Impacts of the Nitrogen Cascade on Ecosystems Presentation to - PowerPoint PPT Presentation

Impacts of the Nitrogen Cascade on Ecosystems Presentation to NYSERDA October 8, 2003 William Moomaw Fletcher School, Tufts University

Reactive N and Unreactive N 2 ‹ Unreactive N is N 2 (78% of earth’s atmosphere) ‹ Reactive N (Nr) includes all biologically, chemically and physically active N compounds in the atmosphere and biosphere of the Earth ‹ N controls productivity of most natural ecosystems ‹ N 2 is converted to Nr by biological nitrogen fixation (BNF) ‹ N 2 is converted to Nr by humans fossil fuel combustion, the Haber Bosch process, and cultivation-induced BNF.

Reactive N and Unreactive N 2 ‹ Unreactive N is N 2 (78% of earth’s atmosphere) ‹ Reactive N (Nr) includes all biologically, chemically and physically active N compounds in the atmosphere and biosphere of the Earth ‹ N controls productivity of most natural ecosystems ‹ N 2 is converted to Nr by b iological nitrogen fixation (BNF) ‹ N 2 is converted to Nr by humans f ossil fuel combustion , the Haber Bosch process , and cultivation-induced BNF. ‹ Bottom Lines – Humans create more Nr than do natural terrestrial processes. – Nr is accumulating in the environment. – Nr accumulation contributes to most environment issues of the day. – Challenge is to reduce anthropogenic Nr creation.

Reactive N and Unreactive N 2 ‹ Unreactive N is N 2 (78% of earth’s atmosphere) ‹ Reactive N (Nr) includes all biologically, chemically and physically active N compounds in the atmosphere and biosphere of the Earth ‹ N controls productivity of most natural ecosystems ‹ N 2 is converted to Nr by b iological nitrogen fixation (BNF) ‹ N 2 is converted to Nr by humans f ossil fuel combustion , the Haber Bosch process , and cultivation-induced BNF. ‹ Bottom Lines – Humans create more Nr than do natural terrestrial processes. – Nr is accumulating in the environment. – Nr accumulation contributes to most environment issues of the day. – Challenge is to reduce anthropogenic Nr creation. ‹ But, this is complicated by fact that Nr creation sustains most of the world’s food needs. – The real challenge is how can we provide food (and energy) while also reducing Nr creation rates and arresting the nitrogen cascade ?

zyxwvutsrqponmlkjihgfedcbaWUTSRPONMLKJIHGFEDCBA Reactive Nitrogen Cuts Across Multiple Global Issues and Environmental Agreements ‹ Regional air quality (LRTAP) ‹ Climate change (UNFCCC & Kyoto Prot.) ‹ Ozone Depletion (Montreal Protocol) ‹ Biodiversity loss (CBD) ‹ Transboundary water quality (Non-navigational Uses of International Water Courses ‹ Estuary damage (Regional Seas) ‹ Fisheries loss (Law of the Sea?)

Need for an Integrated Analytical Policy Approach to Reactive Nitrogen ‹ First explain history of human alteration of nitrogen cycle ‹ Identify the reasons why reactive nitrogen cascades through so many segments of the global ecosystem ‹ Describe the International Nitrogen Initiative

The History of Nitrogen --Global Population & Discovery of N-- 7,000 6,000 5,000 4,000 3,000 2,000 N-Discovered 1,000 0 1750 1800 1850 1900 1950 2000 2050 Humans, millions Galloway JN and Cowling EB. 2002; Galloway et al., 2002a

The History of Nitrogen --Major N processes-- 7,000 6,000 5,000 4,000 3,000 2,000 BNF N-Discovered N-Nutrient 1,000 0 1750 1800 1850 1900 1950 2000 2050 Humans, millions Galloway JN and Cowling EB. 2002; Galloway et al., 2002a

Nr Creation by Cultivation --So that’s why we plant soybeans-- 7,000 200 6,000 150 5,000 4,000 100 3,000 2,000 BNF 50 N-Discovered N-Nutrient 1,000 0 0 1750 1800 1850 1900 1950 2000 2050 Humans, millions Legumes/Rice, Tg N Galloway JN and Cowling EB. 2002; Galloway et al., 2002a

Nr Creation by Fossil Fuel Combustion --Nr produced by accident-- 7,000 200 6,000 150 5,000 4,000 100 3,000 2,000 BNF 50 N-Discovered N-Nutrient 1,000 N 2 + O 2 --> 2NO 0 0 1750 1800 1850 1900 1950 2000 2050 Humans, millions Legumes/Rice, Tg N NOx emissions, Tg N zyxwvutsrqponmlkjihgfedcbaWVUTSRQPONMLIHGFEDCBA Galloway JN and Cowling EB. 2002; Galloway et al., 2002a

The History of Nitrogen --A British chemists view-- 7,000 200 6,000 150 5,000 4,000 100 World is running out of N * 3,000 2,000 BNF 50 N-Discovered N-Nutrient 1,000 N 2 + O 2 --> 2NO 0 0 1750 1800 1850 1900 1950 2000 2050 Humans, millions Legumes/Rice, Tg N NOx emissions, Tg N zyxwvutsrqponmlkjihgfedcbaWVUTSRQPONMLIHGFEDCBA * 1898, Sir William Crookes, president of the British Association for the Advancement of Science Galloway JN and Cowling EB. 2002; Galloway et al., 2002a

The History of Nitrogen --German science at the forefront-- 7,000 200 6,000 150 5,000 N 2 + 3H 2 4,000 --> 2NH 3 100 3,000 2,000 BNF 50 N-Discovered N-Nutrient 1,000 N 2 + O 2 --> 2NO 0 0 1750 1800 1850 1900 1950 2000 2050 Humans, millions Legumes/Rice, Tg N NOx emissions, Tg N zyxwvutsrqponmlkjihgfedcbaWVUTSRQPONMLIHGFEDCBA Galloway JN and Cowling EB. 2002; Galloway et al., 2002a

Nr Creation by Haber-Bosch --most used for fertilizer-- 7,000 200 6,000 150 5,000 N 2 + 3H 2 --> 2NH 3 4,000 100 3,000 H-B 2,000 BNF 50 N-Discovered N-Nutrient 1,000 N 2 + O 2 --> 2NO 0 0 1750 1800 1850 1900 1950 2000 2050 Humans, millions Haber Bosch Legumes/Rice, Tg N NOx emissions, Tg N zyxwvutsrqponmlkjihgfedcbaWVUTSRQPONMLIHGFEDCBA Galloway JN and Cowling EB. 2002; Galloway et al., 2002a

N r Creation by Food and Energy Production 7,000 200 6,000 150 5,000 4,000 100 3,000 BNF H-B 2,000 50 N-Nutrient N-Discovered 1,000 0 0 1750 1800 1850 1900 1950 2000 2050 Humans, millions Energy Production Food Production Galloway JN and Cowling EB. 2002; Galloway et al., 2002a

N r Creation by Food and Energy Production 7,000 200 6,000 150 5,000 4,000 { 100 3,000 Nr, natural H-B 2,000 BNF 50 N-Nutrient N-Discovered 1,000 0 0 1750 1800 1850 1900 1950 2000 2050 Humans, millions Total N Fixed, Tg Galloway JN and Cowling EB. 2002; Galloway et al., 2002a

N Drivers in 1860 Grain Production Meat Production Energy Production

The Global Nitrogen Budget in 1860 and mid-1990s, TgN/yr 5 5 N 2 N NO y NO NH x NH 2 y x 1860 120 120 Galloway et al., 2002b

The Global Nitrogen Budget in 1860 and mid-1990s, TgN/yr 5 5 N 2 N NO y NO NH x NH 2 y x 1860 120 120 15 15 0.3 0.3 Galloway et al., 2002b

The Global Nitrogen Budget in 1860 and mid-1990s, TgN/yr 5 5 6 N 2 6 N NO y NO NH x NH 2 y x 9 9 8 6 8 6 1860 120 120 8 11 8 7 7 11 15 15 6 6 0.3 0.3 27 27 Galloway et al., 2002b

Nitrogen Drivers in 1860 & 1995 Grain Production Meat Production Energy Production

The Global Nitrogen Budget in 1860 and mid-1990s, TgN/yr 5 5 6 N 2 6 N NO y NO NH x NH 2 y x 9 9 8 6 8 6 1860 120 120 8 11 8 7 7 11 15 15 6 6 0.3 0.3 27 27 5 5 mid-1990s N 2 N NO y NO NH x NH 2 y x 110 110 Galloway et al., 2002b

The Global Nitrogen Budget in 1860 and mid-1990s, TgN/yr 5 5 6 N 2 6 N NO y NO NH x NH 2 y x 9 9 8 6 8 6 1860 120 120 8 11 8 7 7 11 15 15 6 6 0.3 0.3 27 27 5 5 mid-1990s N 2 N NO y NO NH x NH 2 y x 33 33 110 110 100 100 25 25 N 2 + 3H 2 2NH 3 Galloway et al., 2002b

The Global Nitrogen Budget in 1860 and mid-1990s, TgN/yr 5 5 6 N 2 6 N NO y NO NH x NH 2 y x 9 9 8 6 8 6 1860 120 120 8 11 8 7 7 11 15 15 6 6 0.3 0.3 27 27 5 5 6 6 mid-1990s N 2 N NO y NO NH x NH 2 y x 26 23 26 33 16 16 33 23 18 18 110 21 110 21 25 39 25 39 100 100 25 25 N 2 + 3H 2 48 48 2NH 3 Galloway et al., 2002b

zyxwvutsrqponmlkjihgfedcbaWVUTSRQPONMLIHGFEDCBA Nr Riverine Fluxes 1860 (left) and 1990 (right) TgN/yr 9.1 21.8 5 7.8 4.4 8.3 7.7 8.5 7.4 9.7 zyxwvutsrqponmlkjihgfedcbaWUTSRPONMLKJIHGFEDCBA 2.1 2 -> all regions increase riverine fluxes -> Asia becomes dominant Galloway et al, 2002b; Boyer et al., in preparation

Nitrogen Deposition Past and Present mg N/m 2 /yr 5000 2000 1000 750 zyxwvutsrqponmlkjihgfedcbaWUTSRPONMLKJIHGFEDCBA 500 250 100 50 25 5 1993 1860 Galloway and Cowling, 2002; Galloway et al., 2002b

Mid-Course Summary Summary Next Questions ‹ Humans mobilize ~50% ‹ What are the consequences more Nr than natural of Nr accumulation? terrestrial ecosystems. – Food production accounts ‹ What is projected for future? for 75% ‹ Nr is widely dispersed ‹ How can science and policy – Atmospheric Nr emissions respond? have increased 3-fold since 1860; NH 3 twice as important as NO x ‹ Nr is accumulating in ecosystems and the atmosphere.

Nr and Agricultural Ecosystems ‹ Haber-Bosch has facilitated agricultural intensification ‹ 40% of world’s population is alive because of it ‹ An additional 3 billion people by 2050 will be sustained by it ‹ Most N that enters agroecosystems is released to the environment.

Nr and the Atmosphere ‹ NO x emissions contribute to OH, which defines the oxidizing capacity of the atmosphere ‹ NO x emissions are responsible for tens of thousands of excess- deaths per year in the United States ‹ O 3 and N 2 O contribute to atmospheric warming ‹ N 2 O emissions contribute to stratospheric O 3 depletion