Contact: Science Press Package
American Association for the Advancement of Science
Earth's disappearing animals
[Credit: Mauro Galetti]
This week, a special issue of Science highlights humans' role in the recent extinctions of many species. There have been five mass extinction events on Earth, documented by the fossil record, and researchers say that the planet is currently in the midst of a "sixth extinction wave."
Scientists widely agree that humans are speeding this trend by destroying wild lands, hunting some animals for resources or luxuries, and killing other animals because they're viewed as threats or competitors. But when humans battle this defaunation, as it's called, by reintroducing species to the wild—a process known as refaunation—strange, unexpected things can happen, they say.
In a Review article, Rodolfo Dirzo and colleagues say that 322 vertebrate species have gone extinct in the past 500 years—and that both vertebrates and invertebrates have been in decline that whole time. The authors also note that, although large species like tigers, rhinos and pandas tend to get the most attention, it's clear that even the disappearance of the smallest beetle can fundamentally change how an ecosystem works.
A second Review article by Philip Seddon and colleagues explains how humans have attempted to reverse—or at least slow—this global trend of defaunation. Sometimes animals are reintroduced to wild populations and other times entire populations are reintroduced to areas where they'd previously gone extinct. Most of these attempts at refaunation have produced conflicting results, but a few success stories provide some hope for the future, they say. The authors also discuss the possibility of de-extinction, or the resurrection of extinct species with breeding or cloning technology.
In an Opinion article, Joshua Tewksbury and Haldre Rogers argue that people do generally care about animals—just not as much as food, jobs, energy or money. In order to ensure a future for the billions of people on Earth, leaders and politicians must recognize the importance of animals and ecosystems in their everyday lives, they say.