NPR News

In parts of the southeastern US, aggressive fire ants have been driven out by an even more recent arrival, the tawny crazy ant. Edward LeBrun, a researcher at the University of Texas at Austin, describes the newcomers and how one invasive species can out-invade another.

A series of tornadoes struck the central United States this week, including a powerful storm in Oklahoma that killed at least 24 people. Marshall Shepherd, the president of the American Meteorological Society, describes the ingredients of major tornadoes, and how they are predicted.

Last year scientists reported that a skin cancer drug appeared to reverse the effects of an Alzheimer's-like disease in mice. But four studies out this week in Science question the original results. Ronald Petersen, director of the Mayo Clinic's Alzheimer's Disease Research Center, talks about the new findings, and the hunt for Alzheimer's drugs.

Scientists say climate change could increase pests and weeds, lengthen growing seasons and turn dry soil to dust. Farmers are already on the offensive, adopting no-till cropping methods to conserve water and experimenting with different seeds. And scientists are using a technique called gene silencing to develop new crops--without tinkering with the plants' DNA.