Is Modern Agriculture Sustainable?An Ecologist’s View of Agricultural
Science
Charles J. KrebsDepartment 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
Yield (tons per ha)
0
2
4
6
8
10
Wheat
Rice1.0% 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
Land area (km2 x 10
6) 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 plant species per 100 m
2
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/ha0 50 100 150 200 250 300 350
Cor
n gr
ain
(tonn
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.
Prod
uctio
n (M
g/ye
ar)
Year
World Rock Phosphate Production
Peak phosphorus ≈ Peak oil
World Phosphorus Fertilizer Use
1960 1970 1980 1990 2000 2010
Million tons P
2O5
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
ShellfishSnall pelagics
Large pelagicsWhitefish
SalmonidsInvertebrates
FinfishMilk
CarpTilapia
ShrimpEggsPork
CatfishChicken
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
Year1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020
Frac
tion
of th
e pl
anet
bein
g ut
ilise
d
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 !