Mangroves are not adapting fast enough to escape the effects of rising sea levels and could disappear by 2050, according to a new study. This is because if greenhouse gas emissions continue unabated, these forests will not be able to keep up with the rate of sea level rise. These trees play an important role in storing carbon dioxide on Earth and protecting communities from storms and coastal erosion.
The study, published in the journal Science, found that mangroves are at risk of being submerged when sea levels rise by more than 6mm a year. Scientists say the threshold could be reached within 30 years if people do not reduce greenhouse gas emissions. Global sea levels are already rising at a rate of more than 3 mm a year, although in some places it has changed even more.
Mangroves have many benefits for human beings and the earth. Restoring mangroves is a way for scientists in places like Florida to try to protect coastal communities from climate change. “We have the opportunity to take action here to keep the rate of sea level rise below these critical thresholds, which is part of the reason for this important study,” said Erica Ashe, a postdoctoral scientist at Rutgers University and one of the study’s authors.
These trees can block destructive storm surges, prevent encroaching oceans from devouring more land, and shelter wildlife. In addition, mangroves store more carbon dioxide than rainforests of comparable size. Between 1980 and 2010, one fifth of the world’s mangroves died out. These trees can usually adapt to rising water levels by moving inland, but now human development along the coastline is hampering their development. The problem, known as “coastal squeeze,” is unfolding in Florida, where one of the most extensive mangrove systems on Earth is playing out. One of its largest estuaries, Tampa Bay, has lost almost half of its mangroves in the past century.
To find out what specific effects sea level rise has on mangrove survival, Ashe and her colleagues studied sediment cores at 78 sites around the world. This reveals data on mangrove growth over the past 10,000 years. There is not enough information on the impact of recent human-induced sea level rise (caused by melting ice and warm water expansion) on mangrove forests. So the researchers looked for when ancient mangroves appeared. They found that mangrove ecosystems only develop edify when sea level rise rates drop to about 7mm a year.
“Governments should find solutions to keep sea level rise below this threshold” to mitigate climate change and protect millions of people who depend on mangroves for shelter, flood control, food and fibre,” University of Queensland professor Catherine Lovelock wrote in an article commenting on the study. This means reducing the use of fossil fuels and giving mangroves more time and space to adapt to the changing world.