Restoring Wetlands: A Strategy to Address Climate, Biodiversity, and Water

March 22, 2023

By Dr. Kristen Dybala, Principal Ecologist

No matter where you live, you’re likely to have a wetland somewhere nearby. Wetlands include any land that is saturated with water at least some of the time, like marshes and mangroves along our coasts, floodplains and wet meadows along rivers and streams, and vernal pools and prairie potholes. And all of these wetlands touch our lives in many ways you may not realize. In a new report produced by Point Blue Conservation Science and the Natural Resources Defense Council, we compiled evidence for a wide range of benefits wetlands provide us every day. Across all types of wetlands, we found evidence for a broad array of benefits, but what became clear is that wetland restoration is an important strategy for addressing three major challenges we face here in California and around the world: climate change, biodiversity conservation, and water management.

Wetlands store huge amounts of carbon in their rich soils, and in the case of mangroves and riparian forests, in the trees as well. Wetlands excel at removing CO2 – the primary greenhouse gas – from the atmosphere. Intact wetlands will continue to sequester additional carbon every year, contributing to a net cooling effect and helping to mitigate the impacts of climate change. They are also often sources of abundant food and water for fish, birds, and other wildlife, making them well-documented biodiversity hotspots: up to 40% of the world’s species live or breed in wetlands. For example, coastal wetlands act as important nurseries for shrimp, crab, and fish, while prairie potholes provide critical breeding habitat for waterfowl, and vernal pools serve as oases for wildlife in arid landscapes. Riparian forests and floodplains also support a rich diversity of fish and wildlife, and they serve as important corridors of connectivity for wildlife trying to move through a developed landscape. And all types of wetlands provide important habitat for birds, ranging from the Ridgway’s Rails nesting in the tidal marshes of San Francisco Bay, to the Yellow-billed Cuckoo and Least Bell’s Vireos that rely on riparian habitat along our rivers, to millions of waterfowl and shorebirds that depend on the managed wetlands and flooded agriculture in the Central Valley during the winter or as a stop on their long migrations.

In addition to carbon and biodiversity benefits, wetlands can help us manage the extremes of floods and droughts, which are expected to become more common with climate change. For example, in California, where the majority of cost-effective locations for dams and reservoirs are already in use and groundwater is severely depleted, wetlands can act as natural water reservoirs, providing the space for flood water to spread out, slow down, sink into their spongy soils, and even recharge groundwater. The extreme winter storms and flooding we’ve seen in California this year make it clear that rivers and streams need more space to spread onto adjacent floodplains. Efforts to improve connectivity between river channels and their floodplains, such as building setback levees or installing beaver dam analogues, can be successful in dispersing flood water into areas where it can safely contribute to providing carbon and biodiversity benefits and away from nearby communities. Likewise, coastal wetlands provide demonstrated protection against storm surges, slowing wave energy and providing space for flood waters to spread out. High in the mountains, wet meadows can also store snow and water during winter storms, reducing pressure on the reservoirs and levees below, and then slowly releasing water downstream during dry periods, extending water supplies longer into the summer. The value of the flood protection benefits alone, in terms of avoided damage to infrastructure and property, has been estimated at thousands of dollars per acre per year, not to mention the estimated value of other benefits like avoided cost of engineered solutions to storm surge protection or the economic value of commercial fisheries that rely on wetland habitat.

Wetlands directly contribute to addressing three major challenges we face today, making it clear that protecting and restoring wetlands is a high priority for climate-smart conservation. Disturbances to existing wetlands, such as pumping water out, cutting off their water supply, or excavating their soils, not only reduce their ability to support biodiversity and manage water, but also contribute to making climate change worse. This is because when wetland soils dry up or are otherwise exposed to air, their rich carbon stores immediately begin to be released into the atmosphere, reversing centuries – or even millennia – of carbon storage. The bad news is that there have been tremendous wetland losses globally over the last 100–200 years, including an estimated 53–62% loss in the United States. The good news is that we found strong evidence that wetland restoration can substantially improve, if not fully recover, many of the benefits they provide. However, we note that new wetlands do produce significant amounts of methane – a potent greenhouse gas – and at higher rates in freshwater wetlands, and these methane emissions are enough to offset their carbon sequestration benefits in the short-term. So, while large-scale wetland restoration is an essential long-term strategy for addressing climate change, that will also provide more immediate biodiversity conservation and water management benefits, it should be paired with policies to reduce fossil fuel emissions and advance other nature-based climate solutions.

Wetland conservation and restoration is a big part of our work at Point Blue, and a big part of many of our partnerships. For just a few examples, we work toward the restoration of wet meadows in the Sierra Nevada through the Sierra Meadows Partnership, and the restoration of riparian areas in Marin and Sonoma counties through our STRAW program, in partnership with local schools and private landowners. Within the San Francisco Estuary, we work with the San Francisco Bay Joint Venture and many others to collaborate on tidal wetland restoration projects and manage native plant nurseries to grow plants to support these restoration efforts. In the Central Valley, we work with the Migratory Bird Conservation Partnership, the Water for Wetlands Coalition and other partners in the Central Valley Joint Venture to support and inform restoration of managed wetlands and riparian forests, as well as incentive programs that provide temporary wetland habitat for shorebirds and waterfowl in the Central Valley. Our report demonstrates that these wetland conservation and restoration efforts are directly benefiting local communities in ways we haven’t always been able to demonstrate, and policies and programs to support wetland conservation and restoration to provide multiple benefits are key to effective climate-smart conservation.

Based on the evidence for the multiple benefits of wetland conservation and restoration documented in our report, our partners at NRDC have developed a companion issue brief that identifies opportunities to advance wetland protection and restoration through existing policy tools. For example, making wetlands a priority in global, federal, and state efforts to achieve 30×30 goals – protecting 30% of land, inland waters, and oceans by 2030 – will help stabilize the climate and protect biodiversity as well as help protect communities from some of the impacts of climate change. And because wetlands can have so many benefits for climate, biodiversity, and water, wetland restoration can also be an effective strategy for achieving the goals of many federal land managers, agencies, and programs such as the Federal Emergency Management Administration’s “Building Resilient Infrastructure and Communities” program or the U.S. Department of Agriculture’s “Climate-Smart Agriculture and Forestry Initiative”. With so much interest and momentum building in climate-smart conservation actions, at global, federal, state, and local levels, I hope our report provides timely and compelling evidence for much-needed investment in wetland conservation and restoration.