Eravikulam grasslands at risk from invasive plants

Giji K. Raman
KATTAPPANA,  
The Hindu, November 8, 2014 

The grasslands of the Eravikulam National Park are under threat from two invasive alien plants.

Eagle fern and goatweed, native to California and Brazil, respectively, have spread across the grasslands, damaging the park’s flora and posing a threat to herbivores, especially the Nilgiri tahr, say recent studies.

The studies are a prelude to documenting the main aggressive plants of the State.

Eagle fern ( Pteridium aquilinum ), also known as bracken, is a large fern that grows to over three ft and readily colonises areas, hampering the growth of grasses and other plants. On the underside of the leaves is sori, which produces spores that, like seed, travel in the wind and create new colonies.

Goatweed ( Ageratum conyzoides ), known as Murianpacha locally, is a flowering plant that grows up to 80 cm.

“Both the plants are unpalatable to herbivores and make colonies, are highly invasive, and prevent the growth of grasses and other plants,” says T.V. Sajeev, Head, Department of Entomology, Kerala Forest Research Institute, Peechi.

He says these plants have spread wide and could be hindering the growth of fodder for wild animals, especially the Nilgiri tahr.

Eagle fern is allelopathic, that is it lets out chemicals that keep other plants from growing. Because of the chemical effect, animals do not feed on its leaves.

The plant contains carcinogenic agents, and is a threat to human beings and animals.

K.G. Ashok Kumar, who led a team to document the two plants as part of the Save Biodiversity Campaign, told The Hindu that eagle fern was heavily distributed in the low-lying areas of the park and posed a bigger threat than expected.

The plant could replace natural vegetation, and once it spread was difficult to control.

He said the dry leaves of the eagle fern caught fire readily, and the ashes facilitated the growth of the plant.

Mr. Ashok Kumar said the two plants were dangerous to animals and human beings, and it would be a huge challenge for the authorities to control them.

Murianpacha, he said, was also found in parts of Kottayam, Kollam, Pathanamthitta, Palakkad, and Wayanad districts, and could grow in different soil types.