The decision isn't surprising. In its scorecard of votes on environmental issues for the first session of the current Congress, the group gave Obama a score of 67. John McCain got a zero. The Arizona senator did not show up for any of the votes the group scored.
The group says Obama has "the most comprehensive plan" it has ever seen to move toward clean energy and combat global warming.
Friends of the Earth and the Sierra Club announced their support for Obama earlier this year, citing McCain's support for more offshore drilling, expanding nuclear power and a gas tax holiday.
None of the three groups has ever backed a Republican.