1. Charles J. Krebs Department of Zoology University of British Columbia
Is Modern Agriculture Sustainable? An Ecologist’s View of Agricultural Science
Charles J. Krebs
Department of Zoology
University of British Columbia

2. 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

3. The
Politics of
Ignorance

4. Basic Principle # 1
The earth has physical, chemical, and biological limitations - it is the only planet we have

5. Are Current World Practices Sustainable ?
Three key areas - Agriculture - Biodiversity - Population
Two steps for ecologists: - evaluate the current situation - suggest solutions to current problems

6. Global Distribution of Hunger: Quantified by the 2012 Global Hunger Index
Wheeler, T. and J. von Braun Climate change impacts on global food security. Science 341: 6

7. Global Yield Trends in Rice and Wheat
target
target
Ray, D. K. et al Yield trends are insufficient to double global crop production by PLoS ONE 8:e66428.

8. Global Agricultural Land Area
Since 1991 no change in land area used
Source: FAOSTAT, 2013. 8

9. 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 Can we feed the world and sustain the planet?
Scientific American 305 (5): 9

10. Maize Yield in Africa Cropland
Currently operating at 10-30% of potential
tonnes per ha
Yield in 2000
Potential Yields
Under optimum use of rainwater, nutrient, weed, and disease management
Bindraban, P. S. et al. (2012). Assessing the impact of soil degradation on food production. Current Opinion in Environmental Sustainability 4: 10

11. 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?

12. Agriculture – Fundamental Issues
Agriculture reduces biodiversity is this reversible?
Agriculture exacerbates climate change - can we neutralize this?

13. 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?

14. 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

15. 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

16. 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

17. Global nitrogen fixation, natural and anthropogenic, for 2010
Biological Nitrogen Fixation
Global nitrogen fixation, natural and anthropogenic in both oxidized and reduced forms through combustion, biological fixation, lightning and fertilizer and industrial production through the Haber–Bosch process for The arrows indicate a transfer from the atmospheric N2 reservoir to terrestrial and marine ecosystems, regardless of the subsequent fate of the Nr. Green arrows represent natural sources, purple arrows represent anthropogenic sources.
Fowler, D., et al The global nitrogen cycle in the twenty-first century. Philosophical Transactions of the Royal Society of London B: 368: doi /rstb

18. Effects of Nitrogen Fertilizer Input on Plant Biodiversity in Europe
more nitrogen fertiliser = fewer plant species
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: 18

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

20. 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 20

21. World Rock Phosphate Production
Peak phosphorus ≈ Peak oil
Production (Mg/year)
Year
Dery, P. and Anderson, B Peak phosphorus. Energy Bulletin 13 August 2007.

22. World Phosphorus Fertilizer Use
Cordell, D. and S. White. (2011). Peak phosphorus: Clarifying the key issues of a vigorous debate about long-term phosphorus security. Sustainability 3: 22

23. 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 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. 23

24. 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 Global phosphorus scarcity: identifying synergies for a sustainable future. Journal of the Science of Food and Agriculture 92: 2-6. 24

25. 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)
years
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)
years
0.7% to 2% increase to 2050
Vaccari (2010)
90 years
2099
At current rates
Van Kauwenbergh (2010)
years
Cordell, D. and S. White. (2011). Peak phosphorus: Clarifying the key issues of a vigorous debate about long-term phosphorus security. Sustainability 3: 25

26. “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 26

27. 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. 27

28. 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 Peak phosphorus - peak food? The need to close the phosphorus cycle. Science Progress 96: 28

29. 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? 29

30. Soil Degradation Penalty for Food Crops in China
Business
as usual 2030
Double soil
Degradation 2030
Food production decline of 14% to 30%
Business
as usual 2050
Double soil
Degradation
2050
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: 30

31. 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…. 31

32. 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 Rising atmospheric carbon dioxide concentration and the future of C4 crops for food and fuel. Proceedings of the Royal Society B: 276: 32

33. Percentage of agricultural land used for the production of C4 crops in 2006
Main C4 crops are maize, sugar cane, millet and sorghum
Leakey, A. D. B Rising atmospheric carbon dioxide concentration and the future of C4 crops for food and fuel. Proceedings of the Royal Society B: 276: 33

34. Change in Cereal Production and Population Growth, 1970-2010
cereals
End of the Green Revolution
people
Average change by decade (i.e. 1960s, 1970s, etc.)±s.e., in per cent growth of eight basic cereals (barley, corn, millet, oat, rice, rye, sorghum, wheat) as directly consumed by the human population (i.e. not used for biofuels or animal feed) and the average change by decade in per cent population growth. Gains in cereal production over population represent the ‘green revolution’ of the 1960s. Around 2003, net per cent gains in cereals and those in population were roughly equivalent, and the green revolution ended. Data are from Food and Agriculture Organization statistics, available at
Source: FAO

35. 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 35

36. 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 The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review). 36

37. for catfish aquaculture
Energy Used
In Production
Energy (MJ per 40 g protein
better
worse
Aquaculture
Capture
fisheries
Livestock
best for milk, worst
for catfish aquaculture
Hilborn et al. (2014) PNAS 37

38. Greenhouse Gases outputs best for molluscs, worst
Greenhouse Gas output (Kg CO2 per 40 g protein
better
worse
Aquaculture
Capture
fisheries
Livestock
best for molluscs, worst
for beef production
Hilborn et al. (2014) PNAS 38

39. 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 The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review). 39

40. 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 The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review). 40

41. worse
better
Hilborn, R., J. Banobi, and S. J. Hall The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review). 41

42. 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) 42

43. Biodiversity
Premise: biodiversity provides a planet that is inhabitable by humans - if this is correct, protecting biodiversity must become a major societal goal 43

44. 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 44

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: 45 45

46. The Population Problem
Ecological Generalization # 3: - no population increases indefinitely
The human population of the Earth now exceeds the carrying capacity of the planet
Bringing the human population back to some sustainable level is a critical social issue

47. Global Ecological Footprint
Source: Living Planet Report 2010 47

48. 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

49. 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

50. 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 50

51. 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

52. 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…)

53. Thanks for listening !