Brazilian president Dilma Rousseff (left) has chosen climate-change sceptic Aldo Rebelo (right) to lead her science ministry. Credit: Ueslei Marcelino/Reuters/Corbis

Brazilian president Dilma Rousseff survived an unexpectedly strong challenge from a prominent environmentalist to stay in office. Now, less than three months into her second term, Rousseff has sparked controversy by appointing an avowed climate-change sceptic as science minister.

The choice of Aldo Rebelo, a Communist law-maker who last July called the idea of global warming “incompatible with current knowledge”, follows a decade in which Brazil has slowed Amazon deforestation and claimed a leadership role in international climate policy. Rebelo promised to uphold the government’s climate stance when he assumed his post at the Ministry of Science, Technology and Innovation on 2 January, but his appointment has stirred fears that Brazil may backslide on environmental protection.

“In general, scientists are sceptical and disappointed,” says Jean Ometto, coordinator of the Earth System Science Centre at the government’s National Institute for Space Research in Sao Jose dos Campos. “But the scientific centre is strong, and there’s going to be pressure from the scientific community not to change the way that climate change is governed.”

Rebelo earned his reputation as a skilful politician in the lower house of Brazil’s National Congress, and he played a leading part when the ‘ruralistas’ — a voting bloc representing rural agriculture — weakened protections for Brazil’s forests in 2012. Most scientists say that Rebelo largely ignored the scientific community during that debate, although some think that he may move to the political centre as minister of science.

In a written statement provided to Nature, Rebelo dismissed concerns about his position on global warming. “The debate about climate change exists independent of my opinion,” he said. More broadly, Rebelo said that his duty as minister of science is to listen to — and fight for — the academic and scientific community in Brazil.

He has limited power to influence climate policy, although the ministry does oversee some national assessments and some climate reports to the United Nations. One area that will receive considerable attention is the ministry’s funding for science, which has been squeezed by competing demands in recent years.

But Rebelo is not the only appointment to raise eyebrows. Rousseff named Kátia Abreu, who fought environmentalists as a senator and agricultural lobbyist, to head Brazil’s agriculture ministry. And both appointments come at a sensitive time: although the rate of Amazon deforestation has dropped by 82% since 2004, the pace of land clearing spiked sharply in 2013 — and it seems to be on the rise once again.

Rousseff has never had a good relationship with environmentalists, who say that she is hiding behind Brazil’s relative success in reducing deforestation while pushing for major dams and ports that will only increase pressure on forests. Now, after a bruising election, she is looking to rebuild support in Congress in the middle of corruption scandals that have tainted her party.

The Communist party, of which Rebelo is a member, has been a “small but loyal” member of the governing coalition led by Rousseff’s Workers’ Party, and it is also friendly with the agricultural caucus, says Steve Schwartzman, an anthropologist with the Environmental Defense Fund in Washington DC, who has worked in Brazil for decades.

One key to Brazil’s success in curbing deforestation and carbon emissions over the past decade was the involvement of multiple agencies, but that kind of coordinated approach could be more difficult today, Schwartzman says. “These ministerial appointments cast a lot of doubt on what we can expect from this government.”

Helena Nader, president of the Brazilian Society for the Advancement of Science, takes a more conciliatory approach: she says that scientists should give Rebelo some time at the ministry before judging him. More broadly, Nader says that she isn’t expecting a major backslide on environmental issues by the new Rousseff government.

“Nevertheless,” she says, “only time will show.”