Nutrient Pollution of Coastal Waters: Trends, Drivers, and Potential - PowerPoint PPT Presentation

Nutrient Pollution of Coastal Waters: Trends, Drivers, and Potential Solutions Robert Howarth Cornell University Ithaca, NY USA Ocean Hypoxia and its Impacts on Ecosystems UNDP Side Event at GESAMP #39 New York City, USA 18 April 2012

Global status of earth’s 10 life-sustaining biophysical systems nitrogen (Rockstrom et al. 2009)

Nitrogen (and not phosphorus) is the primary culprit for coastal eutrophication and hypoxia (although controlling both is best policy)

+ phosphorus + nitrogen + nitrogen & phosphorus No nutrients added Oviatt et al. 1996

Seine and Scheldt Basins and Belgian coast of North Sea North Sea English Channel

annual mean discharge, m3/s Freshwater discharge 800 Seine River basin 600 400 200 0 1970 1980 1990 2000 2010 3000 300 TN load TP load TN flux, kgN/km²/yr 2500 TP flux, kgP/km²/yr 250 2000 200 150 1500 100 1000 50 500 0 0 1975 1980 1985 1990 1995 2000 2005 2010 1970 1980 1990 2000 2010

30 Chlorophyll in max Chla, mg/m3 20 North Sea on 10 Belgian coast 0 1970 1980 1990 2000 2010 3000 2500 TN flux, kgN/km²/yr 2000 Seine River N load 1500 1000 500 0 1970 1980 1990 2000 2010 4000 TN flux, kgN/km²/yr 3000 Scheldt River N load 2000 1000 0 1970 1980 1990 2000 2010

Global trends in nitrogen use per year 200 Total human inputs Teragrams of nitrogen 150 Natural N fixation on the continents 100 Fertilizer N fixation in agro-ecosystems 50 Fossil fuel burning 0 1900 1920 1940 1960 1980 2000 (modified from Howarth et al. 2005)

Regional scale perspective important for nutrients. Changes are driven by global energy and agricultural policies. But with exception of N 2 O, nutrient cycles are altered at local to regional scales, not global scales, and effects are manifested at these local to regional scales.

New York Times (4/30/08) Townsend & Howarth 2010

Natural background flux Republic of Korea 9 North Sea watersheds 8 Northeastern U.S. 7 Yellow River basin 6 Mississippi River basin 5 Series1 Baltic Sea watersheds 4 St. Lawrence River basin 3 Southwestern Europe 2 Labrador and Hudson’s Bay 1 0 500 1000 1500 2000 Flux of nitrogen from the landscape to coastal oceans in rivers for contrasting regions of the world in the temperate zone (kg per km 2 of watershed area per year; from Howarth et al. 2005).

North Atlantic Ocean Kg N km -2 year -1 NANI (net anthropogenic N inputs) International SCOPE N Project (Howarth et al. 1996)

(Howarth et al. 2012) ~ 150 watersheds on two continents ~ 25% of NANI exported to coastal oceans on average from 150 watersheds in Europe and the US

Chinese watersheds Swaney et al. 2012

(Hong et al. 2011)

NANI Hong et al., 2012 NOy deposition Fertilizer Ag N fixation Net food & feed

Per capita NANI by region (partial analysis) Sum of Nutrient NOx N fixation Consumption Reactive fertilizer Emission and net relative to Nitrogen Region consumption (kg flux of N safe (kg N (kg N/capita, N/capita, in food operating per 2009) 2000) and feeds boundary capita) Africa 2.5 0.9 ? 3.4 0.7 South America 12.2 1.2 ? 13.4 2.6 Southeast Asia 12.7 0.7 ? 13.4 2.6 India 13.0 0.5 ? 13.5 2.6 North America 35.9 9.6 ? 45.5 8.9 Europe 18.4 3.1 ? 21.5 4.2 East Asia 24.3 1.2 ? 25.4 5.0 Australia 30.8 7.9 ? 38.8 7.6 Other 10.5 0.6 ? 11.0 2.2 Global 15.4 1.5 4.6 21.5 4.2 UNEP Sustainable Resource Use Panel (2011 draft)

Technical solutions for nitrogen pollution : • Agricultural fields: reduce fertilizer amount and timing; change cropping systems; plant winter cover crops; control drainage seasonally • CAFOs: treat wastes as society does for human waste • Vehicle exhaust: tighten emission standards; encourage hybrid vehicles and electric vehicles • Power plants: tighten emission standards; encourage renewable electricity (solar, wind) • Sewage treatment: require denitrification treatment Howarth et al. (2005) Millennium Ecosystem Assessment

But also think about policy solutions, particularly regarding diet and biofuels….

Farm nitrogen balance for US (~1995; Tg per year for entire US) NH NH 3 Denit itrif ifie ied? NH 3 NH Bui uildi ding up i ng up in s n soi oil? La Landf ndfilled? d? La Landf ndfilled? d? Leac eached ed? Denit itrif ifie ied? 0.2 (4. 4.2) 2) (1. 1.2) 2) (0. 0.8) 8) Hum uman n Cons onsum umpt ption on 1.3 1.9 18.5 18. 1.4 Fie ield ld 10. 10.5 Lev evel Harvested i d in n crops ops Was astew ewat ater er 0.9 & Denit itrif ifie ied 5.9 3.6 2.1 Animal Cons onsum umpt ption on (3. 3.1) 1) Leac eached ed t to wat ater er Expor ported f d from om U.S. Leac eached ed t to wat ater er? Denit itrif ifie ied? (Howarth et al. 2002)

If everyone in increasing grain exports, standard US diet the US ate this : constant grain exports, standard US diet 20.0 constant grain exports, 18.0 Swedish diet -1 constant grain exports, fertilizer use, TgN yr 16.0 Mediterranean diet 14.0 12.0 10.0 8.0 6.0 Instead of this: 4.0 (Howarth et al. 2002) 2.0 0.0 1960 1970 1980 1990 2000 2010 2020 2030 The country would use only 1/3 rd as much fertilizer, and would have much less nitrogen pollution!

Biofuels Globa obal P Produc oduction of on of Li Liqui quid B d Biof ofue uels: 1200 15 billion liters 1000 Ethanol 800 Biodiesel Equiv. Peta Joules 600 400 200 0 1975 1979 1983 1987 1991 1995 1999 2003 2007 Year Howarth et al. 2009

2009: National goal to reduce nitrogen pollution down Mississippi River by 45% to limit size of dead zone. Several models indicate national ethanol policy will make this difficult or impossible, and instead nitrogen pollution likely to increase…. 30% to 40% or more (Donner and Kucarik 2008; Simpson et al. 2008, 2009; EPA 2009; Costello et al. 2010)

Predicted Nitrogen Load from Mississippi River basin to meet US Ethanol Targets (Costello et al. 2010) 2015 targets 2022 targets 2.0 Million tons nitrogen per year National target to reduce area of Dead Zone 1.0 0

CONCLUSIONS : Nitrogen is the primary culprit. Nitrogen pollution is growing globally, with agriculture as the primary driver. Technical solutions exist, and can help, often at little cost. But policy considerations of diet (meat!) and energy (liquid biofuels!) are critical.

Thanks for invitation to participate! Thanks for many collaborators, especially: Coastal Hypoxia • Dennis Swaney Research Program • Bongghi Hong • Roxanne Marino • Christine Costello • Gilles Billen • Josette Garnier • Christoph Humborg Agriculture, Energy & Environment Program at • Alan Townsend Cornell University