With global warming and extreme weather intensifying, can animals raise their thermal tolerance to cope with a continuously warming environment? A joint research project by the Division of Science at Lingnan University and an international research team conducted experiments on tropical intertidal snails that live under the scorching sun.
The team simulated real-world conditions of coastal rocks heating up under intense sunlight in the Hong Kong SAR and Singapore and discovered that the maximum temperatures of some rocks have approached the upper physiological thermal limit of these intertidal snails. Because this can cause cardiac arrest and an inability to maintain normal physiological functions, their thermal tolerance may not be able to increase indefinitely as the environment continues to warm. Extreme heat in the future may increase their risk of mortality.
The findings are published in the journal The Biological Bulletin.
Tracking heat on exposed shores
The research team, from the Division of Science at Lingnan University, the University at Buffalo, New York, the National University of Singapore and The University of Hong Kong, focused its study on rocky shore snails in the genus Nerita—tropical intertidal snails with high thermal tolerance—to understand how they cope with the stress of extreme heat on tropical rocky shores exposed to the blazing sun for prolonged periods.
The team selected six sites in the Hong Kong SAR and Singapore: Tai Tam, Stanley, Lung Kwu Tan and Pak Nai in Hong Kong, and Palawan Beach and the Rimau coast in Singapore. Temperature loggers were deployed to continuously monitor the rocks' surface temperatures for approximately one month.
When heat becomes physiological stress
The team collected 126 adult tropical intertidal snails of similar size from the six rocky shore sites: 62 Nerita undata and 64 Nerita yoldii, both belonging to the family Neritidae. The snails were brought to the laboratory for analysis.
Using a programmable water bath to simulate natural conditions on rocky shores in the Hong Kong SAR and Singapore as they heated up during low-tide exposure, the team attached infrared photocoupler sensors to the snails' shells. This allowed real-time monitoring of their heart rates and body temperature responses during the heating process, thereby estimating their upper physiological thermal limit and metabolic performance.
The results revealed that the snails' heart rates accelerated as their body temperatures rose, indicating an increased metabolic rate. However, when body temperatures reached approximately 40–45°C (104–113°F), their heart rates began to plunge sharply.
The team hypothesized that when organisms are exposed to extreme heat for prolonged periods, they may reduce energy consumption by lowering their heart rates and metabolic levels. The tests also found that when the snails' body temperatures rose to approximately 47.7–51.4°C (118–125°F), their hearts stopped beating and they could not maintain normal physiological functions. This indicates that this temperature range is close to the upper physiological thermal limit and that thermal tolerance may not increase indefinitely with continuously rising temperatures.
Singapore's thinner margin for survival
The team pointed out that rock temperatures in the Hong Kong SAR, where the maximum recorded temperature was around 50°C (122°F), are lower than those in Singapore. Temperatures in rock crevices and shaded microhabitats were generally below 42°C (108°F), providing a thermal buffer zone where the snails could shelter and cool down.
Their thermal tolerance in the experiment increased as environmental temperatures rose. But in Singapore's hotter climate, the maximum rock surface temperature reached 57°C (135°F), and even the crevices and shaded areas used for sheltering recorded temperatures exceeding 55°C (131°F)—comparable to the upper physiological thermal limit the team recorded.
Analysis showed that although the overall thermal tolerance of the Singapore population was higher than that of the Hong Kong SAR population, it did not increase further in the hotter habitat. This indicates that some tropical organisms may already have approached their upper physiological thermal limit and that more frequent extreme heat waves in the future may increase their mortality risk.
Rising costs of staying cool
Tommy Hui Tin-yan, the paper's first author and an assistant professor in the Division of Science at Lingnan University, explained that physiological thermal tolerance refers to an organism's capacity to withstand higher body temperatures without dying. Tropical intertidal snails typically move away from sun-exposed areas to shelter during low tides.
However, as extreme weather intensifies, they will have less time to forage for microalgae and biofilms on rock surfaces. Consequently, they must expend energy to maintain physiological functions while reducing energy intake because of restricted foraging, creating a vicious cycle of increased expenditure and decreased replenishment that exacerbates stress and risks to their survival.
Hui further explained, "Many people assume that organisms will adapt naturally to climate warming. However, the results of this study demonstrate that even tropical intertidal snails that live under the blazing sun for long periods and possess exceptionally strong thermal tolerance may not be able to cope with rising temperatures indefinitely.
"Whether in the Hong Kong SAR or Singapore, as habitats become increasingly hot, the buffer zone between the actual environmental temperature and the upper physiological thermal limit becomes narrower. Organisms may need to pay a higher energetic cost to maintain basic physiological functions, which limits their capacity to adapt to even hotter temperatures."
A warning beyond the shoreline
Hui noted that the study's findings also offer insights for human society. Global warming will extend periods of high temperatures, which may prolong the time people spend sheltering from heat in air-conditioned rooms. This intensifies global warming by increasing power consumption and affects other economic activities, such as agriculture, construction and logistics.
The high consumption and intensified warming parallel the vicious cycle faced by tropical intertidal snails. The impact of extreme heat on ecosystems is far greater than people imagine, and society should not assume that humans can adapt to global warming over the long term. Therefore, the challenges brought by climate change are no longer a distant threat, and more robust climate action is urgently needed.
More information
T. Y. Hui et al, How Does Local Temperature Shape Thermal Tolerance? A Test Using Congeneric Snails on Tropical Rocky Shores, The Biological Bulletin (2025). DOI: 10.1086/741537
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Citation: Tropical species near thermal limits as global warming compresses safety margins (2026, July 27) retrieved 28 July 2026 from https://phys.org/news/2026-07-tropical-species-thermal-limits-global.html
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