Northern geometrids and climate change: from abiotic factors to trophic interactions.

Abstract

The subarctic mountain birch forests have been periodically disturbed by geometrid moth outbreaks since at least the mid-19th century. The effects of these disturbances can be seen from landscape-level dieback of the birch forest to local-level changes in soil processes. Recent research efforts have demonstrated that the geometrid moth-birch forest system is undergoing changes that could be linked to the ongoing climate warming. Milder winter and spring temperatures influence winter survival and outbreak ranges of the moths, and are also alleviating range expansions and the spread of new species to the area. Moreover, phenology matching with the host plant may be altered. The outcome appears to be intensified outbreaks and a potential for altered species interactions and dynamics with ecosystem wide consequences. This chapter will first introduce the prevailing dynamics of the mountain birch-geometrid system and the reported ecosystem effects of geometrid outbreaks. Second, the chapter summarizes observations of ongoing abiotic changes in the area and presents the potential known and unknown effects on the study species. Finally, the chapter discusses the future scenarios for this northern ecosystem and the possibility of major ecosystem changes.