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It‚Äôs standard news to hear about the rapid decline of wildlife these days: As humanity‚Äôs environmental impact has surged since the Industrial Revolution, animals have suffered the brunt of the consequences. But megafauna‚ÄĒi.e. very large animals‚ÄĒhave been the target of human activity for much longer, and many of them went extinct thousands of years ago, often due to over-hunting. But a recent study offers unexpected signs of hope for some of these long-suffering megafauna, which make up Earth‚Äôs most imperiled group of species.

According to a study published in Ecography, megafauna, defined as plant-eating terrestrial mammals weighing more than 100 kilograms (220 pounds) on average, are establishing themselves in new and often unexpected places outside of their historic native ranges. These introduced populations would typically be considered invasive species, but the authors think a better term might be ‚Äúsurvivors.‚ÄĚ Furthermore, the giant animals, which include everything from hippopotamuses to donkeys, might offer unexpected benefits to their new homelands. In a recent article in The Conversation, the authors write that ‚Äúthese ‚Äėferal‚Äô populations are rewilding the world with unique and fascinating ecological functions that had been lost for thousands of years.‚ÄĚ


Arizona State University‚Äôs Erick Lundgren, lead author of the study, told Earther that ‚Äúwhile the conservation community is very concerned with declines of native megafauna, we have for the most part ignored these introduced populations or considered them myopically as pests.‚ÄĚ

‚ÄúThe data suggests that if we were to broaden our value system towards these organisms we would find a wilder world, full of interesting and hereto largely unstudied wildlife,‚ÄĚ he said.


There are 76 existing megafauna species, and according to the study, 22 of these now have introduced populations outside of their historic range. Which is good for them‚ÄĒbecause of the species that have seen new populations emerge, around two-thirds are either threatened, extinct or declining in their native ranges. A 2015 report in the journal Science Advances found that large herbivores are facing steep population declines across the planet, and that roughly 60% are threatened with extinction. This rapid decline is due to over-hunting, competition with livestock, and habitat loss through deforestation, cultivation, and development. And climate change will likely make this all the more challenging as habitats change.

In the new study, the researchers divided megafauna gains geographically and determined that introductions have increased megafauna species richness‚ÄĒthat‚Äôs the total number of species present‚ÄĒby 11% in Africa and Asia, by 33% in Europe, by 57% in North America, by 62% in South America, and by 100% in Australia. This makes‚Äúregional megafauna species richness substantially higher today than at any other time during the past 10,000 years.‚ÄĚ

This should not be confused with total numbers of megafauna, which continue to decrease.


Lundgren said the real question now is if there will be ‚Äúspace and tolerance‚ÄĚ for these new organisms to continue to exist in their native or non-native ranges.

‚ÄúSome introduced populations are targets for eradication campaigns and others are being utilized and persecuted like native megafauna‚ÄĒdomestic and wild donkeys are being harvested at an astonishing rate for Chinese medicine,‚ÄĚ he said.

While some of these species, such as wild cattle, wild horses and wild camels, survived in large part due to domestication of their ancestors‚ÄĒhelping them bridge the gap between the onset of the Holocene 10,000 years ago and today‚ÄĒother survival stories seem almost fictional. For instance, a small group of wild hippopotamuses has recently settled into South America after escaping Colombian drug lord Pablo Escobar‚Äôs abandoned private zoo about halfway between Medellin and Bogota. They are known as the ‚Äúcocaine hippos.‚ÄĚ


Australia, a continent that was once rich with amazing large wildlife such as giant wombats and kangaroos, has shown the greatest gain in megafaunal diversity, since all of its native megafauna went extinct tens of thousands of years ago. Now eight species of introduced megafauna live Down Under, including the only existing population of wild dromedary camels.

In the Sonoran Desert, which occupies the Southwestern U.S. and parts of Mexico, introduced wild donkeys‚ÄĒwhich are critically endangered in their native habitat‚ÄĒaid local biodiversity by digging wells that provide a valuable water sources to at least 30 different mammals and birds. According to the authors, this is just one way that introduced megafauna can benefit their new surroundings.

As with all introduced or ‚Äúalien‚ÄĚ species though, the ecological impacts will be wide-ranging and not entirely predictable. More research into each of these individual occurrences will likely be needed to understand the bigger picture. Regardless, the study‚Äôs finding underscore the notion that in an era of human-dominance, we might have to start expanding our thinking on what it means for ecosystems to be ‚Äėwild.‚Äô


‚ÄúTo conserve megafauna diversity effectively we shouldn‚Äôt discount introduced or feral populations,‚ÄĚ said Lundgren. ‚ÄúThey also require large areas to roam‚ÄĒnecessitating landscape scale conservation. The conservation of these animals can end up being important to many other species because by protecting these large animals‚Äô landscapes we protect the homes of many others.‚ÄĚ