Earth/Environment

Trees’ mighty appetite

Forests across the globe sop up an estimated 2.4 billion metric tons of carbon per year from the atmosphere, a new calculation shows, mostly in the form of carbon dioxide. But because many existing forest stands get harvested each year and release their stored carbon, the net result is slightly more than 1 billion tons more carbon entering forests than leaving them, an international team of researchers reports online July 14 in Science. Although the amount of carbon capture within the environment was known to be large, exactly how much was stored in the environment and where — such as in trees — has been uncertain. —Janet Raloff

A growing climate paradox

The release of two climate-warming gases will accelerate in response to growing carbon dioxide emissions. Carbon dioxide fertilizes plant growth, which ties up the gas in plant tissues and soils. This environmental carbon capture should slow the expected acceleration of global warming. However, measurements by scientists in the United States and Ireland now show that carbon’s fertilizing effect can also boost soils’ release of nitrous oxide and wetlands’ release of methane, both greenhouse gases. Such emissions could erase more than 16 percent of the climate benefits expected from carbon’s capture by plants and soil, the scientists report July 14 in Nature. —Janet Raloff

Plastics compound may slow boys’ development

The higher a pregnant woman’s exposure to phthalates —compounds used in plastics and as solvents — the more likely her son will score somewhat low on standard indices of mental and motor development by 6 months old. Developmental scores for girls showed no link to phthalates, researchers in Korea report online July 7 in Environmental Health Perspectives. Other studies have also found males to be more sensitive than girls to prenatal phthalate exposures. Urinary markers of three phthalates — each tallied during the third trimester of pregnancy — were slightly lower among the 460 Korean moms in this study than in some studies of American women. —Janet Raloff

Pinpointing uranium

Catching nuclear smugglers may become a tad easier thanks to a new way to tell where a sample of uranium came from. The key is looking at a group of chemical elements called rare earths, researchers from Nancy-Université in France write in the August Terra Nova. The team’s analyses of uranium oxides from 18 locations worldwide find unique chemical makeups in the rare earth elements found alongside uranium in ore. The different compositions are linked to the geological conditions in which the rocks formed, the researchers say. The method could help to identify the source of smuggled uranium. —Alexandra Witze