Brazil’s House of Representatives last month approved profound changes to the Forest Code, a series of laws to regulate the country’s land use. The changes would jeopardize ecosystems and allow deforestation of about 20 million more hectares than the original Forest Code, according to estimates by Gerd Sparovek of the University of São Paulo (see go.nature.com/n8lwfu). The Brazilian Senate must seize its last opportunity to block the changes.

The proposed changes would substantially increase carbon emissions. Assuming that half of the newly affected forest (10 million hectares) will be given over to agriculture and that the average carbon biomass in the Amazon, Atlantic Forest and Cerrado is 50 megagrams per hectare (L. F. Alves et al. Forest Ecol. Manage. 260, 679–691; 2010), emissions would amount to some 500 teragrams of carbon — on top of the 100–300 Tg that arise annually from deforestation of the Amazon (J. P. H. B. Ometto et al. Oecologia 143, 483–500; 2005).

The government’s efforts to decrease Amazon deforestation would be wasted, as would investments made in the ethanol industry for a cleaner environment. Brazil’s commitment to the environment could lose credibility internationally, causing developed countries to raise import taxes on Brazilian agricultural products, making them less competitive. 

Such serious consequences would offset any short-term gain by the Brazilian agricultural sectors that might result from changes to the Forest Code.