Wednesday, January 25, 2012
Restored Wetlands Rarely Equal Condition of Original Wetlands
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.