Three-quarters of all land on Earth is now significantly affected by human activity and the few remaining pockets of wilderness are themselves at risk of becoming ecological deserts. Agriculture, industry, urbanisation, climate change - all these are decimating ecosystems and destroying biodiversity. Some 60 percent of the world's animals have been wiped out since the 1970s. In response, a worldwide movement is under way to "rewild" the countryside. Rewilding is the restoration of an entire ecosystem to its natural state, by removing foreign species while reintroducing and protecting native ones. It begins with the removal of livestock, allowing vegetation to flourish. This encourages insects and other animals, attracting birds and other small predators. When you take the fences down you see wildlife coming back in, because for 80 years it's been excluded from the best grasses. It's very exciting to see the grasslands and the forests begin to restore themselves, and that's the joy of taking fences down. Kris McDivitt Tompkins, philanthropist and conservationist Removing fences allows for the return of herbivores, which are preyed on by apex predators - those at the top of the food chain - which then also multiply. Species in critically low numbers or who are totally absent are rehabilitated. And ultimately, prey and predator populations regulate one another and the ecosystem evolves into a balanced and self-sustaining wilderness. One rewilding initiative - right at the tip of South America, in Chile's Patagonia - is exceeding all expectations. There, two billionaire philanthropists, Kris McDivitt Tompkins and her late husband Doug Tompkins, have helped create one of the largest national parks in the world. Kris, the founder and CEO of the clothing brand Patagonia, and Doug, the founder of Esprit and North Face spent $345m buying up vast tracts of land for restoration and rewilding. "Predators have been systematically persecuted for decades and decades, so their numbers get precariously low," says Kris. "Every ecosystem has what's called their apex species ... and if you take out the very top predator, everything cascades down from that, and comes out of order." "When you take the fences down you see wildlife coming back in, because for 80 years it's been excluded from the best grasses," she adds. "It's very exciting to see the grasslands and the forests begin to restore themselves, and that's the joy of taking fences down." In what has become recognised as the biggest land donation in history, Tompkins will soon be handing it over to the Chilean state to be run as a national park, alongside four million hectares of land contributed by the state. Areas decimated by overgrazing are now being restored to their original wild state and vulnerable wildlife populations are being revived. "Even though it's early here in the park in terms of rebalancing, we can see some big changes: where there are water systems, the grasslands are definitely coming back; the numbers of pumas in the park; the numbers of guanacos in the park; foxes," Kris says. "But the success comes when all of those species are truly back in a system that's functioning without human intervention." earthrise heads to Patagonia in Chile, where a four-million-hectare national park is being brought back to life. - Subscribe to our channel: http://aje.io/AJSubscribe - Follow us on Twitter: https://twitter.com/AJEnglish - Find us on Facebook: https://www.facebook.com/aljazeera - Check our website: https://www.aljazeera.com/