Climate change, impacts and vulnerability in Europe ... - MemoFin.fr

Climate impacts on environmental systems3.4.4 Distribution of plant speciesRelevanceClimate change affects ecosystems in complexways. The composition of many plant communitiesis changing (Pompe et al., 2010), often to suchan extent that completely new assemblages areappearing (Urban et al., 2012). The extinction risk isparticularly large at the trailing edge (i.e. southernor lower altitudinal range margins) of a species(Dirnböck et al., 2011). The ecological implicationsof these changes and their effects on the provisionof ecosystems services are difficult to assess andquantify. However, it is clear that climate changeis an important threat for long-term biodiversityconservation. It threatens the ability of meeting theEU policy target to halt biodiversity loss by 2020.The favourable status of Natura 2000 sites is also indanger (Thuiller et al., 2011; Hickler et al., 2012).with wide altitudinal and ecological ranges showedthe greatest increases in abundance and altitudinaladvances, while species with more restricted habitatdemands have declined. High-altitude species havedisappeared from their lower-elevation sites andincreased their abundance at the highest altitudes.In the Swiss Alps an upward shift of vascularplants by 13 m was observed based on unpublisheddata of 'Biodiversity Monitoring Switzerland' ( 53 ).A study involving 171 forest species in 6 mountainregions in France found significant upward shiftsin species' optimum elevation, averaging 29 m perdecade, but with a wide range from + 238 m perdecade to – 171 m per decade (Lenoir et al., 2008).Land-use changes are the most likely explanation ofthe observed significant downward shifts in someregion (Lenoir et al., 2010). There is further evidenceof increases in the distribution range due to climatechange for several plant species (Berger et al., 2007;Walther et al., 2007; Pompe et al., 2011).Past trendsNew results have corroborated and refined earlierknowledge regarding distribution changes ofspecies as a result of climate change. Mountaintop floras across Europe have shown a significantchange in species composition between 2001and 2008, with cold-adapted species decreasingand warm-adapted species increasing (Gottfriedet al., 2012). Most species have moved upslope onaverage. These shifts had opposite effects on thesummit floras' species richness in boreal-temperatemountain regions (+ 3.9 species on average) andMediterranean mountain regions (– 1.4 species)(Pauli et al., 2012). In central Norway, an increasedspecies richness was found on 19 of 23 investigatedmountains in a 68-year study (Klanderud and Birks,2003). Lowland species, dwarf shrubs and speciesProjectionsPrevious modelling exercises projected a highspecies loss in Alpine species. More recent studiesthat have considered the large microclimaticheterogeneity in mountain regions suggest thatmany species would find climatically suitablehabitats within reach when forced to migrate undera changing climate (Scherrer and Körner, 2011).Accordingly, mountain flora seems to possess agreater small-scale persistence than previouslyassumed (Randin et al., 2009). Nevertheless, a recentmodelling study comprising 150 high-mountainplant species across the European Alps projectsaverage range size reductions of 44–50 % by theend of the 21st century (Dullinger et al., 2012).An assessment of the impacts of climate changeon 2 632 plant species across all major EuropeanKey messages: 3.4.4 Distribution of plant species• Several European plant species have shifted their distribution northward and uphill. These changes havebeen linked to observed climate change, in particular to milder winters.• Mountain ecosystems in many parts of Europe are changing as plant species expand uphill andcold‐adapted species are projected to lose climatically suitable areas.• By the late 21st century, distributions of European plant species are projected to have shifted severalhundred kilometres to the north, forests are likely to have contracted in the south and expanded in thenorth, and about half of the mountain plant species may face extinction.• The rate of climate change is expected to exceed the ability of many plant species to migrate, especiallyas landscape fragmentation may restrict movement.( 53 ) See http://www.biodiversitymonitoring.ch/en.Climate change, impacts and vulnerability in Europe 2012135