Global warming and the onward march of the pine

Climate change could dramatically increase the forest cover of the Earth’s mountains, ecologists are predicting. Using data from the Austrian Alps, ecologists have developed a model that predicts the area covered by the local pine, Pinus mugo Turra, will increase from 10% today to 60% by the turn of the next millennium. The findings are published in the current issue of of the British Ecological Society’s Journal of Ecology and, the authors believe, this is the first paper to model tree line dynamics driven by climate change on a landscape scale in both time and space.

The Earth’s climate has warmed approximately 0.6°C over the past 100 years and the rate of warming looks set to accelerate. Alpine tree lines are assumed to be particularly sensitive to climate change, with high mountain forests predicted to shift their ranges up-slope at the expense of alpine vegetation.

According to one of the authors, Dr Stefan Dullinger of the University of Vienna: “Shrinkage and fragmentation of alpine habitats, as a consequence, may pose a serious threat to populations of many alpine plants, especially to regional endemics. On the other hand, expansion of mountain forests may also improve certain ecosystem services for human welfare, such as erosion control and increased water holding capacity in many high mountain water catchments.”

The findings will help the City of Vienna use pines to protect its drinking water catchment from erosion and pollution, Dr Dullinger says. However, he warns that the Viennese model is not easily transferable to other tree line systems: “Tree lines may respond quite idiosyncratically to global warming. Our model highlights the complex interactions of temperature rise, species specific traits and resident alpine vegetation cover in driving a possible future tree line expansion.”