Beach replenishment is an expensive and temporary method of maintaining barrier-island beaches. In the absence of alternatives — and many have been tried in vain — state and local governments and most of society are committed to pumping sand from the ocean floor for the foreseeable future.
As the post-Hurricane Sandy rebuilding of all the beaches along New Jersey’s 127-mile Atlantic coast nears completion, an additional potential cost is becoming clear: Replenishment might be creating dead zones on land and at sea. That’s not sufficient reason to stop sand dredging (without a new and better option), but it’s worrisome enough that governments should adjust their practices and possibly even their funding mechanisms.
Even casual beachcombers can see the loss of natural life on the maintained beaches that dominate the Jersey Shore’s tourism towns. Compared to the increasingly rare beach that isn’t periodically buried under dredged ocean-bottom material and mechanically raked clean regularly, a maintained beach is like a desert, a big sandbox for people to relax and play in.
Recently, a researcher with the Program for the Study of Developed Coastlines at Western Carolina University said studies have shown something similar happening on the other end of the fat, miles-long dredging pipe. Small to minute forms of ocean life — clams, crustaceans, sponges, worms and much tinier creatures — are vacuumed from the ocean floor, dumped on the beach and buried under sand, killing them. The dredged area where life has been removed sometimes fills with silt, further delaying its recovery.
Governments are planning to continue dredging ocean sand onto beaches for at least another half-century, so there is a danger it will create enough dead-zone acreage to adversely affect the richly complex coastal web of life. Recreational and commercial fishers say it already is.
Hundreds of sand ridges line the Mid-Atlantic Ocean bottom. They’re the dunes, beaches and barrier islands of an ice age tens of thousands of years ago. That means they have sand exactly the right size and composition for beach replenishment. And that means they’re the preferred sand source for such projects.
Biologists and fishing experts say the underwater sand ridges are also especially rich with life, which makes them preferred fishing grounds. They say dredging can destroy that life and ruin the fishing grounds.
Unfortunately, the science on this issue is thin. Details on dredging’s effect on living ocean ridges and even beaches aren’t known. An environmental review of planned dredging of a ridge off Manasquan, for example, found “no significant impact.”
Steps to minimize the creation of dead zones could include making the effect of dredging on beach and ocean floor life a significant part of the consideration. Maybe some ridges have more biomass, maybe the ones closer to shore that are fed by the richness of the nearby coastal habitat.
Beach-replenishment projects, of course, also prefer to mine sand from ridges closer to shore, which reduces the already high cost. A better understanding of the long-term effects of dredging might support doing more of it from the 800 million cubic yards of available sand in federal waters at least 3 miles off New Jersey, and less from the 450 million cubic yards in closer state waters.
To cover the higher costs, government might consider an assessment on barrier-island properties, which are the beneficiaries of the massively expensive projects. People living inland already chafe at the amount of general tax revenue spent on coastal communities, so barrier-island user fees would help maintain society’s support for such projects. Replenish it, sort of.