Vanishing fauna

Science  25 Jul 2014:
Vol. 345, Issue 6195, pp. 392-395
DOI: 10.1126/science.345.6195.392

During the Pleistocene epoch, only tens of thousands of years ago, our planet supported large, spectacular animals. Mammoths, terror birds, giant tortoises, and saber-toothed cats, as well as many less familiar species such as giant ground sloths (some of which reached 7 meters in height) and glyptodonts (which resembled car-sized armadillos), roamed freely. Since then, however, the number and diversity of animal species on Earth have consistently and steadily declined. Today we are left with a relatively depauperate fauna, and we continue to lose animal species to extinction rapidly. Although some debate persists, most of the evidence suggests that humans were responsible for extinction of this Pleistocene fauna, and we continue to drive animal extinctions today through the destruction of wild lands, consumption of animals as a resource or a luxury, and persecution of species we see as threats or competitors.

Animals are rapidly disappearing from forests in Borneo and across the world.


Such global loss of animal species, or defaunation, is increasingly recognized as a problem akin to deforestation in terms of scale and impact. Though for emotional or aesthetic reasons we may lament the loss of large charismatic species, such as tigers, rhinos, and pandas, we now know that loss of animals, from the largest elephant to the smallest beetle, will also fundamentally alter the form and function of the ecosystems upon which we all depend (see Dirzo et al., p. 401).

Identifying the drivers of these extinctions is straightforward, but stemming the loss is a daunting challenge. Animal species continue to decline in, and disappear from, even large, long-protected reserves, due both to direct impacts, such as poaching, and indirect ecological feedbacks, such as habitat fragmentation. Though hunting and poaching might seem obvious candidates for targeted policy and management interventions, there are complex social issues underlying these activities that will require coordinated and cooperative actions by nations (see Brashares et al., p. 376).

Twilight for animals

Large numbers of animal species face extinction in Southeast Asia, the Amazon, and the Andes, as shown in this map of mammals, amphibians, and birds. Animals also face high rates of extinction in Europe and North America, where fewer species are found overall.


While stemming this loss remains a challenging goal, attempts to reverse the extinction trend are increasing. Such “refaunation” efforts involve a variety of approaches, including breeding animals in captivity, with the hope of reintroducing them to the wild, and assisting recolonization of areas where species have become locally extinct (see Seddon et al., p. 406). Active reversal of animal extinctions is proving just as challenging as preventing extinctions in the first place, but a few success stories provide some hope. Many note and mourn the loss of animals but have not recognized that the impacts of this loss go beyond an aesthetic and emotional need to maintain animals as a part of nature. Current research reveals startling rates of animal declines and extinctions and confirms the importance of these species to ecosystems (see Stokstad, p. 396). Further, and more broadly, it suggests that if we are unable to end or reverse the rate of their loss, it will mean more for our own future than a broken heart or an empty forest.

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