is modern agriculture sustainable? an ecologist’s view of agricultural scienc e charles j. krebs...

Is Modern Agriculture Sustainable?An Ecologist’s View of Agricultural

Science

Charles J. Krebs

Department of Zoology

University of British Columbia

Outline of Talk

Ecology to what purpose? A triumvirate of problems:

Agriculture – Biodiversity - Population

Ecological principles for guidance in helping to solve the agricultural crisis

Summary

Ecologicalunderstanding

Managem entrecom m endations

Policyim plem entation

ThePoliticsof Ignorance

Ecologicalunderstanding

Managem entrecom m endations

Policyim plem entation

Basic Principle # 1

The earth has physical, chemical,

and biological limitations

- it is the only planet we have

Are Current World Practices Sustainable ?

Three key areas - Agriculture- Biodiversity- Population

Two steps for ecologists:- evaluate the current situation- suggest solutions to current

problems

Global Distribution of Hunger: Quantified by the 2012 Global Hunger Index

Wheeler, T. and J. von Braun. 2013. Climate change impacts on global food security. Science 341:508-513.

1960 1970 1980 1990 2000 2010 2020 2030 2040 2050

Yie

ld (to

ns

pe

r ha

)

0

2

4

6

8

10

Wheat

Rice

1.0% per year

0.9% per year

2.4% per year

Ray, D. K. et al. 2013. Yield trends are insufficient to double global crop production by 2050. PLoS ONE 8:e66428.

Global Yield Trends in Rice and Wheat

target

target

Global Agricultural Land Area

1970 1980 1990 2000 2010

La

nd

are

a (km

2 x

106

) ha

0

1

2

3

4

5

6

Total Agricultural Area

Meadows and Pastures

Arable Land and Crops

Source: FAOSTAT, 2013.

Since 1991 no change in land area used

Five Solutions

Stop expanding agriculture’s footprint Close the world’s yield gaps Use resources more efficiently Shift diets away from meat Reduce food waste

Foley, J. A. 2011. Can we feed the world and sustain the planet? Scientific American 305 (5): 60-65.

Maize Yield in Africa Cropland

Yield in 2000Potential YieldsUnder optimum use ofrainwater, nutrient, weed,and disease management

tonnes per ha

Bindraban, P. S. et al. (2012). Assessing the impact of soil degradation on food production. Current Opinion in Environmental Sustainability 4:478-488.

Currently operating at 10-30% of potential

Agriculture

Premise: Agriculture is applied ecology - if this is correct, agriculture must

operate under the principles of applied ecology

What principles of applied ecology are applicable?

Agriculture – Fundamental Issues

Agriculture reduces biodiversity - is this reversible?

Agriculture exacerbates climate change - can we neutralize this?

Agricultural Sustainability - # 1

Ecological Generalisation # 1: ecosystems must run on solar energy - current agriculture runs on non- renewable resources (oil, natural

gas, coal) Agriculture must transition to

renewable energy - whither industrial agriculture?

Agricultural Sustainability - # 1

Agriculture can continue to use non-renewable resources only if it can remove their harmful effects on

the air, water, and land This is a very important technical

problem in energy engineering that is beyond my expertise to discuss

Agricultural Sustainability - # 2

Ecological Generalization # 2: nutrient input = nutrient output - crop production depends on fertilizer inputs

Nitrogen limits productivity in many soils

Phosphate is also required in fertilizer

Fertilizer Problems - # 1

Nitrogen is both a positive and a negative factor - crop production depends on

fertilizer inputs- biodiversity declines with

nitrogen inputs- water pollution results from

excessive nitrogen runoff

Global nitrogen fixation, natural and anthropogenic, for 2010

Fowler, D., et al. 2013. The global nitrogen cycle in the twenty-first century. Philosophical Transactions of the Royal Society of London B: 368: doi 10.1098/rstb.2013.0164.

BiologicalNitrogen Fixation

Annual Nitrogen input (kg/ha/year)

0 50 100 150 200 250 300 350 400 450

No

. of p

lan

t sp

ec

ies p

er 10

0 m2

0

10

20

30

40

50

60

70

80

Effects of Nitrogen Fertilizer Input on Plant Biodiversity in Europe

Kleijn, D. et al. (2009). On the relationship between farmland biodiversity and land-use intensity in Europe. Proceedings of the Royal Society of London B 276:903-909.

more nitrogen fertiliser = fewer plant species

Corn Yield - Iowa

Nitrogen fertilizer - kg/ha

0 50 100 150 200 250 300 350

Co

rn g

rain

(to

nn

es p

er h

a)

4

6

8

10

12

Cerrato, M.E., and Blackmer, A.M. 1990. Comparison of models for describing corn yield response to nitrogen fertilizer. Agronomy Journal 82: 138-143.

Agricultural Sustainability - # 3

Fertilizer- nitrogen is produced from natural

gas- phosphate comes from rocks

Nitrogen production is tied to oil in availability and price

Phosphate is limited to rock formations

Dery, P. and Anderson, B. 2007. Peak phosphorus. Energy Bulletin 13 August 2007.

Pro

du

cti

on

(M

g/y

ear

)

Year

World Rock Phosphate Production

Peak phosphorus ≈ Peak oil

World Phosphorus Fertilizer Use

1960 1970 1980 1990 2000 2010

Millio

n to

ns P

2

O5

0

10

20

30

40

50

4.6% growth

1.8% growth

Cordell, D. and S. White. (2011). Peak phosphorus: Clarifying the key issues of a vigorous debate about long-term phosphorus security. Sustainability 3:2027-2049.

Phosphorus - # 1

An essential element for all living organisms Renewable P from bird guano

- Nauru, Christmas Island, now gone Non-renewable P from igneous and

sedimentary rocks- Morocco, China, USA mainly- a finite resource

Scholz, R. W., and F.-W. Wellmer. 2013. Approaching a dynamic view on the availability of mineral resources: What we may learn from the case of phosphorus? Global Environmental Change 23:11-27.

Phosphorus - # 2

Will we run out of phosphorus? Quality and accessibility of remaining

reserves are decreasing- costs will thus increase

Extremely variable estimates of how much phosphorous is left in rocks

Neset, T.-S. and D. Cordell. 2012. Global phosphorus scarcity: identifying synergies for a sustainable future. Journal of the Science of Food and Agriculture 92: 2-6.

Lifetime of World Phosphate Rock Reserves

Author Estimated

lifetime of

reserves

Estimated year

of depletion

Assumptions

Tweeten (1989) 61 years 2050 3.6% increase in demand

Runge-Metzger (1995) 88 years 2083 2.1% increase in demand

Steen (1998) 60-130 years 2058-2128 2-3% increase in demand

Smil (2009) 80 years 2080 At current rate of extraction

Fixen (2009) 93 years 2102 At 2007 production rate

Smit et al. (2009) 69-100 years 2078-2109 0.7% to 2% increase to 2050

Vaccari (2010) 90 years 2099 At current rates

Van Kauwenbergh (2010) 300-400 years 2310-2410 At current rates

Cordell, D. and S. White. (2011). Peak phosphorus: Clarifying the key issues of a vigorous debate about long-term phosphorus security. Sustainability 3:2027-2049.

“If ‘Plateau Phosphorus’ does describe future production, the new reserve figures could add 168 years to production availability.”

Mew M. Future phosphate rock production – peak or plateau? Retrieved June 12, 2012,from http://www.fertecon-frc.info/page15.htm

Phosphorus - # 3

Does the “Peak Phosphorus” curve apply to future supplies?

The analogy with oil production is not valid because oil can be substituted by other energy sources

There is nothing known that can substitute for phosphorus

Scholz, R. W. and F.-W. Wellmer. (2013). Approaching a dynamic view on the availability of mineral resources: What we may learn from the case of phosphorus? Global Environmental Change 23:11-27.

Phosphorus - # 4

There is a limited amount of phosphorus available on the Earth

- everyone seems to agree on this Recycling and recovery must be part of the

phosphorus management strategy There are now movements in this direction

Rhodes, C. J. 2013. Peak phosphorus - peak food? The need to close the phosphorus cycle. Science Progress 96: 109-152.

Agricultural Sustainability - # 4

Soil erosion is a critical problem that is a central issue in nutrient losses

What is the state of soil erosion in agricultural areas?

Soil Degradation Penalty for Food Crops in China

Ye, L. and E.Van Ranst. (2009). Production scenarios and the effect of soil degradation on long- term food security in China. Global Environmental Change 19:464-481.

Businessas usual

2030

Double soilDegradation

2030

Double soilDegradation

2050

Businessas usual

2050

Food production decline of 14% to 30%

Agricultural Sustainability - # 5

Climate change is happening Four broad impacts on agriculture:

- changes in the distribution of rainfall and temperature

- increased variability of weather- changing crop productivity (C3, C4)- coastal crops and sea level rise

Soils do not move….

Rising CO2 Levels

Increasing CO2 increases the yield of C3 crop plants

Increasing CO2 does not increase the yield of C4 crop plants

Drought stress can be reduced in C4 plants because of lower stomatal conductance

Leakey, A. D. B. 2009. Rising atmospheric carbon dioxide concentration and the future of C4 crops for food and fuel. Proceedings of the Royal Society B: 276:2333-2343.

Percentage of agricultural land used for the production of C4 crops in 2006

Leakey, A. D. B. 2009. Rising atmospheric carbon dioxide concentration and the future of C4 crops for food and fuel. Proceedings of the Royal Society B: 276:2333-2343.

Main C4 crops are maize, sugar cane, millet and sorghum

Change in Cereal Production and Population Growth, 1970-2010

End of the Green Revolution

cereals

people

Source: FAO

Agricultural Sustainability - # 6

Solutions- recycle nutrients- reduce fossil fuel use

- low tillage, organic agriculture?

- develop better crops, diversify- improve grazing management- integrate crops and livestock- stop using food for biofuels- invest in agriculture

Agricultural Sustainability - # 7

What should you eat? Ray Hilborn and his research group

have computed the environmental impact of animal foods

213 studies, 16 production technologies, 9 measures of impact

Life Cycle Assessments

Hilborn, R., J. Banobi, and S. J. Hall. 2014. The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review).

Energy (MJ per 40 g protein

better worse

Energy Used In Production

Hilborn et al. (2014) PNAS

best for milk, worst for catfish aquaculture

Aquaculture

Capturefisheries

Livestock

Greenhouse Gas output (Kg CO2 per 40 g protein

better worse

Greenhouse Gases

outputs

Hilborn et al. (2014) PNAS

best for molluscs, worst for beef production

Aquaculture

Capturefisheries

Livestock

Agricultural Sustainability - # 8

What should you eat? Rank all food groups by 9 measures:

- energy - greenhouse gases- acidfication - eutrophication- land used - water used- pesticides - antibiotics - soil loss

Hilborn, R., J. Banobi, and S. J. Hall. 2014. The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review).

Agricultural Sustainability - # 8

What should you eat? Rank all food groups by 9 measures:

- energy - greenhouse gases- acidfication - eutrophication- land used - water used- pesticides - antibiotics - soil loss

Hilborn, R., J. Banobi, and S. J. Hall. 2014. The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review).

Environmental Impacts of Food Groups

Average Rank

0 2 4 6 8 10 12 14 16

Shellfish

Snall pelagics

Large pelagics

Whitefish

Salmonids

Invertebrates

Finfish

Milk

Carp

Tilapia

Shrimp

Eggs

Pork

Catfish

Chicken

Beef

Hilborn, R., J. Banobi, and S. J. Hall. 2014. The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review).

better

worse

Agricultural Sustainability - # 9

The Bottom Line: What should you eat? Food security for the Earth would be

improved if we ate more vegetables Even with this change, there are many

problems that need addressing For any meat consumption, the devil is in

the details, e.g. milk (good for energy, poor for water use, antibiotics, soil)

Biodiversity

Premise: biodiversity provides a planet that is inhabitable by humans

- if this is correct, protecting biodiversity must become a major societal goal

Biodiversity – Constraints

We do not have a description of the existing life on earth

We have a rudimentary understanding of how ecological communities operate

Land clearing for agriculture has been a major cause of biodiversity loss

- yet we need more food

45

Ecosystem Services

Coda:- there is an ever growing literature about

the value of biodiversity and ecosystem services- much of this discussion is good political ecology but hopeless scientific ecology- we should protect biodiversity because we cannot eat iron ore or coal or phosphate rock or paper money…..

Power, A.G. (2010). Ecosystem services and agriculture: tradeoffs and synergies. Philosophical Transactions of the Royal Society B 365: 2959-2971.

The Population Problem

o Ecological Generalization # 3: - no population increases indefinitely

o The human population of the Earth now exceeds the carrying capacity of the planet

o Bringing the human population back to some sustainable level is a critical social issue

Year

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020

Fra

ctio

n o

f th

e p

lan

etb

ein

g u

tilis

ed

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

Carrying capacity of the Earth

1976

Global Ecological Footprint

Source: Living Planet Report 2010

The Politics of Ignorance

Operational Principle: what you do not know cannot hurt you

- you can operate in this state by ignoring evidence-based science, or- you can fail to fund the scientific

research that will shed light on specific problems

The Politics of Ignorance # 2

Major current example: climate change- “there is no need to do anything until we have scientific certainty”- how should we respond to scientific uncertainty ?- technological optimists vs. technological pessimists

The Bottom Line

Scientists do not make policy But we know a great deal about the natural

world that should inform policy but is not used

We must continue to do good science and ask our governments to use evidence-based policies

There is some hopeful evidence that the ecological world view is slowly replacing the economic world view

Summary - # 1

Three critical world problems have their roots in ecology:

- agricultural production- biodiversity conservation- human population growth

Our job as scientists is to recognize the connections between these three problems and to work toward ethical solutions

Summary - # 2

There is encouraging signs that we are moving in the direction of sustainability but perhaps more slowly than scientists would like

Agricultural scientists are the heros of our day and should continue to lead the way to sustainable agriculture and human betterment

- (I will not list who the bad guys are…)

Thanks for listening !