Abstract
Tropical montane habitats, grasslands, in particular, merit urgent conservation attention owing to the disproportionate levels of endemic biodiversity they harbour, the ecosystem services they provide, and the fact that they are among the most threatened habitats globally. The Shola Sky Islands in the Western Ghats host a matrix of native forest-grassland matrix that has been planted over the last century, with exotic timber plantations. The popular discourse on the landscape change is that mainly forests have been lost to the timber plantations and recent court directives are to restore Shola forest trees. In this study, we examine spatiotemporal patterns of landscape change over the last 40 years in the Palani Hills, a significant part of the montane habitat in the Western Ghats. Using satellite imagery and field surveys, we find that 66% of native grasslands and 31% of native forests have been lost over the last 40 years. Grasslands have gone from being the dominant, most contiguous land cover to one of the rarest and most fragmented. They have been replaced by timber plantations and, to a lesser extent, expanding agriculture. We find that the spatial pattern of grassland loss to plantations differs from the loss to agriculture, likely driven by the invasion of plantation species into grasslands. We identify remnant grasslands that should be prioritised for conservation and make specific recommendations for conservation and restoration of grasslands in light of current management policy in the Palani Hills, which favours large-scale removal of plantations and emphasises the restoration of native forests.
Highlights
Tropical montane habitats harbour great diversity but are threatened by climate change [1] and conversion to other uses [2], such as agriculture [3] and plantations [4]
We used historical and current satellite images and extensive ground data to establish the widespread loss of tropical montane habitats in the Palani Hills landscape from 1973–2014
The former increased dramatically by 1097% and the latter by 236% during this period. This loss of native habitats contradicts other studies that indicate an increase in forest cover in the Palani Hills [61, 62]
Summary
Tropical montane habitats harbour great diversity but are threatened by climate change [1] and conversion to other uses [2], such as agriculture [3] and plantations [4] These habitats do harbour relict species [5] and disproportionately high endemism across the world [6,7,8] and can serve as an early warning system for the impacts of climate change [9]. Grasslands play an important role in the global carbon cycle due to the slower decomposition rates of organic materials and by allocating as much as 90% of their biomass to underground storage [15] They serve as a water source for downstream communities in different parts of the world [7, 16, 17]
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