The update to the country's 1965 Forestry Code would reduce both the amount of vegetation landowners must preserve and the future penalties paid for those who currently flout environmental laws. After valuable wood is sold, much of the land in deforested areas ends up being cleared for grazing cattle and agriculture.
"The project approved in Congress is the fruit of a torturous legislative process, made to serve the interests of a small part of society that wants to increase the possibility of deforestation and give amnesty to those who have already cut it down illegally," said Maria Cecilia Wey de Brito, head of the World Wildlife Fund in Brazil.
Rousseff suffered a surprise defeat in April at the hands of Congress' ruralista voting bloc, which represents farming interests. The lawmakers managed to push through a version of the bill that rolled back environmental protections and gave amnesty to past violators.
Since then, she has faced widespread pressure from those opposed to the changes _ scientists, public figures, celebrities, as well as business leaders and politicians _ to veto the bill. However, facing long odds of winning approval for tougher environmental legislation in Congress, she announced Friday only a partial veto, leaving it much more lenient than the laws currently in place.
Though Rousseff enjoys widespread support among Brazilians, her party controls only 15% of the seats in a Congress divided between more than 20 parties. Rousseff often has difficulty corralling a coalition to support her positions and may not have been able to hold back revisions to the forestry law any more than she did, analysts say.
"In environmental terms, the law should have been vetoed completely," Luiz Antonio Martinelli, agronomist at the University of Sao Paulo, told the Folha de Sao Paulo newspaper. "But we know that would be very difficult politically."
Over the weekend, activists from Greenpeace blocked a shipment of pig iron used by the U.S. steel industry from leaving a port, saying its production relied on illegal deforestation and slave labor. Q'orianka Kilcher, the American actress who played Pocahontas in the 2005 film "The New World," participated last week by climbing the anchor chain of a cargo ship to stop it from docking. The protest was meant raise awareness of the issue outside of Brazil, which will host the United Nations' "Rio+20" environmental conference next month.
For decades the Amazon rain forest, the world's largest, has been shrinking steadily. The forest is so vast that the Brazilian government monitors the rate of deforestation using satellite imagery.
The destruction had slowed in the last decade under tougher government enforcement, but at the same time the country has lived through an economic boom fueled largely by selling commodities. The producers of products that rely on cleared land, such as soybeans and beef, have increased the country's monetary wealth and become politically more powerful.
Environmentalists fear the new bill those interest groups helped shape could bring Brazil back to the bad old days of rapid clearing.
The government insists that the new bill, which is likely to pass, does not grant full amnesty to those who broke previous rules. But many who ignored them will have little reason to regret it.
This month, activists and journalists took a small plane over what used to be the forest in the northeastern state of Maranhao, snapping pictures of widespread illegal logging in the few remaining patches of forest in the region.
Amnesty means that "the small percentage of landowners that actually obeyed the law will end up being the clowns of history," said Tatiana Carvalho of Greenpeace Brazil. "Everyone else will get the message that they can continue on chopping down without fear."
By Vincent Bevins, Los Angeles Times