India's biodiversity hotspots face climate change challenges

It has been more than a decade since Nature published the much cited 'Global Biodiversity Hotspots' article¹ . Yet there are no comprehensive studies particularly on the biodiversity hotspots of India: the Himalayas, Indo-Burma, Western Ghats and Sundaland. In the face of predicted climate change and the 'sixth major mass extinction'² , these eco-regions face new challenges of conservation and sustenance.

Majority of the 34 global biodiversity hotspots harbour exceptional concentrations of endemic species and are facing tremendous anthropogenic pressure. Conservation of endemic plants might also provide an umbrella for the protection of herbivorous insects, nematodes, fungi and large proportion of their parasites³ . Nonetheless, the parts of four biodiversity hotspots in India are facing their own challenges.

The threats

Climate change and over increasing human disturbance are major causes for forest destruction and species extinction. Analysis of global human population data⁴ shows higher human population density in hotspots located in the tropics, where the Western Ghats accommodate the highest human population density among all global hotspots — more than 300 persons/km 2 .

The regional rate of climate warming in Himalaya has been observed to be higher than the global warming rates⁵. This could lead to extinction of native flora in the Himalayas because further pole-ward migration is not possible due to the topographic barriers. Most of the vegetation cover of Indo-Burma hotspot exhibits high levels of forest fragmentation⁶.

Recent extreme events such as the Indian Ocean tsunami have caused tremendous loss of forest cover in Andaman and Nicobar Islands, which form part of Indo-Burma and Sundaland hotspots⁷. Threats such as invasive alien species, forest fires, and droughts put undue stress on the vegetation of these hotspots.

Studying the hotspots

India's biodiversity hotspots cover a significant proportion (16.86%) of the total global area under biodiversity hotspots. Among the hotspots under India's political boundaries, the Western Ghats account for 64.95%, Indo-Burma 5.13%, Himalaya 44.37% and Sundaland 1.28%)⁸ . However, the protected areas in most of them is less than 17%, which is minimal as per the Aichi targets of the Convention of Biological Diversity, 2010.

There have been no studies on accounting of the biological attributes, neither are there any estimates of the anthropogenic drivers of forest degradation in these hotspots. A few studies (except in the tiny islands of Sundaland) conducted at local scales in these hotspots were based on the estimates of diversity and endemism. Such studies suffer from the limitation of replicating and updating⁹.

Climate change induced species' shifts have been observed and predicted across the globe¹⁰. However, only some isolated studies have been attempted on India's flora¹¹. In the face of global environmental change, there is need to identify the transition zones in the distribution of endemic plants due to climate change induced species' migration, which could be addressed by designing dynamic networks such as the 'Protected Areas Resilient to Climate Change' (PARCC) developed by UNEP¹². Modelling species' migration under different climate scenarios and exploring the role of environmental heterogeneity on species richness and endemism may help to identify future spatial shifts of biodiversity hotspots¹³.

There has been some remote sensing-based vegetation cover mapping and monitoring in parts of these hotspots¹⁴. However, these estimates do not provide a broad view of the present status of vegetation cover of India's hotspots because of variations in the scale of study, data, method and the classification scheme.

The vegetation map of India¹⁵ presents precise and reliable assessment of the vegetation types in the country. However, it does not provide the latest estimates of forest cover in these hotspots. The estimates of forest cover published by Forest Survey of India in 2009 were criticized for being misleading¹⁶ .

There is a need for remote sensing based vegetation characterisation of biodiversity hotspots in India, with a consistent spatio-temporal scale and vegetation classification. A comprehensive study could provide reliable, accurate and up-to-date estimates of biological attributes, vegetation types, diversity, endemism, anthropogenic disturbance, human population density and forest fragmentation.

It could also make bioclimatic predictions of climate change-induced species shifts, which could provide baseline data for effective conservation prioritization of the biodiversity hotspots in India.