Neither surf nor turf, land or sea, salt marshes are a spongy, mucky, stinky in-between zone full of biting, stinging, snapping creatures. Yet they are stunning to the eye — think Poucha Pond, Mattakesett Bay, Nashaquitsa Pond. And more importantly they are one of the most productive ecosystems on earth.

Salt marshes — our local coastal wetlands — provide recreation, jobs, human health and safety protections, and an incredible array of environmental benefits.

So much of what we love to do on the Island is tied to the salt marsh: We swim, fish, dig and dipnet shellfish, canoe, kayak, hunt ducks, watch birds, eat local seafood, admire, photograph, paint, drive, walk and run along the coastal ponds and shoreline. These are some of the recreational values that salt marshes provide.

The economic power of wetlands is astounding. The U.S. Environmental Protection Agency (EPA) estimates the dollar value of wetlands worldwide at $14.9 trillion.

Wetlands nourish the food we pluck from the sea. A seminal 2007 study entitled Confronting Climate Change in the U.S. Northeast reports that “one-third of all the commercial fish and shellfish species harvested off the Northeast’s coast depend on estuaries and wetlands for food or protection during their juvenile or adult stages. These include such key species as lobster, clams, bay scallops, conch, winter flounder, menhaden, alewife, and several species of shark . . . {and] recreationally important species such as bluefish and striped bass also depend on wetlands to supply the small fish on which they prey.”

Like sponges, salt marshes absorb storm water and thereby protect people, roads, and property from flooding and storm damage. They slow shoreline erosion, absorb pollutants, and recharge groundwater supplies.

They provide human health advances. Lorna Seitz, currently the executive director of the International Consortium for Law and Development, authored a report titled Protecting U.S. Salt Marshes from the Effects of Global Warming. In it she writes: “The medical profession uses an extract from the horseshoe crab’s blue, copper-based blood to test the purity of medicines . . . the horseshoe crab’s shell has been used to speed blood clotting and to make absorbable sutures.”

Some say salt marshes are the most valuable ecosystem on earth; they serve as the base of the marine food chain. According to the Seitz report, 70 per cent of commercial fish depend specifically on salt marshes for all or part of their lives. The EPA reports that salt marshes provide habitat for both aquatic and terrestrial plants and animals including mammals, plants, insects, amphibians, and reptiles, and play a role in the life cycle of up to 90 per cent of fish caught recreationally.

Salt marshes are vital for birds. “As many as one-half of all North American bird species nest or feed in wetlands,” according to the EPA, and “migrating birds use wetlands to rest and feed during their cross-continental journeys and as nesting sites when they are at home.”

Before we understood their extraordinary value, 80 per cent of the salt marshes in southern New England were destroyed. In 1972 Massachusetts became the first state to pass a Wetlands Protection Act. Now most Massachusetts towns also have local wetlands bylaws that add more specific protections to these amazing ecosystems.

But here comes another disturbing era for the mighty salt marsh — climate change due to global warming.

When faced with a rising sea, salt marshes naturally migrate inland, but doing so is impossible when development rings the shoreline. Recently retired Martha’s Vineyard Commission water resources planner Bill Wilcox explains: “Homeowners with views are armoring their shores to get the maximum amount of life out of their property and homes. But we have to provide places for marshes to move inland to provide all the good services they provide . . . with ecosystems, it’s a chain of reactions.”

A 2005 Massachusetts Audubon Society report by Dr. Robert Buchsbaum concludes that “Salt marshes at sanctuaries like Felix Neck . . . will become more significant because they will be surrounded by protected conservation uplands and therefore could migrate upwards.”

The Confronting Climate Change report warns that “because of the erosive impact of waves (especially storm waves), the extent of shoreline retreat and wetland loss is projected to be many times greater than the loss of land caused by the rise in sea level itself.”

The Massachusetts Office of Coastal Zone Management reports that in addition to rising global sea levels, “the tectonic plate that Massachusetts rests on is subsiding, resulting in relative sea level rates that are even more extreme.”

As salt marshes give way to open ocean water, the agency continues, “many benefits of the system will be lost. Important habitats for fish, shellfish and birds will be drowned, space for beach recreation will be reduced, and storm damage prevention to inland areas will be compromised.”

Some reports point to sea level rise as a cause for salt marsh die-backs on Cape Cod. Climate change will bring more intense rainfall that could overwhelm the marshes’ ability to absorb water, adding pollutants to the coastal ponds, and increasing the growth of invasive species like phragmites. Warmer salt water can alter the composition of species that dwell in marshes.

The Confronting Climate Change study concludes that “Salt marshes in the Northeast already appear to be unable to accrete fast enough to keep up with sea level rise.”

The Seitz report says: “Species that cannot migrate upland at the same rate as the sea will become swamped . . . and they may be incapable of surviving.”

Some species, however, could benefit from the changes. A PEW Center of Global Climate Change report states that the effects of climate change on salt marshes could be positive or negative, depending on the species: “Birds that require the marsh for rearing young (e.g., black and clapper rails, some terns and plovers) will be affected negatively by its loss, whereas birds that feed in shallow water or on intertidal sand and mud flats that replace the marsh (e.g, dabbling ducks, some shorebirds) will be affected positively.”

In their book The Rising Sea, coastal geologists Orrin H. Pilkey and Rob Young write that “Coastal marshes . . . have survived two million years of sea level fluctuations . . . a testament to their robustness and adaptability.”

The Seitz report concludes that “Ensuring the long-term survival of large, healthy, and productive salt marshes is of critical local, regional, and international importance,” and their loss “would constitute enormous economic, ecological and aesthetic loss to society.”

The author adds: “Their preservation should be a high priority for all environmentalists, land use planners, fishermen, fish consumers, bird lovers, and coastal residents.”

Let’s add to that list local businessmen and women. Everyone who makes a living on this Island will be impacted by the changing climate. The Island will change dramatically in the coming decades. Business dollars will be lost as the shoreline reshapes itself in ways that hinder recreation, jobs, and property. Let’s not become known as an Island generation that did nothing, that ignored the big picture, that failed to care for the future. Let’s start planning to adapt to the coming changes. Doing so will take courage and strong leadership, involvement from every segment of society, and a lot of money.

Doing nothing amounts to a human, economic, ecologic and moral failing.

Liz Durkee is the conservation agent for the town of Oak Bluffs. This is the eighth part in an occasional series she is writing for the Gazette Commentary Page about climate change and what it means for the Vineyard.