VUB study is first to map global dispersal and connectivity patterns in mangroves
Research provides important insights for better understanding the response of mangrove forests to global warming
Friday, February 1, 2019 — Researchers from VUB and NASA’s Jet Propulsion Laboratory have studied the global dispersal and connectivity patterns of mangroves, tropical coastal forests that are regularly flooded by the tides. Their findings, published in Proceedings of the National Academy of Sciences of the United States of America (PNAS), show that the trees’ seeds spread mainly along the coast but can also cross entire oceans via major ocean currents. These insights contribute to a better understanding of how mangroves – which serve a vital ecological function – can colonise new areas in a changing climate.
Mangroves produce seeds and fruits that can float for several days or months, and develop roots when stranding at a favourable place. Their buoyancy period, combined with ocean currents, determines both the spatial scale of dispersal and the genetic structure of mangrove populations.
Professor Nico Koedam from VUB’s Department of Biology and colleagues from NASA’s Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology (Caltech), used a numerical ocean model to simulate potential dispersal patterns of mangrove seeds and connections between mangrove populations worldwide.
“Studying the distribution of biological materials via ocean currents remains challenging, especially due to the large spatial scale,” says Dr Tom Van der Stocken, a VUB alumnus who now works at JPL. “To make a first estimate of global dispersal and connectivity patterns in mangroves, it seemed a logical next step to combine VUB’s mangrove expertise with the oceanographic expertise here at JPL, where we have high-resolution data of ocean surface currents and the necessary computing power.”
The research team found that while mangrove trees spread mainly via coastal currents, they could also cross the Atlantic, Indian and Pacific Oceans. Direct crossings of these oceans – which cover 70% of the earth’s surface – are possible via equatorial ocean surface currents, while in the Pacific, archipelagos such as Galapagos, Polynesia and Micronesia are important stepping stones between populations on both sides of this enormous ocean basin.
Breakwaters and champions in CO2 storage
This study helps to better understand the spatial shifts of mangrove forests in a changing climate. Mangroves, along with other wetland plants, provide an important natural buffer against storms, flood waves and coastal erosion. This means they protect vulnerable coastlines and coastal communities around the world against flood disasters, making them invaluable in an era of accelerating sea level rise and an increasing risk of coastal flooding. They also provide habitat for numerous animal species, many of which are of economic importance, and store up to four times more carbon than other tropical forests. Today mangroves and their ecosystem services are under threat from deforestation and coastal development.
Koedam: “Changes in the range of mangrove species have already been demonstrated in various areas around the world and are associated with changes in climate, among other things. By combining knowledge and instruments from biology and physical geography in our study, we are getting a better understanding of the underlying mechanism of these shifts.”
For more information, please contact:
Professor Nico Koedam (VUB, Biology)
02/629 34 13
Dr Tom Van der Stocken (JPL, Earth Science Section)
https://www.pnas.org/content/116/3/915?fbclid=IwAR2O7FJYJ3vwa218nlhXT8uiLPmCJGdJlY_nkI7pd0rOrGVYX7gHRO81_xc