Tally it all up and the world lost 67,000 square kilometres (25,900 square miles) of precious primary tropical forest, an area double the size of Belgium or Taiwan.

The loss was 80 percent higher than in 2023, according to the Global Forest Watch think tank.

"This level of forest destruction is completely unprecedented in more than 20 years of data," its co-director Elizabeth Goldman said in a briefing. "This is a global red alert."

Fires are responsible for nearly half of these losses, surpassing for the first time agriculture as the main driver of destruction.

Loss of tree cover in 2024 -- from deforestation and fires, deliberate or accidental -- generated more than three billion tonnes of CO2 pollution, exceeding India's emissions from fossil fuel use over the same period.

Tropical forests, which harbour the highest concentrations of biodiversity, are the most threatened of any forest biomes on the planet.

They are also sponges for CO2, helping to prevent global temperatures from rising even faster than they have.

Forest fires are both a cause and effect of climate change, injecting billions of tonnes of CO2 in the atmosphere that in turn accelerate warming and the conditions leading to more destructive fires.

- Extreme conditions -

The exceptional fires last year were fuelled by "extreme conditions" that made them more intense and difficult to control, the authors said.

Climate change driven by the massive burning of fossil fuels and boosted by natural El Nino weather phenomenon made 2024 the hottest year on record, with temperatures averaging more than 1.5 degrees Celsius (2.7 degrees Fahrenheit) above preindustrial levels.

Historically, most fires in tropical forests are set to clear land for agriculture and livestock, especially the so-called "big four" commodities: palm oil, soy, beef and timber.

Brazil saw 2.8 million hectares (6.9 million acres) of primary forest destroyed last year, two-thirds to fires typically started to make way for soybeans and cattle.

In 2023, Brazil made measurable progress in reducing forest loss during President Luiz Inacio Lula da Silva's first year after returning to office.

"But this progress is threatened by the expansion of agriculture," said Sarah Carter, a researcher at the World Resources Institute in Washington.

The Brazilian Amazon was most affected, with destruction at its highest level since 2016.

Global Forest Watch reports on forest destruction from all causes, deliberate or accidental.

This stands in contrast to the Brazilian government's monitoring network MapBiomas, which published figures last week showing a sharp decline in deforestation in 2024 -- but based on narrower criteria and not including many areas ravaged by fire.

- New phenomenon -

Forest protection is high on the agenda of the COP30 UN climate conference that Brazil will host in November in the tropical city of Belem.

Neighbouring Bolivia's forest loss -- 1.5 million hectares -- skyrocketed by 200 percent last year, with a record 3.6 percent of primary forests destroyed in a single year, mostly due to fires set to clear land for industrial-scale farms, according to the report.

The picture is mixed elsewhere, with improvements in Indonesia and Malaysia but a sharp deterioration in Congo-Brazzaville and the Democratic Republic of Congo.

While policies have resulted in a slowdown of the extent of forests lost to palm oil plantations, notably in Asia, the destructive footprint of other commodities has expanded, including avocados, coffee and cocoa.

"We shouldn't assume that the drivers are always going to be the same," said Rod Taylor, director of the WRI's forest programme.

"One new driver we are seeing, for example, is linked to mining and critical minerals."