Deforestation in the Brazilian Amazon rainforest has reached a 15-year high, newly released data shows. The surge is prompting environmentalists and scientists to question the government’s willingness to meet the pledge it made at the COP26 climate summit earlier this month to end illegal woodlands destruction by 2028.

About 5,100 square miles of Brazil’s Amazon—bigger than the size of Connecticut—was denuded in the 12 months between August 2020 and the end of July, a rise of 22% from the previous year and the most deforestation in one year since 2006, according to Brazil’s space research agency, INPE.

The data release incensed environmentalists, who questioned the timing of the announcement. INPE uploaded its findings on deforestation onto a federal government database on Oct. 27—four days before the United Nations climate change conference began, an official at the agency said. The government only publicly released the data late Thursday.

Brazil’s Environment Ministry denied that it delayed the release of the INPE’s data, which are estimates based on satellite images. “We only had access to the data yesterday,” said a spokesman for the ministry.

Environment Minister Joaquim Leite said at the summit that Brazil would end illegal deforestation by 2028, two years earlier than the government had promised previously, raising hopes that Mr. Bolsonaro was getting more serious about protecting the Amazon. Mr. Bolsonaro, who has jokingly referred to himself as Captain Chainsaw, has cut funding for environmental enforcement in his nearly three years in office and publicly expressed support for ranchers and miners in the Amazon.