Box 1 - The pine processionary moth Thaumetopoea pityocampa

- Forests and climate change - lessons from insects

The winter pine processionary moth, Thaumetopoea pityocampa offers a possibility to test for the effects of global warming on an insect population over a wide area of the Mediterranean basin and southern parts of Europe, where it is the most important pest of pine forests (Pinus spp.). Its geographic range lies within precise limits of elevation and latitude ([17]), primarily as a function of the average winter temperatures. Because the larvae are oligophagous, potentially feeding on all Pinus spp., but also on Cedrus spp. and the introduced Pseudotsuga menziesii, host plant distribution does not restrict the present range of the insect; many usual or potential host species grow in areas where the insect is absent. Consequently, if the climatic conditions become favourable in higher latitudes or at higher elevations, the insect may expand its range to these areas, often coupled with host switching ([7], [41]). This relative importance of temperature over biotic factors in defining the geographic distribution makes the moth a particularly suitable model to study the range shift in relation to global warming ([14]).

An important forest pest in many areas, the moth has shown in the last decades a substantial expansion of the outbreak area both northward and upward ([29], [26], [7]), aggravated by extreme climatic events such as the summer of 2003 ([8]). This has resulted in high attack rates in areas previously largely unaffected by the insect ([51]). The case deserves special interest for the implications it may have on the management of European forests and plantations, as well as on ornamental trees.