Moths devour mangroves on coastline

MUMBAI, Oct 1: A new threat to Mumbai's ecology is looming in the skies. A swarm of moths that has devastated the city's mangrove forests...

MUMBAI, Oct 1: A new threat to Mumbai’s ecology is looming in the skies. A swarm of moths that has devastated the city’s mangrove forests along its coast and is now moving up towards Kalyan on the eastern side and Bhayander in the west, may soon swamp large residential and industrial areas.

An aerial survey of Mumbai’s coastal stretch has revealed that large areas of mangrove forests have been destroyed along the Thane Creek extending from the mudflats of Sewri upto the estuaries that lead into Bhiwandi and Kalyan.

The moths have also defoliated plants dotting the coast of Navi Mumbai-Belapur leaving large tracts of brown patches which are actually mangroves stripped to their roots by the moths. Wildlife scientists point out the devastation assumes significance in light of the fact the ecologically sensitive mangroves play a very important role in maintaining the biodiversity along the shores of Mumbai. Besides breeding and spawning ground for fish and other marine life, they also prevent the shorelinefrom being eroded by the sea.

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According to Bombay Natural History Society principal scientist, Dr Sanjay Deshmukh, the insects, identified as Hyblaea Purea, will be attracted to light in residential areas and industries located along the coast once they run out of food. However, they won’t survive too long on the land and may perish within three weeks, he said.

Dr Deshmukh added that the moths have been defoliating the Avicennia Marina species of mangrove plants every Navratri season since 1996. However, their origin is still a mystery. “It has been observed since 1996 that the moths become very active during the Navratri festival (late September and early October). Once they run out of food, they get attracted to light and swamp human habitations,” Dr Deshmukh said. Residents of some localities in the eastern and western suburbs have already been complaining of moths invading their houses after dusk. The extent of threat can be assessed from the fact that production had almost come to standstill in afactory at Vikhroli for two days after it was invaded by moths.

BNHS curator, N Chatturvedi, explained that though two species of mangroves are found along the coastal stretches Hyblaea Purea are attracted to only Avicennia Marina. According to Chatturvedi, Hyblaea Puera species of moths, commonly referred to as teak defoliator, are probably attracted to Avicennia Marina because there is a common component like Tannine in both the plants.

About their control he said: “There are two commercially available insecticides – Baculovirus and Bacillus Thuringerous – which can control moth population.” However, he pointed out that no efforts were being made at any level to control the destruction.