“Dead Zone” in the Gulf: Addressing Agriculture’s...
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The Northern Gulf of Mexico’s hypox- ic (oxygen-deficient) waters represent one of the Western Hemisphere’s largest “dead zones”—areas where lack of oxygen kills fish, crabs, and other marine life. The size of the zone varies but at its peak, it stretches along the inner continental shelf from the mouth of the Mississippi River westward to the upper Texas coast, cover- ing about 7,000 square miles, an area as large as New Jersey. Long-term conse- quences to biodiversity, species abun- dance, and biomass in the Gulf are not yet known, but experience with other coastal dead zones has shown significant ecologi- cal deterioration and depleted fisheries. Scientists believe that Gulf hypoxia is caused by nitrogen loads from the Mississippi River. Nitrogen fuels the rapid growth of large populations of algae and plankton. When they die and sink to the bottom, their decay robs the water of oxygen. Because two-thirds of the nitrogen in the Mississippi River comes from use of fertilizer and manure on agricultural lands, reducing agricultural nitrogen is a major component of the strategy for con- trolling the hypoxic zone. Two basic approaches can be taken: (1) induce changes in the appli- cation and manage- ment of nitrogen fer- tilizer on farm fields, or (2) restore wet- lands along rivers and streams to inter- cept and filter out the nitrogen before it reaches surface waters. Because the geo- graphic scale of the problem is so large, any policy to reduce nitrogen from agricul- ture will affect commodity prices, and con- sequently farmers and consumers both inside and outside the basin. An ERS analysis of the two approach- es found farm-based controls on nitrogen fertilizer use to be more cost-effective than restoring wetlands when up to 1.2 million metric tons (26 percent) of basin- wide nitrogen losses (nitrogen leaving the land and entering the water system) must be eliminated. Until that point, crop yields are little affected by the controls on nitrogen use. But when nitrogen losses must be cut by more than 1.2 mil- lion metric tons, a turn- around occurs and wet- land restoration becomes the more cost-effective strategy. The reason for the turnaround is that when reduction in nitro- gen use reaches a certain point, crop yields decline significantly, causing subsequent increases in prices of some agricultural products. The price increases also result in more intense production of the commodi- ties outside the Mississippi Basin, increas- ing erosion and nutrient runoff in those regions. However, these calculations don’t include (because of insufficient data) other environmental benefits of wetlands not related to nitrogen reduction, such as increased habitat for wildlife. Inclusion of these benefits would cause the wetland option to become the more cost-effective approach at a lower level of nitrogen reduction. Marc Ribaudo, [email protected] This finding is drawn from . . . “Least-cost Management of Nonpoint Source Pollution: Source Reduction Versus Interception Strategies for Controlling Nitrogen Loss in the Mississippi Basin,” by Marc O. Ribaudo, Ralph E. Heimlich, Roger Claassen, and Mark Peters, in Ecological Economics, May 2001. Abstract available at: www.ers.usda.gov/publications/ erselsewhere/eejs0207/ RESOURCES AND ENVIRONMENT 6 5 4 3 2 1 0 Controls on nitrogen fertilizer use are more cost- effective than wetland restoration up to 1.2 million tons of nitrogen loss reduction 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Reduction in nitrogen loss within the Mississippi Basin (million tons) Cost per unit ($1,000/ton) Wetland restoration approach Fertilizer reduction approach 1.0 “Dead Zone” in the Gulf: Addressing Agriculture’s Contribution Mississippi River Basin Missouri Hypoxic Zone Upper Mississippi Arkansas- Red-White Gulf of Mexico Ohio Tennessee Lower Mississippi F I N D I N G S 8 AMBER WAVES ECONOMIC RESEARCH SERVICE/USDA VOLUME 1 ISSUE 5 F I N D I N G S
Transcript of “Dead Zone” in the Gulf: Addressing Agriculture’s...
The Northern Gulf of Mexico’s hypox-ic (oxygen-deficient) waters represent oneof the Western Hemisphere’s largest “deadzones”—areas where lack of oxygen killsfish, crabs, and other marine life. The sizeof the zone varies but at its peak, itstretches along the inner continental shelffrom the mouth of the Mississippi Riverwestward to the upper Texas coast, cover-ing about 7,000 square miles, an area aslarge as New Jersey. Long-term conse-quences to biodiversity, species abun-dance, and biomass in the Gulf are not yetknown, but experience with other coastaldead zones has shown significant ecologi-cal deterioration and depleted fisheries.
Scientists believe that Gulf hypoxia iscaused by nitrogen loads from theMississippi River. Nitrogen fuels the rapidgrowth of large populations of algae andplankton. When they die and sink to thebottom, their decay robs the water of oxygen.
Because two-thirds of the nitrogen inthe Mississippi River comes from use offertilizer and manure on agriculturallands, reducing agricultural nitrogen is a
major component ofthe strategy for con-trolling the hypoxiczone. Two basicapproaches can betaken: (1) inducechanges in the appli-cation and manage-ment of nitrogen fer-tilizer on farm fields,or (2) restore wet-lands along riversand streams to inter-cept and filter out the nitrogen before itreaches surface waters. Because the geo-graphic scale of the problem is so large,any policy to reduce nitrogen from agricul-ture will affect commodity prices, and con-sequently farmers and consumers bothinside and outside the basin.
An ERS analysis of the two approach-es found farm-based controls on nitrogenfertilizer use to be more cost-effectivethan restoring wetlands when up to 1.2million metric tons (26 percent) of basin-wide nitrogen losses (nitrogen leaving theland and entering the water system) must
be eliminated. Until thatpoint, crop yields are littleaffected by the controls onnitrogen use. But whennitrogen losses must becut by more than 1.2 mil-lion metric tons, a turn-around occurs and wet-land restoration becomesthe more cost-effectivestrategy. The reason forthe turnaround is thatwhen reduction in nitro-
gen use reaches a certain point, crop yieldsdecline significantly, causing subsequentincreases in prices of some agriculturalproducts. The price increases also result inmore intense production of the commodi-ties outside the Mississippi Basin, increas-ing erosion and nutrient runoff in thoseregions. However, these calculations don’tinclude (because of insufficient data)other environmental benefits of wetlandsnot related to nitrogen reduction, such asincreased habitat for wildlife. Inclusion ofthese benefits would cause the wetlandoption to become the more cost-effectiveapproach at a lower level of nitrogen
reduction.
Marc Ribaudo, [email protected]
This finding is drawn from . . .
“Least-cost Management of Nonpoint Source
Pollution: Source Reduction Versus
Interception Strategies for Controlling
Nitrogen Loss in the Mississippi Basin,” by
Marc O. Ribaudo, Ralph E. Heimlich, Roger
Claassen, and Mark Peters, in Ecological
Economics, May 2001. Abstract available at:
www.ers.usda.gov/publications/
erselsewhere/eejs0207/
RESOURCES AND ENVIRONMENT
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Controls on nitrogen fertilizer use are more cost- effective than wetland restoration up to 1.2 million tons of nitrogen loss reduction
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
Reduction in nitrogen loss within the Mississippi Basin (million tons)
Cost per unit ($1,000/ton)
Wetland restoration approach
Fertilizer reduction approach
1.0
“Dead Zone” in the Gulf:Addressing Agriculture’sContribution
MississippiRiver Basin
Missouri
Hypoxic Zone
UpperMississippi
Arkansas-Red-White
Gulf of Mexico
Ohio
TennesseeLower
Mississippi
F I N D I N G S
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ECONOMIC RESEARCH SERVICE/USDA
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