Phenology – A Tool to Monitor Climate Change: A Need in Sikkim Himalaya

Hemant K. Badola, G.B. Pant Institute of Himalayan Environment and Development, Sikkim Unit, Gangtok, Sikkim 737 101 ([email-masked], [email-masked])

The existing biodiversity and high use pressure on them often appear as a global debate. In present context, especially for the mountains, sustainability of resource availability not only depends upon the use pressure but also on the unprecedented climate changes, especially global warming. The mountains, for their greater verticality, provide short distance changes in temperature, moisture regime and sun-light exposure, directly influencing the type and dynamics of biodiversity and habitats. The resilience in biota and ecosystems to sustain adversities, within a wide range of eco-physiological regime, caused due to climatic change has a limiting point.  Any flux in temperature beyond optimum requirement can disrupt the existing delicate web of ecosystem, resulting to aberration in adaptive dynamics of the species. However, the significant changes in global climate have now exerted a definite pressure on the same; the resilience has started showing breaking the thin line between existence and extinction, as natural ecosystems do not always offer immediate recoveries. The forests, as the carbon sink, have shown fragmentation worldwide; the abrupt variability in rainfall, loss of biodiversity and soil water storage, shifting in biological calendar of the plants and shrinking glaciers are some of visible indicators of climate change and desertification. In Himalayan viewpoint, the losses resulting from global warming could be multifold; and Sikkim being one of the smallest states in India (7096 Km2 area), representing very rich biodiversity components within a short vertical distance is expected to be highly vulnerable, especially for its uniqueness, rich species diversity per unit area basis and high endemism, as per existing researches.

The impacts of global warming on physical and biological systems can earlier be examined identifying appropriate indicators and using suitable scientific tools. The high sounded and quite visibly adopted indicators have been the glaciers for their unprecedented vulnerability towards global warming in recent years. However, biological diversity at terrestrial level depicts several apparent and pragmatic drifts and alteration owing to global warming. Amongst them, the earlier commencement of spring events in species and prolonged growing period in vegetation, resulting to alternation in plant life cycle and changing pattern in productivity. These alternations in seasonal cycle of species cause their rising vulnerability towards diseases and pest, etc; several high altitude medicinal herbs are found sensitive to high temperature. Often unnoticed events, such as altering adaptability and shifting biological rhythms in wild animals and plants, etc. are some of the examples of quiet processes. A wide range of organisms may be used detecting phenological changes as a response to global warming.  Amongst top indicators of climate change, butterflies are highly popular groups, basically for their greater sensitivity towards minor temperature fluxes, and then for being the subject of long term monitoring programme in many countries. Such an altered adaptability in species caused due to global warming exerts adverse pressures on their existence particularly in case of endemic, rare and endangered biota and sensitive habitats. As a consequence the change in geographical distribution of species may be used in forecasting global warming, especially those growing in high altitudes of Himalaya. Recently, in 2009, ICIMOD, Nepal reviewed extensive reporting on the upward shifts in tree line and resultant invasion of woody taxa on alpine meadows, including the alarming rise of tree line at a rate of 5 to 10 m per decade in eastern Himalaya. In such cases, the perfect visible effect can be noticed by observing phenology of plants.

Understanding and recording of the timing of seasonal biological events, referred as phenology, include bud flushing and flowering dates and also faunal migration, can chronologically predict the on-going changes using their date wise records, is one of the ideal indicators of climate change, which has been gaining tremendous impetus in recent years, worldwide. The plant phenology, especially in buds, is a cheaper and convenient but a very potential tool to handle, fundamentally determined by species genetics and environmental factors, and to monitor climate change.  Climatic changes corresponding with rising pattern in temperature, either at location specific or extensively across political boundaries can be observed by using a single taxa or a group of taxa. Any smallest amount of change in global warming may possibly be detected by recording periodical phenological events. By setting up of phenological gardens, scientists in many countries have been monitoring global warming for several decades. Huge amount of phenological network data are in place to simulate past and future trends in climate change. For example, a paper published in an international journal, Global Change Biology by Menzel and colleague in 2006, made enormous interpretation of phenological data sets from 21 European countries (1971 to 2000), revealed an average advancement of 2.5 day/decade of spring/summer in Europe between 1969 and 1976. This finding was significantly discernible in the Intergovernmental Panel on Climate Change, 4th Assessment Report (IPCC AR4).  Under UK Phenology Network, the largest ever studies into the timing of the commencement of the seasons now involves over 50,000 people in England, appeared as significant effort monitoring climate change.

The Himalayan plant species, including those from Sikkim can be effectively used to monitor climate change and global warming, as potential tool. Amongst many, the Rhododendron arboreum (Gurans), widely distributed in Indian Himalayan belt and neighbouring countries, for its extended altitudinal distribution (sub-tropical to alpine) and very sensitive meristematic cells inside buds towards slight change in weather conditions, especially towards spring flushing and flowering, offers it as ideal taxa for monitoring climate change on long term basis by establishing phenological stations at various altitudes along the same transect, as per author’s long years’ research experience in Himalaya. Similarly, R. grande, very sensitive alpine herb of Sikkim, Rheum nobile (for its temperature govern shifting distribution along altitudes), and other identified herbs, in Sikkim, can be used for phenological monitoring of global warming for their high sensitivity towards environmental factors.

In Himalaya, including Sikkim, the phenology, especially the buds as indictors of climate change have never been taken as a priority, as adopted in Europe in recent years; in spite of having immense potential of using bud phenology, this science is yet to receive adequate attention by the scientists, area managers and policy makers. In conclusion, the spring phenological signals, especially in buds need to be taken sensibly to monitor global warming as highly appropriate indictor of climate change. In Sikkim, the need is to establish a network of plant phenological gardens or stations along different altitude zones taking suitable taxa for monitoring, such as, sensitive medicinal herbs and identified woody taxa. At the same time identification of a group of scientists and area managers for their coordinated efforts, would be vital for successful monitoring of climate change and global warming using phenology as a tool.

Half blossomed bud of Rhododendron arboreum (Photo: H.K. Badola)