Two-fifths of Amazonian forest is at risk.

The Amazon basin's forest will lose 2.1 million square kilometers of its 5.3 million [k.sup.2] by 2050 if current development trends go unabated, according to a new projection. However, aggressive policy changes could prevent deforestation on 1.3 million [km.sup.2] of the threatened area, scientists report in the March 23 Nature.

Last week, at the eighth United Nations conference on biodiversity in Curitiba, Brazil, the Brazilian government announced that it now protects nearly 800,000 [km.sup.2] of Amazonian forest and has beaten a 2012 deadline for achieving that goal.

But governments in the region will need to set aside more protected areas and simultaneously curtail forest clearance by private landowners to prevent substantial deforestation, say researchers led by Britaldo Silveira Soares-Filho of the Federal University of Minas Gerais in Belo Horizonte, Brazil.

For the calculations, the team estimated the consequences of anticipated expansions of cattle ranching, soy farming, and roads. The scientists compared that scenario with the potential protection conferred by policies aimed at, for example, expanding and more vigorously guarding protected areas, curtailing road construction, or requiring landowners to set aside private forest reserves.--B.H.