Presentation is loading. Please wait.

Presentation is loading. Please wait.

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

Similar presentations


Presentation on theme: "Is Modern Agriculture Sustainable? An Ecologist’s View of Agricultural Scienc e Charles J. Krebs Department of Zoology University of British Columbia."— Presentation transcript:

1 Is Modern Agriculture Sustainable? An Ecologist’s View of Agricultural Scienc e 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. 2013. Climate change impacts on global food security. Science 341:508-513.

7 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

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

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

10 Maize Yield in Africa Cropland Yield in 2000 Potential Yields Under optimum use of rainwater, 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

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 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. Biological Nitrogen Fixation

18 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

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

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

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

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 3:2027-2049.

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. 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.

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. 2012. Global phosphorus scarcity: identifying synergies for a sustainable future. Journal of the Science of Food and Agriculture 92: 2-6.

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) 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.

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 http://www.fertecon-frc.info/page15.htm

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.

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

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?

30 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. Business as usual 2030 Double soil Degradation 2030 Double soil Degradation 2050 Business as usual 2050 Food production decline of 14% to 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 (C 3, C 4 ) - coastal crops and sea level rise  Soils do not move….

32 Rising CO 2 Levels  Increasing CO 2 increases the yield of C 3 crop plants  Increasing CO 2 does not increase the yield of C 4 crop plants  Drought stress can be reduced in C 4 plants because of lower stomatal conductance Leakey, A. D. B. 2009. Rising atmospheric carbon dioxide concentration and the future of C 4 crops for food and fuel. Proceedings of the Royal Society B: 276:2333-2343.

33 Percentage of agricultural land used for the production of C 4 crops in 2006 Leakey, A. D. B. 2009. Rising atmospheric carbon dioxide concentration and the future of C 4 crops for food and fuel. Proceedings of the Royal Society B: 276:2333-2343. Main C 4 crops are maize, sugar cane, millet and sorghum

34 Change in Cereal Production and Population Growth, 1970-2010 End of the Green Revolution cereals people 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

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. 2014. The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review).

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

38 Greenhouse Gas output (Kg CO 2 per 40 g protein betterworse Greenhouse Gases outputs Hilborn et al. (2014) PNAS best for molluscs, worst for beef production Aquaculture Capture fisheries Livestock

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. 2014. The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review).

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. 2014. The environmental cost of animal source foods. Proceedings of the National Academy of Sciences USA (in review).

41 better worse

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)

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

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

45 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.

46 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

47 Global Ecological Footprint Source: Living Planet Report 2010

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

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 !


Download ppt "Is Modern Agriculture Sustainable? An Ecologist’s View of Agricultural Scienc e Charles J. Krebs Department of Zoology University of British Columbia."

Similar presentations


Ads by Google