An international team of scientists, including Leonida Fusani and Ivan Maggini from the Konrad Lorenz Institute of Ethology of the Vetmeduni, conducted a review of literature on the response of tropical birds to thermal variation, with a focus on their vulnerability to warm conditions. The team used an integrative or synthetic review approach, which involved searching online databases for relevant studies. They analyzed the empirical data from the retrieved studies and tied it together with the physiological processes that can confer vulnerability or resilience to answer questions about the thermal tolerances of tropical birds and their vulnerability to global warming.
The scientists explored the influence of microclimatic alterations, such as those caused by land-use change and humidity, on physiological vulnerability. They identified knowledge gaps and suggested future research directions to guide comprehensive analyses of tropical bird vulnerability to the effects of global warming. The team emphasized the importance of addressing the void of knowledge on the physiological response of tropical birds to global warming before attempting to relate distributional rearrangements to thermal sensitivity, as previously recommended.
They were able to confirm that the assumption that tropical species are more sensitive to climate change due to low physiological capacity to withstand temperature fluctuations and being near their limits of heat tolerance under current climatic conditions is not a fundamental characteristic of tropical birds, as indicated by evidence from the literature. While community-level rearrangements such as biotic attrition and elevational shifts have been observed in birds, there is no consistent evidence of direct physiological sensitivity to warming. Before examining the relationship between distributional changes and thermal sensitivity in tropical birds, it is crucial to address the lack of understanding regarding their physiological response to global warming.
More research is needed to understand how different ecological contexts affect the response of populations and species to warming, which would provide a better understanding of current and future community rearrangements in tropical birds. It is predicted that tropical communities will be affected more by climate change than those in higher latitudes, leading to frequent redistributions of tropical communities and turnovers benefiting warm-adapted species, leading to the thermophilization of communities. While it is commonly assumed that thermal sensitivity is the main driver of these rearrangements, empirical evidence from physiological studies is limited, especially for tropical endotherms like birds.
In conclusion, the researchers suggest that many tropical bird species possess sufficient physiological resilience to withstand thermal variation within the range of predicted future warming levels. Tropical birds are not necessarily more physiologically threatened by warming in the short term than birds residing at other latitudes. Nevertheless, some avian species in arid regions outside the tropics, such as southern Africa, Australia, the North American southwest, and the Iberian Peninsula, may face more imminent threats due to rising temperatures.
This does not mean, however, that tropical birds are entirely insensitive to warming, especially if the local average temperature increases by 5°C as predicted in worst-case scenarios. For instance, birds living in open areas and relying on gradients for passive heat dissipation would need higher levels of hyperthermia, which can prove challenging. (Hyperthermia is a condition where the body temperature rises above the normal range. In animals, including birds, this can occur due to exposure to high temperatures, which can lead to overheating and other physiological stresses) Also, birds inhabiting hot and arid or semi-arid environments that experience reduced or absent water sources during heat waves are equally vulnerable. Furthermore, climate-driven variations in rainfall regimes can cause more intense wet and dry seasons, altering the frequency of stronger humid-heat events and extending the dry season. Although climate change is a significant concern, it must be emphasised that anthropogenic habitat loss and degradation remain the major imminent threats to biodiversity. Land-use changes not only directly affect tropical bird diversity but also reinforce climate-driven threats by altering the microclimate.
To protect tropical bird diversity, the most promising approaches are to preserve vast forested areas along ecological gradients and to improve land management strategies.
The article "Physiologically vulnerable or resilient? Tropical birds, global warming, and redistributions" by Otto Monge, Ivan Maggini, Christian H. Schulze, Stefan Dullinger, and Leonida Fusani was published in Ecology and Evolution.