Global Nitrogen Cycle, Eutrophication, and Coastal Hypoxia: State of Knowledge and Management Robert J Díaz diaz@vims.edu http://www.vims.edu/deadzone/

Bringing the problem into focus

How Eutrophication/Hypoxia Became a Global Problem Economic growth from expanding population caused increasing input of nutrients to coastal areas over last 60 years resulted in system overload. Strong correlation through time between: population growth and agriculture expansion increased nutrient discharges and disruption of global cycles increased primary production increased occurrence of hypoxia and anoxia. 7,000,000,000 by end of 2011. 9,000,000,000 by 2050. www.abe.msstate.edu

Bringing the problem into focus From the start of the ‘Industrial Revolution’ in 1700s it has taken >100 years to alter global Carbon Cycle. With the start of the ‘Green Revolution’ in 1940s it took <50 years to alter global Nitrogen Cycle.

Fate of Haber-Bosch Nitrogen 14% of N produced in Haber-Bosch process enters the human mouth...... if you are a vegetarian. 4% of N used for animal production enters human mouth. 82% of N is lost to the environment.

Reactive Nitrogen Galloway et al. 2008

Global Nitrogen Cycle Gruber & Galloway 2008

What are Consequences? Caddy 2000

What is at stake for our future What is at stake for our future? Coastal and Continental Shelf Habitats Fisheries Production

Eutrophication Driven Dead Zones Oxygen Minimum Zones 550 Hypoxic Areas 60 Hypoxic Areas in recovery 250 Eutrophic Areas in Danger of Hypoxia OMZ Touching 1,150,000 km2 of Seabed Helly & Levin 2004 Diaz et al. 2010

Area of Ecosystem Affected Hypoxic Habitat: Total Area (Km2) Hypoxic Area (Km2) Habitat Hypoxic Global Flow Lost to Hypoxia Shelf from OMZ 26,600,000 1,150,000 4.3% 0.4% Nutrients 170,000 0.6% 0.1% Estuaries 1,800,000 70,000 6.9% Costanza et al. 1997, Helly and Levin 2004, Diaz and Rosenberg 2008

What are the direct causes? Coastal dissolved oxygen trends are driven by: Runoff from land Point discharges Global climate change

Two Part Key to Future Hypoxia Diaz & Breitburg 2010

Management of Hypoxia Prevention and long-term remediation can be achieved by reducing excess nutrients (N & P) entering from the land, atmosphere, and groundwater. Nutrient reduction will require: Knowledge of local environmental conditions. Diagnosis of main nutrient sources. Integrated, cross-sector land & sea management.

Management of Hypoxia Science supporting hypoxia reduction is complex. But Current scientific understanding is sufficient to support managing in an ecosystem context.

Recovered with Nutrient Management There is encouraging news. Small and large systems such as the Black Sea and Boston Harbor have responded positively to decreased anthropogenic stressors. In all cases where hypoxia has be significantly reduced, it has been achieved through intense nutrient management or reduction. 60 systems have responded positively.

Mangement of Hypoxia Not all hypoxia can be readily controlled but case-specific knowledge can clarify solutions. Causes and effects are embedded in economic and societal values: Land-use and development policies can constrain nutrient reduction actions. Changing relationship of ecosystem response to nutrients and hypoxia. Coastal regime changes or threshold shifts will require managers to work with new conditions

Policy Issues to Overcome to Solve Hypoxia Management Side: Cross-sector mission conflicts. Inadequate pollution management. Low environmental awareness among policymakers and public as to the ecological and economic costs. Lack of a master plan for the coastal area as a whole (Coastal Zone Planning).

Knowledge Gaps to Overcome to Solve Hypoxia Science Side: Habitat loss/alteration impacts on populations and economies. Nutrient sources, loadings, and transformations. Natural factors and climate change. Provide holistic ecosystem view.