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Reefs, mangroves and swamps at risk of “drowning” due to sea level rise

Reefs, mangroves and swamps at risk of “drowning” due to sea level rise

Millions of people around the world depend on coastal ecosystems, but most of them will be prone to submersion due to rapid sea level rise if global warming exceeds 2°C above pre-industrial levels. This emerges from a study published in Natureled by Macquarie University (Australia).

To what extent this is the case was previously unclear Rising sea level increases their vulnerability and what thresholds should not be crossed. To assess this, the authors collected data from the last glacial maximum 19,000 years ago, as well as more recent data from various coastal ecosystems. The paleo records These included flooding of tidal flats and the emergence 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, such that the instability of currently protected coasts would be one of the consequences.

Neil Saintilan, researcher at Macquarie University

“Today, the vast mangroves and tidal marshes along the world’s coasts act as a line of sorts Protection from waves of storms “The retreat and narrowing of these habitats will expose more areas to erosion, so the instability of the currently protected coasts would be one of the consequences,” he told SINC. Neil SaintilanResearcher at Macquarie University and lead author of the study.

“Another important contribution of these wetlands is to support fisheries,” he adds. The fragmentation and loss of these ecosystems is likely to have some impact on wild fisheries.”

The study considered projected sea level rise in different scenarios. These increases ranged from 4 mm to over 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 between 2080 and 2100.

If warming reached 3.0°C, almost all mangroves and coral reef islands of the earth and 40% of the mapped tidal marshes will experience a rise of more than 7 mm per year.

Solomon Islands. /Simon Albert

Because of this, there will most likely be destabilization of coral reefs from increased coastal erosion and wave inundation, and tidal flats 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”Saintilan points this out.

“Some are already disappearing in parts of the world where sea levels are rising rapidly. In the group of Solomon Islandstectonic movements have led to an increase in Sea level quite rapidly in recent decades, and several have been lost. With a 2.0°C rise in temperature, a much larger proportion of coral islands are exposed to these rates,” he points out.

How should we proceed?

The results show that the thresholds of an unsafe workspace for coastal ecosystems they are converging and will be determined by future emission trajectories.

“In tidal marshes and mangroves, they establish root systems that expand the swamp area upwards. Coral reefs can also grow vertically and still protect coral islands from wave attack. There are other coastal habitats (rock platforms or beaches) but they do not undergo a biological adaptation process to sea level rise. “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, in particular due to the salinity of drinking water

Neil Saintilan

The work underscores the importance of mitigating local environmental stressors such as coral reef pollution and the importance of restoring deforested and degraded wetlands to increase resilience to climate change and coastal recession.

“Unfortunately, the population in some places is already leaving the small island states due to the effects climate change, especially due to the salinity of the 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 and increase erosion in other areas.”

The authors also propose to achieve the goals of Paris Agreement Achieve zero net emissions by mid-century as the most effective means of minimizing disruption to these important ecosystems.

“Basically, we must also ensure that we do not ensure that the land sinks faster by removing drinking water, which contributes to the rapid rise in sea levels in many countries in Southeast Asia,” concludes the expert.

Reference:

Neil Saintilan et al. “Wide warming above 1.5°C is likely to result in large-scale coastal habitat retreat,” Nature.

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