The New York TIMESSAO PAULO, Brazil Brazil has made great strides in recent years in slowing Amazon deforestation and showing the world it was serious about protecting the mammoth rain forest. The rate of deforestation fell by 80 percent over the past six years, as the government carved out about 150 million acres for conservation an area roughly the size of France and used police raids and other tactics to crack down on illegal deforesters, according to both environmentalists and the government. Brazils former environment minister, Marina Silva, became an internationally respected defender of the Amazon. She ran for president in 2010 on the Green Party ticket and won 19.4 percent of the votes. But since Dilma Rousseff was elected president in late 2010, there have been signs of a shift in the governments attitude toward the Amazon. A provisional measure now allows the president to decrease the lands already created for conservation. The government is granting more flexibility for large infrastructure projects during the environmental licensing process. And a proposal would give Brazils Congress veto power over the recognition of indigenous territories. What is happening in Brazil is the biggest backsliding that we could ever imagine with regards to environmental policies, said Ms. Silva, who now devotes her time to environmental advocacy. Now, a bill seeking to overhaul the 47-year-old Forest Code, a central piece of environmental legislation, is the most serious test yet of Ms. Rousseffs stance on the environment. The debate over the law has revealed the stark disconnect between a population that is increasingly supportive of conserving the Amazon and a Congress in which agricultural interests in the countrys rural north and northeast still hold sway. The furor comes as Brazil is set to hold a United Nations conference on sustainable development in Rio de Janeiro in June. Before taking office last January, Ms. Rousseff promised to veto any revision of the Forest Code that granted amnesty to landowners who had previously deforested illegally. Then her government negotiated a version of the code, approved by the Senate in December, that would give amnesty to farmers who broke the law before 2008 provided they agreed to plant new trees. The House is expected to debate the legislation once again in March, with Ms. Rousseff holding final veto power. The fight over the Forest Code has stoked the age-old struggle over development versus conservation in Brazil, a country that bears the weight of international pressure to protect the Amazon from deforestation because its sheer scale could affect global climatic conditions. Ms. Rousseff, a former energy minister, has so far flashed a more pro- development stance, environmentalists say, shifting the balance from the administration of her predecessor, Luiz Inacio Lula da Silva, who appointed Ms. Silva. Agriculture represents 22 percent of Brazils gross domestic product. The so-called ruralists in Congress say that the old code is holding back Brazils agricultural potential and that it needs updating to allow more land to be opened up to production. Environmentalists counter that there is already enough land available to double production and that the