A recent study shows that tea plantations in the Western Ghats harbour less-diverse bat communities — that perform fewer ecological functions — than those found in coffee estates and forests. Protecting existing forest fragments and river stretches in such intensively-cultivated landscapes could be crucial for bats, which are important insect controllers, pollinators and seed-dispersers.
Different bat species can perform these varied ecological functions due to the physical features they have evolved, which help them specialise in hunting different prey across habitats. Bats with short, broad wings, for instance, are better suited to plucking off large insects on the wing, in densely-vegetated patches like the forests of the Ghats.
But forests in this mountain range have changed drastically. In Tamil Nadu’s Valparai, for instance, tea and coffee plantations have fragmented natural forests. To examine how bats respond to such extreme changes in land use, scientists from the Nature Conservation Foundation, National Centre for Biological Sciences and the University of Leeds (UK) quantified bat communities in Valparai, based on their ecological functions. Across different habitats, they examined bat diet, echolocation, body size and wing morphology (which determines their mode of hunting and what habitats they are adapted to).
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The scientists found that tea plantations fared badly: only few insectivorous bats that could adapt to highly modified habitats thrived here. However, rivers running through plantations helped offset this slightly. Coffee plantations did better because of native tree presence which is required for coffee growth; but protected areas and forest fragments were the most ‘functionally’ rich, home to bats with diverse morphologies corresponding to their several functional roles in the ecosystem.
The team’s results show that bats with shorter and broader wings, like the lesser woolly horseshoe bat, are most vulnerable and require urgent conservation action in Valparai. “These bats are insect eaters; they keep ecosystems healthy and functioning by keeping the insects they eat in check,” says lead author Claire Wordley.
Bats and other fauna could benefit if tea plantation owners leave a buffer of native trees on both sides of every river, write the authors. Protecting existing forest fragments and extending them wherever possible could also help.
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“While tea plantations will never be as rich for wildlife as coffee plantations, it can be more biodiversity-friendly if small changes in land use practices are implemented,” says Divya Mudappa of NCF.