"It is worrying that we are losing these big species when we don't know their full role," said Rob Cooke, lead author of the study, to The Guardian. "Without them, things could begin to degrade quite quickly. Ecosystems could start to collapse and become not what we need to survive."

The extinction of so many species will have a ripple effect as it affects ecosystems that humans rely on for food and clean water. Many large mammals disperse seeds, for example. Sure enough, humans are to blame for the impending catastrophe.

"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, urbanization and the effects of global warming," said Cooke in a university press release.

To perform the study, the researchers looked at 15,484 land mammals and birds. They homed in on five traits: size, how many offspring they had, breadth of habitat, diet and length of time between generations. Cooke and his team combined this data with the the International Union for Conservation of Nature's Red List of Threatened Species to determine which animals are most likely to become extinct in the next century.

"If all these extinctions [of larger animals] take place, we are fundamentally restructuring life on this planet," said Cooke to The Guardian.

While the future is bleak for large animals, it's bright for small, fast-lived, highly fertile, insect-eating animals, which can thrive in a wide-variety of habitats, like rodents and songbirds, according to the study's findings.

The researchers see their work as an opportunity for conservationists to protect species at risk. "Extinctions were previously viewed as tragic, deterministic inevitabilities, but they can also be seen as opportunities for targeted conservation actions," said Amanda Bates, Research Chair at Memorial University in Canada and one of the study's authors in a university press release. "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."