While the world’s attention is focussed on the disaster engulfing Houston, and thousands are dying in less publicized floods in India, Bangladesh, and Sierra Leone, scientists have revealed that Hurricane Sandy would have been even worse without wetlands. The lessons learned from that storm may eventually be shown to be relevant for those occurring now.
Wetlands and reefs can soften storm surges, reducing the amount of water that comes ashore. However, it is one thing to know this and another to quantify the protection they provide. By mapping the damage done by Hurricane Sandy in 2012 across all 12 affected states, Dr Siddharth Narayan of the University of California Santa Cruz and colleagues concluded that natural wetlands saved America $625 million dollars. Their results are published in Scientific Reports.
Focusing on a single example, the salt marshes of Ocean County, New Jersey, the authors found a 16 percent reduction in flood damage, not just from Hurricane Sandy, but on an annual basis. Buildings sited closer to the waterline benefited from the presence of the marshes the most.
Preserving wetlands is not always easy. Coastal locations are often prime targets for real estate developers, and faced with rising sea levels, salt marshes may need active maintenance that doesn't come cheap. A quarter of New Jersey's salt marshes have been lost to development over the last century. Although many value fens' natural beauty and role as habitat for vulnerable species, sometimes it is only when wetlands' economic value can be demonstrated that these sites win protection.
In the context of the estimated $46 billion cost of Sandy, the marshes' contribution was a drop, if not in the ocean then at least in a wetland. Nevertheless, over the course of many storms, the value adds up. Moreover, the contribution would have been a lot higher were it not for the fact that the most potentially protective wetlands had already been destroyed.
In New York state, for example, intact marshes were estimated to have reduced damage by $140 million – just 0.4 percent of the state's losses. However, with surviving wetlands covering only 2 percent of the state's coastal floodplain, it's hardly surprising they couldn't provide much benefit. New Jersey has, proportionally, five times as much coverage, and reaped a much greater benefit in both absolute and relative terms.
By zooming in on where the greatest losses were avoided by postcode, Narayan has provided a guide to assessing which wetlands are most important to preserve or even recreate.
The problem with studies such as these is that the findings only come out long after the world's attention has moved on. In this case, however, the coincidence of the timing when so many places are under water may ensure it gets noticed.