Invasive brown tree snakes have gobbled up most of Guam's native forest birds. Without these avian predators to keep their numbers in check, the island's spider population has exploded. Isaac Chellman/Rice University hide caption

itoggle caption Isaac Chellman/Rice University

An artist's re-creation of the first human migration to North America from across the Bering Sea. DEA Picture Library/De Agostini/Getty Images hide caption

itoggle caption DEA Picture Library/De Agostini/Getty Images

The shiny blue berries of the tropical Pollia condensata plant rely on their looks, not nutritional content, to attract birds to spread their seeds. Silvia Vignolini et al. via PNAS hide caption

itoggle caption Silvia Vignolini et al. via PNAS

Heath Powers, a project manager at the Los Alamos National Laboratory's "tree torture" lab, climbs through a maze of wiring outside a tree chamber. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

William Armstrong, fire manager for the Santa Fe National Forest service, says lush forests can be a "plague." David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

Craig Allen, left, a research ecologist with the U.S. Geological Survey, and Jorge Castro, a visiting professor of ecology from Spain, survey a plateau ravaged during last year's Las Conchas fire in New Mexico. The megafire burned over 150,000 acres of forest. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

Jorge Castro, a visiting professor of Ecology from Spain, sips water in the shade of a burnt tree in New Mexico's Bandelier Wilderness area. Last year's Las Conchas fire devastated the area burning over 150,000 acres of forest. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

A Smokey the Bear fire prevention sign sits in Valles Caldera along Highway 4, which was one of the front lines in fighting the Las Conchas Fire in 2011. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

Experts say glass buildings kill millions of birds every year. Scientists at Powdermill Avian Research Center are studying ways to help prevent this. Here, a volunteer tags a black hooded warbler in Rector, Pa., in May. Maggie Starbard/NPR hide caption

itoggle caption Maggie Starbard/NPR

Architect Guy Maxwell holds a printout of his proposed design for the new Bridge Building at Vassar College in Poughkeepsie, N.Y. John W. Poole/NPR hide caption

itoggle caption John W. Poole/NPR

Displayed in the hand of University of Oregon archaeologist Dennis Jenkins are three bases for western stemmed projectiles from the Paisley Caves in Oregon. The bases date to some 13,000 years ago. Jim Barlow/Science/AAAS hide caption

itoggle caption Jim Barlow/Science/AAAS

A water tank truck is seen on the main street in Waynesburg, Pa., on April 13. Scientists say naturally polluted water can rise to the surface of the Marcellus Shale; that finding suggests that frack water could seep out, too. Mladen Antonov/AFP/Getty Images hide caption

itoggle caption Mladen Antonov/AFP/Getty Images