| ||||||||||||||||||||
Montane warning of global warming
It is easy enough to obtain anecdotal evidence for the effects of global warming but we actually need hard data, based on careful floristic and meteorological analysis. Thus, Sanz-Elorza et al. from Madrid and Almeria (pp. 273-280) have studied vegetational changes up to 2430 m in the Peoalara Massif of the Spanish Central Range. At these high altitudes, the main vegetation had been grassland communities, dominated by Festuca supina, while at slightly lower altitudes, the vegetation was more ‘shrubby’, typified by Cytisus oromediterraneus and Juniperus communis alpina. Both these shrubs are easily identified in aerial photographs and the authors have used this in high-resolution analyses of photographs taken in 1957 and in 1991. The results are startlingly clear. Much of the grassland at high altitude has been invaded extensively by the shrub species from the lower climatic zone. ‘On the ground’ vegetational analysis confirms that the shrubs are now indeed abundant at the higher altitudes and are likely to replace the grassland communities completely. The authors have also analysed weather recordings for the region going back to 1941. Of particular note are the steady temperature rise, especially marked for the coldest month of the year, January (leading to fewer frosts), and a redistribution of precipitation, with more in summer and less in winter now than previously. Can we then ascribe the vegetational changes to climate change? The authors point out that the distributions of grass-dominated and shrub-dominated communities may also be affected by land use, especially grazing. However, there has been no change in grazing practices in the study area since the 19th century. The authors therefore conclude that the main factors that have permitted the upward invasion of the shrub species are related to global warming, while more generally they note the vulnerability of isolated and specialized plant communities to the effects of climate change.
Professor J. A. Bryant
University of Exeter, UK
j.a.bryant{at}exeter.ac.uk
| ||||||||||||||||||||