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

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

Nutrient Pollution of Coastal Waters: Trends, Drivers, and Potential Solutions

(Rockstrom et al. 2009)

Global status of earth’s 10 life-sustaining biophysical systems

nitrogen

Nitrogen (and not phosphorus) is the primary culprit for coastal eutrophication and hypoxia

(although controlling both is best policy)

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

Seine and Scheldt Basins and Belgian coast of North Sea

North Sea English Channel

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

Seine River basin

Freshwater discharge TN load TP load

10 20 30 1970 1980 1990 2000 2010 max Chla, mg/m3

Chlorophyll in North Sea on Belgian coast

500 1000 1500 2000 2500 3000 1970 1980 1990 2000 2010 TN flux, kgN/km²/yr

Seine River N load

1000 2000 3000 4000 1970 1980 1990 2000 2010 TN flux, kgN/km²/yr

Scheldt River N load

50 100 150 200 1900 1920 1940 1960 1980 2000

Teragrams of nitrogen Natural N fixation on the continents

Total human inputs Fertilizer N fixation in agro-ecosystems Fossil fuel burning

Global trends in nitrogen use per year

(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 N2O, 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

500 1000 1500 2000 1 2 3 4 5 6 7 8 9 Series1

Republic of Korea North Sea watersheds Northeastern U.S. Yellow River basin Mississippi River basin Baltic Sea watersheds

• St. Lawrence River basin

Southwestern Europe Labrador and Hudson’s Bay Natural background flux

Flux of nitrogen from the landscape to coastal oceans in rivers for contrasting regions of the world in the temperate zone (kg per km2 of watershed area per year; from Howarth et al. 2005).

Kg N km-2 year-1

North Atlantic Ocean

International SCOPE N Project (Howarth et al. 1996)

NANI

(net anthropogenic N inputs)

(Howarth et al. 2012) ~ 150 watersheds

• n two continents

~ 25% of NANI exported to coastal

• ceans on average from 150

watersheds in Europe and the US

Swaney et al. 2012

Chinese watersheds

(Hong et al. 2011)

NOy deposition Fertilizer Ag N fixation Net food & feed

NANI

Hong et al., 2012

Region Nutrient fertilizer consumption (kg N/capita, 2009) NOx Emission (kg N/capita, 2000) N fixation and net flux of N in food and feeds Sum of Reactive Nitrogen (kg N per capita) Consumption relative to safe

• perating

boundary 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

Per capita NANI by region (partial analysis)

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….

Fie ield ld Lev evel

Leac eached ed t to wat ater er Harvested i d in n crops

• ps

3.6 10. 10.5 0.2 (4. 4.2) 2) (1. 1.2) 2) 1.3 5.9 (3. 3.1) 1)

Animal Cons

• nsum

umpt ption

• n

Leac eached ed t to wat ater er? Denit itrif ifie ied? NH NH3

1.9

Denit itrif ifie ied? Bui uildi ding up i ng up in s n soi

• il?

NH NH3 La Landf ndfilled? d? Leac eached ed? La Landf ndfilled? d? Denit itrif ifie ied?

(0. 0.8) 8)

1.4

Was astew ewat ater er & Denit itrif ifie ied

Hum uman n Cons

• nsum

umpt ption

• n

0.9

Expor ported f d from

• m U.S.

2.1 18. 18.5

(Howarth et al. 2002)

Farm nitrogen balance for US (~1995; Tg per year for entire US)

If everyone in the US ate this: Instead of this:

The country would use only 1/3rd as much fertilizer, and would have much less nitrogen pollution!

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 1960 1970 1980 1990 2000 2010 2020 2030 fertilizer use, TgN yr

• 1

increasing grain exports, standard US diet constant grain exports, standard US diet constant grain exports, Swedish diet constant grain exports, Mediterranean diet

(Howarth et al. 2002)

Howarth et al. 2009

Globa

• bal P

Produc

• duction of
• n of Li

Liqui quid B d Biof

• fue

uels:

200 400 600 800 1000 1200

1975 1979 1983 1987 1991 1995 1999 2003 2007 Year Peta Joules

Ethanol Biodiesel Equiv.

15 billion liters

Biofuels

2009: National goal to reduce nitrogen pollution down Mississippi River by 45% to limit size

• f dead zone.

Several models indicate national ethanol policy will make this difficult or impossible, and instead nitrogen pollution likely to increase…. 30% to 40%

• r more (Donner and Kucarik

2008; Simpson et al. 2008, 2009; EPA 2009; Costello et al. 2010)

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

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!

Coastal Hypoxia Research Program Agriculture, Energy & Environment Program at Cornell University

Thanks for many collaborators, especially:

• Dennis Swaney
• Bongghi Hong
• Roxanne Marino
• Christine Costello
• Gilles Billen
• Josette Garnier
• Christoph Humborg
• Alan Townsend