March 2, 2026
THIMPHU – The country’s rangelands have remained largely stable over the past decade, but stability does not necessarily mean improvement, a new nationwide study has found.
The study, which examined changes in grazing lands across the country between 2013 and 2024, reveals a complex picture beneath the surface of seemingly healthy pastures.
Rangelands are natural grazing areas dominated by grasses, herbs, shrubs, and bushes.
In Bhutan, rangelands include alpine pastures in the north, shrublands, and mixed grazing areas used by cattle, yaks, and other livestock. For herders, these lands are the backbone of rural livelihoods, supporting dairy production, meat supply, and traditional grazing systems.
The study, published this year, is the first to assess rangeland extent and vegetation trends across the entire country using high-resolution satellite data.
Researchers analysed images from Landsat 8 and Sentinel-2 satellites and processed them through Google Earth Engine. They measured vegetation “greenness” using two widely used indices: Normalised Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI). These indices estimate vegetation density and health based on how plants reflect light.
To understand how climate influences pasture growth, the researchers also examined rainfall data from 2013 to 2024.
The results show that most rangelands have remained stable. About 7,159 square kilometres stayed within the stability range when comparing the baseline period (2013–2015) to the recent period (2022–2024).
However, the picture is not uniform.
The study found that 1,425 square kilometres showed increasing vegetation greenness, while 442 square kilometres experienced declining trends. These changes are scattered and clustered in certain areas rather than spread evenly across the country.
One key finding is that increased greenness does not mean rangeland recovery.
Shrub and bush rangelands showed the strongest positive greenness trends. However, field observations and consultations with herders indicated that in some areas, the rise in greenness is linked to shrub expansion and invasive weeds.
Shrubs and weeds may appear green and dense in satellite images, raising NDVI and EVI values. However, they are often less palatable to livestock and can reduce the availability of nutritious grasses. This means that while satellite data may show an increase in vegetation, grazing quality may not improve and could even decline.
The study categorised rangelands into three main types: herbaceous rangelands dominated by grasses and herbs, shrub and bush rangelands, and mixed rangelands where grasses, shrubs, and woody plants coexist. Herbaceous and mixed rangelands contained areas of vegetation decline, while shrub and bush systems showed the most visible increases in greenness.
Researchers also stated that mixed rangelands are difficult to classify accurately using medium-resolution satellite imagery because of their complex vegetation structure. This means some results for these areas should be interpreted cautiously.
Another significant finding concerns rainfall.
Contrary to expectations, the study found a weak to moderate negative correlation between annual precipitation and vegetation greenness. In simple terms, higher rainfall did not necessarily lead to greener pastures. NDVI showed a moderate negative correlation with precipitation, while EVI showed a weaker negative relationship.
The researchers suggest several possible reasons. Excess soil moisture can reduce root oxygen, persistent cloud cover can limit sunlight needed for photosynthesis, and steep terrain can affect drainage and plant growth. Heavy grazing during the monsoon season may also offset potential gains from increased rainfall.
The findings indicate that climate variability, topography, soil conditions, grazing pressure, and land-use factors shape rangeland vegetation dynamics in the country. Rainfall alone does not determine pasture condition.
Importantly, the study does not conclude that the rangelands are in widespread decline. Instead, it shows a pattern of overall stability with localised areas of increase and decrease. However, it cautions that satellite-based greenness should not be the sole indicator of ecological health.
For Bhutanese herders, this research matters.
Changes in vegetation composition, especially shrub expansion, can affect livestock productivity, fodder availability, and grazing patterns. Even if the landscape appears green, the quality of forage may differ.
The study establishes a national baseline for future monitoring and suggests that rangeland management should combine satellite analysis with field-based assessments and herders’ knowledge.
