Millions of people around the world depend on coastal ecosystems, but most of them will be vulnerable to being submerged due to rapid sea level rise if global warming exceeds 2°C above pre-industrial levels. This is indicated by a study published in Natureled by Macquarie University (Australia).
Until now it was not clear to what extent this Rising sea levels increases their vulnerability and what thresholds should not be crossed. To evaluate it, the authors collected data on the Last Glacial Maximum, 19,000 years ago, and more contemporary ones from different coastal ecosystems. The paleoregistros they included the drowning of mudflats and the formation of mangroves; current, ground records at a global network of reference points that includes 477 tidal marsh stations and 190 mangrove stations. The work also includes the size changes of 872 coral reef islands.
The retreat and narrowing of these habitats will expose more areas to erosion, so the instability of currently protected coasts would be one of the consequences.
Neil Saintilan, scientist at Macquarie University
“Today, the extensive mangroves and tidal marshes of the world’s coasts act as a line of protection against waves of the storms The retreat and narrowing of these habitats will expose more areas to erosion, so the instability of currently protected coasts would be one of the consequences,” he explained to SINC. Neil Saintilana scientist at Macquarie University and lead author of the research.
“Another important contribution of these wetlands is the support for fishing,” he adds. The fragmentation and loss of these ecosystems is likely to have some impact on wild fisheries.”
The study took into account predicted sea level rise under various scenarios. These increases ranged from 4 mm to more than 10 mm per year. At 2.0°C, researchers have calculated that the area of tidal marshes exposed to a 4mm annual sea level rise could double from 2080 to 2100.
If warming were to reach 3.0°C, almost all mangroves and coral reef islands of the world and 40% of the mapped tidal marshes will be exposed to a rise of more than 7 mm per year.
Solomon Islands. /Simon Albert
For this reason, coral reefs will most likely become destabilized due to increased coastal erosion and wave overflow, and mudflats and mangroves will drown.
“There are several important island groups associated with coral reefs. Among them are the Solomon Islands, Tuvalu, Kiribati, Micronesia, French Polynesia and the Maldives”aims at Saintilan.
“Some are already disappearing in those parts of the world where sea level rise is high. In the group of Solomon Islandstectonic movements have caused a rise in the sea level fairly rapidly in recent decades, and several have been lost. With a 2.0°C rise in temperature, a much higher proportion of coral islands are exposed to these rates,” she emphasizes.
How should we proceed?
The results show that the thresholds of an unsafe operating space for coastal ecosystems they are getting closer and will be determined by future emissions trajectories.
“In the case of tidal marshes and mangroves, they build root systems that expand the marsh upwards. Coral reefs can also grow vertically and still protect coral islands from wave attack. There are other coastal habitats (rocky platforms or beaches), but they do not have a biological process of adjustment to the rise in sea level. The fact that the chosen habitats can be adjusted has sparked a debate about the upper limits of this response”, says the scientist.
Unfortunately, in some places the population is already leaving the small island states due to the effects of climate change, especially due to the salinization of drinking water
The work highlights the importance of mitigating local environmental stressors, such as coral reef pollution, and the need to restore cleared and degraded wetlands to increase resilience against climate change and coastal recession.
“Unfortunately, in some places the population is already leaving the small island states due to the effects of the climate change, especially due to the salinization of drinking water. In some parts of the planet it is possible to armor the coast (hard walls to protect property), but often they can make the problem worse, increasing erosion in other areas”.
The authors also propose to meet the objectives of the Paris Agreement zero net emissions by mid-century as the most effective means of minimizing disturbance to these important ecosystems.
“Something fundamental to do is also to make sure that we are not causing the land to sink faster by extracting drinking water, which contributes to the rapid rise in sea levels in many countries in Southeast Asia,” concludes the expert.
Rights: Creative Commons.
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