The campaigning organisation is due to launch non-fungible tokens for nature tomorrow, in the form of unique digital artworks, field trips and collectibles.

WWF UK hopes the NFTs will raise funds for its conservation work and awareness of 13 of the most endangered species, including types of gorillas, orangutan, and rhino.

But most NFT transactions rely on a cryptocurrency called Eth, supported by the blockchain Ethereum, which pumps out masses of climate-heating carbon dioxide via the vast computer network needed to sustain it.

One Etherum transaction has the same carbon emissions as 140,000 Visa transactions, according to Statista.

What are critics saying about WWF UK's plans?

The idea has sparked backlash, with critics on social media describing it as "grim," "insane" and "unbelievable".

Dr Catherine Flick, senior researcher in computing and social responsibility at De Montfort University, urged the organisation to reconsider and assess the "bigger picture".

"Each Eth transaction is remarkably energy intensive," she told Sky News. "So the minting and further transaction of the WWF NFTs will be remarkably destructive in both the short and long term.

"It's not too late to pull out and stop the 'drop' of these NFTs and their destructive environmental impact."

How has WWF UK responded to the backlash?

The charity says it is using an "eco-friendly" version of Eth by accessing it via - or "minting" it to - a side chain.

A side chain (in this case Polygon) is described by the crypto news site CoinMarketCap as a side blockchain that is linked to another blockchain.

WWF UK says this would be a less carbon intensive way of using Ethereum. The charity says one transaction on Polygon has the equivalent carbon emissions of a single glass of tap water.

Sarah Ward from the charity said: "We are always looking at innovative ways to engage WWF supporters and fundraisers and trial new ideas."

The NFT proceeds would fund "vital conservation work across the globe", she added.

But Dr Flick says that just because a Polygon transaction uses less Ethereum, it doesn't make it eco-friendly.

"It also requires Eth to buy the NFTs, and future transactions of the NFTs will be reliant on Eth as well," she said. "I don't know of any fully environmentally or climate friendly mainstream NFT implementations that are trustworthy."

She added: "Most of them rely on environmentally problematic cryptocurrencies for transactions or are side-chains to problematic blockchains."

Polygon and Ethereum did not immediately respond to a request for a comment.

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