MONROE, Mich. — For decades, government agencies and private groups have been working to rebuild Great Lakes coastal wetlands such as swamps, bogs, and marshes that have been depleted by development. A federal report suggests the work is beginning to pay off.
The eight-state Great Lakes region — extending from western New York to eastern Minnesota — was the only section of the United States where coastal wetland acreage increased during a five-year period when scientists took extensive measurements with satellites and field photography.
The gain was modest — 13,610 acres, an area not quite as large as the New York City borough of Manhattan. Yet it happened as the rest of the nation’s coastal wetlands shrank by 360,720 acres. The loss was less than 1 percent of the US total, but continued a longtime negative trend.
Wetlands are immensely valuable, helping prevent floods by absorbing excessive rainwater. They are known as ‘‘nature’s kidneys,’’ filtering out pollutants that otherwise would wash into lakes and rivers, and also provide vital wildlife habitat.
Scientists say the continental United States has lost roughly half the wetland acreage that existed prior to European settlement. They have been filled and drained for farms, housing, and cities.
Experts say the gains in the Great Lakes region reflected in the study resulted partly from a prolonged drop in water levels, which created new wetland areas as vegetation sprouted along shorelines that had been submerged.
Some of that acreage could disappear if the lakes rise again, said Tom Dahl, a US Fish and Wildlife Service scientist and a report author.