According to a comprehensive study published in the journal Scientific Reports by lead author Melese Wondatir Sisay, combining assisted natural regeneration and active tree planting in Ethiopia’s Kembata Tembaro district significantly reduced severe topsoil loss between 2015 and 2024. The research evaluated the real-world impact of the REDD+ Investment Program, launched in 2015 with funding support from the Norwegian government, by examining high-detail satellite images, ground height maps, and historical rainfall records across six pilot test sites covering more than 107 square kilometres.
Evaluating Land Restoration and Topsoil Reduction in Ethiopian Drylands
In the study area, protecting wild growth and planting new trees successfully reversed severe environmental degradation in dry, hilly terrain. According to the research team, trees covered just 1.9% of these Ethiopian drylands in 2015. Nine years later, helping old roots regrow pushed forest cover above 22% across the region’s varied terrain, which features high flatlands, deep valleys, and rolling hills ranging from 800 metres to 2,600 metres above sea level.
Nearly all the test zones, specifically 95%, sit within the hot, dry lowlands known locally as the Kola zone below 1,500 metres in altitude, with smaller sections extending into mid-altitude hills known as Weyna Dega. Rapid population growth, unpredictable rainfall, and heavy farming in these dry highlands frequently cause steep slopes to lose anywhere from 20 to 100 tonnes of topsoil per hectare every year. This continuous erosion washes away nutrient-rich earth, directly weakening farm yields, damaging agricultural productivity, and threatening food supplies for local communities.
Did you know?
The REDD+ Investment Program has established large-scale community forestry programs across 54 districts in Ethiopia, covering four major administrative regions including Amhara, Central Ethiopia, Sidama, and Oromia, according to project data.
Assisted Natural Regeneration vs. Active Tree Planting
The research compared two distinct land management strategies to measure their effectiveness against soil erosion. According to the findings, three test sites restored using assisted natural regeneration—a strategy focusing on protecting existing root systems and managing surrounding land so native bushes and trees can regrow naturally without expensive nursery planting—saw forest cover grow from 1.9% in 2015 to 22.18% in 2024. Consequently, annual soil loss at these sites dropped from 13.19 tonnes per hectare down to 9.49 tonnes per hectare over the nine-year evaluation period.
Conversely, direct tree-planting programs delivered even larger increases in forest canopy alongside major reductions in washing-away topsoil. Across three pilot sites where new saplings were actively added to bare or deforested land, forest cover expanded from 8.5% in 2015 to 34.92% by 2024. Because these active planting sites suffered from extreme land damage when the project began, initial topsoil loss was extremely high at 43.37 tonnes per hectare per year in 2015. By 2024, protective tree cover helped lower that loss to 31.29 tonnes per hectare per year.
High-Resolution Satellite Tracking and Erosion Modeling
To track these environmental changes accurately over time, the researchers analyzed sharp 4.77-metre resolution satellite photos inside Google’s cloud-based mapping software, using imagery provided by Norway’s International Climate and Forests Initiative. The research team categorized the regional landscape into seven basic cover types: dense forest, open forest, brushland, farmland, grassland, bare dirt, and towns.
According to the study, the satellite mapping achieved an overall accuracy of 81.4% for the 2015 baseline data and reached 86.79% accuracy for the 2024 map when checked against 356 real-world ground locations verified through detailed aerial photos. To estimate how much dirt was actually saved from erosion, the researchers built a computer formula combining long-term rainfall averages from 1990 to 2024, local ground slopes, soil types, and plant cover. Known as the Revised Universal Soil Loss Equation model, this standard calculation scored 0.823 out of a maximum score of 1.0 during standard statistical reliability checks.
Pro Tip for Land Managers:
While planting new nursery seedlings remains necessary on completely bare ground, protecting living root systems and allowing native trees to sprout on their own offers a lower-cost, highly effective way to heal damaged communal land.
Frequently Asked Questions
What is assisted natural regeneration?
Assisted natural regeneration is a land management strategy that focuses on protecting existing root systems and managing surrounding land so native bushes and trees can regrow naturally without expensive nursery planting.
How much did forest cover increase in the study area?
According to the research published in Scientific Reports, forest cover in assisted natural regeneration sites grew from 1.9% in 2015 to 22.18% in 2024, while active tree-planting sites expanded from 8.5% to 34.92% over the same period.
What caused the high initial rates of topsoil loss?
Rapid population growth, unpredictable rainfall, and heavy farming across Ethiopia’s dry highlands frequently cause steep slopes to lose significant amounts of topsoil annually, with active planting sites initially losing 43.37 tonnes per hectare per year in 2015.
Which organization funded the initiative evaluated in the study?
The REDD+ Investment Program was launched in 2015 with funding support from the Norwegian government.
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