| The Department of Interior released some scary maps and graphs about the Dead Zone in the Gulf. If you look at the maps (below) you can which areas are most responsible for causing the dead zone.
The Environmental Working Group says:
In January of 2008, USGS identified commercial fertilizers and animal manure from farmland in 9* states as the cause of over 70 percent of the Dead Zone pollution. Evidence is mounting that the mandated push to increase corn production - one of the most fertilizer intensive crops - for ethanol exacerbates water quality problems within the states and in the Gulf. This year, the USGS identifies and ranks watersheds in the Basin by the amount of pollution that gets to the Gulf.
*The 9 states contributing over 70 percent of the dead zone-causing nitrogen and phosphorus pollutants are: Illinois, Iowa, Indiana, Missouri, Arkansas, Kentucky, Tennessee, Ohio, and Mississippi.
My thought: if we know which watersheds are particularly vulnerable, wouldn't it make sense to provide incentives for farmers in those areas to enroll in conservation programs? EWG agrees with me, in their press release, and they note that the government is NOT doing that already. To be fair, though, this IS the first time we've seen rankings showing who is most responsible for the dead zone so it would have been quite impossible to target funding to those areas before they knew which areas to target. |
The reason for the dead zone is a condition called hypoxia:
The hypoxic zone in the northern Gulf of Mexico refers to an area along the Louisiana-Texas coast in which water near the bottom of the Gulf contains less than 2 parts per million of dissolved oxygen, causing a condition referred to as hypoxia. Hypoxia can cause fish to leave the area and can cause stress or death to bottom dwelling organisms that can't move out of the hypoxic zone. Hypoxia is believed to be caused primarily by excess nutrients delivered from the Mississippi River in combination with seasonal stratification of Gulf waters. Excess nutrients promote algal and attendant zooplankton growth. The associated organic matter sinks to the bottom where it decomposes, consuming available oxygen. Stratification of fresh and saline waters prevents oxygen replenishment by mixing of oxygen-rich surface water with oxygen-depleted bottom water.
The nutrients in question are phosphorus and nitrogen. They come from manure and fertilizer runoff.
Ranking of Total Phosphorus Yields Delivered to the Gulf of Mexico
This map shows which are probably the top 150 watersheds delivering phosphorus to the Gulf.
Ranking of Total Nitrogen Yields Delivered to the Gulf of Mexico
This map shows which are probably the top 150 watersheds delivering nitrogen to the Gulf.
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