Weed worry: Lantana invades MM Hills, Bandipur

In a first-of-its-kind study to understand the changing forest landscape, the Forest Department has found that the invasive weed lantana has spread into core areas of tiger habitats in MM Hills and Bandipur with varying degrees of density.

This has a significant impact on wildlife movement and contributes to man-animal conflict.

Lantana Camara, a weed native to South America and believed to have been introduced in India during colonial rule, has been seen as one of the biggest threats to biodiversity and wildlife. However, there have been limited studies to understand its impact on forests of Karnataka, save for the extensive studies by research institutions in Biligiri Ranganatha Temple (BRT) Tiger Reserve.

The Forest Department’s project with Karnataka State Remote Sensing Applications Centre (KSRSAC) aims to arrive at reliable information on the extent of the weed’s invasion, which will inform decision making in matters related to management of both wildlife and the flora of the protected areas.

In 2020, the Wildlife Institute of India had reported that lantana had invaded 44% of India’s forests.

However, the department’s assessment based on high resolution images (10-metre) showed that the weed was present in 80% of the two landscapes with the assessment showing its presence even in the higher altitudes of MM Hills.

Scientists from KSRSAC divided the high-resolution maps of the two tiger habitats by breaking down the map into thousands of polygons. Spectrum signature of the different vegetation helped in delineating the extent of lantana invasion and differentiate it with the deciduous and scrub forest. Officials took up limited ground truthing to further evaluate the findings.

According to the spatial study, at least half of the 90,000 hectares in MM Hills is occupied by lantana with a density of 40% to 60%. The density of the weed was 20% to 40% in about 20% of the area with the remaining area recognised as a green zone where the density was less than 20%.

In Bandipur, except for about 25% of the 87,224 hectares, the landscape in the rest of the national park was invaded by lantana. A majority of the forest landscape had between 20% and 60% density of lantana. Worryingly, in several pockets, the density of the weed was 60% to 80%, which restricts movement of animals.

Biswajit Mishra, Additional Principal Chief Conservator of Forests (APCCF), Working Plan, said the studies for the other forest landscapes, including tiger reserves, were at various stages of completion.

“We will finalise the data for the remaining landscapes. This will help us take up an evidence-based approach while preparing the plans for management of the landscapes,” he said.

APCCF (WildlIfe) Kumar Pushkar said observations in tiger reserves, especially in the safari routes, have shown that areas where the invasive weed was cleared were better in supporting the herbivores, which in turn provide a rich prey-base for tigers. “Lantana is one of the key issues contributing to the rising man-animal conflict. Removing lantana, however, is a process that requires time and resources,” he said.

Senior officials believe that the shrinking habitat coinciding with increase in the population of tigers and elephants, was driving out both tigers and leopards into human habitats, leading to man-animal conflicts. For instance, Bandipur accounted for 10% of the 40,000 man-animal conflict cases reported from across Karnataka last year.

According to the department, about Rs 60,000 per hectare is required for removing lantana and another Rs 30,000 to maintain grass on the cleared area for the next two years.