At the Swiss Federal Institute of Technology in Lausanne/CH the doctoral candidate Rita Bütler has looked at the question of how much dead wood is enough for biodiversity conservation in managed forests. She examined the presence of the three-toed woodpecker in 24 sub-alpine spruce forests in Switzerland. It was suggested that three-toed woodpeckers be considered as indicators of dead wood and habitat quality. If the woodpecker's habitat is to be preserved, Bütler recommends a lower limit 18 m³ of standing dead wood per hectare of forest.