By measuring the thickness of forest canopies, scientists get a fair idea about the species of animals and plants present therein. Earlier, ecologists took canopy measurements from the ground using a visual procedure called the MacArthur-Horn method. Researchers at the University of Virginia in Charlottesville, US, have hit upon an alternative: a new technique using a laser radar or lidar, that makes the job easier. Carried in a plane flying overhead, the solid-state laser fires infrared pulses at the forest canopy and sensors in it spot reflections from each layer and from the ground. Providing 100 profiles per second, the technique can collect data on forest structure more quickly and cheaply.