One of the many consequences of the increase in global temperatures is that even plants have begun to migrate: some are moving their range northwards, in search of cooler areas, while others are moving up the mountains, leading to an unexpected (and disturbing) greening of the Alpine slopes.
Disturbing because, as explained by a study published in Sciencethe arrival of new species from lower altitudes is creating major problems of coexistence with plants specialized for life at high altitudes.
Is it due to the heat or the competition?
The study is the result of an analysis of data produced by GLORIA (Global Observation Research Initiative in Alpine Environments), a program founded in Austria in 2001 and which has since built a network of 120 high mountain sites spread throughout the world: it is the largest network in the world for the observation and study of high altitude vegetation. The study by the University of Vienna focused in particular on 62 European sites distributed in 16 different regions, monitoring their vegetation for twenty years, from 2001 to 2022.
The team was particularly interested in finding out which plants disappeared between one check and another, and in understanding which of these were direct victims of global warming and which, instead, were due to competition from other species coming from lower altitudes. What they discovered is first and foremost that the concern is well-founded: over the last 21 years, local extinctions of Alpine species have increased in all 62 monitored sites.
The monopoly of the generalists
These extinctions are linked to both hypothesized factors: they occur more often near the lower limits of the habitat of the disappearing plants, and they are more frequent in areas that are warming the most. These two factors contribute both to worsening environmental conditions and to favoring the arrival of low-altitude species, which are more generalist and compete with specialist plants.
The result is that the plant richness of Alpine sites is increasing in quantity: there are more and more peaks that are greening up. What is declining is variety: there are more and more plants coming from lower altitudes, and local species are collapsing – with consequences we cannot yet predict.
Also because several studies demonstrate how a decline in the variety of species is often a prelude to extinction: the risk is that what are now becoming green meadows will “empty” again.
