Rhododendrons of eastern Himalayas under threat

Rhododendron in full bloom. 

Shiv Sahay Singh, TH, KOLKATA, JUNE 10, 2017 :Though home to 97% of the Rhododendron species and sub-species in the country, indiscriminate felling and loss of habitat in the north-eastern States has left many of these beautiful flowering plants vulnerable to extinction.

A recent publication by scientists with the Botanical Survey of India has documented and stressed the need to protect the many unique varieties of Rhododendron — literally rose tree in Greek — found in the region, with 18 species endemic to India.

The publication, Rhododendron of North East India: A Pictorial Handbook by scientists Ashiho A. Mao, Sudhansu Sekhar Dash and Paramjit Singh points out that studies and records suggest that there are 132 taxa (80 species, 25 sub species and 27 varieties) of Rhododendron found in India, of which 129 are found in the north-eastern India alone.

Only three taxa — Rhododendron arboretum nilagiricum found in south India and Rhododendron colletianum and Rhododendron rawatti from the western Himalayas are not found in the north-east.

Arunachal Pradesh is home to the highest number with 119 taxa (74 species, 21 sub species and 24 varieties) of the Rhododendron. The small State of Sikkim is home to 42 taxa (25 species, 11 sub-species and six varieties) while 10 taxa are found in Manipur, four in Mizoram and 11 in Nagaland.

Centre of diversity

“The cold, moist slopes and deep valleys of the eastern Himalayas form a conducive habitat for the luxuriant growth of Rhododendron species. Nowhere in the world, are such unique geographical and ecological formations are found. This is the primary reason for such a diversity of Rhododendron available in the region,” Dr. Dash told The Hindu.

Dr. Dash added that the eastern Himalayas are regarded as one of the centres of diversity for the genus, which means that the Rhododendron has migrated to different parts of world from this region.

A global spread

Dr. Singh, director of the BSI and one of co-authors of the book, said while rhododendrons might not be appreciated in India, they are prized in gardens across Europe.

He pointed out that European researchers and horticulturists had taken seeds from the eastern Himalayas.

Rhododendrons were first recorded by Captain Hardwick in Jammu and Kashmir in 1776 where he spotted the Rhododendron arboretum. But it was a visit by the British botanist Joseph D. Hooker to Sikkim between 1858 and 1850 that revealed the rhododendron wealth of the region.

Found in varied habitats from subtropical forest to alpine shrubs, rhododendrons range from dwarf shrubs to large trees. The smallest are R. nivale and R. pumilum at just 10 to 50 cm while the tallest species, R. arboretum grows over 40 metres tall.

The scientists point to the need for conservation of Rhododendrons, stressing that epiphytic species, which grow on other trees or plants, of rhododendrons with limited population are most vulnerable due to loss of the host trees. Dr Singh said while in high altitude areas of Arunachal Pradesh, rhododendrons are routinely cut for firewood by local people, forest fires in the dry seasons in Manipur and Nagaland were threatening the survival of many species.

The endemic R. wattii from Dzukou hills of Manipur and Nagaland is one of the most critically endangered species in India, with only a few adult trees remaining in their natural habitat. The authors, however, have praised the efforts of Sikkim in protecting and preserving the species.

The Sikkim Forest department and the Sikkim Rhododendron Society have identified nine Rhododedron ecosystems and protected area networks in the State. The two famous Rhododendron sanctuaries in the State are Barsey Rhododendron Sanctuary in the West district, covering an area of 104 sq.km and Shingba Rhododendron Sanctuary in Yumthang valley of North district with an area of 43 sq.km.

The authors emphasise the need to follow Sikkim’s example in other regions, particularly in Arunachal Pradesh, with at-risk varieties. Dr Dash also suggested the need for more Rhododendron societies in other northeastern States.

Climate change signals

Other natural stands of the flowering plants can be found in West Kameng district and Bomdir to Zimithang in Tawang district.

The flowering season starts in February and continues till April in the lower elevations while in the higher reaches, blooms appear in late May and continue till June. The scientists record that studies on the phenology (flowering cycle) of Rhododendrons have revealed that they are prominent indicators of climate change. Other than the ornamental value, use in packaging wood crafts, fragrance and religious use, Rhododendrons also are used in local medicines against colds, coughs and chronic bronchitis and diarrhoea. The petals of R. arboretum are widely used for making juice, jams and jelly.