Invasive weed threatens elephant habitats in Tamil Nadu

Subject :Environment

Section: Ecosystem

Context:

An aquatic weed is threatening elephant habitats and foraging areas in Valparai, a Tamil Nadu hill station close to the Kerala border, and reviving the risk of human-elephant conflicts in the region.

About the weed:

The weed is native to some countries in Central and South America, including Peru.
Ludwigia peruviana, which grows fast along water bodies, locally known as vayals, has invaded the foraging areas of elephants.
The rapid large-scale spread of the weed- which was probably introduced as an ornamental plant for its tiny yellow flowers- has shaken the balance of these perennial foraging grounds, limiting the growth of grass and native plants that are palatable to elephants and other animals including gaur.
It mainly spreads along the swamps in the middle of the tea estates and forms thickets.
These swamps are known for excellent grass covers, sedges and water sources that are very good for herbivores like gaur and elephant in particular.

Threat from Ludwigia peruviana:

Swamps are unique habitats that support amphibians and otters besides the large herbivores. They act as water storage areas that need to be preserved.
If Ludwigia colonises, it completely chokes swamps and does not allow grasses to grow.
The wildlife that had been depending on such swamps will move to other areas and it might lead to negative interactions.
Though Ludwigia is among the 22 priority invasive plants in Tamil Nadu, the State’s drive to remove exotic species from its forests is now largely focused on Lantana camara, Senna spectabilis and Acacia mearnsii (wattle).

Challenges in removal of Ludwigia peruviana:

Unlike other invasive plants, Ludwigia poses a unique challenge as it grows in swamps and there is little scope to use machinery which may further destroy the ecosystem.
Even if Ludwigia is pulled out manually, the soft plant easily breaks and it spreads again from the root or broken stems that fall in the swamp.

Valparai hills:

Located within the Annamalai Tiger Reserve, Valparai’s mosaic landscape of tea estates and fragmented forest patches still serve as key habitats for the elephants that move between Tamil Nadu and Kerala.

Senna spectabilis:

Senna spectabilis is a plant species of the legume family (Fabaceae) native to South and Central America.
They are often grown as ornamental plants due to their bright yellow flowers that bloom during the summer months.
They are also known as golden wonder tree, American cassia, popcorn tree, Cassia excelsa, golden shower tree or Archibald’s cassia.
The plant has become an invasive alien species in parts of Africa such as Kenya, Malawi, Tanzania and Uganda, and also in South India after it was introduced for resources such as firewood as well as to help combat deteriorating ecosystems affected by deforestation and desertification.

Lantana Camara:

Lantana camara (common lantana) is a species of flowering plant within the verbena family (Verbenaceae), native to the American tropics.
Lantanas arrived in India as a decorative shrub during British colonial period but quickly took over several ecosystems as an invasive plant.
The shrub can spread on the forest ground, climb over trees a creeper and entangle with other native plants with ease.
It is a very adaptable species, which can inhabit a wide variety of ecosystems.
Once it has been introduced into a habitat it spreads rapidly between 45ºN and 45ºS and more than 1,400 metres (4,600 feet) in altitude.