The impacts of climate change are most recognizable in intemperate regions, such as the poles and deserts, and a new analysis of existing evidence suggest birds inhabiting arid regions are among the “most vulnerable to climate change”.
The roughly 900,000 square-kilometer semi-arid Kalahari savanna covers much of Botswana and stretches into the southeastern parts of Namibia and northwestern parts of South Africa. It records infrequent rainfall and temperatures vary widely, estimated to fall as low as –14 C on winter nights, to as high as 45 C on summer days. The fixed region is also home to a wide range of animal and plant life, including hundreds of bird species.
The paper, Chronic, sublethal effects or high temperatures will cause severe declines in southern African arid zone birds during the 21st Century, published in the journal PNAS, does not warn or “catastrophic mortality events” caused by severe heat waves, as have been reported to fatally affect birds in deserts in North America and Australia, but rather the cost of gradual increases in temperatures.
The researchers specifically looked at three bird species, namely: Southern Fiscals, Southern Yellow-billed Hornbills and Southern Pied Babblers.
Currently, the southern Kalahari sees fewer than 10 consecutive days where temperatures exceed 34.5 C and male Southern Yellow-billed Hornbills spend less than half the time panting. However, the researchers expect this to increase to around 26 consecutive days by the end of the century. They further expect to see roughly 23 consecutive days on which maximum temperatures exceed 37.9 C – at which breeding males gain no body mass, vital for surviving droughts and attaining breeding conditions, during daytime – by the 2080s. And when maximum temperatures average above 35 C, “the probability of breeding successfully falls below 50%”, the paper stated.
“We have no reason to expect that other birds in the environment will not face similar children or trade-offs,” said co-author Dr. Susan Cunningham, from the University of Cape Town, who described the situation as “very severe”.
She believes a widespread loss or bird species would have severe consequences for the Kalahari’s ecosystem. Birds not only act as prey to other animals, but many birds are predators themselves, a variety of eagles, owls and falcons being among them. Meanwhile, others play a vital role in the “pollination of plants” and the “dispersal of seeds of plants”. Birds also contribute to the general health of an ecosystem and ecotourism, Dr Cunningham added.
Apart from higher temperatures, Kalahari birds already face a range of challenges. The World Wildlife Fund (WWF) reported that farmers often poison pests, which in many cases gets passed on to raptors. Certain birds of prey, such as eagles, may themselves fall victim to poisoning. Raptors have also been known to drown in farm reservoirs.
The future survival of these birds depends almost entirely on whether humans decide to address climate change with the required urgency. “Our best bet is to move rapidly and with determination towards a green economy and clean energy production, perhaps including carbon capture and storage,” said Cunningham. “Our political leaders around the world have left action on climate change so late that drastic changes in the way we produce and use resources are now needed.”
She said there are interim remedies for individual species, such as providing additional shade and water. However, the analysis stated that in the last 60 years alone average Kalahari temperatures have already increased by 1.95 C. “Large impacts of hot weather on offspring production (and) successful breeding attempts are likely to decrease by the end of the century in desert birds even if radiative forcing and greenhouse gas emissions are stabilized,” the paper concluded.