Animals set to ‘downsize’ over the next century as humans destroy their habitats

The animals of the world are set to ‘downsize’ during the next 100 years.

The change in diversity will happen as humans continue to destroy the habitats of larger creatures, according to a new study from the University of Southampton.

Scientists at the university say their study shows more adaptable and smaller animals – such as rodents and songbirds – are likely to predominate.

Rob Cooke, lead author of the study (which has been published in the journal Nature Communications), said: ‘By far the biggest threat to birds and mammals is humankind – with habitats being destroyed due to our impact on the planet, such as deforestation, hunting, intensive farming, urbanisation and the effects of global warming.

‘The substantial ‘downsizing’ of species which we forecast could incur further negative impacts for the long-term sustainability of ecology and evolution. ‘This downsizing may be happening due to the effects of ecological change but, ironically, with the loss of species which perform unique functions within our global ecosystem, it could also end up as a driver of change, too.”

The research team focused on 15,484 living land mammals and birds and considered how body mass, litter/clutch size, breadth of habitat, diet and length of time between generations affect their role in nature. In addition, the researchers used the International Union for Conservation of Nature (IUCN) Red List of Threatened Species to determine which animals are most likely to become extinct in the next century.

A University of Southampton spokesman said: ‘The researchers predict the average (median) body mass of mammals specifically will collectively reduce by 25% over the next century.

‘This decline represents a large, accelerated change when compared with the 14% body size reduction observed in species from 130,000 years ago (the last interglacial period) until today.’ He added: ‘In the future, small, fast-lived, highly-fertile, insect-eating animals, which can thrive in a wide-variety of habitats, will predominate.’

‘These ‘winners’ include rodents, such as dwarf gerbil – and songbirds, such as the white-browed sparrow-weaver. Less adaptable, slow-lived species, requiring specialist environmental conditions, will likely fall victim of extinction. These ‘losers’ include the tawny eagle and black rhinoceros.’

Felix Eigenbrod, professor at the University of Southampton, said: ‘We have demonstrated that the projected loss of mammals and birds will not be ecologically random – rather a selective process where certain creatures will be filtered out, depending on their traits and vulnerability to ecological change.’

Amanda Bates, research chair at Memorial University in Canada, added: ‘Extinctions were previously viewed as tragic, deterministic inevitabilities, but they can also be seen as opportunities for targeted conservation actions.

‘As long as a species that is projected to become extinct persists, there is time for conservation action and we hope research such as ours can help guide this.’

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