Gifts from the Mangroves

Every major Hindu shrine has a sacred tree which is revered as much as the presiding deity. At Chidambaram’s Nataraja temple, the honour goes to the thillai tree, a mangrove species (botanical name Exocoeria agallocha). Temple sculpture depicting the tree dates back to the second century A.D, the thillai grows in abundance in the Pichavaram wetlands nearby.

Over 100 different plant species fall under the category of mangroves with unique characteristics that help them grow on land where rivers meet the sea. Apart from minimising damage to life and property during a tsunami scientists at the M.S. Swaminathan Foundation for Research say that mangroves could have other gifts to give.

Legend has it that a dip in the Chidambaram temple tank will cure the ailing. As indigenous wisdom about a plant’s medicinal properties is often a starting point for scientific research, mangroves seem particularly ripe for “bio-prospecting.” Though it is too early to say if researchers will strike pharmaceutical gold, an initial screening of thillai extracts indicates the presence of compounds with anti-HIV, anti-cancer and anti-viral properties. These compounds are also active against mycobacteria — microbes that cause diseases like leprosy and tuberculosis — under lab conditions, says Dr. Ajay Parida, Executive Director, Biotechnology division, MSSRF.

Mangrove extracts could lower the use of chemicals in pest control. Despite growing in wetlands, the leaves of the thillai have few larval infestations, indicating the presence of terpenoids that act as natural pesticides. Some mangrove species inhibit the growth of mosquitoes.

Mangroves produce a range of novel compounds, including phenols of medicinal value, that help them live in a harsh natural environment, and serve as a treasure trove of natural products, says Prof. K. Kathiresan of Annamalai University’s Centre of Advanced Study in Marine Biology. But conserving the unique ecosystem of the mangrove forest in all its biodiversity is our first challenge, he emphasises.

Geneticists have long been intrigued by the mangroves’ exceptional ability to withstand salt stress but global warming brings a new urgency to understanding this salt tolerance. Food crops that grow in salty soil could become necessary for our survival because the indiscriminate use of fertilizer has turned agricultural tracts saline as well. Inspired by the fact that Avicennia marina can thrive in salt concentrations as high as 90 grams per litre (seawater has 35 grams of salt per litre) MSSRF scientists have developed transgenic paddy, a crop variety with mangrove genes in the rice genome, which is currently being assessed for biosafety and environmental impact in a limited field trial at Kalpakkam.

The venerable mangrove could bail us out again.