Controversy is roiling among scientists about the wisdom of focusing conservation efforts on protecting “hot spots,” areas that cover just 1.4 percent of the Earth’s terrestrial surface but are home to nearly half of all land-based plant species and more than a third of all land animal species. Since 1988, when biologist Norman Myers and colleagues began identifying these spots, $750 million has been directed toward their protection. But a growing number of scientists are warning that the hot-spot strategy could cause big problems down the line. Michelle Marvier and Peter Kareiva, in a new article in American Scientist, argue that just as an investor should maintain a balanced portfolio, conservationists should avoid directing too much attention to a few areas at the expense of others. Marvier and Kareiva point out that the hot-spot concept does not take into account the valuable services humans get from some ecosystems, such as wetlands, which filter water and help control flooding. They also point out that many rare species and major animal groups live outside of the 25 or so identified hot spots.