Geodiversity map of Sikkim Himalayas to aid conservation

By Sahana Ghosh

In a maiden effort, researchers have mapped the plant diversity of the Sikkim Himalayas on the basis of geography and climate data to create a ‘geodiversity index’ that can serve as a tool for biodiversity conservation and disaster risk reduction.

The ‘geodiversity index map’ of flora of Sikkim in the eastern Himalayas would also enable resource managers and conservationists to assess the number of species according to altitude, to understand the nature of environmental change in the region and how the plant species are adapting to the change.

The geodiversity index map recognises the interaction and interdependency of geodiversity and biodiversity, the authors said.

Geodiversity is the diversity of rocks, minerals, fossils, landforms, sediments and soils, together with the natural processes that form and alter them. It is the foundation upon which plants, animals and human beings live and interact, linking people, nature, landscapes and cultural heritage.

“Geodiversity data acts as a surrogate for overall biodiversity. If you conserve high geodiversity areas, then you are conserving high biodiversity areas as well. Areas of high geodiversity and environmental heterogeneity tend to support high biological diversity,” Raunaq Jahan, the lead author of the study, told Mongabay-India. The study is published as part of the ‘Sustainable Development Goals Series’ book series.

Given that healthy and well-managed ecosystems reduce disaster risk by acting as natural buffers or protective barriers, preserving and managing sites that have a rich biodiversity (high geodiversity area) may diminish disaster risks, particularly for locations such as Sikkim.

In the UK, for example, the process of geological conservation has always been linked to ecological conservation within the structure of national natural heritage conservation laws since the mid-20th century.

Noting that natural hazards threaten geoconservation in Sikkim, the study suggests that high geodiversity areas could be taken as high priority areas in terms of reducing disaster risk.

“Deforestation can create a constant risk of landslides or other disasters in hilly regions and this should be banned for high biodiversity areas in Sikkim,” the study said.

Culling data from published flora of Bhutan and Sikkim, the researchers produced a database of 5417 plant species. This database incorporates information on family, habitat, location according to altitude, district and community affiliations.

“If you know the spatial distribution (spread) of high geodiversity areas then you can plan the extent of your conservation areas,” Jahan who is associated with the Institute of Geography, University of Hamburg, Germany, and the department of geography and environment, Jahangirnagar University, Bangladesh explained, referring to the importance of Sikkim’s location and biodiversity.

Decoding Sikkim’s geodiversity

Nestled in the Himalayas, the thumb-shaped state of Sikkim is bound by Nepal in the west and Bhutan in the southeast. Mt. Khangchendzonga, world’s third highest peak, is located along Sikkim’s border with Nepal.

It is India’s least populous state, covering just 0.2 percent of the geographical area of India but is home to significant biodiversity.

Identified as one of the biodiversity hotspots in the eastern Himalayas, the state is endowed with rich floral and faunal diversity. The state is a repository of over 5000 species of plants including 557 species of orchids and 11 oak species as also 28 bamboo species.

Because of the altitudinal range from the plains to summits, the state sustains an assemblage of flora and fauna related to habitats ranging from the tropical to the alpine.

As per information provided by Sikkim’s Tourism Department website, tropical vegetation, mostly along the banks and valleys of the rivers Teesta, Rangit and their tributaries, consists mostly of figs, laurels, sal trees, ferns and a variety of bamboo species. The temperate zone has oak, chestnut, maple, birch, alder, magnolia and silver fir in the higher regions, while the lower alpine zone has juniper, cypresses and rhododendrons.

At the same time, Sikkim is situated in a high-risk area with regards to earthquakes and landslides and is considered one of the most disaster prone regions of India according to Sikkim State Disaster Management Authority.

The study shows that highest species diversity at 5581 is recorded at a height between 500 metres and 2000 m. Beyond 2000 m, number of species starts to dip as the altitude goes up in the Sikkim Himalayas. Between 5500 m and 6000 m, only 24 species are found.

The variation in flora with altitude ties in nicely with the geodiversity range observed across Sikkim.

For example, in the geodiversity index, the Khangchendzonga National Park (KNP), a UNESCO World Heritage Site in the ‘mixed’ category, is placed at the bottom, signifying low geodiversity.

It has an elevation spanning 1829 metres to over 8550 metres. Mt. Khangchendzonga, the world’s third highest peak, towers over the landscape at a height of 8,586 metres.

The altitudinal range of the national park reflects the plunge in floral varieties.

The low geodiversity rank is attributed to the 17 glaciers, snowfields, 19 mountains and peaks and rocky wastes dotting the park. Geodiversity of these glaciers is found to be very low corresponding to the low biological richness.

“Very high altitude, slope, temperature, precipitation are not in favour of high geodiversity index,” Jahan explained.

However, the forest of western and northern part of Mangan city (in North District) at an elevation of around 956 meters shows higher biological richness and ranks higher in the geodiversity index.

“If we compare these areas with the elevation, we can see that the elevation range from 1700 to 3000 metres (temperate broadleaf forest to sub alpine forest areas) has high geodiversity as well as high biological richness. This high biological richness area consists of forest cover, alpine scrub, grass and scrub, glacial moraines and screes,” the study states.

The capital city of Gangtok, which is located in the middle of the East District and is the main urban settlement surrounded by agricultural fields, shows low to moderate geodiversity.

In the West District, the northern areas have high to very high biological diversity as also high geodiversity.

The geodiversity calculation for Sikkim was satisfactory because its distribution almost matches the spatial distribution of biological richness mapped by the Indian Institute of Remote Sensing, the study said.

The authors stressed that these geodiversity indices can aid in land management, more sustainable use of natural resources and identifying priority areas for nature conservation.

“The automated technique presented here is very suitable for global GIS users because all digital information used in this method is free,” Jahan said.

The way forward with geodiversity

To integrate geodiversity with biodiversity, the researchers recommend combining the map with disaster-prone areas of Sikkim and take proper management action to reduce the risk of disaster for biologically rich areas.

In addition to enhancing knowledge on the areas of high-risk areas and high geodiversity areas, the study advises scientifically identifying the main causes of vulnerability to natural and manmade disasters in Sikkim. Further, it recommends raising awareness among local communities on geodiversity and biodiversity to protect from potential natural disasters.

“Low geodiversity or high geodiversity is a part of diversity of natural elements. In mountain regions, the important drivers of environmental change are hydroclimate, relief, human activity, flooding intensity, landslides, erosion, river channel mobility and extreme events. So the first task is to adapt to natural calamities,” Jahan elaborated.

“Kanchenjungha is already a protected area, so the design and management of the conservation of geodiverse, heterogeneous landscapes should therefore enhance biodiversity resilience and sustain abiotic and ecological processes,” she added.