Restored Wetlands: Not as Good as the Original

New research published in the online journal, PLoS Biology, argues that wetlands are some of the most valuable ecosystems on Earth. Mangrove forests and boreal peatlands mitigate the impacts of storms and flooding on coastal communities, limit erosion, store carbon, and provide habitat for lots of fish and bird species. Unfortunately, many communities have never realized this. More than half of wetland ecosystems in North American, Australia, Europe, and Asia, have been destroyed by development. And there’s more bad news. According to the group of researchers from Stanford University, University of California, Berkeley, and other universities, restored, man-made wetlands don’t provide as much value as natural ones. “Restoration performance is limited. Current restoration practice fails to recover original levels of wetland ecosystem functions, even after many decades.”

A “meta-analysis” of more than 600 wetland sites worldwide found that even 100 years post-restoration, “biological structure (driven mostly by plant assemblages), and biogeochemical functioning (driven primarily by the storage of carbon in wetland soils), remained on average 26% and 23% lower, respectively, than in reference sites.” The researchers conclude that either recovery times are “very slow” or some sort of additional disturbances happened to these wetlands — from pollution or development. 

Location and temperature does make some difference in recovery rates, though. “Wetlands restored in warm (temperate and tropical) climates recovered more rapidly than smaller wetlands and wetlands restored in cold climates.” In addition, the sites with more water washing through them did better than “depressional” wetlands. 

For the researchers conducting the analysis, bigger-scale recovery efforts may also help improve the recovery rates. To date, most restored wetlands are just snippets of once vast systems. “Recovery may be more likely and more rapid if more than 100 contiguous hectares of habitat are restored.” 

Their findings don’t bode well for future restoration efforts either, unless restoration approaches change: “If restoration as currently practiced is used to justify further degradation, global loss of wetland ecosystem function and structure will spread.”

David Moreno-Mateos, a wetland ecologist at the Jasper Ridge Biological Preserve at Stanford University and the lead author of the paper, told The New York Times’ Green Blog that means changing the way restored wetlands are evaluated and testing the biological processes: “In traditional restoration, people repair hydrology, put in some plants, and after a few years say the wetlands are good. But if you look at what’s really going on down there, you see the processes are not recovering.”

If the research is further replicated and confirmed, there could be implications for both governments and the development industry. According to Moreno-Mateos, over the last 20 years, the U.S., Canada, and Mexico have spent $70 billion restoring more than seven million acres of wetlands. In addition, developers often “promise to create or restore wetlands in one location in exchange for getting permission to bulldoze wetlands in another location.” The research is saying these new sites just don’t do as well, though.

For example, in newly restored sites, plants are particularly hard hit and take the longest to recover. The New York Times Green Blog writes: “On average, they took 30 years to return but still remained less biodiverse and abundant up to 100 years after restoration.” This “plant lag” may be due to “recovering carbon, nitrogen and phosphorus storage.”

Still, for communities that don’t have any wetland systems at all, unearthing and restoring historic yet damaged systems or creating new ones may still provide value, even while offering lower levels of ecosystem service. As an example, check out a wonderful new project in Los Angeles (see images at top and below), which turned a 9-acre parking lot into a somewhat functioning wetland park. According to The Architect’s Newspaper, the new park has “kidney-shaped storm water pools, deep cleaning retention basins, and banks of native plants chosen for their ability to clean water.” Now, in an area with lots of toxic run-off and little green space, there’s a park that can process up to 680,000 gallons of stormwater a day.

While it may not be as good as the real thing, it still provides enormous social value for an underserved community, along with some intrinsic environmental value: there’s now a way to deal with all that runoff and some species are seen returning to the site.

Image credit: (1-2) South Los Angeles Wetland Park / LAPROPO, (3) South Los Angeles Wetland Park / The City Park

One thought on “Restored Wetlands: Not as Good as the Original

  1. Jim Harris 01/22/2017 / 5:59 pm

    The Technoparc wetland in Montreal currently being horribly damaged by developers claiming to be making improvements is a depressional wetland well under 100 hectares and in a cold climate. If work is allowed to continue that looks like three strikes, you’re out, to me.

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