Invasive plant is overtaking cleared forestland
Environment: The Royal Manas National Park’s (RMNP) attempt to turn 150 acres of forest into grassland in Specialthang has come under attack from an invasive plant, Eupatorium odorata.
Eupatorium, also known as Choromolaena, is a plant, which grows over two meters tall with creamy purple flowers. Conservationist and foresters believe the plant to be a native of South American and spread to the region including Bhutan through transportation, mostly by road.
The unchecked growth of the plant that is colonizing forestland is worrying foresters.
“Eupatorium is the greatest unseen threat to forests because it is invasive and is unpalatable for ungulates,” Biologist with Ugyen Wangchuck Institute for Conservation and Environment (UWICE), Tshering Tempa, said.
According to the institute’s conservationist Nawang Norbu, without natural control the plant can proliferate. Natural control in the form of ungulates – Sambhar, Gaur, water buffalo, Barking deer, Sero or cattle are not feeding on the weed.
“Eupatorium is like the Giant African snails because our predators don’t know what to do with foreign species,” Nawang Norbu said, adding any invasive plant or animal doesn’t bode well for the health of the local ecology.
At the start of the food chain, colonizing grassland could affect the ecosystem, as ungulates, the prey for Tigers are affected.
Park ranger, Tshering Dorji is worried about the impact it would leave on the food chain. “Eupatorium is now growing fiercely in open shrubs and grasslands from Samtse in the south-west to Jomotshangkha in the south-east,” he said.
“Our observation is Chromolaena is taking over most of the degraded forests,” the ranger said.
The growth of other plants are also affected once Eupatorium invades an area according to the conservationists.
The biggest hurdle is the fast-spreading weed cannot be controlled without incurring heavy costs.
“It has to be either cut before flowering season or uprooted,” Tshering Dorji said, adding invasion from Eupatorium could be reduced only if it is cleared consecutively for two-three years.
Former Phibsoo Wildlife Sanctuary forest ranger, Gem Tshering however said past affords to remove Eupatorium proved futile in Phibsoo.
“The sanctuary tried burning Chromolaena in grasslands but it only backfired with even better growth next season,” Gem Tshering said, adding unless cleared and burnt before flowering season, it would be difficult to control its invasion.
If it cannot be controlled, it is spreading fast. Eupatorium is now moving deeper into the country’s higher elevations. “It is also gradually making its way to northern regions,” Gem Tshering said.
The plant had been a menace in many plantations in the region too. In neighbouring India, it attacked coconut plantations as early as the 1960s. Studies done on the weed suggests uprooting as the best possible solution.
By Tempa Wangdi, Manas