'Jhum' cultivation impacts Kohora River Basin ecosystem in Assam: Experts

Traditional 'jhum' cultivation and subsequent growth of bamboo as well as extensive cotton farming in the past have resulted in topsoil loss, degradation of its health and an adverse ecological impact on the Kohora River Basin (KRB) ecosystem in Assam's Kaziranga-Karbi Anglong landscape, experts said on Wednesday.

Efforts were underway to rejuvenate the basin, ranging from the northern fringes of the Karbi Hills to the southern limits of the Kaziranga National Park and Tiger Reserve, as this river system is a critical source of water for thousands of people living in the hills and floodplains that is also home to the famous and largest one-horned rhino population in the world, environmental scientist Firoz Ahmed told PTI.

''The Kohora River plays a pivotal role in the lives of the Karbi indigenous community, who live in and around the basin. Known for their harmonious relationship with nature, they depend on the river for a variety of daily activities, including drinking water and farming,'' he said.

Given the importance of the river system, monitoring its health and water quality is the priority and as part of this effort, the environmental biodiversity group 'Aaranyak' began tracking ''both the water quantity and quality across different sections of the river'', Ahmed said.

A weather station to monitor the micro-climate of the KRB was also set up and the weather data revealed a notable increase in average temperatures and a significant decrease in rainfall between 2019 and 2024, he said.

''The monitoring results indicate a concerning decline in the river's health. Water levels have decreased considerably, primarily due to reduced rainfall and the degradation of the upper canopy, among other factors,'' he said.

Additionally, the river's water quality has been adversely impacted by various household activities and tourist influx in the area, as indicated by the deterioration in physicochemical parameters, Ahmed added.

''Traditional farming called 'jhum' (slash and burn) cultivation with short cycles (less than 10 years) and subsequent invasion of bamboo (Kako bah), as well as extensive cotton farming in the past (around 1975-85), in the upland areas has had a considerable historical ecological impact on the ecosystem,'' the environmentalist said.

''Due to the clearing of the forest and repeated short-cycled 'jhum' cultivation, the forest is lost and invaded by bamboo and other weeds that are ecologically ineffective to restore soil and instead augment topsoil loss,'' he pointed out.

The spreading of the bamboo in the fallow land after 'jhum' cultivation impacts the survival of other trees, herbs and shrub species and also keeps the forest floor barren, and its health decreases due to the diminishing floral diversity, and thus impacting the soil and water health of the region, an official of the forest department said.

''In the absence of forest and topsoil, the water holding capacity of the upland areas has declined very significantly,'' he said.

Available data shows that from the 1970s and 2020s, there has been a loss of depth of the river and loss of water quantity by over 90 per cent, he added.

Kaziranga National Park Director Sonali Ghosh told PTI that all water bodies in the landscape have a vital role to play in the park's ecology and the survival of animals in the plains.

''It is, therefore, imperative that the river's flow is improved and sustained with steps taken to boost its health for the overall well-being of both animals and people,'' she added.

Aaranyak has adopted a project with the idea of ''co-planning and co-creation with the community by incorporating indigenous knowledge, designing restoration plans that align with local environmental and cultural contexts'', Ahmed said.

Integrating traditional knowledge with scientific approaches ensures adaptability and effectiveness, he said.

''We have been working with 21 'jhumia' (shifting cultivators) households, restoring around 30 hectares of 'jhum' fallow land. Approximately 2,500 saplings of 13 native tree species have been planted across such fallow land,'' he said.

Forest floor restoration has also been carried out by planting three quintals of rhizome of fragrant shield plant (Homalomena aromatica).

''Initially, people of the area were averse to the idea of restoration of the fallow land as they felt it would lead to interfering with nature but now several households have come forward to participate in the projects,'' a village head, Bapuram Ingti, said.

He pointed out that the river is an integral part of the Karbi indigenous community and it is important to help revive and restore its earlier flow.

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