Accelerating forest loss in Southeast Asian Massif in the 21st century: A case study in Nan Province, Thailand

TitleAccelerating forest loss in Southeast Asian Massif in the 21st century: A case study in Nan Province, Thailand
Annotated RecordAnnotated
Year of Publication2018
AuthorsZeng Z, Gower DB, Wood EF
Secondary TitleGlobal Change Biology
Key themesAgriculturalModernization, Conversion-FoodSecurity, Environment

Farmers are carving a new agricultural frontier from the forests in the Southeast Asian Massif (SAM) in the 21st century, triggering significant environment degradation at the local scale; however, this frontier has been missed by existing global land use and forest loss analyses. In this paper, we chose Thailand's Nan Province, which is located in the geometric center of SAM, as a case study, and combined high resolution forest cover change product with a fine‐scale land cover map to investigate land use dynamics with respect to topography in this region. Our results show that total forest loss in Nan Province during 2001–2016 was 66,072 ha (9.1% of the forest cover in 2000), and that the majority of this lost forest (92%) had been converted into crop (mainly corn) fields by 2017. Annual forest loss is significantly correlated with global corn price (p < 0.01), re‐confirming agricultural expansion as a key driver of forest loss in Nan Province. Along with the increasing global corn price, forest loss in Nan Province has accelerated at a rate of 2,616 ± 730 ha per decade (p < 0.01). Global corn price peaked in 2012, in which year annual forest loss also reached its peak (7,523 ha); since then, the location of forest loss has moved to steeper land at higher elevations. Spatially, forest loss driven by this smallholder agricultural expansion emerges as many small patches that are not recognizable even at a moderate spatial resolution (e.g. 300 m). It explains how existing global land use/cover change products have missed the widespread and rapid forest loss in SAM. It also highlights the importance of high‐resolution observations to evaluate the environmental impacts of agricultural expansion and forest loss in SAM, including, but not limited to, the impacts on the global carbon cycle, regional hydrology, and local environmental degradation.


Copyrighted journal article



Document Type

Journal Article


Overall relevance: 

This paper argues that farmers are expanding the agricultural frontier in the highland forests of Southeast Asia in a manner neglected by land use and forest loss analyses on a global scale. The research suggests that forest loss derived from smallholder agricultural expansion encroaches on national parks, producing small patches of deforestation in mountainous terrain with higher elevations and steep slopes. The literature review surveys general trends in upland deforestation and highlights some environmental consequences. It also acknowledges the popularisation and expansion of tree crops, critiquing that this does not sufficiently compensate for the substantial forest loss occurring across the Southeast Asian Massif. Focusing on the case study of Nan, the researchers theorise that rising global demand and prices for maize drive the recent boom, confirming that the patches of forest loss reflect long-term changes in land cover rather than short-term disturbances.

Key Themes: 
  • Agricultural modernisation: key ideas and debates relevant to land tenure security - The researchers considered land use dynamics (in particular conversion to cornfields) in relation to topography in six national parks in Nan Province, Northern Thailand. Across these locations, they identify that major forest loss occurs close to areas where average forest cover runs below 60%. This indicates regions where forest fragmentation has occurred. This also means that modernisation of agriculture in these specific areas are not primarily driven by mechanisation, instead enabled by local people farming intensively in the surrounding vicinity.
  • Land zoning, planning, conversion and food security - In Nan Province, maize is the most widely planted crop. This is not meant to support or feed the growing population or sustain local demands for food or fuel. Instead, maize is sold for profits as a cash crop that has become increasingly lucrative with rising global corn prices. The researchers attribute the near-threefold increase in maize prices to the clearance of forests between 2001 to 2012. From 2012, they noted that the conversion to cropland at higher elevations has become especially pronounced, positing different drivers aside from cornfield expansion. Since the forest loss in Nan is sensitive to changes in global market prices and demands, it is suggested that any solutions for deforestation should not only promote forest restoration, but also improve social welfare for upland farmers through win-win policies.
  • Land and the environment: pollution, deforestation, climate change, conservation zoning - Nan province is threatened by environmental degradation, as soil erosion and episodic landslides occur in deforested regions, where damage is often proportional to the gradient and elevation of upland plantations. Detecting these changes in land use thus enables the identification and assessment of impacts before disaster strikes. Furthermore, increasing forest loss means that carbon loss from deforestation over the years has become more substantial and worthy of concern.
Research basis: 

This study is based on a mountainous province in Northern Thailand. Forest loss is studied by comparing countrywide land use and forest cover maps produced by the Royal Forest Department in 2000. Digital elevation models were also used to investigate temporal changes in elevation and slope of areas where deforestation took place. The research outcomes indicate the problem of underestimating upland deforestation, which suggests that much research does not enable a sufficiently accurate picture of land-use change dynamics and livelihood transformations. (Provided by Jiong How Lua)