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Whatsapp As animals are pushed further towards extinction, conservation theorists are proposing to reintroduce the few creatures we have left back into the wilderness to stimulate and restore ecosystems.

Can you imagine an Australian outback filled with herds of roaming African elephants? How about Komodo dragons basking in the sun on top of Uluru? Carl Elliott Smith explores a conservation theory called rewilding, which argues that these drastic solutions are necessary to solve the big problems of our environment.

Rewilding is a conservation theory which explores the idea that some important introduced species could be used to replace our missing or extinct native animals.

As an example, proponents of rewilding argue that Komodo dragons may fill the gap in Australia’s ecosystem left by Megalania, a giant goanna-like species that disappeared thousands of years ago.

But why do we need these giant, potentially dangerous lizards in Australia?

Let’s look at the example of returning wolves to Yellowstone National Park in the United States.

As Dr Donlan from Cornell University explains, after wolves were removed from the reserve, herbivore numbers skyrocketed and this in turn began to affect vegetation.

Once you take one or two species out of that food web, then around them you get lots of cascades of extinction, other species disappear... If you can plug those gaps fairly quickly, then hopefully the aim is that in the long term you will reduce the number of species you lose.

The problem was that the ecological role of a large predator was missing in that ecosystem.

‘Wolf predation affects that ecosystem not only by affecting the large herbivores they prey on but also [by] affecting the plant distribution, because the herbivores changed the way they forage on plants,’ says Dr Donlan, a conservation biologist.

‘So these top trophic level predators have an impact that cascades throughout the ecosystem all the way down to the plant level,’ he says.

Via the reintroduction of keystone species, the basic goal for rewilding is to recreate entire intact ecosystems that function autonomously, without human intervention: essentially the recreation of natural wild areas.

Komodo dragons in Australia?

Although returning wolves to their native homes is roughly in line with existing conservation strategies, the controversial aspect of rewilding is that when native species are extinct or critically endangered, the theory argues that similar non-native species can be introduced instead.

For example, now that the European lion and the Tasmanian tiger are extinct, rewilding proponents argue that we need to find suitable substitute species to replace their extinct cousins, such as the African lion or the dingo.

And theorists such as Dr Donlan are assessing our current environments based on evolutionary timescales, looking back to the late Pleistocene (10,000 to 50,000 years ago) for a benchmark.

This is why Komodo dragons are being championed as a replacement for the goanna-like top predator Megalania which disappeared from Australia around 40,000 years ago.

These similar species may restore important ecological functions, such as controlling the population size of native and introduced herbivores.

In fact, Tim Flannery, now chief commissioner of the Australian Climate Commission, was one of the first to propose the radical step of introducing Komodo dragons to help restore Australian ecosystems in his 1994 book Future Eaters.

Professor David Bowman from the University of Tasmania has echoed Flannery’s ideas in a 2012 paper in the scientific journal Nature.

Bowman, a professor of environmental change biology, says that we need to act now to preserve what’s left of our environment, even if that action seems radical.

He argues that we need to use everything in our toolbox to achieve this goal and says that some of our best available tools are ecological—such as our remaining large mammals.

‘Human beings, like it or not, are undertaking massive ecological engineering programs,’ says Professor Bowman.

‘Rewilding is actually restoring ecological processes to make ecosystems sustainable because we have to choose now, because we can't just stand back and allow, say, the equivalent of a biological catastrophe.’

Professor Bowman, like Dr Donlan, argues that truly pristine environments are extremely rare; nowadays ecosystems are not only missing significant species but they’re also struggling with invasive species.

However, he and others within the rewilding movement claim that if new species are appropriately chosen then they could fix both of these problems. He even thinks Australia should consider the introduction of elephants to help deal with African gamba grass—which is plaguing the country's north.

‘With, say, an out-of-control grass like gamba grass, it was introduced to feed cattle. Cattle can't eat a grass when it grows three metres high,’ says Professor Bowman.

‘A lot of these uncontrolled grass fire cycles are really telling us that the animals that should be consuming that grass are missing, so we should try to put back animals that are large enough to process this biomass which would then reduce the out-of-control fires,’ he says.

‘We have to step up and to realise that these plants are going to take their opportunities, and we have to fight back using a known proven tool, which is a big herbivore.’

Dr Donlan also highlights the potential for rewilding to save the dwindling populations of our remaining large animals—they can fill the gaps left by their extinct cousins while simultaneously rebuilding populations in new safe havens.

Dr Donlan argues that rewilding takes a more proactive approach to conservation, compared to traditional preservation strategies.

But he and Professor Bowman acknowledge that this isn’t without its risks. In Australia especially we’ve seen the potentially catastrophic results of ecological engineering in the form of invasive species such as cane toads and feral cats.

‘I'm not saying I've got the answer,’ says Professor Bowman, ‘obviously this is leading-edge debate. We've got to debate these things and, I would like to think, trial these things.’

One tortoise as good as another

Both Professor Bowman and Dr Donlan have called for controlled, empirical studies to test whether rewilding works.

In 2012 this call was answered when a group of scientists from the University of Bristol, led by Professor Stephen Harris, were able to show in a controlled study that rewilding has the ability to save at risk habitats.

The stage for this study was Ile aux Aigrettes, a 25 hectare island just off the coast of Mauritius.

This small island had a big problem: the native plants, including an endangered endemic ebony tree, weren’t able to compete with alien plants that had been introduced to feed goats.

‘They had no seed dispersal,’ explains Harris. ‘There were none of the big species that used to disperse seeds.’

‘Originally Mauritius was famous for various species such as the dodo which was a flightless pigeon that dispersed big seeds,’ he says. ‘And it was also done by two species of giant tortoise that lived on the islands, and they were exterminated back in the late 1700s.’

To fix this problem, the group of scientists introduced a non-native species of tortoise from the Seychelles called the Aldabra tortoise.

This tortoise, says Professor Harris, 'looked much the same as the original native species, and functioned in the same sort of way, and could actually fill the gap in the ecological processes that the native tortoises fulfilled.’

After a round of experiments in cages on the island, these substitute tortoises were released to see how they impacted upon native plants, including the endangered ebony tree.

‘Straight away the tortoises started eating the fallen fruits, and what you found is that the fruits that had gone through the tortoises' guts had much higher germination rates and also germinated much faster,’ says Professor Harris.

‘So these tortoises were both helping the germination and survivability of the seeds but also rapidly spreading them across the island because much of the ebony had been cleared off the island for fuel back in the past,’ he says.

Professor Stephen Harris and the other authors of this paper claim to have revived an extinct ecological interaction.

‘Once you take one or two species out of [a] food web, then around them you get lots of cascades of extinction, other species disappear. And these cascades last several hundreds or a few thousand years until the ecosystem settles back into a much more depaupered ecosystem,’ says Professor Harris.

‘So if you can act quickly—and remember these tortoises didn't disappear that long ago—if you can plug those gaps fairly quickly, then hopefully the aim is that in the long term you will reduce the number of species you lose in those cascades of extinction.’

Since showing that the Aldabra tortoise could replace the extinct Mauritian tortoises and restore balance to that small ecosystem, Professor Harris and his team have been trialling the idea on other nearby islands.

In a paper soon to be released, they have demonstrated another successful application of rewilding, this time on Round Island, also off the coast of Mauritius.

Wild plans for ecotourism

However, the theory of rewilding is not only being used in scientific settings.

On a much grander scale, Rewilding Europe, a not-for-profit organisation, is well on its way to buying up one million hectares of unused land across the continent to set aside for rewilding.

‘Rewilding Europe is a new initiative in Europe with the aim to make Europe a wilder place, which means more space for wilderness, for wild nature, for wildlife,’ says managing director Frans Schepers.

However, as Mr Schepers explains, the focus of the organisation is not purely conservation.

‘One of the key differences with a lot of other conservation initiatives is, I think, the business component,’ he says. ‘Because we are very actively working to provide benefits to people that live in those areas and who are actually suffering very much from this land abandonment.’

Rewilding Listen to Future Tense to find out more about the strand of conservation theory known as rewilding.

By harnessing the social trend of urbanisation, Rewilding Europe is trying to walk the fine line of simultaneously restoring environments while also bolstering rural economies.

‘If you speak to a mayor in the Romanian Carpathians and he's telling you, well, the last five years half of my population in my village disappeared. We had to close the school, we had to close the library, there are two children born,’ says Mr Schepers. ‘It's a very dramatic situation in some of these areas and people are desperate.’

So far, some of the emerging industries being built around rewilded areas include ecotourism, safari parks and even wild meats.

Although Rewilding Europe does well, at least in theory, to walk the line of rebuilding the environment and providing jobs, it's not without its critics.

The elephant in the room?

Rewilding Europe’s reserves are open and unfenced, often bordering on nearby villages. And the animals being rewilded include bears, wolves, carrion, other mid-range carnivores, and even giant bovine, similar to the extinct aurochs.

Although Rewilding Europe plays down the threat of these animals, instead drawing on polls that show that 80% of people in the Netherlands would welcome the wolf back to Europe, others acknowledge that rewilding is a socially challenging conservation tactic.

Professor Tim Caro, a conservation biologist from the University of California argues that, in terms of the societal impacts and practical obstacles, there are many potential downfalls to introducing animals to an ecosystem, notwithstanding the issues of containment and risk mitigation.

He has been a regular critic of rewilding theory, arguing that aside from the obvious social problems, this theory has significant ecological drawbacks.

In a 2009 review of scientific debate on the topic, he cited many potential problems with rewilding including: the introduction of exotic diseases; a poor track record of introducing new species (both in terms of survivability and the effects on native species); and a lack of empirical evidence to support rewilding. Also, there’s the raw logistics of transporting all of these animals.

Overall though, Professor Caro appears conservatively optimistic about the potential of rewilding as long as it is properly studied and cautiously implemented.

Dr Josh Donlan from Cornell University echoes this point but also argues we should think about implementing rewilding in the short to medium term, as the potential benefits of this radical idea far outweigh the risks.

‘In my view we now impact almost every square inch on the world,’ says Dr Donlan.

‘We’ve learned a lot over the past 50 years with fields of conservation biology, with the fields of restoration biology, that we can do restoration and we can do re-introductions strategically, smartly, and scientifically based.’

Find out more at Future Tense.

