Shimla, March 3 (IANS): More than 230,000 hectares of forests in Himachal Pradesh are under a canopy of exotic lantana weed, a flowering shrub, that is "seriously" threatening the natural regeneration of native plant species, Forest Minister Thakur Singh Bharmouri said on Friday.

He informed the state assembly that in a survey conducted by the Forest Department in 2015-16, a total of 235,492 hectares of forests were affected by the lantana.

The Minister said the state had started the lantana eradication drive in 2013 and it would take at least 20 years to clear it from the state forests.

Kangra district is worst affected (114,311 hectares), followed by Sirmaur, Solan and Bilaspur districts. Shimla is the least affected by lantana with only 501 hectares.

"To root out lantana, a cut-root stock method has been adopted. After clearing the weed, it takes four years to re-green the area with native high-rise foliage species," he said.

In 2016-17, the department spent Rs 22.80 crore for eradicating the weed and for rehabilitating the lantana-affected land.

He said its eradication was also carried out under the Mahatma Gandhi National Rural Employment Guarantee Act, besides launching programmes under the Himachal Pradesh Forest Eco-System and Climate Proofing Project and the Himachal Mid-Himalayan Watershed Development Project.

Expressing apprehension over the huge expenditure, Bharatiya Janata Party leader and former Health Minister Rajeev Bindal said the technique used by the government to uproot the weed was not scientifically managed.

"The speed with which the lantana is spreading across the state, it seems 75 per cent of the total area of the state will come under the weed in the next 20 years," he said.

Himachal Pradesh, with a quarter of its geographical area under forest cover, has become the first in Asia to earn carbon credits. It has received the first installment of Rs 1.93 crore.