RIO DE JANEIRO, BRAZIL -- The vast majority of deforestation in the Brazilian Amazon is illegal, and President Jair Bolsonaro's promise to eliminate it looks doubtful given a lack of transparency on authorized land use, researchers said Monday. 

Under pressure to curb the destruction of the Amazon, Bolsonaro vowed last month at a world climate summit to eliminate illegal deforestation by 2030.

But almost no deforestation can be considered fully legal in Brazil, given that authorities are failing to adequately implement laws on tracking how much and where land is being cleared under permit, said the report, published by a group of university researchers and experts from environmental organizations including the World Wildlife Fund Brazil and the Centro da Vida Institute.

The report found that 94 percent of deforestation in the Brazilian Amazon and surrounding Matopiba region is illegal.

That is partly because even in cases where farmers, ranchers, loggers and others have permits to clear land, the authorities are unable to document how those permits are being used on the ground, it said.

"The differentiation between legal and illegal deforestation is a key factor to ensure that Brazil's agricultural and forestry production is not contaminated by environmental crimes," it said.

Bolsonaro has presided over a surge in deforestation in the world's biggest rainforest since taking office in 2019.

In the 12 months to August 2020, deforestation in the Brazilian Amazon increased 9.5 percent, destroying an area bigger than Jamaica, according to government data.

The far-right president faces international pressure to clean up his government's environmental image -- and backlash from businesses worried how that image will impact the world's number one beef and soy exporter.

"Bolsonaro made that promise of 'zero deforestation,' but how will we even know if the necessary information isn't available?" Paula Bernasconi, coordinator of the Centro da Vida Institute, told AFP.

"We urgently need more technical effort and political will to implement Brazilian environmental and transparency laws," said her co-author Raoni Rajao of the Federal University of Minas Gerais.

"Otherwise, the lack of transparency will continue serving as a shield for the ongoing destruction of our ecosystems."