Coffee and tea plantations are prevalent throughout Asia, and they also support one of the lesser studied group of mammals: bats. In the paleotropics, little is known about how bats respond to habitat fragmentation, or the extent to which connectivity measures such as maintaining forested river corridors make a difference for bat populations.
A new study looks at bat functional diversity in the Western Ghats of India, which are considered the 8th “hottest” biodiversity hotspot in the world. They also have the highest human population density of any other hotspot, and are dominated by tea plantations interspersed with forest fragments and coffee plantations. How does such a fragmented and human-dominated landscape affect where bats are found?
The study included 7 types of habitat: 4 general types (protected forest, fragmented forest, shade-grown coffee plantations, and open canopy tea plantations) and 3 riparian types (rivers in protected forest, rivers with forested corridors, and rivers in open tea plantations). A combination of acoustic sampling and mist-netting helped determine how these different habitats both cause trait filtering and affect functional diversity relative to habitat disturbance.
Results showed that functional diversity in forest fragments and coffee plantations was similar to that of protected forests. Tea plantations had the lowest functional diversity, as well as the highest trait filtering (i.e. most of the species had similar morphological traits). The presence of forested river corridors went a long way toward mitigating much of the diversity loss and trait filtering seen on tea plantations that had no riparian buffer around rivers. These corridors can be useful in keeping bats connected, although they don’t have the same effect as continuous forest on both sides of the river.
What does this mean for bats (and your favorite morning beverage)? Forest fragments are worth maintaining and restoring for bat conservation. Shade coffee grown under native trees is better for bats than tea plantations, which could benefit from having their limited number of exotic, timber trees replaced with native trees. Rivers with the least amount of disturbance are best for bats, and tea plantations could also improve bat conservation by leaving riparian corridors as a buffer. Bats with short, broad wings, along with frugivores, are most vulnerable to habitat loss and modification, and conservation efforts that focus on these species along with improved connectivity measures could boost bat diversity in the region.
Resources
Wordley, C. F., Sankaran, M., Mudappa, D., & Altringham, J. D. 2017. Bats in the Ghats: Agricultural intensification reduces functional diversity and increases trait filtering in a biodiversity hotspot in India. Biological Conservation 210: 48-55.
Protecting the path for bats through Brazil’s largest savannah (March 2016)
Bright lights, big city – and bats? (October 2015)
