Coastal ecosystems are in danger from rising sea levels

Coastal ecosystems such as reefs, mangroves and salt marshes, are facing significant threats due to rising global temperatures. These ecosystems play a crucial role in island systems, as they have the ability to reduce wave energy, protect coastlines, and provide habitats for various species. Therefore, it is essential to take measures to preserve and protect these valuable ecosystems.

Coastal ecosystems are vital for millions of people around the world. However, if global warming exceeds pre-industrial levels by 2°C, many of these ecosystems and the communities that depend on them will be threatened by rapid sea level rise. It is important to take action to mitigate climate change and protect these valuable resources. This is indicated by a study published in Nature, led by Macquarie University (Australia).

Until now, it was not known with certainty how sea level rise affected the vulnerability of coastal areas and what limits should not be exceeded. The researchers collected data on the Last Glacial Maximum, which occurred 19.000 years ago, as well as more current data from different coastal ecosystems to evaluate this situation. Paleorecords are records that contain information about past events, such as the drowning of salt marshes and the formation of mangroves.

On the other hand, current records are obtained in real time through a global network of stations. This network includes 477 stations for monitoring tidal marshes and 190 stations for monitoring mangroves. The work also includes resizing 872 coral reef islands.

Coastal ecosystems as a line of protection

"Today, the extensive mangroves and tidal marshes on the world's coasts act as a line of protection against storm waves. 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.”explains Neil Saintilan, scientist at Macquarie University and lead author of the research.

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

The study considered different scenarios predicting sea level rise. Estimates ranged from 4 mm to more than 10 mm per year. According to the researchers, it is estimated that a temperature of 2,0 °C could double the extent of tidal marshes exposed to a rise in sea level of 4 mm per year between the years 2080 and 2100.

Temperature projections and their impact on coastal ecosystems

If global temperatures rise by 3,0°C, there will be serious consequences for mangroves, coral reefs and tidal marshes. Almost all of these ecosystems would be exposed to sea level rise of more than 7 mm per year, which could have a significant impact on biodiversity and coastal ecosystems.

Due to increased coastal erosion and wave overtopping, coral reefs are likely to become destabilized. Additionally, salt marshes and mangroves are at risk of flooding and drowning.

"There are several important island groups associated with coral reefs. These include the Solomon Islands, Tuvalu, Kiribati, Micronesia, French Polynesia and the Maldives.”says Saintilan.

"Some are already disappearing in those parts of the world where sea level rise is high. In the Solomon Islands group, tectonic movements have caused sea levels to rise quite rapidly in recent decades, and several have been lost. With 2,0°C temperature rise, a much larger proportion of coral islands are exposed to these rates", He emphasizes.    

What should we do?

The results obtained indicate that the limits of an unsafe operating environment for coastal ecosystems are increasingly closer and will depend on future emissions trajectories.

"In the case of tidal marshes and mangroves, they build root systems that expand the marsh upward. Coral reefs can also grow vertically and continue to protect coral islands from wave attack. There are other coastal habitats (rocky platforms or beaches), but these do not have a biological process of adjustment to the rise in sea level. The fact that chosen habitats can be adjusted has sparked debate about the upper limits of this response"says the scientist.

This study highlights the importance of addressing environmental stressors in the local environment, such as pollution of coral reefs. It also highlights the need to restore cleared or degraded wetlands, as this will help increase resilience to climate change and mitigate the negative effects of coastal recession.

Displaced by climate change

"Unfortunately, in some places people are already leaving small island states due to the effects of climate change, especially the salinization of drinking water. Coastal armoring (hard walls to protect property) is possible in some parts of the world, but can often make the problem worse by increasing erosion in other areas.".

The authors suggest that meeting the Paris Agreement goals to achieve net-zero emissions by mid-century is the most effective way to minimize disruption to these important ecosystems.

"A key thing to do is also ensure that we are not causing the land to sink more rapidly by extracting drinking water, which is contributing to the rapid rise in sea levels in many Southeast Asian countries.", Concludes the expert.


Neil Saintilan et al. “Widespread retreat of coastal habitat is likely at warming levels above 1.5 °C”, Nature.

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