Soaring divorce rates around the globe are taking a toll on the environment, American researchers suggested in a study released Monday.

Michigan State University researcher Jianguo "Jack" Liu and his assistant Eunice Yu said the increasing number of divorces leads to more households with fewer people and greater consumption of water and energy. They said housing units require space, construction materials and fuel to heat and cool, regardless of the number of inhabitants.

For example, in the United States in 2005, divorced households consumed an extra 73 billion kilowatt hours of electricity and 627 billion gallons of water. An additional 38 million extra rooms required heating and lighting that same year due to divorced households.

That costs $6.9 billion US in extra utility costs per year, Liu said, plus an added $3.6 billion for water, in addition to other costs such as land use.

"A married household actually uses resources more efficiently than a divorced household," Liu said. He said that in cohabitating households, people will watch the same television, share the air conditioning and heat and use the same refrigerator, all things that use energy at a regularly stable rate regardless of the number of uses.

Liu said he was not condemning divorce, "Some people really need to get divorces." He said cohabitation — whether by a family, friends or even in a commune — was simply a more environmentally friendly option. Additionally, the researchers noted that trends other than divorce are also changing family living structures, such as the end of multiple generations of a family sharing a home and people remaining single longer.

"People's first reaction to this research is surprise, and then it seems simple," Liu said in a release. "But a lot of things become simple after research is done. Our challenges were to connect the dots and quantify their relationships. People have been talking about how to protect the environment and combat climate change, but divorce is an overlooked factor that needs to be considered."

He said the increasing energy demands caused by divorce should be considered by governments when they are creating environmental policies.

The research was published in this week's online edition of the Proceedings of the National Academy of Sciences.

With files from the Associated Press