Climate-Induced Elevational Range Shifts and Increase in Plant Species Richness in a Himalayan Biodiversity Epicentre

Abstract

Global average temperature increase during the last century has induced species geographic range shifts and extinctions. Montane floras, in particular, are highly sensitive to climate change and mountains serve as suitable observation sites for tracing climate-induced biological response. The Himalaya constitute an important global biodiversity hotspot, yet studies on species’ response to climate change from this region are lacking. Here we use historical (1849–50) and the recent (2007–2010) data on temperature and endemic species’ elevational ranges to perform a correlative study in the two alpine valleys of Sikkim. We show that the ongoing warming in the alpine Sikkim Himalaya has transformed the plant assemblages. This study lends support to the hypothesis that changing climate is causing species distribution changes. We provide first evidence of warmer winters in the region compared to the last two centuries, with mean temperatures of the warmest and the coldest months may have increased by 0.76±0.25°C and 3.65±2°C, respectively. Warming-driven geographical range shifts were recorded in 87% of 124 endemic plant species studied in the region; upper range extensions of species have resulted in increased species richness in the upper alpine zone, compared to the 19th century. We recorded a shift of 23–998 m in species’ upper elevation limit and a mean upward displacement rate of 27.53±22.04 m/decade in the present study. We infer that the present-day plant assemblages and community structure in the Himalaya is substantially different from the last century and is, therefore, in a state of flux under the impact of warming. The continued trend of warming is likely to result in ongoing elevational range contractions and eventually, species extinctions, particularly at mountaintops.

Land-use change under a warming climate facilitated upslope expansion of Himalayan silver fir (Abies spectabilis (D. Don) Spach)

“…Reduced land-use intensity is therefore the most likely driver of range expansion in the MCA. The small increase in average atmospheric temperature has not yet impacted species distribution in this ecotone, although it has been noted in other regions (Matteodo et al 2013;Parmesan and Yohe 2003; Telwala et al 2013). However, reduced intensity of land use (Müller et al 2015) may also have synergistic effects with increased warming in the RLI area (Morueta-Holme et al 2015).…”

“…2), it can be seen that the limit has increased at all sites. In the eastern Himalaya, Telwala et al (2013) reported 87 % of endemic plants (out of 124 species) shifted upslope in response to a temperature rise in mean summer temperature of 0.76 and 3.65°C in mean winter temperature. Over the last nine decades, an average upslope shift of 145 m was reported in Engadine valley of Swiss Alps (Frei et al 2010) and in the last half century a 70 m elevational shift in the Montseny Mountains (Catalonia, NE Spain) was reported (Penuelas et al 2007) as a response to global warming.…”

“…Several recent studies document an upslope or poleward shift of species at the treeline and suggest that this is partly as a result of recent global warming (Bhatta and Vetaas 2016;e.g. Matteodo et al 2013;Parmesan and Yohe 2003;Sturm et al 2001;Telwala et al 2013).…”

“…Chen et al 2011;Lenoir et al 2008;Telwala et al 2013), making it difficult to determine the role played by climate in any changed scenario. The upslope shift for different species ranged from 586 to 787 m on the Chimborazo volcano in Ecuador over a 210-year period (MoruetaHolme et al 2015); in the Engadine valley of Swiss Alps, more than 100 m upslope shift has been reported during the last nine decades (Frei et al 2010) and 87 percent of 124 endemic plants species have expanded their range in Sikkim Himalaya during the last ca.…”

“…The upslope shift for different species ranged from 586 to 787 m on the Chimborazo volcano in Ecuador over a 210-year period (MoruetaHolme et al 2015); in the Engadine valley of Swiss Alps, more than 100 m upslope shift has been reported during the last nine decades (Frei et al 2010) and 87 percent of 124 endemic plants species have expanded their range in Sikkim Himalaya during the last ca. 150 years (Telwala et al 2013). The treeline has shifted upwards in Barun valley in central Himalaya in the last 130 years (Chhetri and Cairns 2015), and A. spectabilis has shifted upslope in Manaslu region, central Himalaya in the last ca.…”