Global study shows major seagrass losses around the world

July 06, 2021

Jillian Dunic’s curiosity about seagrass reaches all the way back to her high school science fair experiment on eelgrass, a species of seagrass. Now a PhD student in the Department of Biological Sciences at SFU, Dunic has leveraged the work of researchers around the world to create an exhaustive study on the state of 547 seagrass sites around the globe.

Dunic says that seagrass doesn’t get much attention because their beds are on the bottom of the sea, out of sight of most people. However, they are an important part of the coastal ecosystem as a provider of habitats for small fish such as cuttlefish, shellfish, rays, seahorses and pipefish and a key food source for migratory birds such as ducks, geese and swans. Seagrass beds can be found on every continent in the world except Antarctica and are also critical to improving water quality and storing carbon.

Dunic and her team applied time-series reconstruction to seagrass meadows of 547 sites worldwide that span the last 70 to 130 years and cover 29,283 square kms around the world.

She found that declines in seagrass meadow area has been widespread and substantial over the last century — with 19 per cent of surveyed meadows lost since 1880. “The top two drivers of loss of seagrass meadows are coastal development and water quality,” she says.

Of the seven bioregions that Dunic identified, only two (Mediterranean and Temperate North Atlantic East) have stabilized and have shown a recovery trajectory as of 2000.  “The four bioregions with greatest net losses of area in our study are the Tropical Atlantic, Temperate Northern Atlantic East, Temperate Southern Oceans and Tropical Indo-Pacific.”

Dunic says that the paper also highlights the lack of information available on the status of seagrass beds world-wide. But she is hopeful that things will change, particularly in Canada.

“Research in marine sciences in Canada seems to be moving in the direction of including cumulative impacts and multiple stressors when managing our oceans. I think this paper further indicates that we need to look locally at the specific drivers and impacts on seagrass to improve management of this ecosystem.”

While Dunic’s research highlights the peril facing most seagrass beds, she says that there is still much to be learned. “Our study is the most comprehensive to date, but it still represents only one-10th of known seagrass areas so we can’t say whether our findings are reflective of those unstudied areas.”

She adds, “This study is key to identifying vulnerable sites and regions where monitoring the range of shifts in seagrass should be expanded to allow for improved management.”

Co-author and supervisor Isabelle Côté says, “This is an important paper that will be cited for years to come. We hope it will put seagrass on the map – pun intended – for marine managers, decision-makers and everyone who cares about the ocean.”  

Read the paper here: Global Change Biology