After two years of political wrangling that pitted rural agricultural interests known as “ruralistas” against environmentalists and many scientists, Brazil’s lower house approved legislation late Wednesday that would scale back the country’s vaunted forest protection code.

The legislation would clear the slate on older – and more often than not illegal – deforestation while scaling back protections along rivers and on hills. Deputies approved the main legislation in a 274-184 vote, and additional voting on 21 amendments advanced by the ruralistas went late into the night.

Details remain murky, but environmentalists immediately sounded the alarm. “O início do fim das florestas” Greenpeace Brazil proclaimed in a headline on its website. “The beginning of the end of forests.”

To be fair, such visions of doom should be considered in context. Although pressure on forests is on the rise, deforestation in the Amazon hit a record low last year. If Brazil can sustain and advance those gains, it would represent one of the most remarkable environmental success stories in recent decades. The fear is that weakening the law will reverse this progress and unleash a wave of new deforestation by convincing farmers and ranchers that Brazil doesn’t have the political will to truly enforce the law.

Agricultural interests counter that the legislation is needed to clear the slate and reign in a regulatory system that had become unworkable and overly burdensome (for more from the forces driving the bill, see the Brazilian Agriculture and Livestock Confederation’s earlier analysis, conveniently in English). The confederation has yet to release an analysis of the revised legislation.

Wednesday’s vote was yet another set back for the administration of President Dilma Rousseff, who favoured a version that passed the Senate in December. The question is now whether and how Rousseff will use her veto power, which allows her to strike entire paragraphs and sections from the legislation.

The Senate bill was widely considered to be an improvement on earlier legislation that originated in the house, but environmentalists opposed that bill, too. It is virtually certain that Rousseff will ignore their pleas to veto the entire bill and start anew, although many expect that she will move to strike the most egregious changes approved this week.

Although the lower house did retain a requirement that farmers and ranchers restore forests along riparian areas, the conservation group WWF’s preliminary analysis indicates that the bulk of the votes on Wednesday came down in favor of the ruralistas. “All in all a very bad night for the Amazon and rest of Brazil’s forests,” reported WWF spokesman Brendan Rohr, who spent Wednesday evening helping reporters like yours truly try to track the news from afar.

The bill has been plodding along in one form or another for nearly two years. For a bit of history, see our initial coverage from 2010 as well as an update story last year. Keep an eye on Nature for additional analysis over the coming week.

Photo: Per-Anders Pettersson/Getty Images