Eco-minded criminals might want to take note: The environmental impact of crime, as measured by carbon dioxide (CO2) emissions, is surprisingly high. According to a new study, criminal activity in England and Wales was responsible for producing more than 4 million metric tons of CO2 in 2011. That’s the same amount of CO2 that 900,000 U.K. homes produce in an entire year. How did researchers arrive at their conclusion? They first tallied the costs of all crimes—which included everything from caring for victims to replacing stolen goods to housing convicted prisoners—and converted them into an equivalent amount of greenhouse gases. Researchers concluded that the crime that generates the largest proportion of the criminal carbon footprint is burglary—breaking and entering with the intent to commit a crime—generating about 30% of the total. Aggravated bodily harm contributed 11%, and theft—the taking of someone’s property—also contributed 11%, they report this month in the Journal of Industrial Ecology. Researchers say that although crime reduction might seem like the obvious way to reduce these emissions, that may not be true in all cases. That’s because the money and energy spent on criminal activity could be diverted to other, equally polluting activities if crime were not taking place. Similarly, the money spent to house and care for prisoners—a proxy for measuring their carbon footprint—might be less than the money the prisoners themselves would spend if they were not living behind bars. The researchers hope to study this and other “rebound” effects to find out whether—in the balance—crime costs, or benefits, our environment.