Across sub-Saharan Africa, countries have pledged to restore roughly 90 million hectares of wooded savanna by 2030, but no one knows whether those tree-planting efforts will actually work—or whether they will simply shove deforestation and carbon emissions onto neighbouring land. Current restoration science relies on small, project-level assessments that miss these larger, unintended consequences. This research will fill that gap by analysing over 1,000 restoration projects across 14 countries, using satellite data and field records to track what happens both inside and outside project boundaries. The team will measure how much carbon and habitat each technique—natural regeneration, tree plantations, or on-farm approaches—actually recovers, and whether those gains are offset by displaced farming or wood harvesting elsewhere. If successful, the findings could reshape how international climate and development funders design restoration programmes. Instead of pouring money into plantations that fail or cause leakage, governments and NGOs could target interventions that deliver real, net benefits for carbon storage and biodiversity. The work may also influence land-use planning in savanna regions, where poorly planned tree planting can fragment open habitats that are ecologically valuable in their own right.
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The degradation of natural habitats and farmland undermines efforts to keep global warming below 2°C, and to meeting the United Nations Sustainable Development Goals. The COP26 'Glasgow Leaders' Declaration on Forests and Land use' commits over 100 nations to work together to halt and reverse forest loss and land degradation by 2030. This reaffirms international commitments under the Bonn Challenge to 'restore' 350 million hectares by 2030, a goal set in response to a scientific report indicating that 300-400 million hectares of forest needed to be restored to avoid dangerous climate change. While restoration promises to slow climate change, reverse biodiversity loss, and recover soils, 21st century restoration science lacks a joined-up understanding of the effectiveness of different tree planting options and how their roll-out may generate unintended consequences, especially by the displacement of food or wood production that leads to habitat loss and greenhouse gas emissions elsewhere. The risks of poorly planned and executed large-scale tree planting include restoration failure, deforestation via displacing farming to other areas, and fragmentation of open habitats. There is thus a pressing need to move beyond traditional individual project-level assessments of restoration that may fail to detect these complex and larger-scale impacts. Here we will conduct novel analysis that explicitly account for feedbacks that generate unintended consequences for biodiversity and ecosystem services at large spatial scales. We will implement a region-wide analysis to quantify the effectiveness of different restoration interventions and resolve the degree to which they displace food or wood production. In this way, this project will address the major uncertainty in restoration. This continent-scale integrated programme of research focuses on wooded savanna ecosystems in 14 countries in sub-Saharan Africa, where ~90 million hectares of wooded savanna restoration are planned. It will use the known locations of over 1000 restoration projects implementing the most commonly applied restoration techniques (natural regeneration, tree plantations, and on-farm approaches). Using these data, we will answer the following core questions: (1) How have restoration projects impacted habitat and carbon storage in the project areas (effectiveness)? (2) How much displacement (leakage) of deforestation, wood overharvesting, and tree growth to non-project land do restoration programmes cause? And (3) what are the environmental and socio-economic drivers of restoration effectiveness and leakage? In answering these three questions, this project will deliver a step change in our understanding of the likely consequences of continental-scale restoration, increasing the prospect of achieving its ecological and societal potential and meeting global climate and development goals.
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