This chapter provides an analysis of the changes in the length of fallow periods and land-use intensity of swidden agriculture in montane mainland Southeast Asia from 1988 to 2016. The study uses remote sensing data to examine the spatial and temporal patterns of shifting cultivation and their relation to environmental and socio-economic factors. This research is valuable for understanding the dynamics of swidden agriculture and its implications for sustainable land management in the region.
Key Insights
Swidden Agriculture and Fallow Periods
In more than 60 developing countries in the tropics, between 300 and 500 million upland farmers practice swidden agriculture. This traditional farming system involves slashing and burning natural and secondary vegetation. The length of fallow periods in swidden systems has greatly shortened over recent decades due to population growth, alternative land uses, forest conservation policies, and infrastructure development.
Landsat-Based Algorithm
The study developed a Landsat-based multi-step threshold algorithm that takes advantage of multiple spectral bands of Landsat-8 OLI sensors to generate maps of swidden agriculture. This approach is based on the unique phenological features of swidden agriculture, i.e. the quasi-periodic slashing-and-burning of natural and secondary vegetation in the same place between March and April in certain years.
Redefining Mountainous Areas
The mountainous area of mainland Southeast Asia is redefined based on different parameters of elevation, slope gradient, and local relief. This redefinition, based on the Mountain Research Initiative typology, aims to reduce the spectral noise effects of permanent farmland and corresponding human settlements on the detection of swidden practices.
Annual Dynamics and Land-Use Intensity
The annual dynamics of swidden agriculture are closely related to land-use intensity and the varying length of fallow periods. Changes in the fallow phase of the swidden cycle are typically analyzed on a local scale. This study contributes to fully understanding the intensity of swidden farming as well as its socio-economic and biophysical effects.
Geo-Economic Cooperation and Environmental Governance
Frequent launches of geo-economic cooperation mechanisms since the 1990s and stricter environmental governance since 2011 have impacted swidden agriculture practices. These mechanisms may have been a major factor in both the continuous increment of newly burnt swidden plots and plantations of industrial trees.
Fallow Period Categories
The study identified four categories of fallow periods: short-term (1-5 years), medium-term (6-10 years), long-term (11-20 years), and longer-term (21-28 years). These categories help reveal changes in the length of fallows over the study period.
Key Statistics & Data
- An annual average area of 60,800 sq. km, or 3.15% of the total land area in the uplands, was opened each year for new swidden plots from 1988 to 2016.
- More than 60% of newly burnt plots had an average reoccurrence frequency of five times over the study period, or about five to six years of fallow.
- In Myanmar, newly burnt swidden plots at a very low level of land-use intensity added up to 9.13-million ha from 1988-2016.
- Shan state had the largest total area of newly burnt plots with 7.01-million ha, followed by Kachin state with 3.49-million ha.
- In Laos, the total area of newly burnt plots in Luang Namtha added up to equal 67.06% of the province’s total land area.
- The average areas of swiddens burnt once, twice, thrice, four and five times in the short term fallow (time interval of three years) were approximately 5.5-million ha, 2.4-million ha, 1.73-million ha and 2.07-million ha, respectively.
Methodology
The study utilized a Landsat-based multi-step threshold algorithm of four vegetation-moisture indices (VMIs) and generated 29 longitudinal maps of newly burnt swidden plots in mainland Southeast Asia from 1988 to 2016. The calculation processes were finished with Python language using ArcGIS 10.x software. The study also utilized a ‘space-time conversion’ method. They can be called ‘space-for-time (S-T) substitution’ and ‘time-for-space (T-S) substitution’, respectively.
Implications and Conclusions
The length of fallow periods in shifting cultivation has been greatly shortened by a combination of factors, including population growth, alternative land uses and infrastructure development across the mountainous regions of the tropics from 1988 to 2016. Knowledge of the dynamic processes of natural vegetation regeneration under swiddening is critical for much ongoing research.
The study concludes that longer-term fallows occurred or re-occurred more frequently in the 1980s than in the 1990s, while in the 2000s longer term and short term fallows were not different. Furthermore, geo-economic cooperation under the GMS, involving Cambodia, Laos, Myanmar, Thailand, Vietnam and neighbouring China and India, may have been a strong driver of extensive and rapid land cover and land-use changes.
Key Points
- Swidden agriculture remains a dominant land-use category in montane mainland Southeast Asia.
- Fallow periods in swidden systems have been greatly shortened due to population growth, alternative land uses, and forest conservation policies.
- The study developed a Landsat-based multi-step threshold algorithm to generate maps of swidden agriculture in mainland Southeast Asia and Yunnan province, China.
- The mountainous area of mainland Southeast Asia was redefined based on elevation, slope gradient, and local relief to reduce spectral noise effects.
- The annual dynamics of swidden agriculture are closely related to land-use intensity and the varying length of fallow periods.
- Geo-economic cooperation mechanisms since the 1990s and stricter environmental governance since 2011 have impacted swidden agriculture practices.
- The study identified short-term (1-5 years), medium-term (6-10 years), long-term (11-20 years), and longer-term (21-28 years) fallow periods.