Divya Gandhi

Summer rainfall declines from climate change and deforestation

Bangalore: The increasingly vulnerable tropical montane cloud forests of the Western Ghats, called so because of the low cumulus clouds that cloak the canopy almost perennially, are growing drier, finds a study.

Climate change and deforestation are changing cloud formation and reducing rainfall, threatening one of the world’s most fragile ecosystems characterised by moss-covered forest floors, ferns and epiphytes, suggests a research paper published in the latest issue of Current Science.

The paper is authored by a team of scientists from the National Institute of Advanced Studies, the Indian Institute of Science and the Jawaharlal Nehru Centre of Advanced Scientific Research, among other institutes.

In their study of four montane cloud forest sites in the southern Western Ghats, the team found three to have diminishing trends in rainfall, especially during the summer monsoon.

The Gavi rainforest station in Kerala showed the most dramatic decline in summer monsoon, by around 20 mm in 14 years (1994-2007), followed by Venniyar in Tamil Nadu, which recorded a similar decline of 20 mm in 20 years (1988-2007) and the High Wavy range in Tamil Nadu with a 5-mm reduction in 28 years (1980-2007). Precipitation had, however, increased in the fourth site, Periyar in Kerala, by around 25 mm in 28 years (1980-2007).

These changes in rainfall in montane cloud forests can have a negative impact on the natural ecosystem — which support endangered wildlife such as the lion-tailed macaque — as well as on crops such as cardamom and coffee that are grown here, the paper says. It adds that the obvious reason for the precipitation change can be global warming and local land-use change.

Cloud droplets

The low-hanging clouds play an important role in nurturing the ecosystem through the deposition of “cloud droplets” on soil and vegetation surfaces, a process called “horizontal precipitation,” the research paper explains.

“The formation of a cloud bank is affected not only by global climate change; there is also evidence that regional and local land-use change can have significant influence.”

As tropical cloud forests represent “the core of tropical biodiversity ‘hotspots’… the status of these unique ecosystems is critical and precarious as they are among the most endangered of all forest types,” says the paper.

The two tropical montane cloud forests regions of India, one in the Western Ghats and the other located in the north-eastern States, are some of the world’s least studied and explored forests.