UK Prime Minister Rishi Sunak has been criticised by over 600 scientists across the world for the UK's use of bioenergy, in a letter that said the practice is destroying the "lungs of the earth", with "devastating impacts" on forests.
Bioenergy divides scientific opinion due to the procuring of biomass, which can involve cutting down trees to turn into energy.
The professors and science students warned of the industry's "growing threat to biodiversity" because of the way they say it hacks down trees and habitats.
They warned it undermines a current high-stakes push to slow the rapid loss of life-sustaining nature.
"It is simply not environmentally sustainable," said Kew Gardens' director of science, Professor Alexandre Antonelli, one of the key authors.
"Sustainability means you can do something forever... and because we are losing forests that have been growing for many decades, if not centuries, we are not allowing nature to recover to the level it needs to recover the biodiversity," he told Sky News.
That matters because healthy, old forests house things like mosses, which can slow flooding, and pollinating insects and birds and can soak up more carbon dioxide, he continued.
The scientists want the UK and leaders from other major users or consumers of bioenergy - including President Xi Jinping of China and US President Joe Biden - to abandon the energy form altogether.
The signatories warned the talks may fail unless businesses stop clearing forests for bioenergy, which has boomed in recent years as a replacement for coal.
However, Mark Sommerfield from trade body the Renewable Energy Association, said "biodiversity considerations are an important component of biomass sustainability governance".
He cited a review of 211 studies, 69% of which concluded that forestry had no negative impact on biodiversity.
The letter accused the industry of clearcutting forest - cutting down entire sections rather than keeping continuous cover, and is supposed to be particularly bad for biodiversity.
Sommerfield said bioenergy is part of a "broader forestry economy", often using the residue from the timber industry, and therefore eliminating waste.
In October, 550 academics sympathetic to the industry wrote a letter arguing bioenergy can "substitute fossil energy and is a significant part of climate protection policy".
A government spokesperson said the UK "only supports biomass which complies with our strict sustainability criteria."
"Many biomass feedstocks are likely to be combusted or decomposed anyway, so it is more efficient to use that material as an energy source and displace expensive, volatile fossil fuels in the process," they added.