Agriculture, Diet and the Environment. by David Tilman University of Minnesota, and University of California Santa Barbara

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1 Agriculture, Diet and the Environment by David Tilman University of Minnesota, and University of California Santa Barbara

2 Environmental Impacts of Agriculture N, P, Pesticides Biodiversity Loss; GHG Water CO2, N2O, NH3, SOx NOx, Volatile Pesticides Surface, Ground & Coastal Waters Ecosystem s Air

3 Green Revolution Doubled Global Food Supply Via 600% More N; 200% P; 80% H 2 O More N & P to Ecosystems than All Natural Processes Rivers That Run Dry (Tilman et al Nature)

4 Nitrogen Added to Watersheds & Riverine N Loadings to Oceans Nitrogen From Fertilization of Corn in the Upper Midwest Is a Major Polluter of the Gulf of Mexico, Creating the Dead Zone

5 Low Nitrogen Loading R. Howarth, Cornell U.

6 Nitrogen Addition to Coastal Marine Ecosystems Dead Zones at Mouths of Major Rivers High Nitrogen Loading R. Howarth, Cornell U.

7 Atmospheric Impacts of Agriculture

8 US Livestock Emissions Crop fertilization also directly contributes to emissions

9 Crop Emissions: Greenhouse Gasses PM2.5 primary & precursor PM2.5 has major human health impacts Health Cost: $0.40 per gallon of corn ethanol

10 The Netherlands The Netherlands Atmospheric Deposition of N from Agriculture (~15 g/m2): Loss of Major Ecosystem Type & Its Biodiversity Replaced by Low-Diversity Grassland (Molinia)

11 N Deposition to Terrestrial Ecosystems Native Prairie (experimental control)

12 Chronic Nitrogen Addition to Grassland Ecosystems

13 Species Lost (percent) (from 1982 to 1999) Increased Nitrogen Causes Loss of Biodiversity Chronic Nitrogen Addition Plot Chronic addition of 1 g/m 2 of N, comparable to atmospheric deposition, caused local loss of 30% of prairie species Nitrogen Addition (g) High Nitrogen Addition: Dominated by a European Weed, Quack Grass (Clark & Tilman 2008, Nature)

14 Reducing Agricultural Emissions COUNCIL OF THE EUROPEAN COMMUNITIES Implementation of nitrates Directive 91/676/EEC of 12 December 1991 concerning protection of waters against pollution caused by nitrates from agricultural sources

15 Protein Yield of Crops (t/ha) Germany Since1990, German farmers reduced N application rates ~30% and increased protein yields per hectare by ~25%.

16 LOWER NITRATE IN E.U. GROUNDWATERS

17 Greenhouse Gas Emissions From Agriculture

19 Non-Fossil GHG Emissions

20 Global Agriculture Causes 18% of carbon dioxide emissions 88% of nitrous oxide emissions 47% of methane emissions Carbon dioxide is emitted by land clearing and fossil fuel Use Nitrous oxide comes from N fertilizer and land clearing Methane comes from livestock Food transportation is only ~2% of agricultural emissions

21 40 YR TREND: 950% More Agricultural Pesticides Health Impacts on Humans and Wildlife (Tilman et al 2002 Nature)

22 > Toxic Snow Deposition of Volatiles in Cold Climates

23 Over 40 Years, 570 Million Hectares Were Cleared for Agriculture 800 Million More by 2060 Land Clearing Increases Nutrient & Sediment Loading to Freshwater and Marine Ecosystems and Greenhouse Gas Emissions Habitat Destruction & Extinctions; GHG Emissions (Tilman et al Science)

24 Biodiversity Loss Impacts Ecosystem Services: Productivity Stability Invasion Resistance Resource Use and Water Quality Soil Fertility Carbon Sequestration Foodweb Structure Disease Incidence

25 After 15 years, high diversity grasslands were 240% more productive than monocultures (Reich, Tilman & Isbell Science) Diversity Effects Increased Through Time (Reich et al 2012 Science)

26 Plant Species Number Ecosystem Productivity is More Stable at Greater Diversity

27 Higher Biodiversity Leads to Lower Soil Nitrate & Higher Water Quality Soil Nitrate Concentration

28 Diverse plots store more C in Soil (Tilman et al 2006 Science)

29 Diet, Demand & Environment

Per Capita Demand for Nutritious Crops Results from Direct Consumption + Indirect Consumption via Livestock and Wastage Demand Expressed as Protein: grams/day 1961 2007 1961 2007 Per

30 Per Capita Demand for Nutritious Crops Results from Direct Consumption + Indirect Consumption via Livestock and Wastage Demand Expressed as Protein: grams/day Per Capita Agricultural Demand in Developed Nations is 2.5 times that of Developing Nations and 4 times that of Least Developed Nations Poorer Nations Often Have Higher Rates of Economic Growth

31 Per Capita Agricultural Demand Depends on Per Capita Income (Tilman et al. 2011) Demand Expressed as Kilocalories per day Per Capita Demand = (Nutritious Crop Harvest)/Population

32 Demand for Terrestrial Livestock Meats

34 Global Demand Forecasted For Nutritious Agricultural Crops In % Increase for Crop Protein 100% Increase for Crop Calories About 70% of this increase is from increasing incomes, and 30% from increased population (Tilman et al 2011 PNAS)

35 Some Factors to Consider 1. GHG, Land, Health and Eutrophication Impacts of alternative agricultural practices 2. Methods to reduce these impacts, such as more efficient use of agrichemical inputs, more efficient crops, buffer strips 3. Impacts of US foreign agricultural policies, especially major global benefits from increased yields on already-cleared lands in yield gap nations 4. Conversion of pastures to croplands (rather than forests or native grasslands) in yield gap nations 5. Ways to encourage dietary shifts to nutritionally more appropriate kcal and protein consumption rates, and healthier foods.

36 Demand is Relatively Price Inelastic

38 N and P Loading to Waters Diet, Personal Health, Environmental Health

Life on a Human-Dominated Earth: The Challenges Ahead

# 23 Life on a Human-Dominated Earth: The Challenges Ahead Dr. G. David Tilman February 21, 2003 Produced by and for Hot Science - Cool Talks by the Environmental Science Institute. We request that the