Photo by Paul Wellman
When seawalls are constructed on an eroding coastline they cause the beach to narrow through a process known as passive erosion. Not surprisingly this compression of the beach ecosystem squeezes out the intertidal zone. The result?....
Fewer macroinvertebrates (we call them beach fleas or beach hoppers). It turns out these little guys play a critical role in food web of beaches by devouring kelp that washes ashore and by providing a food source for birds.
Jenny Dugan, a researcher at UCSB, has measured and quantified this effect. She found that:
Shorebirds were more than three times more prevalent in non-armored beaches. Those with sea walls yielded significantly fewer macroinvertebrates as well as intertidal zones — the middle area between the high- and low-tide points on a beach — that were 47 to 67 percent narrower that those of their “unprotected” counterparts. Basically, what Dugan’s research proved was what many a beachgoer has long suspected or at least detected: The beaches in front of sea walls are different.
Read more in this great article from the Santa Barbara Independent:
Life and Death in the Sandy Shadows of Coastal Armor