A third of Europe's forest dwelling species rely on dead or dying trees, logs and branches for their survival, according to a report by WWF, the global conservation organization.

This array of plants, insects, birds and mammals, makes up the single biggest group of threatened species in Europe, WWF says.

"Europe's forests should be allowed to grow old gracefully," said Daniel Vallauri, WWF forest specialist. "By stripping a forest of its decaying timber and old trees we are performing a strange and unnecessary cosmetic surgery on a natural ecosystem which threatens much of its biodiversity."

The removal of decaying timber and old trees has led to a drastic decline in species such as insects, beetles, fungi, and lichens, according to the report, "Deadwood - Living Forests."

Woodpeckers, bats, and squirrels that nest in hollow trees have also lost their natural habitat.

WWF fears Europeans are failing to understand the ecological importance of deadwood. (Photo by B. Boisson courtesy WWF-France)

"When a tree falls in the forest, it creates disturbances that helps some plants to germinate and grow," the report says. "Deadwood falling into streams and rivers also provides important habitats, including assisting the creation of gravel bars and pools, which reduce water flow, creating fish and insect habitat and providing valuable substrate for algae."

Forests with dead and veteran trees are often much healthier and resistant to disease, pests, and climate change than young tidy forests, WWF says.

The report finds deadwood is at a critically low level throughout European forests primarily because of a lack of recognition for its importance and poor management practices within commercial forests as well as in protected areas.

"Increasing the amount of veteran trees and deadwood in forest management can make a big difference to sustaining Europe's biodiversity," said Vallauri. "We need to debunk the myths that deadwood and veteran trees mean a sick forest. In most cases it means a healthy forest with a long life cycle and a very high diversity of habitats for species."

The report finds that western Europe forests have on average less than five percent of the deadwood expected in natural conditions.

Up to 25 percent of timber in rare, existing natural European forests, is deadwood, WWF says.

Healthy forests needs deadwood to maintain a long life cycle and a very high diversity of habitats for species. (Photo by Igor Shpilenok courtesy WWFe)

The conservation group hopes its report will educate policymakers on how deadwood keeps forests productive by providing organic matter and nutrients for trees, preventing soil erosion, and providing long-term storage for carbon.

WWF is calling on European governments, forest owners, and industry to help conserve biodiversity by increasing the amount of deadwood in managed forests, by up to 20-30 cubic meters - about one truckload - per hectare by 2030.

WWF also criticized government subsidies that require the removal of deadwood after storms. The French government, for example, pays up to $2,230 per hectare for salvage felling without any minimum guidance for deadwood.

The conservation group released the report ahead of an international conference on deadwood being held in Chambery, France this week.

The full report can be found here.