Tech Tuesday

Ocean Map Shows Dead Zones

Group maps bad news areas of world's oceans and shows that there's more than one dead zone to worry about. And cattle boost degraded soil.

If I were to say "dead zone" to a group of consumers when talking about the ocean, they would immediately think I was talking about the Gulf of Mexico. And if I asked about others, chances are they wouldn't know of any - thanks to the heavy attention given to on hypoxic zone in the world. But it turns out there are plenty of these hot spots worldwide.

Now the World Resources Institute and the Virginia Institute of Marine Science have collaborated to create a website that identifies more than 530 low-oxygen "dead zones" in the planet's oceans. In addition, they catalog another 228 sites exhibiting signs of marine eutrophication, which occurs when water bodies are over fertilized by nutrients washed into surface waters from farm and urban areas.


This screen capture of the interactive map on the site shows how VIMS and WRI have worked to provide information on a range of hypoxic and eutrophic areas. The map offers you the ability to zoom into specific areas for increased detail.

I'll not debate the causes of hypoxic and eutrophic zones in this column. Instead, take time to look at this map and realize that the issue is widespread. There are areas of improvement that can be found on an interactive map at the website too. As scientists and regulators get a handle on this issue, and farmers and urban homeowners get smarter about nutrient use, this situation will improve near the U.S. Worldwide, of course, is a different matter.

WRI, in its release announcing the site, points out that compiling the information into a central location will help raise awareness and offer solutions for controlling nutrient pollution. The 530 areas and the 228 sites encompass more than 95,000 square miles. The largest is that Gulf zone, but another is in Chesapeake Bay too. Expect greater public aware of this issue now that the site is available.

Check out the page at www.wri.org/eutrophication.

Bringing Back Soil Health

Decades of plowing can deplete land, which often returns to pasture and forest, and often the soil in these plots lacks nutrients and organic matter. But a study funded by USDA-Agricultural Research Service has tested cattle grazing on degraded soil and found that medium to heavy grazing offers some good news.

During a 12-year period, 18 paddocks were used to monitor soils response to different land management practices. Researchers found that paddocks with medium to heavy grazing proved to be the best way to sequester nitrogen and carbon on the soil. This also boosted soil fertility and cut greenhouse gas emissions.

Landowners struggle with the decision to leave land unused to help restore it, or add cattle to graze as an option. This work shows that grazing cattle on that land can improve the soil.

In the study, researchers used four different management techniques to arrive at their conclusion. Paddocks were either moderately grazed, averaging 5.8 steers per hectare (about 2.5 steers per acre); heavily grazed at 8.7 steers per hectare (about 3.6 steers per acre); not grazed, but the grass was cut and used for hay; or not grazed or harvested.

Unused land that was not harvested had the highest surface residue accumulation, which prevents erosion, but it didn't sequester carbon and nitrogen as well as grazing. Land that was not grazed, but harvested for hay resulted in little nutrient retention and was prone to erosion.

The study appeared in the November/December 2010 edition of Soil Science Society of America Journal.

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