Sediments released by many of the world's largest river deltas to the global oceans have been changed drastically in the last 50 years, largely as a result of human activity, says a Texas A&M University researcher who emphasizes that the historical information that can be gathered from sediment cores collected in and around these large deltaic regions is critical for a better understanding of environmental changes in the 21st century.
Thomas Bianchi, a professor in the Department of Oceanography who specializes in estuarine and marine systems, and colleague Mead Allison of the University of Texas have examined sediments from delta areas around the world, most notably the Mississippi in the United States and the (Huanghe) Yellow and Yangtze in China. These sediments contain information that can provide data on past changes in nitrogen application in the drainage basin from agricultural fertilizers, records of past flooding and hurricane events, to name a few, Bianchi says.
Their work is published in the current issue of the "Proceedings of the National Academy of Sciences."
"These deltaic sediments can serve as a history book of sorts on land-use change in these large drainage basins which is useful for upland and coastal management decisions as related to climate change issues," Bianchi explains.
"Although the information stored in these sediments can be altered during its transport from the upper drainage basin to the coast, we still find very stable tracers, both organic and inorganic, that can be used to document changes induced by natural and human forces."
Such sediments are ever-present, the authors say, noting that 87 percent of the Earth's land surface is connected to the ocean by river systems. They also explain that 61 percent of the world's population lives along a coastal boundary, and that number is expected to climb to 75 percent by 2025.
Much of the sediment from rivers forms into what are called large river
|Contact: Thomas Bianchi|
Texas A&M University