There are many ways that human activity is affecting the world’s wildlife, but is it causing the animals to become smaller, too? Researchers of a new study predict that birds and mammals will become smaller in the next 100 years, as the larger mammals eventually go extinct.

Shrinking Animals

It was only recently that researchers determined that humans are placing 1 million species at risk. Now, researchers of a new study are predicting that the Earth’s wildlife will go smaller, while the bigger ones are slowly going toward extinction, also largely as a result of human activity.

In particular, researchers say that the average size of mammals will be reduced by 25 percent in the next 100 years. In comparison, there was only an observed 14 percent reduction in animal size from 130,000 years ago to today.

The researchers determined this shrinking pattern after they studied the characteristics of over 15,000 birds and mammals, and the length of time between generations. They also looked at the International Union for Conservation of Nature (IUCN) Red List of Threatened Species to determine which animals are likelier to go extinct in the next century, and they found that larger animals such as the Sumatran orangutan, the tawny eagle, and the Amur tiger are most at risk of dying out as they are less able to adapt to the ecological changes.

As the years go by, it is the smaller animals that feed on insects that can adapt to a number of environments that are expected to thrive. This includes gerbils, rodents, and song birds.

Human Activity

According to lead researcher Rob Cooke, the biggest threat to mammals and birds are humans. Destructive activities such as deforestation, urbanization, intensive farming, and hunting yield catastrophic results for animals, in that if they do not lose their lives in the process, they lose their homes and their food sources. That said, the researchers are still not losing hope that we can still turn this around for the animals.

“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,” said coauthor Amanda Bates of Memorial University in Canada.

The study is published in Nature Communications. For future studies, they hope to find possible long-term effects of species becoming extinct in an ecosystem or habitat.