Mangroves, known for their vital role in coastal ecosystems, have been found to exhibit remarkable tolerance to high temperatures, making them less vulnerable to the impacts of global warming compared to other species. A new study conducted by researchers from India revealed that mangroves have extreme heat tolerance without crossing their heat tolerance thresholds. By studying 13 mangrove species from Kerala, the researchers discovered that while the maximum leaf temperatures of these species exceeded the surrounding air temperatures, they remained safely below the critical limits. This discovery highlights the resilience of mangroves in the face of rising global temperatures.

Study Highlights Mangroves’ Heat Tolerance and Resilience

The study, published in the journal Science of The Total Environment, was conducted by the Kerala Forest Research Institute (KFRI) in partnership with the Indian Institute of Science Education and Research (IISER), Pune. The research focused on mangrove species along India’s southwest coast, specifically examining their ability to withstand increasing temperatures. Thirteen mangrove species were studied, including the river mangrove (Aegiceras corniculatum), white mangrove (Avicennia marina), Indian mangrove (Avicennia officinalis), and others like the Burma mangrove (Bruguiera gymnorhiza) and red mangrove (Rhizophora apiculata).

The researchers used specific metrics to assess heat tolerance, such as T50 values, which represent the temperature at which photosynthesis function declines by 50%. This decline, if surpassed, causes irreversible damage, eventually leading to leaf death. Thermal safety margins (TSM) were also measured to evaluate how far the species could tolerate rising temperatures before reaching their critical thresholds. These methods allowed the team to determine the resilience of each mangrove species in response to global warming.

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Insights on Mangrove Species’ Adaptation to Extreme Temperatures

According to Deepak Barua, associate professor at IISER Pune and co-author of the study, leaf temperatures in some species can exceed air temperatures by 10 °C or more. TSM is crucial for assessing a species’ vulnerability to future warming. The study found that T50 values ranged from 48.9°C in white mangroves to 55.32°C in upriver orange mangroves, with a mean T50 of 53.3°C across the 13 species studied. Species with broader leaves, like Burma mangrove and crabapple mangrove, demonstrated higher heat tolerance as they experienced greater leaf temperatures.

The study also revealed that the median heat tolerance of mangroves in the region was approximately 5°C higher than that of woody species from tropical, Mediterranean, and temperate regions. This highlights the exceptional ability of mangroves to endure higher temperatures. Additionally, the study recorded maximum leaf temperatures significantly above the maximum air temperature of 35.4°C observed during the study period. For example, maximum leaf temperatures ranged from 38.5°C in black mangroves to 41.4°C in Asiatic mangroves.

This elevated heat tolerance, along with the large thermal safety margins (TSMs), indicates that mangroves in the region are likely well-adapted to withstand extreme temperatures. According to Deepak Barua, this adaptation improves their chances of survival under future climate scenarios. Another of the study’s authors, Ashtamoorthy, recalled that since all the species studied are found in every corner of the globe, the outcomes of this study carry relevant implications for mangrove conservation and ecosystem restoration worldwide.

But Ashtamoorthy was cautious that although temperature might be considered an important factor in realizing heat tolerance, it is only a factor the study was trying out. He suggested that future research should explore the combined effects of other environmental stressors, such as high salinity and light intensity, to gain a more comprehensive understanding of the factors impacting mangrove survival.

Also Read: Why We Need To Conserve Mangroves?

To Conclude

The research conducted by the Kerala Forest Research Institute and IISER Pune throws light on an incredible tolerance of increased temperature by mangrove species on India’s southwest coast. Using T50 values and thermal safety margins, the scientists could gauge just how well these mangroves will hold up against rising temperatures. The findings in the new study show that a number of these species have a significantly higher tolerance for heat than woody plants in most other regions and, thus, are likely to be more resilient in the face of global warming. However, resilience alone is part of but not all of survival; it underlines the call for further research into other factors affecting their sustainable coexistence, such as salinity and light levels. The global significance of these findings emphasizes the critical role mangroves play in climate change adaptation and the need for continued conservation efforts to protect these vital ecosystems.

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