The knowledge learned from these delta areas tell about the history of the region from how the land was used or not used through time, the authors say. The world's largest 25 rivers drain about one-half of the Earth's surface and transport 50 percent of the fresh water and 40 percent of particulate materials into the ocean, they confirm.
The Mississippi River, the largest in the U.S., drains about 40 percent of the country's total land mass, plus parts of two Canadian provinces, the authors say, and we can learn critical information from its delta regions.
In the U.S., hypoxic areas where there is little or no oxygen can in some cases be linked with deltaic regions that are releasing large amounts of water and nutrients, Bianchi explains. "Low oxygen in aquatic systems is clearly not good for the organisms in those systems, but not all aquatic systems respond in the same way," he notes. "It affects marine life in some areas severely, while other areas seem unchanged. We need to find out why.
"Some LDE areas such as the Mississippi/Atchafalaya River system have had significant increases in the nutrient loading from fertilizers" Bianchi adds. "We know we need to reduce the amount of these nutrients from draining into our rivers, but by how much? In this particular case, the linkages between excessive nutrients, hypoxia and their affects on aquatic life are not well understood.
"It's a big problem that China is facing right now as it attempts to manage severe water shortages, over-grazing and desertification issues for a growing population by manipulating natural water sources from their major rivers through damming and diversions. Over the last 20 years, China has become the world's largest consumer of fertilizers and two of its rivers, the Yell
|Contact: Thomas Bianchi|
Texas A&M University