A Richer, Greener and Smaller Alpine World: Review and Projection of Warming-Induced Plant Cover Change in the Swedish Scandes

Abstract

Alpine plant life is proliferating, biodiversity is on the rise and the mountain world appears more productive and inviting than ever. Upper range margin rise of trees and low-altitude (boreal) plant species, expansion of alpine grasslands and dwarf-shrub heaths are the modal biotic adjustments during the past few decades, after a century of substantial climate warming in the Swedish Scandes. This course of biotic landscape evolution has reached historical dimensions and broken a multi-millennial trend of plant cover retrogression, alpine tundra expansion, floristic and faunal impoverishment, all imposed by progressive and deterministic neoglacial climate cooling. Continued modest warming over the present century will likely be beneficial to alpine biodiversity, geoecological stability, resilience, sustainable reindeer husbandry and aesthetic landscape qualities. These aspects are highlighted by an integrative review of results from long-term monitoring of subalpine/alpine vegetation in the Swedish Scandes. This forms the basis for some tentative projections of landscape transformations in a potentially warmer future. Notably, these results and projections are not necessarily valid in other regions and differ in some respects from model predictions. Continued monitoring is mandatory as a basis for generation of more realistic vegetation and ecosystem models.

Changes Versus Homeostasis in Alpine and Sub-Alpine Vegetation Over Three Decades in the Sub-Arctic

“…Thus, our result contradicts some earlier studies and predictions that amelioration of climatic conditions may lead to low-altitude species colonising higher altitude sites (Sundqvist et al 2008;Kullman 2010;Sommer et al 2010), even though our observations span 16-31 years. However, our results agree with other studies which found no increase of lowaltitude species (e.g.…”

“…of species with a significant decrease b 3 0 2 7 9 2 0 a Low-altitude species consist of species with boreal, northern or other origin/distribution sensu Hultén (1950) b According to t tests, see Supplementary Information We found that despite relatively large changes in species composition and species richness at individual sites, the overall changes were relatively moderate. The ecosystems are likely to have high inertia as the open vegetation is dominated by slow-growing clonal species that buffer change (Callaghan et al 2002;Kullman 2010). However, assuming a lack of change might be too early.…”

“…Many clonal graminoids, and deciduous trees and shrubs may out-compete plants that respond less, or not at all to warming. Earlier studies indicate that low-altitude generalist species may increase in alpine regions while alpine/ Arctic species may decrease (Sundqvist et al 2008;Kullman 2010;Sommer et al 2010). At particular risk are slowgrowing and long-lived specialised alpine/Arctic plants such as Saxifraga oppositifolia (Stenström et al 1997), some dwarf shrubs such as Cassiope tetragona (Havström et al 1993;Molau 1997;ACIA 2005), and mosses and lichens (Van Wijk et al 2003;Walker et al 2006).…”

Spatially heterogeneous impact of climate change on small mammals of montane California

“…These conditions leave species with fewer options for shifting their ranges to compensate for changing temperature. Consistent with the contractions observed for several high-elevation mammal species, all sites with disappearing climates occur above 1500 m elevation [53,54].…”

Climate Warming and the Recent Treeline Shift in the European Alps: The Role of Geomorphological Factors in High-Altitude Sites

“…This fact has implications both for modelling treeline responses to climate change and as evidence of the potential biodiversity loss that likely will involve the treeless alpine belt vegetation in mountain environments because of fragmentation and habitat loss (Theurillat and Guisan 2001;Dirnböck et al 2003;Kullman 2010). A treeline upward advance by 200-600 m has been estimated for the next 100 years in the Swedish mountain region: a climatically driven change that could cause a 75-85% of reduction of the alpine areas, with most of the remaining area being constituted by scree slopes and boulder fields (Moen et al 2004).…”