Winter moth progression, from J. U. Jepsen, et al., 2008

Northward expansion of insect herbivores such as the winter moth in northernmost Fennoscandia (intact mountain birch forest is shown in green, severely defoliated forest during the most recent outbreak in 2005 to 2008 is in dark brown, and tundra beyond the tree line is in white; reports of local winter moth outbreaks before the last extensive outbreak period are indicated by yellow dots and years of observation [modified from J. U. Jepsen, S. B. Hagen, R. A. Ims, N. G. Yoccoz, J. Anim. Ecol. 77, 257 (2008)].

Eric Post, et al., Ecological Dynamics Across the Arctic Associated with Recent Climate Change, Science, 11 September 2009: Vol. 325. no. 5946, pp. 1355 – 1358 DOI: 10.1126/science.1173113