In 2008, a Danish scientist borrowed three circus elephants. Morten Lindhard wanted to see how they behaved when released on European moorland. He said it was a "relaxed" experiment and "the animals seemed to have a great time".

Letting elephants run free in Europe seems like a wild idea. But it's gaining support thanks to new evidence that the world's largest land animal is an unexpected ally in the fight against climate change.

A recent study estimates African forest elephantsThe smallest of the three surviving species of elephant. It is native to West Africa and the rainforests of the Congo Basin in Central Africa. could keep 13 billion tonnes of carbon dioxide out of the atmosphere. And they do this by eating trees.

Elephants have huge appetites. When awake, they spend 90% of their time eating. A family may "consume more than a tonne of food per day", according to researcher Ahimsa Campos-Arceiz.

And they are messy eaters, creating what ecologist Fabio Berzaghi calls "elephant disturbance" as they move through the jungle. But as they clear old dead wood and strip young plants, they leave behind tall trees.

Over time this "results in forests having fewer, larger trees", says Campos-Arceiz. The elephants are "environmental engineers", expert gardeners removing unwanted weeds from the ecosystem.

These "woodier" forests are more effective at carbon captureTechnology which captures carbon dioxide from the air and transports it to storage sites underwater, preventing it from warming the atmosphere. . The Amazon rainforest is the largest in the world, but because of the hungry work of elephants, the Congo Basin stores more carbon.

However, it is at risk. In March, the forest elephant was put on a critically endangered red listThe International Union for Conservation of Nature says 6,811 species are currently critically endangered. Forest elephant numbers have declined by over 90%.. Ben Okita of Save the Elephants says it is an "alarm bell" and ivory poachingEconomists calculate the illegal sale of ivory tusks is worth less than £40,000. The elephant's value to the environment is estimated at £1.3m. is "one of the major causes".

Whilst conservationists fight to protect elephants in their natural habitat, others are finding new homes for them in surprising places.

Ecologist Josh Donlan wants to release captive elephants to rewild the American Great Plains. In Australia, pyrogeographerThe study of wildfires. In 2019-20, Australia experienced its worst ever bushfires, burning 186,000 square kilometres of land. David Bowman argues they could help fight wildfires by clearing dry vegetation from the bush.

It's an idea known as PleistoceneThe epoch between 2,580,000 and 11,700 years ago, commonly referred to as the Ice Age. rewilding. During the last Ice Age, tree-eating giants lived on almost every continent. Giant wombats and ground sloths were some of the megaherbivoresAny plant-eating animal that weighs 1,000kg (1 tonne) or above. that roamed the landscape.

Like elephants, they were keystone speciesAny animal or plant with a pivotal role within an ecosystem. Without it, the ecosystem would dramatically change or disappear altogether. supporting biodiverse ecosystems. As well as tearing down trees, big plant-eaters dig holes, creating habitats for birds and frogs. Elephant poo is a rich fertiliser that transports seeds hundreds of miles.

But around 10,000 years ago, humans hunted most of these beasts to extinction. On an island in the Arctic, a few lonely woolly mammoths held out until 6000BC.

Now, a new company has announced ambitious plans to bring them back. The scientists at Colosal want to edit elephant DNA to make a lab grown 21st-Century mammoth.

They even have a home for it. Russian scientists have imported reindeer, elk and bison to a remote part of Siberia. Their aim is to turn tundra into grassland and restore lost ecosystems. They call it Pleistocene Park.

Yes: When it comes to climate change, we need to think big. For millions of years, megaherbivores maintained vast forests, storing carbon and keeping the planet cool.

No: The prehistoric forests and grasslands are now cities and farmland. Where elephants roam wild there are conflicts between humans and animals. Turning Europe into a Pleistocene theme park would be dangerous and impractical and it would take centuries to restore these ancient forests.

Or: We need to keep an open mind and explore many options. Expanding elephant habitats is not a short term fix, but a long term one that will benefit future generations. In the meantime, we should look for quicker solutions - and change our habits to prevent further damage.