Using cropland maps to monitor livestock routes in Sudan

Every year, pastoral communities in central Sudan move south with their livestock along traditional migration routes that can span hundreds of kilometers. These routes are under threat, primarily from the expansion of mechanized farming, which often leads to conflict between farmers and herders. To address this, projects funded by the International Fund for Agricultural Development (IFAD) have helped farming and pastoral communities agree on and officially demarcate these stock routes to allow free movement for livestock.

This case study focuses on one such route, a 1.5-km-wide north–south strip of land that stretches 138 km across Sennar State, southeast of Khartoum. It presents the findings of a study that used satellite imagery and ground surveys to determine what parts of the route were under crops – and which thus might present a barrier to the movement of livestock.

Analysis of the satellite imagery showed that some 60–65 per cent of the route was blocked by cropland from 2017 to 2022. In 2022, the IFAD-funded Sustainable Natural Resources and Livelihoods Programme re-demarcated the route and the state government compensated farmers for giving up their land. The satellite imagery showed that cultivation within the route dropped to around 35 per cent in the following year. Comparing the land in the route with a 3-km strip of land flanking it on either side showed that the demarcation effort was responsible for the majority of this fall in cultivation.

The decline in crop cultivation means that the livestock route became less blocked and more open to livestock movements. This is likely to have reduced the number and intensity of conflicts between herders and farmers. The study shows that cropland maps based on a combination of satellite imagery and ground-truthing are a valuable tool for monitoring stock routes on an annual basis.

Every year, pastoral communities in central Sudan migrate southward in search of pasture for their livestock during the dry season. They follow traditional migration routes spanning several hundred kilometres. Typically, they travel south from October to June to access dry-season grazing areas and return northward for the rainy season, which lasts from July to September.

Transhumance is an ancient adaptation strategy and remains the most sustainable form of agriculture in drylands. Mobility enables herders to convert grassland into meat and milk. It is key to respond to climate shocks such as drought by moving to emergency grazing areas. Mobility is essential for coping with variability.

However, this system is under threat from mechanised, large-scale farming, which is encroaching on traditional routes. Blocked routes force herders to find alternative paths, which is a major cause of conflict between farmers and herders. The animals lose weight because they have to travel longer distances, putting pressure on natural resources, as more animals gather around a few open routes and water points, destroying the vegetation. A healthy, mobile system can cope with climate shocks, but an obstructed system cannot.

Since 2004, developing stock routes has been a critical intervention for the International Fund for Agricultural Development (IFAD). The United Nations specialised agency has funded operations implemented by the Government of Sudan to develop services along such routes and mitigate conflicts between herders and farmers. Key interventions for stock route development included:

IFAD regularly visits these interventions together with the government and project staff, but Sudan is large, and stock routes are located in remote areas, spanning hundreds of kilometers. The ongoing war has made field visits very complicated, and traditional survey methods and reporting mechanisms were unable to provide the full picture, leaving IFAD and the government without an effective and objective way to measure the success of these interventions.

In 2024, IFAD had the opportunity to address this monitoring gap by partnering with the ESA GDA programme. The initiative's objective was to use Earth Observation (EO) to measure the success of stock route development on one route in the Sennar State that IFAD had been developing since 2018.

The central stock route in Sennar State was plagued with multiple farmer-herder conflicts. In 2018, the IFAD-funded Livestock Marketing and Resilience Programme demarcated a 60-km-long, 500-m-wide section of the route using small earth mounds, but this initial demarcation proved insufficient. In 2022, the new Sustainable Natural Resources and Livelihoods Programme launched a re-demarcation effort where the route was expanded to 162 km, with 141 km marked by larger mounds, and its width was increased to 1.5 km.

Although the route was physically demarcated, it was not measured using GIS technology. IFAD hired a GIS expert who mapped the entire 138-km-long, 1.5-km-wide corridor, encompassing 26,500 hectares. The expert also collected crop reference points. This data was then used to produce maps showing the extent and type of cropland from 2017 to 2023. These maps were then overlaid with the stock route area in order to calculate the hectares of cropland within the route for each year. To provide a basis for comparison, the study team created a 3 km buffer zone on each side of the route, where no changes should occur.

The results showed that 60–65 per cent of the route was covered by cropland between 2017 and 2022. Cultivation within the route then dropped to around 35 per cent in 2023, one year after the redemarcation. Over 7,500 hectares of livestock routes were unblocked. Comparison with the 3-km strip on both sides of the route showed that 4,300 hectares of blockages could be attributed to the IFAD project.

The numbers complemented what project reports and community testimonies were saying. Since the blockages were removed and herders were able to move freely without harming farmers’ livelihoods, incidences of conflict dropped sharply, from 264 in 2021 to 35 by July 2024.

Farah, manager of the agricultural sector in Ad-Dali & al-Mazmoum locality, noted, the successful demarcation of the central livestock route led to fewer disputes between farmers and pastoralists, less crop damage, an increased bulk of animal products, better delivery of veterinary services, and the protection of forests that fall within the route domain.

Cropland extent and type maps were produced by VITO under the European Space Agency’s Global Development Assistance Programme using the WorldCereal methodology developed by Van Tricht et al. (2023).

In October 2023, a national GIS expert collected field data along the Sennar stock route. The expert recorded stock route boundaries by mapping earth mounds, serving as markers for the stock route's boundaries. These individual points were then combined to create a route polygon representing the stock route's extent. The expert also recorded the types of crops cultivated in the fields immediately surrounding the livestock route. A total of 105 locations were documented, indicating crop types such as cotton, maize, millet, sesame, sorghum, sunflower, and watermelon.

Cropland maps at 10 m resolution were created from 2017 to 2023 using optical satellite data from Sentinel-2 L2A, and the crop-type field data were used as training points. A cropland binary model was applied to the optical features. The cropland maps were further classified by crop type. For this analysis, the following crop types were considered: sesame, sorghum, sunflowers and all other crops. Annual crop type maps were produced for the period 2017–2023.

The cropland extent and type maps made it possible to measure the impact of stock route interventions: Over 7,500 hectares of livestock routes were unblocked of which 4,300 hectares can be attributed to the IFAD project.

The study suggests that cropland maps derived from remote sensing can be used to monitor how a stock route is used annually, tracking abandonment and encroachment in order to measure the success of development projects and identify potential areas of conflict. This approach is independent and objective, as well as being scalable and cost-effective.

IFAD will continue to invest in this approach, as the organization is now scaling up these methods with ESA WorldCereal to monitor encroachment and the success of interventions on other stock routes.