White House report on coastal dead zones
Yesterday the White House released a major report on hypoxia in US coastal waters. The document is ponderous, written by a committee from a number of government agencies and partakes of the weightiness of major government scientific reports. For example, just to make sure we get it right, the first thing the document does is to instruct us how it should be cited:
“Committee on Environment and Natural Resources. 2010. Scientific Assessment of Hypoxia in U.S. Coastal Waters. Interagency Working Group on Harmful Algal Blooms, Hypoxia, and Human Health of the Joint Subcommittee on Ocean Science and Technology. Washington, DC.”
Hard to believe but by using an approach that reminds one of a new regulation by the Internal Revenue Service, the report has gotten almost no publicity. This is so even though the freely available, 164 page pdf file is filled with color photos which have almost nothing to do with the subject.
The neglect might have to do with the fact that the first chapter is about the “Legislative Background” authorizing the study and the report’s “development process.” There really is nothing like settling back to read about how Congress passed some laws directing various agencies to study a problem. Or to read about how those agencies went about their work. Maybe it has to do with the page of 72 acronyms which are used identify the groups, agencies, departments and so forth that had some involvement. It also could not have helped to describe the report as one dealing with hypoxia rather than “dead zones” — the term in common use for the problem.
The fact is that if this inter-agency group wanted to conceal the results of its work, they could hardly have done a better job. But this is unfortunate because the report contains stunning evidence of yet another threat we have created for our own well-being that will shortly have serious consequences for us. Perhaps the authors intended to avoid the perception that they were overselling the problem so as to avoid the fate that climate science now faces. That would explain how they frame the conclusion to the executive summary:
“If properly planned and executed, adaptive management of nutrient inputs will lead to significant reductions in hypoxia. However, if current practices are continued, the expansion of hypoxia in coastal waters will continue and increase in severity, leading to further impacts on marine habitats, living resources, economies, and coastal communities.” (p5.)
If they indeed drew a lesson from the global warming deniers, they drew the wrong one. Global warming deniers aren’t skeptic because they thought they were being lied to. They claim that they were being lied to because they fear that confronting the problem will cost them money. Perhaps there is nothing that could bring mainstream media attention on the problem of coastal dead zones, short of a redneck preacher threatening to throw hundreds of copies of Rachel Carson’s Silent Spring into a bonfire. But if anything could make people wake up to the threat of killing the ocean it is the facts contained in this report.
First, let’s define the problem. Most large-form ocean life (life other than bacteria, algae and plankton) lives near continental shelves. The vast portion of what we harvest from the ocean lives there. Beginning in the 1970s it was observed that patches of these coastal waters were devoid of fish. On examination it was discovered that the cause was low levels of dissolved oxygen. (The same phenomenon was observed in large freshwater lakes.) It was soon learned that these dead zones followed the same pattern. Large amounts of nitrogen (and to a lesser extent phosphorus) accumulate in an area of a water body. These nutrients allow phytoplankton (given sufficient sunlight to photosynthesize) to multiply. Normally nitrogen is the limiting factor under Liebig’s Law to phytoplankton growth. When the phytoplankton die, the dentrivores that decompose the organic matter use up as part of the decomposition process the oxygen in the water creating hypoxic conditions. (Some hypoxic/anoxic events have been caused by algal blooms rather than phytoplankton. But the process is the same.) Hypoxia occurs when the dissolved oxygen is less than 3 milligrams per liter of water. Anoxia occurs when the amount of dissolved oxygen approaches zero.
Hypoxic water effects large organisms in numerous ways: by interfering with reproduction, affecting behavior, stunting growth, killing eggs and larvae, and so forth. According to a chart on p11 of the report, oxygen levels do not have to reach hypoxic conditions before having adverse and even lethal affects on marine life. Perch, shad and bass require 5-6 mg/L oxygen. Blue crab and anchovies need 3 mg/L.
Since dead zones were first identified their number and extent has greatly increased. Table 1 (p13) shows the growth in the number of the estuaries and coastal water bodies with reported hypoxic conditions.
|Region||% Hypoxic 1980s||% Hypoxic 1990s||% Hypoxic 2000s||% Hypoxic 2000s|
|North Atlantic||6 (1 of 17)||22 (4 of 18)||35 (7 of 20)||26 (10 of 38)|
|Mid-Atlantic||50 (19 of 38)||59 (13 of 22)||64 (14 of 22)||42 (76 of 180)|
|South Atlantic||18 (9 of 51)||64 (14 of 22)||91 (20 of 22)||55 (77 of 139)|
|Gulf of Mexico||69 (38 of 55)||84 (32 of 38)||68 (26 of 38)||51 (105 of 205)|
|Pacific||21 (6 of 29)||26 (10 of 39)||35 (13 of 37)||46 (37 of 80)|
|Great Lakes||1 of 5 lakes||2 of 5 lakes||2 of 5 lakes|
|Total Nation||38 (73 of 190)||52 (73 of 139)||58 (80 of 139)||47 (307 of 647)|
The second-largest eutrophication related dead zone in the world is now in the northern Gulf of Mexico at the mouths of the Mississippi and Atchafalaya Rivers. In the mid-1980s it was measures at 4,000 km². In 2008 it was measured at 20,719 km². (The largest hypoxic sea is the world is the Baltic, with a hypoxic area of about 80,000 km². But all coastal waters around the US have seen large increases in hypoxic areas, as can be seen from the following map (p14 of the Report).
The question is where does the excess nitrogen come from? When the problem was first detected, a large source was untreated sewage dumped into rivers which created pools of high nitrogen at the mouths. In the intervening years clean water laws have reduced the discharge of raw sewage, but now the problem is to a great extent nitrogen from agricultural runoffs. But there are other sources such as atmospheric pollution and industrial and sewage effluvia. In some areas it may be caused by global warming or even “natural” causes, as we’ve seen. But the problem is largely related to population density and industrial activity is demonstrated by the following map showing the areas of hypoxia around the world. (You can also compare NASA’s map of world dead zones, which we discussed before.)
The relative combination of these sources differs with the area studied. See for instance this chart on page 15 shows that 75% of the nitrogen pollution in the Gulf of Mexico comes from agricultural sources. In the Narragansett Bay, however, about 80% comes from industrial and sewage runoffs. Appendix III of the report details the extent of the problem by listing all major bays and river mouths with the latest results of tests of dissolved oxygen.
The point the Report tries to make is that there is no single regulatory scheme that is designed to rationally respond to the problem at its sources. The Report also tries to consider the effect of global warming on the problem. Although there does not appear to be any new research in the Report, it does summarize existing work and make recommendations, however general. The Report loses some focus given that it has to demonstrate what various agencies have been doing and these sections suffer from science gee-whizism and bureaucratic self-justification. Despite the fact that the writing is less than a clear clarion, there is more than enough information to generate a call for action, if this country were capable of resolving to marshal its forces to save itself. But that’s an entirely different matter.