Loss, as a proxy for conversion, is found as the transition from grassland, shrubland and savanna to cropland, pastureland or a built-up area. To calculate this, we used three complementary datasets:
- The grassland extent collection 1.1 by Global Pasture Watch (GPW), which provides annual, 30 meter (m) maps of grassland extent ecosystems from 2000-2024. A cross-validation assessment for this GPW product is available in the source publication, Parente et al. 2024.
- The Global Land Analysis and Discovery (GLAD) land cover product, which consists of annual (2015-2024) maps of land cover at 30 m spatial resolution. An accuracy assessment of the GLAD land cover product is available in the source publication, Potapov et al. 2022.
- The Global Forest Change (GFC) dataset, which is available on Global Nature Watch, provides tree cover loss from 2001 to 2024 at 30 m spatial resolution. An accuracy assessment of the GFC land cover product is available in the source publication, Hansen et al. 2013.
To calculate grassland, savanna and shrubland loss, we needed to separate temporary losses from those that are permanent or semipermanent, which are a proxy for conversion, by harmonizing the GPW and GLAD datasets into a single combined annual map. To that end, we reclassified the GLAD land cover from classes from Potapov et al. 2022 into seven categories: bare ground, short vegetation, trees, water, snow/ice, cropland, and built-up areas (Table 1). We then replaced the GLAD short vegetation class with the GPW grassland categories (cultivated and natural or seminatural), where available. This reclassification produced an annual combined GLAD-GPW product from 2015 to 2024 that enabled spatially explicit, annual tracking of grassland, savanna and shrubland loss and that can be regularly updated contingent on the continued availability of input data layers.
Additionally, since our definition of this ecosystem extent is very broad and overlaps with areas of tree cover, we applied a mask based on tree cover loss data (GFC) available on Global Nature Watch. We identified all pixels with >30% tree canopy cover in 2000 that experienced tree cover loss at any time between 2001 and 2024 and excluded them from the grassland, shrubland and savanna loss analysis. This ensures that we are not counting loss twice — once as forest loss and then again as grassland, shrubland and savanna loss. Qualitative assessment showed that at the global scale, the masking is conservative and does not reduce grassland loss notably.
Table 1: Definitions for Global Pasture Watch class categories
| Class | Short definition | Called here | Original source |
|---|
| Cultivated grassland | Areas where grasses and other forage plants have been intentionally planted and managed, as well as areas of native grassland-type vegetation where they clearly exhibit active and “heavy” management for specific human–directed uses, such as directed grazing of livestock. | Pastureland | Parente et al. 2024 |
| Natural/seminatural grassland | Relatively undisturbed or sparsely managed native grasslands/short-height vegetation, such as open shrublands and savanna, as well as areas that have experienced varying degrees of human activity in the past, which may contain a mix of native and introduced species due to historical land use and natural processes. | Grasslands, shrublands and savannas |
| Bare ground | Land with 0-19% vegetation fraction. | | Potapov et al. 2022 |
| Short vegetation | Non–treed vegetation cover with 20% or more vegetation fraction. | |
| Tree cover | An area with tree height ≥5 m at the Landsat pixel scale; includes wildland, managed, and planted forest, agroforestry, orchards and natural tree regrowth. | |
| Water | Open surface water (inland) that covers ≥50% of a pixel for 20% or more of the year and is not obscured by tree canopy, floating vegetation, bridges or ice. | |
| Snow/ice | Land covered by glaciers and snow that remains throughout the entire year. | |
| Cropland | Land used to produce annual and perennial herbaceous crops for human consumption, forage, and biofuel; excludes tree crops, permanent pastures and shifting cultivation. | |
| Built-up | Man-made land services associated with infrastructure, commercial and residential uses; defined as pixels containing any man-made surfaces even if they are not dominant. | |
We completed this analysis at 30-m spatial resolution globally from 2016 to 2024, with 2015 serving as a baseline year using the harmonized and masked dataset described above. To estimate annual grassland, shrubland and savanna loss, we summed the area of all pixels classified in the grassland, shrubland and savanna class that transitioned to pastureland, cropland or built-up areas, as these transitions were most likely to represent lasting, human-driven loss. We excluded all losses of grassland, shrubland and savanna to the remaining GLAD classes such as snow, ice, bare ground, short vegetation or water, as they were likely temporary. Such transitions are often driven by natural seasonal dynamics or interannual variability, such as melting snowpack, retreating glaciers or temporary drying of water bodies, and do not represent intentional or lasting ecosystem loss. This analysis also does not include transitions from grassland, shrubland or savanna to tree cover. While such transitions may represent ecosystem conversion in some contexts, the majority of changes between these classes in the data are associated with rotational plantation cycles or natural vegetation dynamics, such as secondary succession or regrowth following disturbance. As a result, these transitions were excluded to avoid overestimating permanent ecosystem loss. Together, this approach produces a conservative estimate of grassland, savanna and shrubland loss by requiring strong evidence of a lasting human-driven transition and filtering out ambiguous or post-deforestation changes.
Grassland, shrubland and savanna loss as a conversion proxy indicator has several limitations. It is subject to the errors of commission and omission present in the input GLAD and GPW datasets. Area estimates for this analysis were derived using pixel counting, which involves summing the number of 30 m pixels classified as grassland, shrubland and savanna and converting this count to an area estimate. However, this method does not account for classification uncertainties or biases. Gross losses capture the extent of land cover change from grassland, savanna and shrubland to cropland, pastureland or built-up areas.
- While grassland, shrubland and savanna areas can and do support grazing by wild ruminants and domestic livestock, these areas can still retain significant ecological value. These ecosystems continue to provide carbon storage, biodiversity habitat and ecosystem services such as water regulation, pollination and soil stabilization. However, once converted to cropland or pasture (through intensive management actions like ploughing or planting), or built areas (e.g., cities or energy infrastructure), many of those benefits are lost or severely diminished.
- Due to the exclusion of water from the analysis, some meaningful losses, such as ecosystems permanently inundated by the construction of new dams or reservoirs, are not captured.
- Very long crop rotations or shifting cultivation systems may be captured in our analysis as loss events. While these land use changes may be temporary or part of cyclical agricultural practices, they can resemble permanent conversion in satellite-based land cover datasets, particularly when vegetation structure changes significantly or persists across multiple years.
- This analysis does not capture the extent or severity of degradation within grassland, savanna and shrubland. While it is true that pixels with very heavy signs of livestock impact on the landscape tend to be classified as pastureland (and therefore are outside of the grassland, shrubland and savanna class), subtle or functionally degraded areas may remain within the grassland, shrubland and savanna class. For example, many forms of degradation, such as declines in plant diversity, aboveground productivity, soil health or subtle structural changes, may not result in a detectable land cover change and are therefore not reflected as loss in this analysis. As such, this indicator likely underrepresents the full extent of degradation occurring within these ecosystems.
- Data for the most recent years is subject to greater uncertainty because classification relies on limited temporal context, making it more difficult to distinguish between temporary disturbances (such as shifting cultivation or short-term land use change) and permanent conversion. As additional years of data become available, some areas currently classified as loss may be reinterpreted as part of cyclical or reversible processes, leading to potential revisions in the final estimates.