Frogs disappear from urban landscape

Unlike the house sparrow, the vanishing frogs haven’t yet caught the public’s fancy
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First Published: Tue, Jul 02 2013. 11 28 PM IST
Frogs have been around for 350 million years and are an integral part of many ecosystems. Photo: Nirmal Kulkarni/Mint
Frogs have been around for 350 million years and are an integral part of many ecosystems. Photo: Nirmal Kulkarni/Mint
The frog that doesn’t croak is a bit like the dog that didn’t bark— the silence has meaning; especially now, with most of the country covered by the monsoon. In most of India’s cities, the sound of frogs croaking is no longer a nightly accompaniment to the rain.
“In the pursuit of economic development, we are becoming more alienated from other living creatures. Little animals like frogs don’t have any space in our hearts or minds. We use pesticides to kill insects and don’t realize the importance of frogs in controlling pests and keeping the delicate balance of nature from tipping,” said batrachologist K.S. Seshadri. Batrachology is the study of amphibians.
Unlike the house sparrow, the vanishing frogs haven’t yet caught the public’s fancy.
Once commonly sighted during the monsoon, species such as the common toad, the skittering frog, the cricket frog, the bull frog and the narrow-mouthed frog have all slowly disappeared from the urban landscape.
Frogs have been around for 350 million years and are an integral part of many ecosystems.
“Amphibians are regarded as one of the best biological indicators due to their sensitivity to even the slightest changes in the environment and hence they could be used as surrogates in conservation and management practices,” said K.V. Gururaja, a frog specialist at the Indian Institute of Science, Bangalore.
He recently launched the Frog Find Android app as an extension to his book Frogs and Toads of Western Ghats.
“Frogs have long been associated with the rains and are known to be indicators of the environment. They respond to changes in moisture and temperature. Changing habitats have spelt doom for frogs, which simply cannot eke out a living in the urban jungle,” said Seshadri.
The alarming decline in amphibians is a global phenomenon and cause for concern among scientists. Amphibians survive on insects, including mosquitoes; in turn, they are a source of food for birds and snakes, putting them in the middle of the food chain, which is why they are important indicators of environmental health.
Their thin, permeable skins cannot adapt to even subtle changes in the aquatic and terrestrial environments that they require for their unique lifecycle. Thus they provide early warnings of environmental change, serving as bio-indicators—similar to canaries in a coal mine.
According to the red list of threatened species of the International Union for Conservation of Nature (IUCN), at least 1,856 amphibian species are threatened with extinction (this represents 32% of all known species of amphibians). Of the rest, 427 species are considered critically endangered, 761 are endangered, and 668 are vulnerable worldwide. Scientists across the world fear that more than 50 amphibian species have become extinct over the last 15 years alone, which includes more than 18 in South Asia.
In the face of such adversity, 114 new amphibian species have been discovered in India since 2000. India’s current amphibian species count is 342 (as of April), up from 281 in 2006.
All the discoveries have either been made in the Western Ghats or the pristine forests of north-east India, both regarded as global ecological hotspots but now facing the brunt of development.
An assessment of India’s amphibian population under the Conservation Assessment and Management Plan (CAMP) lists 32 species as critically endangered, 71 as endangered, 52 as vulnerable and nine as near threatened. It says no data is available on another 63. More than 50 species are thought to be lost.
The search for this last group is the focus of a Delhi University programme called Lost! Amphibians of India. The campaign has 250 members and has carried out 30 different expeditions in various parts of the country.
The discoverers of new species are not all frog scientists. Anil Zachariah is a veterinary surgeon who has discovered two new genus of frogs in the Western Ghats. Sanjay Sondhi, an engineer, discovered the Bompu Litter Frog at the Eaglenest Wildlife Sanctuary in Arunachal Pradesh.
While the discoveries (and rediscoveries) have spurred an interest in batrachology, scientists say that it is now a race against time to describe new species to science before they are lost to the forces of development.
“We have a long ground to cover for a fuller understanding of the amphibian diversity and ecology,” batrachologist K.S. Seshadri said.
“New species are being described every other year. We know very little of their ecology or natural history, both of which are very important for biodiversity conservation. There needs to be a strong emphasis on documenting the basic natural history, ecology and behaviour of amphibians if we are to conserve them,” added Seshadri, who discovered a new species of the shrub frog genus Raorchestes in the Agastyamalai hills in the southern Western Ghats.
The Western Ghats, which accounts for about 6% of India’s landmass is home to more than 30% of the country’s vertebrate and plant species. The region has more than 4,000 species of flowering plants (38% endemic), 330 butterfly species (11% endemic), 289 fish species (41% endemic), 135 amphibian species (78% endemics), 157 reptile species (62% endemic), 508 bird species (4% endemic) and 137 mammals (12% endemic).
Amphibians are the predominant vertebrates with a high degree of endemism (78%) in the Western Ghats, and hence, the most at risk.
“Today the Western Ghats is reeling under a tremendous pressure from human induced changes in terms of developmental projects like hydel or thermal power plants, big dams, mining activities, unplanned agricultural practices, monoculture plantations and illegal timber logging,” said Gururaja.
This has led to the once contiguous forest habitats getting fragmented, which in turn has led to space shrinking for wildlife, changes in the hydrological regime of catchment areas, decreased inflow in streams and human-animal conflict, he added.
The story is similar in north-east India, where a series of hydropower projects poses a threat to the fragile ecology of the region. Habitat destruction is now said to be the biggest reason for the alarming decline in India’s amphibian population.
According to a WWF India report, there have been 16 new amphibian discoveries in the Eastern Himalayas over the past 10 years.
“A caecilian and a diverse chorus of 14 frogs and a toad have revealed themselves for the first time in the last decade,” it said.
At least 353 new species have been discovered in the Eastern Himalayas between 1998 and 2008, equating to an average of 35 new species every year, which includes 242 plants, 16 amphibians, 16 reptiles, 14 fish, two birds and two mammals, and at least 61 new invertebrate discoveries.
Tracking the Vanishing Frogs: an Ecological Mystery, a 1994 book by journalist Kathryn Phillips, attributes the demise of amphibians to a number of reasons such as acid rain, air and water pollution, depletion of the ozone layer and ultraviolet radiation, drought, over-grazing and logging, off-road vehicles, dams and the introduction of non-native fish.
Being a far less high-profile subject than eagles or large carnivores, they remain out of the public eye, Philips writes.
That echoes what TV host Jeff Corwin said in his 2008 documentary, The Vanishing Frog.
“It was hard to get people to see that frogs are sexy things,” he said. “There are currently 6,000 species of amphibians and within just a few years, we would lose 3,000 of them.”
The illegal trade in frogs for food is another serious threat to wild populations. Though this trade was banned in 1985, frogs are still illegally taken from the wild to satisfy the international demand for frogs’ legs. In India, the illegal trade focuses on the green pond frog and the Indian bullfrog.
The threat of climate change presents a serious threat to amphibian survival. Given the prediction of heavy rain interspersed with a prolonged period of drought, the fate of amphibians seems to be sealed. Nature’s own mosquito slayer is now fighting a losing battle.
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First Published: Tue, Jul 02 2013. 11 28 PM IST