Environmentalists have filed a suit at the US District Court in Phoenix to block woodland management work in the Grand Canyon which the Forest Service says is needed to prevent fire and preserve habitats.

The Forest Service wants to remove 51,000 trees, including old ponderosa pine, spruce and fir, from the Kaibab Plateau on the northern rim of the Canyon. It acknowledged that the sale of the timber would bring in US$900,000, but it insisted the work is vital to allow other old-growth trees to thrive, to protect habitats and reduce wildfire risk.

The Sierra Club and Center for Biological Diversity green groups, however, say that the project would mean “sacrficing old-growth trees for commercial gain, while doing little to prevent catastrophic fires”.

The environmentalists and the Forest Service are at odds over the definition of “old-growth” trees and the greens say that the best strategy to prevent the spread of forest fires would be to remove smaller trees that “clog the forest floor”.

The Forest Service responded that less than 1% of the trees it proposes to fell have trunk diameters over 24in.