An entire multi-billion dollar industry is built on the idea that developers can replace/restore wetlands that they destroy during construction. The only problem: Restored wetlands rarely reach the quality of a natural wetland, a recent study suggests.

“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 by building on it. And 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 250 acres – or if they are disconnected from the ebb and flood of tides or river flows. That’s not “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, U.C. Berkeley professor of integrative biology.

The study found that restored wetlands contained about 23 percent less carbon than untouched wetlands, while the variety of native plants was on average 26 percent lower after 50 to 100 years of restoration. While restored wetlands may look superficially similar – and the animal and insect populations may be similar, too – the plants take much longer to return to normal and establish the carbon resources in the soil that make for a healthy ecosystem.

Moreno-Mateos noted that numerous studies have shown that specific wetlands recover slowly, but his meta-analysis “might be a proof that this is happening in most wetlands.”

“To prevent this, preserve the wetland, don’t degrade the wetland,” he said. “Current thinking holds that many ecosystems just reach an alternative state that is different, and you never will recover the original.”

Image: Colorado Fish and Wildlife.

In affiliation with Summit County Citizens Voice. Environmental coverage made possible in part by support from Patagonia. For information on Patagonia and its environmental efforts, visit www.patagonia.com.

Tagged as: climate change, conservation, environment