A highway's signature
In the 1970s, the Brazilian state of Rondônia contained over 200,000 square kilometers of dense rainforest. The landscape began to change dramatically with government settlement programs designed to populate the Amazon. Central to this transformation was the BR-364 highway, a road first opened in the 1960s that cuts northwest through the state. Its paving in the early 1980s, largely funded by the World Bank's Polonoroeste development program, made the remote region accessible year-round for the first time.
The Polonoroeste project, which began in 1981, aimed to promote agriculture and absorb migrants from southern Brazil. The plan laid out a geometric grid for settlement. Secondary roads were built at right angles to the main BR-364 highway, branching deep into the forest. Migrant families were given plots of land along these new access roads. As settlers cleared their individual lots for crops and pasture, the famous "fishbone" or "feather" pattern began to emerge, a direct visualization of the road network's design. This systematic clearing, visible from orbit, is an example of tropical deforestation.
An orbital perspective on consequences
The entire process has been documented by decades of remote sensing data, primarily from the NASA/USGS Landsat satellite program. Landsat imagery provides an unbroken observational record from the 1970s to the present, showing the fishbone gashes widening and coalescing over time. By 1978, about 4,200 square kilometers of forest in Rondônia had been cleared. A decade later, that number jumped to 30,000 square kilometers. By 2003, the cleared area had expanded to 67,764 square kilometers, an area larger than the state of West Virginia.
The agricultural boom was often short-lived. Much of the Amazon's soil is nutrient-poor. Once the forest is cut and burned, the initial fertility provided by the ash is quickly exhausted or washed away by heavy rains. Crop yields decline after just a few years. Farmers often convert the depleted land to cattle pasture, which supports fewer people and requires larger areas, and then move deeper into the forest to clear new plots. This cycle of clearing, depletion, and expansion drives the deforestation frontier further into the Amazon, collapsing the distinct fishbone patterns into large swathes of cleared land. The Amazon, long considered a planetary carbon sink, has in some areas become a net emitter of carbon due to such large-scale land-use change.