“You Asked” is a series where Earth Institute experts tackle reader questions on science and sustainability.
The following question was submitted through our Instagram page by one of our followers. The answer was provided by Dorothy Peteet.
Can you tell me more about wetland mitigation banking and how wetlands interact with their surroundings?
Wetlands are unique ecosystems that function as the “kidneys” of the earth’s surface, cleaning water and recharging aquifers. They protect shorelines, provide nursery habitat for extensive wildlife, and are responsible for food production in both tidal and freshwater environments.
In recent years, northern and mid-latitude peatlands have also been recognized as extremely important carbon storage repositories, and critical to the global carbon cycle. “Blue carbon” systems — such as mangroves and tidal salt marshes — along rivers and shorelines are also recognized now as increasingly important, storing carbon at a rate 10 times greater than forests.
Wetlands are becoming better recognized for their myriad values as humans face rising seas, more intense rainfall events, and higher surface air and ocean temperatures. However, their losses continue as population pressures increase, pollution worsens, environmental degradation continues, and protections for wetlands decline. Small wetlands are particularly vulnerable, yet important; recent studies note that they’re responsible for filtering out 60 percent of nitrogen from upstream pollution, yet are less protected than larger wetlands by state laws.
Wetland mitigation banking
Some development projects, like airport expansions, seek to compensate for unavoidable impacts to wetlands by restoring, creating, or enhancing wetlands at another location (somewhat like the concept of carbon offsets). This process, called wetland mitigation banking, is successful in some ways but not others. Wetlands compromised by agriculture can sometimes be restored in terms of their function through hydrological modifications. Less successful are enhanced wetlands, which are modified to focus on a single function that is emphasized, such as supporting a particular type of wildlife. Least successful of all are “created” wetlands, which do not have long-term functions equivalent to natural wetlands but may look attractive on the landscape. They do not sequester the carbon that natural wetlands have accumulated over millennia, and they do not filter water in the same way that natural wetlands function.