Across the world, regions at high elevations have been warming at an accelerated pace—with average temperatures in the Himalayas having risen more than twice the global average of 0.7oC in the last century. What does this mean for the future of Himalayan forests, grasslands and glaciers? A recent collaboration between researchers at the University of Kashmir, Srinagar and the Indian Institute of Science (IISc), Bangalore, published in Climatic Change, projects that under business-as-usual emissions scenarios the face of the Himalayas will dramatically change within the next hundred years. By the year 2085, we might have shrublands, savanna, and evergreen forests in areas now covered with tundra and ice.
Himalayan plant species are already migrating up the mountains as temperatures rise. In order to see how that change might progress, the researchers modelled shifts in vegetation from the present to the end of the 21st century in the Kashmir Himalayas under three different climate change scenarios called A1B, RCP 4.5 and RCP 8.5. Under each such scenario—standardized by the IPCC (Intergovernmental Panel on Climate Change) to enable easy comparison of results between research groups—greenhouse gas accumulation follows a trajectory determined by underlying socio-economic factors. The A1B scenario belongs to an earlier class of climate change models from 2000, each of which bases itself on a particular storyline of human development. Here, the economy grows rapidly, and so do novel efficient technologies – with a balance between the use of fossil fuel and non-fossil fuel energy. RCP stands for “Representative Concentration Pathways,” a class of models published in 2013. These start with a particular emissions trajectory from now until the end of the century (again, depending on human action), and predict the consequent level of radiation that will be trapped by the earth’s atmosphere in 2100.
From emissions, the researchers extrapolated climate—and from climate data, combined with soil type and topography in the Kashmir Himalayas, the researchers modelled possible vegetation changes in the coming decades. At each of these three levels there is uncertainty, however—and any errors will multiply with each subsequent level. Consequently, the researchers fed the averaged output from five different climate models arising from the above scenarios into their vegetation model. They also projected the vegetation model not just into the future but onto the present, to see how well it accorded with observed vegetation data. Model and observation matched by 87.15%, although the authors give the caveat that present vegetation data in Kashmir from satellite maps could not always be confirmed through ground observations.
The results across climate change scenarios showed substantial changes in the vegetation of the Kashmir Himalayas by the end of 21st century. By 2035, in each case, much of the area presently under polar conditions could be replaced by boreal evergreen forests, with grasslands vanishing. Temperate evergreen broadleaf forests may proliferate at lower altitudes, where there is now open shrubland. By 2085, boreal evergreen forests start to be usurped in turn by shrubland and savanna—most notably in the RCP 8.5 scenario, where the levels of the sun’s radiation trapped by Earth’s atmosphere continue to rise by the end of this century.
Irfan Rashid, author on the study and Assistant Professor at the University of Kashmir, stresses the effect on water security if the snow and ice-covered regions in the Himalayas were to disappear. “This definitely would have serious implications for streamflows, hydropower generation, tourism, agriculture and drinking water,” he says. He also warns of the loss of livelihoods for forest-dependent communities, and the potential extinction of wildlife as their habitats shift upwards and shrink. Rajiv Chaturvedi, another author on the study and National Environmental Sciences Fellow at IISc, suggests that we need to maintain corridors for flora and fauna to aid their migration in the face of climate change. “The benefit of wildlife and the benefit of trees are not separate,” Chaturvedi says.
The next step is to expand the study to an all-India level, with a 25x25 km2 resolution rather than the 50x50 km2 resolution used in this study. “This will be the first attempt to project vegetation using observed climatology at India level at a high resolution,” says Rashid.