Small creatures will rule in a world dogged by climate change

23 May 2019

Image: © kulthiwat/

Over the next century, researchers predict that small creatures and mammals will significantly outnumber large ones because of humanity’s influence.

If climate change is to continue unabated, life on Earth will rapidly get smaller in order to survive, according to a paper published to Nature Communications by a team from the University of Southampton. It forecast that over the next 100 years, smaller creatures and mammals that can thrive in a variety of habitats will come out on top.

Small, fast-lived, highly fertile, insect-eating animals will be the winners of this race to survive, including rodents such as the dwarf gerbil, and songbirds such as the white-browed sparrow-weaver. However, while there are winners, there will also be losers.

The research team predicted that larger animals – such as the tawny eagle and black rhino – will likely fall victim to extinction. Over the next century, the average body mass of mammals will collectively reduce by 25pc. This decline represents a large, accelerated change when compared with the 14pc body size reduction observed in species from the last interglacial period 130,000 years ago until today.

Extinction not ‘ecologically random’

“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.

“The substantial ‘downsizing’ of species … 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.”

Focusing on 15,484 land mammals and birds, the study considered five characteristics that relate to the role of each species in nature: body mass, litter/clutch size, breadth of habitat, diet, and length of time between generations.

Then, the team combined it with 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.

Prof Felix Eigenbrod added that the projected loss is clearly not “ecologically random” but rather “a selective process where certain creatures will be filtered out”.

The team now hopes to look in more detail at the longer-term effects of species becoming extinct on habitats and ecosystems.

Colm Gorey was a senior journalist with Silicon Republic