Rewilding to sustain biodiversity

At the same time, large wild herbivores are being restored to some European landscapes. These animals include European bison and even breeds of cattle selected to resemble the aurochs, a massive beast that was the ancestor of domestic cattle and went extinct in the 17th century.

Another big turnaround has been in the population of the Eurasian beaver, which was hunted almost to extinction by the end of the 19th century but is back up to 30 million.

These changes are all part of a new philosophy of nature conservation called rewilding, which aims to re-establish ecologically powerful animals like these big herbivores and predators so that they can influence ecosystem processes and sustain biodiversity.

The emphasis on very big animals is not just due to their charisma; it is a recognition of the crucial roles they play in ecosystems.

Powerful predators

Top predators like wolves keep populations of smaller predators in check and thus protect many other animals that would be threatened if these smaller predators were freed from control. They also regulate populations of herbivores and therefore prevent overconsumption of vegetation.

Large herbivores, on the other hand, can help to maintain the diversity of plants and habitats by creating open areas in otherwise dense vegetation. Beavers are powerful “ecosystem engineers” that physically transform whole environments. In Europe, reintroduced beavers have recreated wetlands with a high diversity of plants and animals.

The problem that rewilding aims to solve is that the biggest animals have disappeared from most of the world’s ecosystems. This began about 50,000 years ago when a global wave of extinctions known as the “Pleistocene megafaunal extinction” saw the end of mammoths, ground sloths and many other giants, probably at the hands of human hunters.

Substituting species

The few megafaunal species that survived into the modern world are now typically rare, and a large proportion are continuing to decline towards extinction.

Rewilding projects try to rebuild some of the lost structure of ecosystems by restoring megafauna. Where possible, this is done by protecting surviving species and helping them recover some of the ground they have recently lost, like those wolves and bison in Europe.

It can also mean substituting different species for those that went extinct thousands of years ago, if the substitutes are similar enough to the originals that they could perform the same ecological functions. There have been serious proposals, for example, to introduce elephants to parts of Europe to make good the loss of Europe’s own elephants. We could throw in a few lions and hippos for the same reason.

Rewilding in Europe has not gone quite that far yet, but it has given us some conservation success stories that stand out as bright spots in the generally dark picture of global decline in biodiversity.