"Many of the allegedly available restoration areas are clearly unsuitable for more trees than they currently support. If you look closely at the map, a large proportion of these areas are in regions where soils are permanently frozen," says Eike Luedeling, a climate change researcher and professor of horticultural sciences at the University of Bonn.

Jan Börner, Luedeling's colleague and a professor for economics of sustainable land use at the University of Bonn, is similarly skeptical. Börner says that some areas being proposed for restoration under the current study are already in use for other purposes. Börner considers the study to be an "interesting academic exercise ... but as a [climate change] mitigation strategy proposal (and it is being advertised as such!), it sends a misleading signal to the international climate policy debate.