Rats and gerbils to thrive while larger animals like rhinos and eagles will die out in the next 100 years, study says

‘By far the biggest threat to birds and mammals is humankind’

As humans continue to destroy the habitat of larger creatures, the average animal size is set to "shrink" by 25 per cent over the next century, according to a new study.

Larger, less adaptable, slow-lived species like tawny eagles and rhinos will become extinct, while smaller and adaptable creatures like rodents, dwarf gerbils and songbirds are likely to predominate, researchers at the University of Southampton said.

Unless radical action is taken to protect wildlife and restore habitats, whole ecosystems could collapse.

“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," said Rob Cooke, lead author of the study published in the journal Nature Communications.

“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 predicted declines are particularly large when compared to the 14 per cent body size reduction observed in species since the last interglacial period 130,000 years ago.

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.

They also 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.

Small, highly-fertile insect-eating animals that can thrive in a variety of habitats will be the most resilient, they found.

“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," said Felix Eigenbrod, a professor at the University of Southampton.

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.”

Additional reporting by Press Association