OK – the Mid-West!)

Agriculture

Forest

Agriculture

Forest

Abandoned

Equilibrium proportions of different habitatuse under different mean persistence times

Pristine habitat

AgriculturallandSpeed of

succession

10

20

100

50

Global trends in land-use changeGreen, Cornell, Scharlemann & Balmford, Science, 28 January 2005

Developed

Developing

CR

OP

LAN

D

PA

STU

RE

CR

OP

YIE

LD

ME

AT

PR

OD

UC

TIO

N

Global Change


Urban AreasWater

Humans Humans

Humans

What happens if agricultural productivityis dependent upon forested habitat?

Ranomafana NP,Madagascar

Global Change


Urban AreasWater Food

Humans Humans

Humans

So what happens if we include Ecosystem Services in our land use change model?

Modified land use change model

dF sU dPFdt

dA dPF bU aAdt

( )dU aA b s Udt

dP A hPrPdt A

0*

1

ah sFd s b

Pah

s b* ah sFd s b

**

( )aAUs b

* *A hP

Forest

Agriculture

‘Degraded’

Human Population

Settles monotonically to equilibrium

Type 2 Functional ResponseA~> AF/(F+F50)

50(1 )F

AF hPdP FrPdt AF

* * 50*1

FA hP

F1/ 2* 21 1

1 1 1 502 2 4F c c c F1 ( )

sahcd b s

* ** 0

*50

( )F F FPa b sh F F

b s

Land-use change with agricultural dependence on water

Proportion of land forested

Agr

icul

tura

l pro

duct

ivity

0 1.0

50% max

Type I Dependence

Ecosystem service dependence, F50

0.0 0.2 0.4 0.6 0.8 1.0

Prop

ortio

n of

Hab

itat

0.00

0.05

0.10

0.15

0.20

0.25

Forest w/o dependenceAgricultureForest w dependence

Equilibrium landscape proportions

Type II Functional response

Land-use change with agricultural dependence on water

50% max

Proportion of land forested

Agr

icul

tura

l pro

duct

ivity

0 1.0

Type III Functional Response --- Multiple Stable States,

Type II Dependence


0.0 0.2 0.4 0.6 0.8 1.0

Prop

ortio

n of

hab

itat

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Forest w/o dependenceAgricultureForest w dependence

Equilibrium landscape proportions

But Type III Functional response :So may collapse suddenly!

Human Population Density


0.0 0.2 0.4 0.6 0.8 1.0

Hum

an p

opul

atio

n de

nsity

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

Type IType II

Equilibrium human population

Area x Trophic and Species Diversity

Area (proportional)

0.0001 0.001 0.01 0.1 1

Trop

hic

& S

peci

es D

iver

sity

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Species (proportion)Mean Trophic LevelFood Chain Length

Lago Guri Island Data (Terborgh et al )Total Species = 59.7799+0.0427*x

Plants = 30.2564+0.0087*x1ry Consumers = 2.3606+0.0075*x2ry Consumers = 1.8723+0.0034*x

0.5 5.0 50.0 500.0

Area

0.25

0.50

0.75

2.50

5.00

7.50

25.00

50.00

75.00

250.00

Num

ber o

f Spe

cies

Trophic diversity on Islands in Lago Guri, Venezuela, the graph illustrates trophic diversity on islands of different sizes in a recently flooded lake in Venezuela. The study provides the classical example of ecological meltdown when the loss of top predators leads first to an increase in the abundance of herbivores, before these in turn are lost leaving only plants on the smallest islands. John Terborgh’s study in Venezuela

Mean trophic level

Variance of trophic level - >trophic diversity

Mean – 95%c.l.

Conclusions• Understanding the structure and dynamics of food webs

is THE scientific challenge of the 21st Century.

• Understanding how Ecosystem Services map onto food-web structure and dynamics is a major challenge for conservation biology.

• Understanding how food webs-collapse as natural ecosystems are degraded may provide important insights into how ecosystem services will collapse.

• Many thanks to the MA Scenarios Team for many inspiring discussions.

2022-15 workshop on theoretical ecology and global...

Documents