Localised warming, however, even to the tune of just a few degrees, can be bad news for other less generalist species than humans. Although many species are capable of adapting their behaviour and physiology to new temperature ranges, many more require very specific conditions to survive. Such species typically live in high biodiversity areas, like rainforests, where each species fulfils a very particular ecological niche – eating specific species, foraging or hunting using a very specific method, living in specific places, and so on. This means that small changes, if they occur too quickly for a population to adapt, can have profound consequences.
In Queensland, Australia, for example, the rainforests are home to a great diversity of possum species. One of these species, the green ringtail possum, P. archeri, (pictured) is found only at elevations above 300m limited by its inability to successfully regulate its body temperature at warmer lower altitudes. This is because it has ‘adaptive heterothermy’, meaning that as temperatures rise above and beyond 30°C it ceases to increase its rate of perspiration, in an attempt to avoid severe dehydration. The narrow ecological niche of the green ringtail possum restricts it to the forest canopy, where it obtains most of its fluid from eating foliage. Poisonous compounds in the leaves it eats – a defence against overgrazing – stop the possum from quickly rehydrating itself, eating less often so it has time to break down the harmful compounds it ingests. These possums evolved over many millennia to take advantage of a highly stable ecosystem and climate, which favoured adaptive heterothermy. But with localised warming in the Queensland region, this fine balance is being disturbed, and the green ringtail possum and other species are being constrained to smaller and smaller territories at higher altitudes, which can’t support the same number of possums.
Relevant studies: Krockenberger et al. (2012) ‘The limit to the distribution of a rainforest marsupial folivore is consistent with the thermal intolerance hypthesis’; Benning et al. (2002) ‘Interactions of climate change with biological invasions and land use in the Hawaiian Islands: Modeling the fate of endemic birds using a geographic information system.’