Wetland restoration is a billion-dollar-a-year industry in the United
States that aims to create ecosystems similar to those that disappeared
over the past century. But a new analysis of restoration projects shows
that restored wetlands seldom reach the quality of a natural wetland.
"Once you degrade a wetland, it doesn't recover its normal assemblage
of plants or its rich stores of organic soil carbon, which both affect
natural cycles of water and nutrients, for many years," said David
Moreno-Mateos, a University of California, Berkeley, postdoctoral
fellow. "Even after 100 years, the restored wetland is still different
from what was there before, and it may never recover."
Moreno-Mateos's analysis calls into question a common mitigation
strategy exploited by land developers: create a new wetland to replace a
wetland that will be destroyed and the land put to other uses. At a
time of accelerated climate change caused by increased carbon entering
the atmosphere, carbon storage in wetlands is increasingly important, he
said.
"Wetlands accumulate a lot of carbon, so when you dry up a wetland
for agricultural use or to build houses, you are just pouring this
carbon into the atmosphere," he said. "If we keep degrading or
destroying wetlands, for example through the use of mitigation banks, it
is going to take centuries to recover the carbon we are losing."
The study showed that wetlands tend to recover most slowly if they
are in cold regions, if they are small -- less than 100 contiguous
hectares, or 250 acres, in area -- or if they are disconnected from the
ebb and flood of tides or river flows.
"These context dependencies aren't necessarily surprising, but this
paper quantifies them in ways that could guide decisions about
restoration, or about whether to damage wetlands in the first place,"
said coauthor Mary Power, UC Berkeley professor of integrative biology.
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