# 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 use of these materials include an acknowledgement of the presenter and Hot Science - Cool Talks by the Environmental Science Institute at UT Austin. We hope you find these materials educational and enjoyable.
Ecosystem Services and Life on a Human-Dominated Earth The Challenges and Opportunities Ahead Dr. G. David Tilman Dept. of Ecology, Evolution, and Behavior University of Minnesota John Haarstad, U. Minnesota
What Are Ecosystem Services? Copyright 1992 Laura Cunningham Services of value to humans provided by natural and managed ecosystems
Purification of air and water The Catskill Mountains provide New York City with a service worth about $1 billion/yr. Steve Carpenter, U Wisconsin
Generation and Renewal of Soil Fertility Prairie grasslands and savannas of North America generated the fertile soils that feed 200,000,000 people.
Humans Have Benefited From The Vast Diversity of Potential Food Plants Potato Varieties USDA-ARS
When we want food, we go to nature Fine Dining on Whilshire Boulevard, Los Angeles, 9000 BC (copyrighted image of mastodon in tar pit could not be included on this CD) Dining at the La Brea Tar Pits, 9000 BC
Earth s Biodiversity is also the Major Source of Human Medicines More than 60% of the 50 best selling medicines are derived from nature. So are the two most important medicines ever discovered, Aspirin and.
and I thought it was wine
Other Ecosystem Services Include: Detoxification and decomposition of wastes Pollination of crops Control of many agricultural pests Moderation of climate Natural production of fish, forage, biomass fuels, and industrial products Amelioration of flooding Maintenance of genetic resources Aesthetic beauty
Ecosystem Services Have been essential to human success Are provided for free by natural ecosystems Are becoming less available as human population size and consumption increase Copyright 2001 Laura Cunningham
The two largest global human impacts come from our need for Food and Energy USDA-ARS
Human Global Ecosystem Domination 45% of terrestrial ecosystem production is appropriated by humans Half of useable freshwaters is appropriated by humans (irrigation, hydroelectric power) Doubled rates of nitrogen fixation and of phosphorus liberation Unprecedented extinctions via habitat destruction and invasions by exotic species Elevated pesticide levels in humans Elevated greenhouse gases (CO 2, methane)
Final Period of Rapidly Expanding Human Environmental Impacts? In the next 50 years Population is projected to increase from 6 to 9 or 10 billion a 50% increase Global per capita GDP is projected to increase 140% Global population and consumption drive agricultural demand which could double if demand for meat continues to increase globally
World Food (10 9 metric tons) Benefits of the Green Revolution 4 1.97-fold increase in 35 year 3 2 1960 1970 1980 1990 2000 Year Global food production doubled in 35 years. photo credit: USDA-ARS
Nitrogen and Phosphorus Fertilizer (10 6 metric tons; World-USSR) Global Irrigation (10 9 hectares) Costs of the Green Revolution 80 60 40 20 0 H 2 O N P 0.30 0.28 0.26 0.24 0.22 0.20 0.18 0.16 0.14 0.12 1960 1970 1980 1990 2000 Year 7-fold Increase In N Fertilization Doubling The N Economy Of the Earth (from Tilman, Fargione, Wolf et al Science)
Global Pasture Land (10 9 hectares) Global Crop Land (10 9 hectares) Costs of the Green Revolution 3.45 3.40 3.35 3.30 3.25 3.20 3.15 3.10 3.05 3.00 Pasture Land Crop Land 1.54 1.52 1.50 1.48 1.46 1.44 1.42 1.40 1.38 1.36 1.34 1.32 1960 1970 1980 1990 2000 Year Destruction Of Natural Habitats For Agriculture Contributing To a major Extinction Event (from Tilman, Fargione, Wolf et al Science)
If We Stay on the Course Set in the Past 35 years: Environmental Variable Increase by 2050 Global N Fertilizer 210% Global P Fertilizer 140% Global Pesticide Production 170% Global Agricultural Land 20% (27% of usable land still in nature) (Area of USA) (from Tilman, Fargione, Wolf et al Science 2001)
Conversion to agriculture decreases ecosystem diversity, decreases ecosystem services, and increases extinctions. photo credit: USDA Forest Service
Native Prairie Receiving No Added Nitrogen A Control Plot in a 207-Plot Nitrogen Addition Experiment
Species Lost (percent) (from 1982 to 1999) Increased Nitrogen Causes Loss of Biodiversity 100 Chronic Nitrogen Addition Plot 80 60 40 20 Chronic addition of only 1 g/m 2 of N, comparable to atmospheric deposition, caused local loss of 30% of prairie species. 0 0 5 10 15 20 25 Nitrogen Addition (g) High Nitrogen Addition: Dominated by a European Weed, Quack Grass
What Determines the Flow of Ecosystem Services? Does Biodiversity Matter? Does biodiversity influence ecosystem stability, productivity, nutrient dynamics, disease dynamics, or susceptibility to invasion by exotic species? Could the loss of biodiversity impact the supply of ecosystem services of value to society?
The Cedar Creek Biodiversity Experiments 172 Large Plots Random Species Choice Species Pool of 18 Grassland Plants
Soil NO (0-20 cm depth) Diverse Systems Use Limiting Resources More Efficiently 0.5 0.4 0.3 0.2 0.1 1997 1998 0.0 0 2 4 6 8 10 12 14 16 Number of Different Species
Our Research Shows: Total biomass (kg/ m 2 ) Ecosystem biodiversity enhances productivity, nutrient use efficiency Greater diversity leads to greater ecosystem stability and predictability Greater diversity leads to less disease The quality and quantity of ecosystem services depends on the diversity and composition of managed and natural ecosystems 1.4 1.2 1.0 0.8 0.6 0.4 0.2 Diverse Systems Are More Productive 0.0 0 2 4 6 8 10 12 14 16 Number of Species
How Can We Optimize Ecosystem Services on a Human-Dominated Earth? By using not fighting ecological processes and principles With cradle-to-grave analysis of the full costs and benefits of all agricultural, forestry, and manufactured products and processes By basing policy, ethics and actions on processes and products that maximize the long-term net return to all of society
Forests, Farms and Ecosystem Services Farmers and foresters are the major land managers of the earth Current incentives are to produce crops at lowest price, ignoring costs to ecosystem services We could maximize total return to society by paying land managers for the value of both the goods and ecosystem services they provide. USDA-ARS
New York City and Catskill Water Production New York City invested $2 billion to preserve the watersheds of the Catskills and their ecosystem services. This is saving $1 Billion per year. Steve Carpenter, U Wisconsin
Optimizing Ecosystem Services Forested ecosystems remove and store some of the carbon dioxide released by fossil fuel use Colors depict sources of CO2 emissions: white, light of cities; red, forest & agricultural fires; yellow, gas flares. Source: Gene Feldman, NASA; W.T. Sullivan, III, University of Washington; Defense Meteorological Satellite Program of USAF
How much more Carbon could be stored in diverse forests? Grasslands with 16 species store 2.7 times more Carbon than mono-cultures. John Aber, U. New Hampshire
Three grasses Corn, Wheat and Rice provide 60% of human caloric needs. photo credit: USDA-ARS
Illustrated London News Irish Potato Famine Low Crop Diversity: Ireland Depended On One Strain of One Crop
Genetic Diversity in Seed Banks and Nature is Used to Fight New Diseases North Central Regional Plant Introduction Station Ames, Iowa
Northern Corn Blight C. Martinson, Iowa State U. Gary Munkvold, Iowa State U.
The Three Most Abundant Plants On Earth Corn, Wheat, Rice Hosts for New Pathogens? photo credits: USDA-ARS
Crop Strength Through Diversity Rice Diversity Fights Disease and Eliminates Fungicide photo credits: NASA
Livestock Production Disease Manure Efficiency Grain Use Doug Argue (Weisman Art Museum)
World Cattle (Millions) 1400 1300 1200 1100 1000 900 800 700 600 500 400 Meat Production Methods World Cattle World Pigs Cattle, evolved for living on low-protein grasses, must be given antibiotics when fed high-protein grains. *Antibiotic resistant novel pathogens *Manure and water pollution problems *50% of grains fed to livestock 300 1960 1965 1970 1975 1980 1985 1990 1995 Year photo credit: USDA-ARS
Overuse and Rapid Evolution of Resistance: Penicillin 1946 Methicillin 1961 Antibiotic Resistance & Pesticide Resistance: Loss of valuable medicines and agri-chemicals Vancomycin 1986 Zyvox 1999 It is time to incorporate the insights of ecology and evolution into medicine, agriculture, forestry and environmental management. (based on Palumbi 2001)
Population (billions) Ethics and Policies for A Human-Dominated World 6.0 5.0 4.0 3.0 * Evolution of Human Behavior * Formulation of Ethics/Religions * Formulation of Laws/Policies 2.0 1.0 0.0-8000 -6000-4000 -2000 0 2000 Years B.C. A.D.
Global Ecosystem Domination: Challenge Challenges and Solutions To improve the long-term welfare of all of society by assuring a sustainable and equitable flow of vital goods and ecosystem services for current and future generations. Solutions Measure the full costs and benefits of alternative practices; Determine which practices maximize the net benefits to society; Incorporate this knowledge and the search for ever better practices into policy and ethics.
There are solutions, and we will find better and Once moving in the right direction Copyright 1991 Laura Cunningham even the giant ground sloth could have moved fast enough to solve these problems. better solutions, once we focus on the problems
Dr. G. David Tilman Dr. Tilman is the Distinguished McKnight University Professor in the Department of Ecology, Evolution, and Behavior, at the University of Minnesota, and the director of the Cedar Creek Natural History Area. His research interests include the ecological effects of human domination of the earth, population ecology and theory of community dynamics and biodiversity, the role of resource competition, biodiversity and ecosystem functioning, and the effects of habitat destruction. Dr. Tilman is intrigued by the causes of broad, general patterns in ecological systems, especially patterns in the biological diversity, structure and dynamics of plant (and sometimes insect) communities. He also focuses on a related issue - the effects of biodiversity on the stability and functioning of ecosystems, which is scientifically intriguing and of great importance to society. Finally, he is interested in the impacts of human domination of global ecosystems, especially in the impacts of nitrogen deposition, habitat destruction/fragmentation, and invasive exotic species. He studies mechanisms of resource competition among terrestrial plants, especially in the grasslands of Minnesota s Cedar Creek Natural History Area. These collaborative projects take place at Cedar Creek and are supported by the NSF Long-Term Ecological Research Program or The Andrew Mellon Foundation.