The world鈥檚 animals are collectively shrinking, as humans drive big beasts such as elephants and tigers extinct, with far-reaching consequences for ecosystems.
have shown bigger animals are at a greater risk of extinction and there is evidence humans have helped wiped out megafauna in the past, . Now an assessment of the next 100 years has found that habitat destruction, poaching and other human pressures will cause mammals and birds to experience 鈥渟ubstantial ecological downsizing鈥�.
Researchers ran a thousand scenarios on the future of the 15,500 species on the Red List of endangered species. Each species was assigned a probability of extinction by 2119. Critically endangered ones such as the black rhinoceros were given a 99 per cent likelihood of disappearing, while vulnerable ones such as leopards had a 10 per cent probability.
Advertisement
The results showed the loss of big species would see the average body mass of animals drop around 9 per cent from today, to 64.1 grams in 2119.
鈥淚t鈥檚 due to the loss of these big charismatic species like elephants and tigers, and you鈥檙e left with songbirds and rodents,鈥� says Rob Cooke of the University of Southampton, who led the research. There will also be a shift to insect-eating species with shorter lifespans, and ones that can thrive in a variety of habitats.
The real change is likely to be worse, says Richard Twitchett of the Natural History Museum, because we know from the fossil record that even the survivors of past extinctions are likely to be smaller.
Downsizing matters, and not just because . Big species do jobs crucial for ecosystems, such as herbivores keeping grass productive. They also perform roles that help humans, like scavenging 鈥� .
鈥淲e can see what the future will look like, but we still have time to prevent these extinctions and therefore avoid the worst ecological outcomes,鈥� says Cooke.
Journal reference: Nature Communications,
