Brazil's congress voted late Wednesday to approve a bill that eases regulations on how much forest farmers are required to preserve on their land, marking a victory for the country's influential agriculture lobby and a setback for environmentalists.

Farming lobbyists supported the bill, saying previous regulations hindered agricultural production. Although the bill requires millions of acres of cleared land to be replanted, environmental groups have condemned it, saying it will lead to further deforestation of the Amazon if regulations for farmers are relaxed.

Brazil's President Dilma Rousseff, who has made forest conservation a priority of her administration, also opposed the bill. The bill now goes to her to be signed into law, and she may use her veto power to strike it down.

President Rousseff made a promise that she would not tolerate laws promoting new waves of deforestation or amnesty for past forest crimes, said Maria Cecilia Wey de Brito, CEO of World Wildlife Foundation-Brazil, in a statement. She knows these changes are bad for Brazil and bad for the environment. We ask her to uphold her promises.

Rousseff had vowed to veto earlier versions of the bill. In its final form, it allows Brazil's federal states to decide how much forestland farmers are required to preserve, allowing states with large agriculture industries to minimize the requirements for compliance.

The head of Brazil's National Agriculture Confederation, Katia Abreu, defended the bill, saying that state would not necessarily impose more lenient restrictions on farmers than the federal government would have, Reuters reported.

She added that under a previous bill, farmers would have been required to replant 74 million acres (30 million hectares) of forest, forcing them to sacrifice land that could be used to produce billions of dollars in crops and livestock.

As an agricultural powerhouse and home to the largest rainforest in the world, Brazil stands to reap economic benefits in the short term with increased crop and livestock output, though it will ultimately come at the expense of the environment with the long-term economic impacts being much more difficult to calculate.  

In June, Brazil will host the U.N. Conference on Sustainable Development, which will bring world leaders together to discuss environmental challenges facing the planet and planning out sustainable options for future growth.

In a year that will see world political, business and civil society leaders gather in Rio de Janeiro for the U.N. Summit on Sustainable Development, it would be a shame indeed for Brazil to surrender its position as a global leader in forest conservation, said Jim Leape, Director General of WWF International, in a statement.