Just ten species make up almost half the weight of all wild mammals on Earth

Wild mammals once dominated the mammal kingdom. Not anymore. Today, humans and our livestock account for 98% of the world’s land mammals by weight, while wild land mammals are just 2%.1

But it’s not just the total number of wild mammals that matters. Having a broad range of different mammals that flourish does too.

There are various reasons why we should care about biodiversity, having a variety of animal and plant life in the world.

Some of those are “functional” and focus on what species do biologically in terms of managing ecosystems and providing services. Having a diverse range of mammal species is important for regulating diseases.2 It also helps to disperse seeds, control pests, cycle nutrients, and engineer ecosystems. Species such as beavers heavily influence their environments by felling trees and creating dams, which can reduce downstream flooding and create wetlands that store carbon. Bats are effective in controlling crop and forest pests.3

But there are also intrinsic arguments for biodiversity based on the argument that species carry value in and of themselves: humans can value diversity simply for its wonder, awe, or beauty. If biodiversity is valuable in itself, then morally we have a duty not to cause extinction and to maintain it.

If you care about any of the reasons above, having a diverse mammal kingdom matters.

If we want to understand global biodiversity and how it’s changing, we can’t only look at quantity. We also need to look at the composition of the world’s wild mammals, which is the focus of this article.