Wetlands carbon-storage function increasingly important in the face of climate change
By Summit Voice
SUMMIT COUNTY — For years, land managers and elected officials have permitted the destruction of ecologically valuable wetlands under the assumption that those areas can be replaced somewhere else with artificially created wetlands.
That development model has created a billion-dollar-per-year wetlands restoration industry, but a recent study suggests that restored wetlands rarely 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.
The study found that restored wetlands contained about 23 percent less carbon than untouched wetlands, while the variety of native plants was 26 percent lower, on average, 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,” he said.
In future studies, he will explore whether the slower carbon accumulation is due to a slow recovery of the native plant community or invasion by non-native plants.
Moreno-Mateos, Power and their colleagues will publish their analysis in the Jan. 24 issue of PLoS (Public Library of Science) Biology.