Until the 1970s the vast majority of that loss was agricultural, from farmers draining land for crops. The country is still losing wetlands to agriculture, but it’s also seeing them flooded away, lost to sea-level rise and logging, converted to artificial lakes and ponds and drained for suburban development, the report found.
“Over time our wetland policies at a national level have become less stringent,” Lang said. “And now we’re kind of burning the candle at both ends — we’re still losing wetlands to people ditching and filling them, but we’re also losing them to these more complicated factors.”
The report shows that one of the major ways the Upper Midwest has been losing vegetated wetlands — swamps, bogs and marshes covered with shrubs, cattails or trees — is by converting them into open-water ponds. That can happen when a housing developer drains an intact marsh to build a subdivision and then digs a larger shallow pond that supports little or no wildlife in the middle of that subdivision. And it happens when loggers clear cut the trees out of a swamp, and saplings fail to regenerate.
Ponds and treeless swamps are still wetlands, but they don’t come close to producing the same levels of wildlife, water quality or carbon storage as before. As vegetated wetlands have declined, the number of ponds and nonvegetated wetlands has risen in Minnesota and across the country, which can obscure the magnitude of the loss, the Fish and Wildlife Service warned.
Efforts are needed to protect the old wetlands and not simply replace them with less valuable ponds, the report said. The first step would be to create a data set that maps out the location, type and abundance of the nation’s wetlands, and to model the functions and services the landscapes provide. That would help regulators better protect the most valuable wetlands and make sure that any that are lost to development are replaced by those of the same quality.
In Minnesota, the biggest losses have been to the state’s forested wetlands — the swamps and floodplains with heavy tree cover. Of the 140,000 acres of forested wetlands in the state that were lost between 2006 and 2020, about 20% were expected to return, according to data from the Minnesota Department of Natural Resources. Much of the rest was degraded into open water or “emergent” wetlands with little tree cover.
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Publish date : 2024-08-27 10:52:00
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