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Prolonged heat stress has a dramatic effect on wildlife and ecosystems


 Prolonged thermal stress , connected to dehydration and the impossibility of dissipating heat, can have dramatic effects on wild animals, especially birds, up to death . To avoid this unfortunate outcome, it would be enough to have some precautions in the design and construction of the structures intended to house them.

Here is the conclusion reached by the researchers of the University of Milan and the University of Padua who, together with the Higher Institute for Environmental Protection and Research ( ISPRA ), the CNR-IRSA and the Province of Matera , have just published the results of the empirical experiment in Global Change Biology , in Open Access.

The increase in the frequency and intensity of heat waves in the Mediterranean area in recent years, a consequence of the current climate crisis, is in fact having profound repercussions on the biodiversity of this area, but the study of the effects of extreme events is however complicated by the their relative temporal unpredictability and requires long-term studies.

The study was conducted in Matera during the heat waves that hit southern Italy in June 2021 and 2022, where temperatures above 37°C were recorded for several consecutive days, extreme temperature conditions never encountered in this area in the previous 20 years. The researchers tested an innovative nest cooling methodology , to experimentally quantify the effect of exposure to intense and prolonged heat waves on the reproductive success of a species of colonial bird of prey characteristic of the Mediterranean regions, the lesser kestrel ( Falco naumanni ) .

In fact, Matera hosts one of the largest breeding colonies of this species in the world, with about a thousand nesting pairs, and is an integral part of the city's cultural heritage. Once extremely abundant, the lesser kestrel is a small migratory bird of prey (about 140 g) of conservation interest at European level , protected by the Birds Directive , which suffered a drastic decline in populations in the second half of the last century, caused by agricultural intensification and by drought events in the Sahel region where it spends the winter.

In the Mediterranean regions, the species nests in urban areas, in cavities of buildings, monuments and rock faces, and often frequents nest boxes purposely positioned by researchers to study its ecology and reproductive behavior and to favor its conservation.

The experimental cooling took place by simply shading the nest boxes , which made it possible to lower the internal temperature of the nest boxes by about 4°C compared to the unshaded ones. The reproductive success of the species in the unshielded nest boxes has been dramatically reduced: only a third of the eggs laid have generated chicks ready to fly, while in the shaded nest boxes this value is within the norm (about 70%). In unshaded nest boxes there have been widespread episodes of chick mortality, all in correspondence with the hottest days(with air temperature higher than 37°C in the shade and internal temperatures of the nest boxes higher than 44°C), while such events were very rare in the shaded nest boxes. Furthermore, chicks raised in shielded nest boxes were found to be in much better physical condition and larger in size, characteristics which promote their survival once fledged.

" These results highlight how phenomena of extreme temperatures, extremely rare in the past and in some cases never recorded before, can have profound and very rapid effects on wild animal populations. Given that climate change scenarios predict a further increase in the frequency and intensity of heat waves in the coming decades, particularly in the Mediterranean region, this could pose a further serious threat to the biodiversity of the affected regions," explains Professor Diego Rubolini from the 'University of Milan.

Among other things, the current persistence of the African anticyclone has led to even warmer conditions in 2023 than in 2021-2022 and the preliminary results of our monitoring activities indicate an even worse effect on lesser kestrels than previously observed.

" These results also suggest that limited considerations in the design and construction of structures intended to house wild animals, such as an increase in the thermal insulation of the nest boxes, should be carefully considered as they can significantly favor the success of conservation projects in one global warming scenario ," concludes Professor Andrea Pilastro , from the University of Padua.

The study was carried out with the partial support of the LIFE funding program of the European Community ( LIFE FALKON project ) and of the MUR ( PRIN 2017 ).

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