The value of nature: seagrass beds save beaches and money

Seagrass (Thalassia testudinum). Image: James St. John.
Biodiversity

The Royal Netherlands Institute for Sea Research reports on recent research, carried out in the Caribbean, that shows how seagrass saves beaches and money by preventing erosion and reducing the need for artificial beach nourishment:

Seagrass beds are so effective in protecting tropical beaches from erosion, that they can reduce the need for regular, expensive beach nourishments that are used now. In a recent article in the journal BioScience, biologists and engineers from The Netherlands and Mexico describe experiments and field observations around the Caribbean Sea. “A foreshore with both healthy seagrass beds as well as calcifying algae, is a resilient and sustainable option in coastal defense”, says lead author Rebecca James, PhD-candidate at the University of Groningen and the Royal Dutch Institute for Sea Research (NIOZ), The Netherlands. “Because of erosion, the economic value of Caribbean beaches literally drains into the sea.”

The authors looked at beaches of the Caribbean Sea, where almost a quarter of the Gross Domestic Product is earned in tourism, mainly around the beaches. 

To find out to what extent seagrass beds are able to hold sand and sediment on the beach foreshores, James and her promotor, professor Tjeerd Bouma (NIOZ and Utrecht University), conducted a simple but telling experiment. With a portable and adjustable field flume to regulate water motion in a Caribbean bay, they observed when particles on the sea bed started moving. “We showed that seagrass beds were extremely effective at holding sediment in place”, James says. “Especially in combination with calcifying algae that “create their own sand”, a foreshore with healthy seagrass appeared a sustainable way of combating erosion.”

“By looking at beaches with and without protection of healthy seagrass beds, we showed that the amount of erosion was strongly linked to the amount of vegetation: more seagrass, meant less erosion”, co-author dr. Brigitta van Tussenbroek of the Universidad Nacional Autónoma in Mexico says. At beaches where seagrass beds were destroyed, the researchers saw a sudden strong increase in erosion, resulting in an immediate need of expensive beach nourishments.

The research was carried out by marine scientists from the Netherlands (NIOZ, Utrecht University, Radboud University Nijmegen, Technical University Delft and Deltares) and Mexico (Universidad Nacional Autónoma de México) and St. Eustatius (Caribbean Netherlands Science Institute). The resulting journal article was published this month in BioScienceMaintaining Tropical Beaches with Seagrass and Algae: A Promising Alternative to Engineering Solutions.

[Image: James St. John]

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