12.1 Introduction
Mountain plant species are already showing strong responses to climate change, for
instance through upwards shifts in distribution limits (Grabherr et al. 1994; Walther
et al. 2002; Lenoir et al. 2008). Species distribution models predict that this will
lead to a contraction or total loss of high-alpine species’ distribution ranges in the
longer term (Engler et al. 2011), as their potential new habitat decreases in area at
higher altitude (Körner 2007), while they might become out-competed and replaced
by species from lower elevations (Engler et al. 2011). Through these mechanisms,
species distribution models predict losses of over one-third of all species of the
alpine vegetation belt for some regions of the Alps, and even higher extinction rates
in other European mountain ranges (Engler et al. 2011).
This chapter will give an overview of our current knowledge of vegetation
change in alpine regions with a particular focus on mountain summits in the Swiss
Alps and across Europe. First, results from different monitoring approaches will be
reviewed. One way to study vegetation changes is to repeat historical surveys, as
many historical species lists from mountain summits are available from about a
century ago, in some cases even from 170 years ago. Another suitable approach is
standardised monitoring that was initiated relatively recently but capture shorter
term vegetation changes in great detail (e.g. Roth et al. 2014). The Global
Observation Research Initiative in Alpine Environments (GLORIA) for instance
was initiated in 2001 across many European mountains and has now research sites
on summits all over the world (Grabherr et al. 2000). The first analyses from
GLORIA have demonstrated rapid vegetation changes on European summits (Pauli
et al. 2012; Gottfried et al. 2012).
This chapter will then focus on different factors influencing mountain vegetation.
The most discussed cause for vegetation changes is climate warming, but it is
important to take also other factors of global change into consideration, such as
atmospheric CO 2 concentrations, nutrient availability, land use, etc. Although
temperature is, without a doubt, an important climatic driver of alpine plant distribution, it probably strongly interacts with precipitation and soil moisture
(Elmendorf et al. 2012a, b) especially in the form of snow (Grytnes et al. 2014).
Given ongoing climate and vegetation change, the question arises how threatened mountain flora actually is. On the one hand, habitat for high-alpine specialists
will most likely shrink in a warming climate. On the other hand, the high diversity
of microhabitats on mountains (Scherrer and Körner 2011) and the longevity of
many mountain plants may prevent extinctions or at least result in a delayed
extinction debt (Dullinger et al. 2012). This book chapter will outline our current
knowledge about the extinction risk of alpine plants.
Finally, the key question remains whether humans can contribute to the
preservation of alpine plants or to prevent their local extinctions. Hence, the final
section of this chapter will outline opportunities for conservation, appropriate forms
of land-use, conservation and restoration measures in high-alpine environments.
286
C. Rixen and S. Wipf
Mountain plant species are already showing strong responses to climate change, for
instance through upwards shifts in distribution limits (Grabherr et al. 1994; Walther
et al. 2002; Lenoir et al. 2008). Species distribution models predict that this will
lead to a contraction or total loss of high-alpine species’ distribution ranges in the
longer term (Engler et al. 2011), as their potential new habitat decreases in area at
higher altitude (Körner 2007), while they might become out-competed and replaced
by species from lower elevations (Engler et al. 2011). Through these mechanisms,
species distribution models predict losses of over one-third of all species of the
alpine vegetation belt for some regions of the Alps, and even higher extinction rates
in other European mountain ranges (Engler et al. 2011).
This chapter will give an overview of our current knowledge of vegetation
change in alpine regions with a particular focus on mountain summits in the Swiss
Alps and across Europe. First, results from different monitoring approaches will be
reviewed. One way to study vegetation changes is to repeat historical surveys, as
many historical species lists from mountain summits are available from about a
century ago, in some cases even from 170 years ago. Another suitable approach is
standardised monitoring that was initiated relatively recently but capture shorter
term vegetation changes in great detail (e.g. Roth et al. 2014). The Global
Observation Research Initiative in Alpine Environments (GLORIA) for instance
was initiated in 2001 across many European mountains and has now research sites
on summits all over the world (Grabherr et al. 2000). The first analyses from
GLORIA have demonstrated rapid vegetation changes on European summits (Pauli
et al. 2012; Gottfried et al. 2012).
This chapter will then focus on different factors influencing mountain vegetation.
The most discussed cause for vegetation changes is climate warming, but it is
important to take also other factors of global change into consideration, such as
atmospheric CO 2 concentrations, nutrient availability, land use, etc. Although
temperature is, without a doubt, an important climatic driver of alpine plant distribution, it probably strongly interacts with precipitation and soil moisture
(Elmendorf et al. 2012a, b) especially in the form of snow (Grytnes et al. 2014).
Given ongoing climate and vegetation change, the question arises how threatened mountain flora actually is. On the one hand, habitat for high-alpine specialists
will most likely shrink in a warming climate. On the other hand, the high diversity
of microhabitats on mountains (Scherrer and Körner 2011) and the longevity of
many mountain plants may prevent extinctions or at least result in a delayed
extinction debt (Dullinger et al. 2012). This book chapter will outline our current
knowledge about the extinction risk of alpine plants.
Finally, the key question remains whether humans can contribute to the
preservation of alpine plants or to prevent their local extinctions. Hence, the final
section of this chapter will outline opportunities for conservation, appropriate forms
of land-use, conservation and restoration measures in high-alpine environments.
286
C. Rixen and S. Wipf