Divorce has been blamed for everything from falling academic grades to rising crime rates — and now a new report says broken homes are partly to blame for environmental devastation. According to a study appearing in the journal Nature, social trends such as living alone, having fewer children, divorcing more often, and remaining single longer have led to an increase in the number of smaller households. That, in turn, has taken a heavy toll on the world’s natural resources, because home construction leads to increased demand for building materials, appliances, and energy, as well as increased waste production. Although many environmentalists worry about population growth, the study says a more accurate indicator of environmental harm is the growth in number of housing units. It found that, in countries where the environment is especially imperiled by human activities, population grew by 1.8 percent per year, while housing units grew by 3.1 percent per year. In countries where human activity is not having as great an effect, both population and household growth were about 1.7 percent. In the U.S., one-quarter of all homes are inhabited by just one person.