Human production of fixed nitrogen, used mostly to fertilize crops, now accounts for about half of the total fixed nitrogen added to the Earth both on land and in the oceans.

More than 5,893 leaks from aging natural gas pipelines have been found under the streets of Washington, D.C., by a research team from Duke University and Boston University. A dozen of the leaks could have posed explosion risks, the researchers said. Some manholes had methane concentrations as high as 500,000 parts per million of natural…