Sudoor Manthan- IIRS Science Portal
Shifting cultivation, a traditional agricultural practice, has long influenced forest cover dynamics across Southeast Asia. This cyclical process of vegetation clearance, burning, and regrowth carries substantial environmental and socio-economic consequences. In India, shifting cultivation—locally known as jhum—is prevalent in the northeastern states, including Tripura. Over time, socio-economic changes and policy interventions have altered traditional jhum cycles, influencing land use patterns.
This study analyses the spatio-temporal patterns of vegetation disturbance and regrowth associated with shifting cultivation in Tripura over the past three decades using multi-temporal satellite data and advanced time-series analysis. Vegetation dynamics were assessed through temporal segmentation of Landsat time-series data from 1991 to 2020. Normalized burn ratio trends were extracted using the LandTrendr algorithm, and validation was conducted with the TimeSync tool. The approach enabled detailed mapping of disturbance and regrowth, capturing key metrics such as the year of peak change, magnitude, duration, and rate. Results revealed that 2,533.96 km² of the study area remained undisturbed, while 568.43 km² experienced low-magnitude disturbance, 1,501.11 km² showed moderate disturbance, and 184.82 km² underwent high-magnitude disturbance. Low disturbance areas typically reflected a single slash-and-burn event over the study period. Moderate disturbance was associated with fallow periods exceeding ten years, whereas high disturbance corresponded to shorter fallow cycles of less than eight years. The peak regrowth occurred in 1991, covering 426.42 km². The duration allowed for regrowth emerged as a key factor influencing its magnitude.
Fig. 1 Overall vegetation disturbance and regrowth patterns in shifting cultivation landscapes.
To assess overall vegetation disturbance and regrowth in the study area, a ternary phase diagram and corresponding RGB composite (Fig. 1) were generated using LandTrendr-derived parameters: rate of disturbance, rate of regrowth, and duration of regrowth. The rate of change was calculated as the ratio of magnitude to duration. LandTrendr treats each pixel independently, without accounting for spatial context. In Fig. 1, purplish areas indicate strong disturbance with low regrowth and long recovery, often representing abandoned cultivation sites. Bluish areas show prolonged regrowth with low vigour, while yellowish areas reflect high disturbance followed by rapid regrowth—potentially favouring pioneer species. These zones may also indicate short-term cultivation or intercropping of commercial species like areca nut, papaya, or rubber.
Fig. 2 Conventional shifting cultivation practice and transition to long-term agriculture or mixed agroforestry.
A clear transition from traditional shifting cultivation to more permanent agricultural systems was observed in parts of Tripura (Fig. 2). Economic incentives have driven cultivators to adopt long-term farming of pineapple, areca nut, and rubber, alongside intercropping of papaya, banana, lemon, tapioca, pepper, and ginger. However, these plantations are often abandoned once their profitability declines. The spread of monocultures has curtailed land availability for jhum, leading cultivators to revisit previously used plots more frequently. This study represents a first-of-its-kind attempt in the Indian context to assess shifting cultivation dynamics using a time-series-based remote sensing approach. The findings highlight the evolving patterns of an age-old agricultural practice and provide insights into the long-term implications of land use transitions on forest landscapes.
For further detailed insights, please refer to the following publication:
Bhat, Y., Nandy, S., Das, K., Tamang, M., Padalia, H., Nath, A. J., Majumdar, K., Pebam, R., Thongni, P., Kurmi, B., Das, A.K., Kushwaha, S.P.S. & Singh, R.P. (2024). Vegetation disturbance and regrowth dynamics in shifting cultivation landscapes. Scientific Reports, 14(1), 28324. https://doi.org/10.1038/s41598-024-78089-9