The world’s natural coastlines, teeming with vital ecosystems like mangroves, tidal marshes, and coral islands, play a pivotal role in safeguarding our environment. These habitats provide essential services, such as supporting fisheries, protecting against wave impact, and filtering pollutants. However, the profound impacts of global warming and escalating sea levels are putting these ecosystems at risk.
Recent research has illuminated a remarkable phenomenon: wetlands have the capacity to respond to rising sea levels by bolstering their root systems, simultaneously drawing carbon dioxide from the atmosphere. This revelation has sparked enthusiasm for the concept of “blue” carbon sequestration, propelling restoration initiatives for mangroves and tidal marshes.
While these ecosystems have demonstrated remarkable resilience, their endurance does have boundaries. The quest to determine the upper limits of mangrove and marsh resilience in the face of accelerated sea level rise is a subject of significant interest and debate.
In a groundbreaking study published in the journal Nature, research delves into the vulnerability and exposure of mangroves, marshes, and coral islands to rising sea levels. The findings underscore the critical importance of curbing global warming within 2 degrees of the pre-industrial baseline. The comprehensive research amalgamated all available evidence on the response of mangroves, tidal marshes, and coral islands to sea level rise. This encompassed:
1. Geological investigations into how coastal systems reacted to previous sea level rises during the last Ice Age.
2. Utilization of a global network of survey benchmarks situated in mangroves and tidal marshes.
3. Analysis of satellite imagery to discern changes in the extent of wetlands and coral islands at varying sea level rise rates.
Collectively, the international research team scrutinized 190 mangroves, 477 tidal marshes, and 872 coral reef islands across the globe. Subsequently, computer modeling was employed to gauge the extent of exposure these coastal ecosystems would face under projected scenarios of warming.
Mangroves, tidal marshes, and coral islands exhibit resilience against modest sea level rise rates, remaining stable and flourishing. Most notably, it was discovered that these ecosystems are keeping pace with the current rates of sea level rise, approximately 2–4mm per year. Even coral islands appear stable under these conditions.
However, some regions experience land subsidence, amplifying the relative rate of sea level rise. In such areas, the rate could double, exceeding the 2–4mm range, akin to what is anticipated under future climate change. In these instances, research revealed marshes struggling to match the pace of sea level rise, progressively succumbing to inundation and, in some cases, disintegration. Strikingly, these rates parallel the historical records of marsh and mangrove submersion.
These scenarios offer a glimpse into the future within a warming world. If the rate of sea level rise accelerates to 7 or 8 millimeters annually, the likelihood of mangroves and tidal marshes falling behind becomes “very likely” (90% probability), with coral islands facing “likely” (approximately 67% probability) rapid transformations. These rates will materialize once we surpass the 2.0℃ warming threshold.
Even at the lower rates of sea level rise, which would be observed between 1.5℃ and 2.0℃ of warming (4 or 5mm per year), extensive loss of mangrove and tidal marsh ecosystems is anticipated. Notably, tidal marshes, owing to their occurrence in regions where the land is rising, face lower exposure to these accelerated sea level rise rates than mangroves.
As the research highlights, the preservation of these critical coastal ecosystems hinges on our ability to mitigate global warming. The urgency to curb emissions and adhere to temperature targets is paramount to secure the continued vitality of these ecosystems that play an indispensable role in preserving our planet’s health.
News Mania Desk / Agnibeena Ghosh 5th September 2023
