In a late-night session on Tuesday, the lower house of Brazil's Congress approved a bill aimed at relaxing environmental licensing for a proposed highway that would cut through the heart of the Amazon rainforest. Scientists warn that this project could pose a significant threat to the world's largest tropical rainforest.

The bill, which still needs Senate approval, includes provisions to allocate funds received from conservation donations to finance the controversial highway project. Among these funds, the $1.3 billion Amazon Fund, supported by the U.S. and European allies, is included.

The highway in question was originally constructed in the 1970s during the military government's push to populate the Amazon. However, it was quickly abandoned, and by the late 1980s, the majority of the 560-mile road from Porto Velho in Rondonia state to Manaus in Amazonas state had deteriorated into an impassable dirt road.

Currently, much of the route is only viable during dry months when vehicles must navigate broken pavement, huge potholes, and debris from the surrounding jungle. The proposed project aims to repave the road, researchers say that this could trigger rampant deforestation in Amazonas state, home to Brazil's best-preserved rainforest area due to its lack of existing roads.

Experts warn that previous highway projects in the Amazon have resulted in increased land grabbing and illegal deforestation. They fear that if the BR-319 highway is revitalized, it would create a new frontier for logging, potentially pushing the rainforest beyond a point of no return.

However, proponents of the project argue that it is necessary to reduce the isolation of Amazonas and Rondonia states. Currently, when the BR-319 is impassable for most of the year, the city of Manaus is only accessible by river and air travel from the rest of Brazil.

The bill referred to the proposed highway as "critical infrastructure, indispensable to national security, requiring the guarantee of its trafficability." If passed by the Senate, the legislation would authorize the use of donations received by Brazil to aid in the recovery, paving, and capacity expansion of the highway.

The approval of this bill has ignited a heated debate between conservationists and those advocating for improved regional connectivity. As the fate of the Amazon rainforest hangs in the balance, the decision now rests with the Brazilian Senate to determine the future of this contentious project.