'Decline in frog population in Mumbai has led to rise in mosquitoes'

Jul 18, 2013, 11:46 IST | Ranjeet Jadhav

A common sight in the past, the amphibians have all but disappeared from the city, owing to widespread concretisation, and leading to proliferation of mosquito-borne diseases

This little creature with its loose tongue and bouncy gait was a more familiar spectacle in the years gone by. But, in its giant leap towards infrastructure development, Mumbai managed to step on a majority of the thousands of frogs that dotted the city’s landscape.

Graphic/Amit Bandre

According to experts, the dwindling numbers of this amphibian has resulted in proliferation of mosquitoes and, consequently, cases of malaria and dengue.

Concretisation has brought with it rampant real estate construction, pavers on roads, and extermination of ponds and gardens. Apart from this, the expanding quantity of pesticides and insecticides released in rivers by companies and factories has also upset the frog count.

Speaking to MiD DAY, Bittu Sahgal, editor, Sanctuary Asia, said, “The reasons are clear. Every muddy open space, every pond, every wetland is being cemented, or otherwise destroyed. Pesticides and chemicals are invading whatever water bodies the frogs need to survive, such as Mithi River. These amphibians help keep the city free of mosquitoes.”

Sahagal also said that citizens could help frogs by keeping small, green, wet parcels of land free from pavers, tar and cement.

Speaking about the impact that the fall in number of frogs will have, Varad Giri, senior scientist, Bombay Natural History Society (BNHS), said, “The most important bearing will be increase of insect population. There are some tadpoles, which also feed on mosquito larvae, and with their population declining, mosquitoes are growing and creating problems. No frogs means lack of food for snakes and other vertebrates, so their numbers would also take a hit.”

According to the official figures from BMC, from January to June this year, 4,337 cases of malaria and 257 cases of dengue have been reported. An additional 501 cases of malaria and 25 cases of dengue have been recorded in this month. The civic body, however, claims that there have been no deaths so far.

In 2012, there were 907 cases of dengue (the highest since 2010), while in the previous year 416 instances were registered. Around 16,000 malaria cases were reported in 2012. 45 died due to malaria that year, and five owing to dengue.

Commenting on the decline in number of frogs, Zeeshan Mirza, studying wildlife conservation at The National Centre for Biological Sciences, said, “Amphibian decline is a global phenomenon and one major reason is chytrid fungus (Batrachochytrium). The presence of this fungus has been reported from most parts of the world, but not yet India. The main cause for spread of this fungus is global warming. Frogs are indicator species and their decline is a clear sign that things are going wrong. They are biological pest controllers and keep the number of disease-causing insects like mosquitoes in check.”  

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