RICHMOND — Without state conservation measures or global emissions reductions that could slow the pace of sea level rise, Virginia could lose 42% of its tidal wetlands by 2100, researchers with research nonprofit Climate Central found in a study published last week in Environmental Research Communications journal.
State and local government decisions about whether to conserve land along coastlines where wetlands can migrate as sea level rises will be “a decisive factor in the sort of outcomes that we will likely see this century,” said Benjamin Strauss, one of the authors of the study and Climate Central’s chief scientist and CEO.
Coastal wetlands, which are also known as tidal or salt marshes, are critical ecosystems that not only serve as a home to an array of fish, plants, birds and other species but store carbon and protect communities from encroaching seas.
One study found that wetlands along the northeast coast of the U.S. avoided $625 million in damages from Hurricane Sandy in 2012.
“These are very dynamic systems,” said Hillary Stevens, coastal resilience manager with nonprofit Restore America’s Estuaries, during a panel discussion convened by Climate Central June 8. “They are highly productive. Plants that grow there grow very rapidly.”
Sea level rise, however, is now posing an existential threat to many of these ecosystems.
Tidal wetlands are capable of expanding their size both by growing vertically and by “migrating” farther inland, with former marshes transformed into open water and former dry land transformed into wetlands — a conversion already underway on Virginia’s coasts.
But if the pace of sea level rise outstrips the pace of upward growth, or if there’s no land backing up the marshes into which they can move, the wetlands drown in place and are lost.
“The solution is conserve what’s behind so [the wetland] has a fighting chance to migrate,” said Mary-Carson Stiff, policy director of Norfolk-based nonprofit Wetlands Watch.
Molly Mitchell, a coastal ecologist with the Virginia Institute of Marine Science, said the Climate Central finding that roughly 42% of the state’s tidal wetlands could be lost by the end of the century was “a reasonable estimate of that kind of worst-case scenario.”
A higher estimate of potential losses appears in Virginia’s Coastal Resilience Master Plan, a blueprint for dealing with sea level rise drawn up under former Gov. Ralph Northam.
That document found that by 2080, roughly 89% of Virginia’s tidal wetland acreage will have been transformed into open water, although the plan acknowledges the estimate doesn’t include potential expansions of tidal marshes that could occur through migration.
Mitchell said that whatever the overall percentage, losses won’t occur uniformly as sea level rise reshapes the coast.
“It’s more nuanced in that there will be areas where we see marshes increase,” she said. Areas such as Poquoson, Gloucester, Mathews, parts of the Eastern Shore and the York and Lower York regions could see marshes expand in the coming years. Meanwhile, losses in freshwater tidal marshes, such as those found farther upriver from the Chesapeake Bay along the James, are expected to be high.
While some wetlands will be lost to rising waters because the lands behind them lie at too high of an elevation to allow migration, others will simply have no place to go because of encroaching development.
A new mapping tool developed by Climate Central and released alongside last week’s study shows which counties will see the biggest changes in wetlands areas by 2050 depending on whether the lands behind them are conserved or developed.
For example, if those backing lands — known as “refugia” — are fully developed, Northumberland County could lose an estimated 31% of its coastal wetlands by midcentury. If all refugia were conserved, wetlands could increase by 30%.
“I think the important part of the study is the understanding that some, not all the changes in wetlands could be affected by the way we manage our coastal lands,” said Mitchell. “In areas of low elevation, if we can conserve the land behind the marshes and don’t develop it, we can preserve the land for migration.”
Wide-ranging conservation may be a difficult sell politically, but Wetlands Watch Executive Director Skip Stiles said the consequences of losing major swathes of Virginia’s coastal marshes will be severe.
Large-scale losses would “dramatically impact fisheries, water quality, you name it,” he said. In the U.S., an estimated 90% of all fish and shellfish harvested recreationally and 75% of those harvested commercially depend on wetlands for food or habitat.
East Carolina University coastal engineer Siddharth Narayan said June 8 that the many vital services provided by wetlands, from critical habitat to coastal protection to carbon absorption, have contributed to a growing push to recognize the ecosystems as critical “natural infrastructure.”
“The idea being that if these wetlands were to be damaged, then it is worth it to pay money to repair them for the money that we’re going to get back,” he said.
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