When it comes to wetlands, once you lose them, they’re gone. So says a new study from UC Berkeley, which concludes that restored wetlands rarely match the quality (in ecological terms) of the original environment. Considering wetlands provide an enormous host of benefits, from biodiversity conservation, fish production, and water purification, to erosion control and carbon storage, degradation of those environments is costly.That’s big news considering that wetland restoration has become a billion-dollar-a-year industry in the United States. It also suggest that, after a century of wetland destruction in the U.S., we may not ever be able to recover lost wetlands and the full scope of species they harbor. That’s bad news considering that half of all the wetlands in North America, Europe, China, and Australia were destroyed in the 20th century.“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,” Berkeley postdoctoral fellow and study author David Moreno-Mateos said. “Even after 100 years, the restored wetland is still different from what was there before, and it may never recover.”Moreno-Mateos’ study flies in the face of a common strategy used by land developers who fill in, repurpose, and other otherwise destroy natural wetlands: They just build new ones elsewhere. But while flooding a new area and planting wetland-native plant species may create what looks like a wetland, that reconditioned land is fundamentally lacking many of the features that natural wetlands have developed over centuries. One of the key aspects of this is carbon sequestered within the wetland ecosystem.“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,” Moreno-Mateos 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 report is a meta-analysis of 124 primary studies of work at 621 wetland restoration sites around the world, with those results compared to studies of natural wetlands. One bright spot is that 80 percent of those restoration projects were in the U.S., some of which were restored more than a century ago, suggestion that wetland restoration has been of importance in the States for some time. On the other hand, those number might just mean we’ve long had a history of figuring that whatever wetlands we destroy can be rebuilt.That’s simply not the case. According to Moreno-Mateos, restored wetlands are on average 25 percent less productive than natural wetlands. That includes lower biodiversity — the number of individual native plant species was 26 percent lower, on average, after 50 to 100 years of restoration — which suggests that biodiversity losses caused by habitat loss may never recover. Restored wetlands also sequestered about 23 percent less carbon than untouched land. The two may be correlated: Less diversity means plants take longer to store and establish a solid base of available carbon that’s required for a fully-functioning ecosystem.The takeaway is that even if something looks like a natural wetland, it may not be functioning like one. That’s important to keep in mind when developing conservation policy. When it comes down to it, untouched ecosystems have had millennia to ramp up to maximum operating efficiency. Once they’re gone, we may be able to create something similar. But while that’s better than nothing, restored lands are still not as quality as the natural lands they’re meant to replace.
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