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Posts tagged Delta Subsidence

Climate Change Affecting Mississippi Delta Region, USA – January 25th, 2013

29.9N 90W

January 25th, 2013 Category: Image of the day, Wetlands

USA – January 17th, 2013

This image shows the Mississippi Delta Region, which represents one of the most vulnerable regions of the Gulf Coast. The combined effects of engineered and altered landscapes, natural subsidence, and climate change will have tremendous consequences for human well-being, natural resources, and biodiversity.

Over the past century, the nearly 1.3 million square mile watershed of the Mississippi River has experienced major environmental changes, including conversion of more than 80 percent of forested wetlands to agriculture and urban areas, channelization, dam construction, and river levees. The construction of massive structures that keep the river from switching channels has restricted sediment and freshwater supply to the flood plain.

These changes have been especially damaging to the region’s wetlands. The coastal wetlands associated with the Mississippi River delta make up nearly 40 percent of the total coastal salt marsh in the lower 48 states of the U.S. These wetlands are disappearing at an average rate of 25 square miles per year, about 50 acres each day. Already, more than one thousand square miles of freshwater wetlands in Louisiana have been lost or converted to other habitats. Only about 20 percent of the original bottomland hardwood forests and swamps in the lower Mississippi River valley remain today.

Some of these wetland losses are due to delta subsidence (sinking), which results in relative sea-level rise. Although subsidence is a natural process, human interference with river and sediment flow and withdrawal of groundwater have exacerbated it (click here for more information).