A new study shows that beach replenishment harms invertebrates and coastal ecosystems.

In order to battle beach erosion, beach replenishment has become an easy and popular choice, but experts believe it does damage to intertidal invertebrates that are vital for coastal ecosystems.

A research team from the University of California, San Diego has found that dumping offshore sand to an eroding beach has significantly reduced the population of invertebrates 15 months after beach replenishment. Polychaetes, a class of ringed worms, were particularly affected.

The scientists chose eight Southern California beaches to measure the abundance of biodiversity. A control plot and a beach replenishment plot were set up in each of the beaches. Measurements were made after four, 12 and 15 months.

The researchers say the diminishing of numbers of these invertebrates are hurting the ecosystem because this results in unavailability of prey for fish and shorebirds. 

The study came about after the San Diego Association of Governments (SANDAG), together with the U.S. Army Corps of Engineers, replenished eight beaches that covered about 1.76 cubic meter (62 cubic feet) of sand. In the project, each beach was only partially replenished to allow birds and fish to forage.

"This provided the strongest experimental system yet to assess the effects of replenishment," said Joshua Kohn, a professor of biology who headed the study published in the journal Estuarine, Coastal and Shelf Science. "With replenished and control sections of each beach, we could assess both the general effects of replenishment as well as variation among beaches in their invertebrate communities and responses to replenishment."

The study also shows that, although some animals were able to recover from initial losses, the tiny worms failed to do so after 15 months.

Scientists suggest that further studies are necessary to identify the length of the negative effects. Study author Tyler Wooldridge expressed that studies should also include the extent of beach replenishment one can do and if it should be done on a particular season.

 In 2014, a beach replenishment project in New Jersey paved the way for the discovery of a rare arrowhead that dates back to 10,000 years ago.