Can sustainable management of land commons offer a nature-positive solution? Initial insights from land use-based above-ground carbon stock modeling in the Thoria Watershed, India

By Upeksha Hettiarachchi, Zhe Guo, Wei Zhang

International Food Policy Research Institute (IFPRI)

A wealth of publicly available satellite data and open-source models allowed researchers to measure carbon stocks in a watershed in India, despite a paucity of on-the-ground data. They found that despite rapid urbanization over the last 20 years, carbon stocks remained relatively stable – possibly due to successful reforestation activities. The research points to how nature-positive solutions can be designed and measured at scale. The research also lays the foundation for global studies to promote a deeper understanding of ecosystem services and sustainable land management.

Commons provide many ecosystem services that support the livelihoods of billions around the world but their economic (and non-economic) contribution to people and nature are rarely assessed. As part of the effort to support the Promise of Commons initiative led by the Foundation for Ecological Security (FES) in India, a collaborative research team comprised of FES, the International Food Policy Research Institute (IFPRI) and other CGIAR centers has been examining the linkages between commons and ecosystem services.

As land fragmentation grows and degradation worsens in the climate change crisis, local households in India increasingly depend on common lands to meet their food, domestic and productive needs. A recent study using value transfer method estimated that the average value of ecosystem services provided by land commons in India, which cover 66.5 million hectares, was $90.5 billion per year (range $24 – 192 billion).

Such findings about the economic contribution of land commons need to be complemented by land use and land cover mapping and ecosystem services modeling to support decision-making about nature-positive land use planning and investment in commons management. This collaborative research began under the CGIAR Research Program on Water, Land and Ecosystems (WLE) and is now continuing under the CGIAR Initiative on Nature-Positive Solutions. The first step is to leverage publicly available satellite data and open-source ecosystem models to explore how land cover changes affect carbon storage, using a case study of the Thoria watershed, located in Rajasthan, India (Fig. 1). By employing a cost-effective method suitable for data scarce contexts, our preliminary analysis uncovers the impact of land cover and land use changes on carbon storage ecosystem service.

Fig. 1: Map of study area in India. (Thoria is the little red dot in the northwest; map of Thoria Watershed, bottom.)

The study used the Global Land Cover and Land Use Change datasets for 2000 and 2020 to create land cover maps for the Thoria watershed. It included five main categories: woodland and tree cover, waste land, cropland, built-up areas, and water bodies. To capture the spatial variations within land cover types, the Normalized Difference Vegetation Index (NDVI), derived from high-resolution 10-meter Sentinel satellite, is adopted to further refine the existing classes. NDVI values greater than 0.4 were categorized as “NDVI high” and values lower than 0.4 as “NDVI low”. The refined land cover classification expands to 10 classes for each of 2000 and 2020 (Fig. 2). A noteworthy observation is the clear progression of urbanized regions, depicted in red on the maps. Another intriguing trend is the increase in agricultural land from 2000 to 2020, primarily concentrated along the peripheries of the pre-existing cropland in 2000.

Fig. 2 Disaggregated land cover map of 2000 (top) and 2020 (bottom), Thoria watershed, India. “_High” or “_Low” in the legend refers to “NDVI high” or “NDVI low.”

The ground truth data for above-ground biomass and carbon stock were collected from 128 locations in the Thoria watershed in 2019 by FES. Based on consultations with local experts and authorities, we developed two future land use scenarios: 1) 20% expansion of cropland, and 2) 20% expansion of wooded land and tree cover. Utilizing the free, open-source InVEST models, we estimated carbon stock in 2000 and 2020 and projected carbon stock change for two future scenarios in the watershed (Fig. 3).

Fig. 3: From top to bottom: Estimated carbon stock in 2000, 2020, scenario of 20% more cropland, and scenario of 20% more wooded land and tree cover.

Despite the pressure from population growth and economic development over 20 years (e.g. the built-up area increased significantly from 985 km2 in 2000 to 3,361 km2 in 2020), the total carbon stock in the watershed remained at similar levels with a slight decline from 2,669.86 tons in 2000 to 2,583.07 tons in 2020. Meanwhile, there was commendable growth of wooded land and tree cover area, suggesting positive strides in forest protection through sustainable land management and reforestation activities.

Two alternative scenarios were also considered: one with a 20% expansion of cropland, resulting in a total carbon stock of 2,533.15 tons, and another with a 20% expansion of wooded land and tree cover, which yielded a total carbon stock of 2,602.05 tons. A key nuance is that certain cropland (with high NDVI) can sequester similar levels of carbon as wooded land and tree cover in Thoria, especially wooded land and tree cover area with lower carbon sequestration capacity (with low NDVI). However, the GHG emission mitigation benefit of wooded land and tree cover would be more enduring, as compared to cropland cultivated with annual crops.

Our analysis offers important insights into carbon dynamics in relation to land use/cover, particularly in semi-arid regions. The potential for carbon storage in wooded land and tree cover differs significantly from dense forests in wetter climates. Despite the expansion of wooded land in semi-arid zones, the increase in carbon storage isn’t as substantial as observed in wetter climates. It is crucial to employ adaptive land management approaches that take into account the distinct characteristics of the region.

The suggested methodology utilizes the wealth of publicly accessible satellite data and associated products, along with open-source ecosystem models. This provides a valuable approach for conducting spatially explicit analysis of ecosystem services such as above-ground carbon stock, particularly in data-scarce settings, to inform the design of nature-positive solutions. Investments in sustainable land commons management offer a pathway for “nature for climate,” addressing land degradation and safeguarding communal wooded and grazing areas crucial for carbon sequestration. Results emphasize the vital role of preserving forests amid urban development, impacting carbon storage and local community well-being. Shedding light on the complex interplay between land cover and carbon dynamics, this research lays the foundation for global studies, promoting a deeper understanding of ecosystem services and sustainable land management.