Alpine Plant Biodiversity in the Central Himalayan Region: Perspective of Global Climate Change
Increase in surface temperature at global scale has already affected a diverse set of physical and biological systems in many parts of the world and if it increases at this rapid rate then the condition would be worst one could have ever thought off. Garhwal Himalaya, major part of the great Himalayan mountainous system is also much sensitive and vulnerable to the local, regional and global changing climate. Due to strong altitudinal gradient, varied climatic conditions and diverse set of floral and faunal composition, the impact of climate change seems to be much higher. This paper highlights some important features of the changing pattern of vegetational composition, distribution and impact of climate change on the phenological aspect of major alpine plant species present in the Garhwal Himalayan region. It also shows cumulative changes, which operate at local level but are globally pervasive. These cumulative changes include change in the land cover/ land use and other anthropogenic activities, which are related to the climate change. Overall biodiversity in the Himalayan region has been depleted as the consequences of complex and multitude pressure of climate change. The depleted biodiversity has indirectly affected the socio-economic development of the local communities on which their sustenance depends and is inherently critical to the consideration and management of natural resource.
Plant diversity and Status
The varied altitudinal, climatic and topographical conditions in the Himalaya results in different types of microhabitats. Geographic isolation, glaciations, evolution and migration of the species in the past all together have contributed to the high level of biodiversity in this mountain system. As per genetic, species and ecosystem level resources, Himalaya is one of the hotspots of biodiversity in the world, which represents about one-tenth of the worlds known species of high altitude plant and animal species. Some parts in the Himalayan region are center for origin of many crops and fruit species and are important source of gene for their wild relatives. The floral diversity of this region shows assemblage of many endemic and exotic species of plants from the adjoining regions. A large number of western Himalayan flora in the Garhwal – Kumaon region seems to have been invaded from Tibet, western China and adjoining north-east Asia (Rau, 1975).
In the present scenario biodiversity seems to have been depleted in these regions due to land degradation, habitat fragmentation, increasing population pressure, over exploitation of bio-resources and finally due to the changing pattern of the climate. Nearly 10% of flowering plants are listed under various categories of threatened species. Red Data Book of Indian plants listed about 620 threatened species, of which, 28 are presumed extinct, 124 endangered, 81 vulnerable, 160 rare and 34 insufficiently known (Nayar and Sastry, 1987, 1988), however, Red list of threatened plants indicates 19 species as extinct. Among others, 1236 species are listed as threatened, of which, 41 taxa are possibly extinct, 152 endangered, 102 vulnerable, 251 rare and 690 of indeterminate status (IUCN, 1997). From the Himalayan region the important plant species included in threatened categories are mostly the valuable medicinal and aromatic plants, which, support the economic condition and health care system of the local communities.
It is well known that, in the context of the present scenario of climate change especially due to global warming many of the high-elevated ecosystems are severely sensitive and vulnerable. Their fragility may accelerate the changes occurring in their composition and structure to the slight variations in climatic factors. These regions include glacier, alpine pasture/ meadows and timber line ecosystem, which are the important source of the seasonal runoff, freshwater, valuable medicinal and aromatic plants, grazing land, source of timber and wild edibles for the mankind.
Future scenario of climate change: –
According to the Third Assessment Report of Intergovernmental Panel on Climate Change (IPCC) 2001, average global temperature close to the earth’s surface has increased by 0.6 °C ± 0.2° C since 19th century mainly due to the emission of CO2. If human beings do not act to reduce the present level of CO2 there will be additional increment in temperature of 1.4° C to 5.8° C in the next 40 – 100 year. Current information available on the pattern of future climate change through General Circulation Models (GCMs) suggested that the annual mean warming would increase about 3°C in the decade of 2050s and about 5°C in decade of the 2080s over the land region of Asia. Precipitation would increase annually about 7% and 11% in decades of 2050s and 2080s respectively. There would be a decline in the summer precipitation that seems likely to be over the central part of arid and semi-arid Asia. GCM also showed high uncertainty in future projection of winter and summer precipitation over south Asia, because much of tropical Asian climate is noticeably associated with the annual monsoon cycle. In Central Himalayan region, through the assessment of people perception it is interpreted that, climate change resulted in the increase in warming, decline in rainfall during March- May, high rainfall during Aug- Sept instead of normal peak in July- Aug, decline in the snowfall intensity and winter precipitation in Jan-Feb instead of Dec-Jan (Saxena et al., 2004). This scenario can hardly trigger to think about the changing pattern of climate or its negative and positive impacts at local, regional and global level.
Although assessment of future climate change scenario through some of scientific models needs a better infrastructure and high technological inputs, specific impact of climate change on different ecosystems can be discerned by comprehensive studies on long term monitoring of the different aspects of ecosystem which is lacking in the Indian context especially in the Garhwal Himalayan region due to poor infrastructure and management practices. So, as per as need concern in these remote areas the assessment of impact on the natural resources in future climate changes can be done through the site-specific sensitivity analysis and it can be related to the traditional knowledge’s of the peoples living in this particular region of the Himalaya. Sensitivity analysis would help to assess what will be happen if various climatic variables changed, and analysis also evaluates the positive or negative impacts of changing climate on the natural resources. This assessment would help us to make the local communities realize the importance of conservation and management practice so that the endangered and threatened species could be saved from becoming extinct. Assessment of vulnerability and adaptive capacity of the various ecosystems and to develop indigenous knowledge based coping mechanism are important to determine the impact of climate change. This also links the ecological processes to the social processes and appreciates the relationship between the biodiversity and ecosystem functioning.
Climate change: Impact on different vegetation zone
Natural ecosystems at high elevations are much more sensitive to the climatic variations (Ramakrishnan et al., 2003) or global warming then the managed systems. Their sensitivity is prominently attributed to their limited productivity during snow-free growing season (Price et al., 2000), low dispersal capability, geographically localized, genetically impoverished, highly specialized and slow reproducing ability of the high altitude plants (McNeely, 1990; WWF, 2003). As a consequence of global warming the present distribution of species in high altitude ecosystems projected to shift higher as results of upward altitudinal movement of the vegetation belts. Although the rate of vegetation change is expected to be slow and colonization success would depend on the ability of adaptation and interaction of the plant species with the climate and other associated species, weeds, exotic and invasive species. Their success also depends on their ecological niche width and their role in the ecosystem functioning. Increase in the temperature would result competition between such species and new arrivals. As the result, species which have wide ecological tolerance have an advantage to adapt and those which are at the edge of range, genetically impoverished, poor dispersal ability and reproducer are under the threshold of extinction.
A likely impact of climate change is also observed over the phenological aspect of vegetation in the alpine, sub alpine and timberline zone. Changes in the pattern of snowfall and snowmelt in these mountain regions and increase in mean annual surface temperature has pronounce impact on the date and time of the flowering and other phenophases of certain valuable, keystone species of plants. Earlier snowmelt simulate early flowering in some early growing plants and possibly increase in surface temperature may extend the growing period and productivity of certain grass species in the cooler climatic region. There is a gradual decrease in the growing period from timberline to the snow line, Rawat and Pangtey, (1987) reported about 20 weeks growing period near timberline and barely 4-6 weeks above 5000 m asl. Thus, increase in the average temperature due to global warming the growing period of the vegetation would be seems to extend at high altitudes. Evidences of climate change through people perception in Garhwal Himalaya reveals that increase in the warming results decline in the yield of apple fruits and shortening the maturity period of winter crops, whereas, the production of cash crops like potato, peas and kidney beans under warm condition increases. Change in rainfall pattern, snowfall intensity will increase large-scale mortality and damage to the crops, which are close to the maturity on the other hand, Barley and wheat crop production is severely affected due to winter precipitation in months of Jan- Feb (Saxena et al., 2004).
Vulnerability of different vegetation belts in the Garhwal Himalaya.
Dominant tree species in the low and mid altitude zone have a wider range of distribution. Shorea robusta the climax species of lower elevation is distributed over moist to dry deciduous bio-climates in central India where temperature is much higher while rainfall is quite low. Quercus spp. the climax species at mid elevation is also distributed over a wide range (1100- 1800m) The mid – altitude which is dominated by broad leaves and coniferous forest (Rao, 1994) mainly species of Quercus spp. and Pinus spp. on response to the warming may be replaced by the species like Shorea robusta and Terminalia spp. Warming also increases the chance of greater fire risk in dry or moist deciduous forests, these impacts on the forest can directly influence the local livelihood based on fuel and fodder (Ramakrishnan et al. 2003).
Rhododendron arboreum is a very prominent forest species because of its red flowers covering almost the whole canopy. At higher elevations this species used to attain peak flowering stage in February / March but now due to warming flowering time in this species seems to shift in the months of January/February. The phenological calendar at lower altitude has thus shifted to the higher altitudes. Exact times of leaf fall, flushing, flowering and fruiting may vary depending upon the elevation indicating sensitivity of phenophases to temperature and moisture stress regime. Flowering and fruiting start earlier about a month with increase in elevation by 600 m (increase in temperature by 2.4 degree C) in Rhododendron arboreum, Prunus cerasoides, Myrica esculenta, Pyrus Pashia and Reinwardtia indica in Central Himalaya. Leafless period in deciduous species like Aesculus indica and Alnus nepalensis is longer at higher altitude as compared to lower altitude. At higher elevation (1500-3300m) in Central Himalaya, evergreen and winter deciduous species occur equally across the elevation/temperature gradient. All across the elevation / temperature gradient, majority of tree species show vernal flowering. Species showing vernal flowering (before 15 June) increased in frequency and those with aestival flowering (between 15 June – 15 September) decreased with increase in annual temperature drown based on the elevation gradient. Thus, change in the temperature would affect flowering and fruiting time of different species or also induce change in species composition.
Vegetation of the timberline in different parts of world not only differs in terms of species composition but also exhibit different types of species (Crawford, 1989). In some regions the timberline represents exclusively evergreen conifers while in some it represents totally deciduous broad-leaved trees (Purohit, 2003). In the central Himalaya the Betula utilis, Abies pindrow and Rhododendron campanulatum, are the native species of timberline (Rawal and Pangtey, 1993), and have a complex, spatial habitat and reservoir of large number of medicinal and aromatic plants and wild edibles. During recent past, timberline, the most prominent ecological boundary in the Himalaya where the sub-alpine forests terminates, has been identified as sensitive zone to environmental change and could be effectively modeled / monitored for future climate change processes.
The species from tree-line have a narrow range of distribution, as temperature optima for most of these species is higher than the temperature in their natural habitats, warming will be expected to promote their growth but they may be threatened if they fail to compete with the changing climatic conditions (Saxena et al., 2004). Due to the over exploitation and changing global climatic condition many of the medicinal and aromatic plants in and around the timberline shrunk in size and distribution from their natural habitats and some of them are listed rare, threatened and endangered. Besides, the herbs some tree species of the timberline across the western Himalaya viz. Taxus baccata, Betula utilis etc. are also facing sever threats of depletion (Purohit, 2003). Most of the species valued by local communities have a poor soil seed bank, there could be large-scale local extinction of these species if seed production on a landscape scale decline (Saxena et al., 2004).
Swan (1967) identified two parts of the alpine region i.e. above timberline (Lower alpine zone; 300 -4000 masl) and higher alpine zone (4000 masl – snowline). Grasses and sedges are dominating members of alpine vegetation at lower altitude but they are characteristically replaced by non- grassy dwarf plant species at higher altitude near snowline. The area immediate above timberline and zone of stunted trees & shrubs marks the alpine scrub. The vegetation of the lower alpine zone consists of dwarf shrubs, cushionoid herbs, grasses and sedges, Salix, Rosa, Lonicera, Ribes, Cotoneaster and Berberis etc. form the major shrub species at lower alpine zone (Kala et. al., 1998). The herbaceous flora of this zone represent spectacular array of multicolored flowers and include many short period growing cycle plant species. The major herbs of this zone are Potentilla, Geranium, Fritillaria, Lilium, Corydalis, Cyananthus, Anemone, Ranunculus, and Impatiens etc.
The vegetation of the higher alpine zone is rather sparse, dotted with moraines, boulders and rocky slopes forming suitable habitat for the patches of shrubs e.g. Rhododendron lepidotum, Juniperus spp. Betula utilis and many species of colourful flowering plants, grasses and sedge etc. In the alpine with the onset of summer, the physical condition of the every patches of ground undergoes constant change, this is the root cause for the instability and succession of plants. Another feature of alpine plant distribution is that in the same habitat one could see the growth of several related or unrelated species and only one species dominate in the entire habitat almost to the exclusion of the other species. This difference may be due to the Physico- chemical properties of the soil. Initiation of growing season depends on the intensity of snowfall in the proceeding season and start of the melting of snow during spring (April – May).
In alpine region flowering is started during the month of May in some species, but in most of the species flowering occurs during June to late July and it goes up to early August (Nautiyal et al., 2001). Jennifer A. Dunne et al. (2003) reported that in experimental condition, increasing 2°C average soil temperature during the growing season for every two weeks of earlier snowmelt flowering time is advanced by 11 day in the sub-alpine region. Senescence at community level was gradually starts from July to September depending on the growth cycle of the plant species in Central Himalaya (Nautiyal et al., 2001). However in a study conducted by Zhang and Welker (1996) in Tibetan Tundra alpine the community senescence, which actually starts in September was postponed until October under warmer condition and stimulates the growth of grasses. It indicates that the warmer condition as result of increase CO2 enrichment extend the growing period and increase in the grass productivity and distribution may suppress the growth of forbs, shrubs (Zhang and Welker, 1996), similarly the valuable medicinal plants also affected (Ramakrishnan et al., 2003). It is possible that timber productivity in the high altitudes/ longitudes could increase as result of climate change, but it could take decades to occur and the newly form forests habitats are likely to retain lower level of native biodiversity due to loss of species that are unable to cope and some species will become more abundant and widely distributed (Alward et. al., 1999)
Biotic invasion is another important cause of change in the geographical distribution of the plant species, which is derived or accelerated by the global change. Elevated CO2 might enhance the long-term success and dominance of exotic grasses and their shift in species composition mainly driven by global change has potential to accelerate fire cycle and may reduce biodiversity (Smith et al, 2000). The water use efficiency due to increase atmospheric CO2 can allow increase in potential distribution of Acacia nilotica spp. indica in Australia and increase temperature favour its reproductive life cycle (Kriticos et al, 2003). As the glaciers are receding at a fast rate the newly formed moraine belt is an excellent area to study the invasion of plants from the adjacent mountains and pastures.In recent several land uses and land covers of the high altitude is eroded due to the glacier melting, avalanches and land slides, which favour to extend the distribution of Polygonum polystachyum, a fast growing herb, is mostly found on freshly eroded slopes, past camping sites, river banks and avalanche tracks (Kala et. al., 1998). The other successful invaders found in these habitats are species of Lonicera and Berberis followed by Rosa and Ephedra. Increase temperature may results higher pathogen survival rate and most of the plant species will be severely threatened due to insect, pest and fungal disease.
To the changing climate, plants can respond following possible ways firstly no change in their species composition but change in productivity and biogeochemical cycle. Secondly, evolutionary adaptation to the new climatic condition either through plasticity (i.e. shift in phenology) or through genetic response. Followed by emigration to the new areas, as warming observed in the alpine has been associated with upward movement of some plant taxa by 1-4 meter per decade on mountain tops and loss of some taxa that formally were restricted to higher altitude (Grabherr et.al., 1994). Ultimately, they may undergo extinction (Bawa and Dayanandan 1998, Ramakrishnan et al.2003). Most of the plant species changes over time through the process of succession, with pioneer species preparing the way for others, identifying the species present, the physical forms plant takes and the area they occupied are the way for observing change. All the changes involve dynamic and that are difficult or impossible to predict, natural ecosystems in this regard serve as a kind of natural laboratory, where natural mechanisms of change such as change in climatic condition and change in the feature of physical and biological systems observe practically. Appropriate management strategies need to developed in such a way that it may have to find a new balance between traditional conservation and maintenance of biodiversity and other ecosystem functioning.
Effect on the vegetation:
Adverse impact on the timber production of forest.
Effect on the agro-system:
Effect on Physical system:
Socio-economic conditions of the humankind severely affected:
Table: Distribution of some major plant species at different altitudinal belt of Garhwal Himalaya.
Altitude (m asl)
Shrubs: Zizyphus xylopyrus, Woodfordia fructicosa,
Trees: Rhododendron arboreum, Shorea robusta, Dalbergia sisso, Acacia catechu, Adina cardifolia, Terminalia, Cassia fistula, Mallotus philippensis, Bombax ceiba.Agele,
Herbs: Clematis montana, Anemone rivularis, A. obturiloba, Ranunculus hirtellus, Thalictrum chelidonii,Barbarea vulgaris, Silene indica, Malvia verticillata, Geraanium nepalense, Fragaria indica, Potentilla fulgens Epilobium pulustre,Bupleurum falcatum, Aster peduncularis, A. thomsonii, , Gentiana aprica etc.
Shrubs: Prunus cornuta, Rosa macrophylla, Zizyphus xylopyrus, Woodfordia fructicosa
Trees: Rhododendron arboreum, Shorea robusta, Dalbergia sisso, Acacia catechu, Pinus roxburghii,P. wallichiana, Quercus leucotricophora, Q. semecarpifolia, Adina cardifolia,
Herbs: Anemone rivularis, A. obturiloba, Ranunculus hirtellus, Thalictrum chelidonii, T. minus, T. elegans, Aquilegiaa pubiflora, Caltha palustris Clematis montana, Clematis barbellata, Delphinium vestitum, Podophyllum hexandrum, Corydalis cornuta, Arabis nova, Viola canescens, Silene edgeworthii, S. Indica, Stellaria monosperma, Geranium collinum, G. himalayense, Trigonella emodi, Geum roylei, Potentilla fruticosa, P. fulgens, P. gelida, P. leuconota, P. polyphylla etc.
Grasse & Sedge: Carex cruciata, Agrostis pilosula,Poa supina, P. alpina, Danthonia.
Shrubs: Cotoneaster macrophylla, Cotoneaster acuminatus, Lonicera, Salix, Rubus foliolosus, Spiraea bella, Berberis glaucocarpa, Myricaria bracteata, Skimmia laaureola, Astragallus candolleanus, Rosa macrophylla. Ribes himalense,
Trees: Betula utilis, Taxus baccata, Rhododendron campanulatum, Alnus nitida, A. nepalensis, Abies pindrow, Cedrus deodara, Pinus wallichiana, Acer ceasium, Junipers
Herbs: Cypridium elegans*, C. himalaicum, Epipogium aphyllum, Dactylorrhiza hatagirea, Listera tenuis, Neottianthe secundiflora, Aconitum balfouri, A. falconeri, A. heterophyllum, A. violaceum, Ranunculus pulchellus, Thalictrum alpinum, Podophyllum hexandrum, Acer caesium*, Meconopsis aculeate, Corydalis sikkimensis, Megacarpaea polyandra, Astragallus himalayanus, Nardostachys graandiflora*, Picrorhiza kurrooa*, Pleurospermum angelicoides, Saussurea costus*, S. obvallata, Angelica glauca, Ribes griffithii, Lonicera asperifolia, Waldhemia tomentosa, Primula glomerata, Arnebia benthamii, Geranium pratense, Impatiens thomsonii, I. racemosa, Dioscorea deltoidea*, Allium humile, A. stracheyi*, A. wallichi, Clintonia udensis, Thamnocalamus falconeri, Orobanche alba, Sedum ewersii, S. heterodontum,Pimpnella diversifolia, Morina longifolia
Grasse & Sedge: Elymus thomsonii, Agrostis munroana, Calamagrostis emodensis, Danthonia cachemyriana, Festuca polycolea, Poa pagophila, Stipa roylei, Carex infuscate, C. nivalis, Kobresia royleana, K. duthei etc.
Shrubs: Cotoneaster duthiana, Cotoneaster acuminatus Hippophae tibetana, Rosa sericea, Sorbus macrophylla, S. ursine, Rhododendron anthopogon,
Trees: Sorbus aucuparia, Cedrus deodara, Betulla utilis,
Herbs: Oxygraphis glacialis, Ranunculus pulchellus,Corydalis bowerii, Alyssum canescens,Draba altaica, Silene gonosperma, Potentilla sericea, Sedum bouverii, Saussurea obvallata, S. simpsoniana, Christolea himalayensis
Rau, M. A. (1975). High altitude flowering plants of west Himalaya. BSI, Howrah, India, pp.214.
Singh, D. K. and Hajra, P. K., in Changing Perspectives of Biodiversity Status in the Himalaya (eds Gujral, G. S. and Sharma, V.), British Council Division, British High Commission, Publ. Wildlife Youth Services, New Delhi, 1996, pp. 23-38.
Dunne, J.A., Harte, J. and Taylor, K. (2003). Sub alpine Meadow Flowering Phenology Responses To Climate Change: Integrating Experimental And Gradient Methods, Ecological Monographs 73 (1), pp. 69-86.
IPCC (2001). Climate Change-2001: Impacts, Adaptation and Vulnerability, contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change.
Kriticos, D.J., Sutherst, R.W., Brown, J.K., Adkings, S.W. and Maywald, G.F. (2003) Climate Change and The Potential Distribution of an Invasive Alien Plant: Acacia nilotica ssp.indica in Australia, Journal of Applied Ecology, 40; 111-124.
Nautiyal, B.P., Prakash, V and Nautiyal, M.C. (2000). Structure And Diversity Pattern Along An Altitudinal Gradient In An Alpine Meadow Of Madhyamaheshwer, Garhwal Himalaya, India. Indian Journal of Environmental Science 4(I). 39- 48.
Nautiyal, M.C., Nautiyal, B.P. and Prakash, V. (2001). Phenology And Growth Form Distribution In An Alpine Pasture At Tungnath, Garhwal Himalaya. Mountain Research and Development, Vol. 21, No. 2, 177-183.
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