SÃO JOSÉ DOS CAMPOS, BRAZIL—Science reports that a new survey of lidar data suggests that thousands of sites containing evidence of human activity lie undiscovered in the Amazon rain forest. Researchers led by Vinicius Peripato, a remote sensing scientist at Brazil’s National Institute for Space Research, reviewed 2,050 square miles of lidar data and identified more than 900 known earthworks in the Amazon, along with 24 previously unknown constructions. These included what they suspected were ceremonial sites, fortified villages, and megalithic structures. The survey area covers just 0.1 percent of the Amazon’s total area of 2.6 million square miles. Extrapolating from their findings, the researchers estimate that 16,187 earthwork sites remain undiscovered in the Amazon. The model estimates that most of the unknown earthworks are concentrated in the southwest of the Amazon. To read about a lidar survey in Cambodia, go to “Angkor Urban Sprawl.”