The coastlines of Massachusetts and other eastern states have been battered recently by severe storms ranging from hurricanes to blizzards. These fierce storms may be increasing in both intensity and frequency because of global warming. Adapting to these changes will not be easy, particularly in these congested zones of high population densities.
While property damage has been extensive, erosion has also taken its toll on coastal banks, dunes, and shorelines. These dynamic regions are always changing and shifting, sometimes in small, incremental ways and other times in dramatic alterations. In the past the solutions have included a number of engineered structures such as jetties, seawalls, and riprap. But we now know that these structures will exacerbate the erosion problem. They focus wave energy on small sections of a beach, channeling and removing existing sand.
I can remember local campaigns many years ago in which we placed our discarded Christmas trees on dunes in an effort to stabilize the movement of sand from wind and storms. Again, good intentions don’t always make good science. The Christmas trees prevented the growth of dune plants which can send out roots and rhizomes to hold the sand in place while also growing surface leaves that can block the damaging effects of wind.
We now understand that the most stable dune or bank is a vegetated one. We also know that stability increases with a vegetation cover that is diverse and not just a monoculture of beach grass (Ammophila breviligulata). Imagine the analogy to a wheat field. If you grow wheat exclusively then whatever likes to consume wheat will also increase. Consequently, we resort to chemicals such as pesticides to control such pests. Monoculture crops are highly vulnerable to herbivores and disease.
If, on the other hand, you grow a diversity of species, then you reduce the incidence of a crop failure. The same is true on a sand dune or coastal bank. Both primary and secondary dune systems benefit from a variety of species including seaside goldenrod (Solidago sempervirens), dusty miller (Artemisia stelleriana), and beach plum (Prunus maritima). These plants trap moving sand particles, stabilize the system, and provide cover and food for wildlife. They are adapted to coastal storm activity, though even the hardiest of any species is vulnerable in a massive hurricane or blizzard. They certainly are a more cost-effective way of protecting a shoreline compared to groins, jetties, and seawalls. When one considers the billions of dollars needed to repair buildings and other structures after a severe storm, a program of selective plantings is a successful way of reducing erosion.
Copyright Gil Newton 2009 Thanks to Chris Dumas for logo image.