Trees planted across Sudan's drylands over the past several decades are delivering measurable environmental benefits that become stronger with age, according to a new study examining how Acacia senegal plantations transform the land beneath them. The research found that as these hardy, drought-resistant trees grow older, they gradually increase the amount of organic carbon stored in the soil and improve the ground's ability to retain water — two critical improvements for one of the world's most climate-vulnerable regions.
Acacia senegal, commonly known as the Sudan gum tree, has long been cultivated across the Sahel region for its gum arabic production, a substance widely used in food, pharmaceuticals, and industrial applications. The recent findings add a significant dimension to the tree's value: beyond its economic importance, it plays a meaningful role in restoring degraded soils in arid and semi-arid landscapes.
The study compared multiple sites of varying ages, from newly established plantations to mature stands that have been growing for many years. What researchers observed was a clear pattern — older Acacia senegal stands contained significantly higher levels of soil organic carbon than younger ones or nearby unplanted areas. This accumulation occurs as the trees drop leaves, shed roots, and support microbial activity beneath the surface, slowly building up the nutrient-rich layer that defines healthy soil.
Equally important was the finding related to soil moisture retention. Older plantations showed a greater capacity to hold water in the ground after rainfall events, which is a crucial advantage in regions where rain is sparse and unpredictable. However, the data also revealed a nuanced result: undisturbed grassland areas adjacent to or near the plantations still retained slightly more soil moisture than the tree-covered plots. Scientists suggest this may be because grasslands, with their dense root mats and continuous ground cover, lose less water to evaporation under extreme heat — a factor that becomes more pronounced as the trees age and their canopy shades the understory less effectively in some cases.
Experts say the findings have direct implications for Sudan's reforestation strategy and similar dryland restoration programmes across the Sahel. They note that while grasslands should not be neglected or converted into plantations, the data supports continued investment in Acacia senegal as part of a mixed-vegetation approach to land recovery. The trees offer carbon sequestration and soil improvement benefits that grow stronger the longer they remain standing, making patience and long-term land management essential to seeing results.
Climate change has intensified drought cycles across Sudan in recent years, making soil restoration through native tree planting increasingly urgent. The study underscores that such efforts are not quick fixes but gradual processes whose full benefits unfold only after years of growth and care.
