Environmental groups scored a victory in a court decision involving four timber sales in the Tongass National Forest in southeast Alaska.

The 9th Circuit Court of Appeals issued an opinion Tuesday finding that the U.S. Forest Service erred in approving the sales, which would have cut 33 million board feet of timber from old-growth forest.

The court says the Forest Service failed to explain its decision to approve the timber projects, especially given its mandate to manage the Tongass for viable populations of Sitka black-tailed deer and Alexander Archipelago wolves.

The court says it also found the agency's computer model for determining how many deer could live on the lands in the areas of the timber sales puzzling.

The lawsuit was brought by Greenpeace and Cascadia Wildlands.