Short answers, pulled from the story.
Drylands occupy approximately 40-41% of Earth's land area, and between 10% and 20% of those drylands are already degraded. The total area affected by desertification is estimated between 6 and 12 million square kilometers, with a billion people at risk from further desertification.
The immediate cause of desertification is the loss of vegetation, driven by drought, climatic shifts, overgrazing, tillage for agriculture, and deforestation. Human population pressure has made previously sustainable farming and grazing techniques unsustainable, while anthropogenic climate change has degraded 12.6% of the world's drylands between 1982 and 2015.
Lake Chad has shrunk by over 90% since 1987, primarily due to water withdrawal for irrigation and decreased rainfall. The lake's dramatic reduction has displaced millions of inhabitants, and despite recent restoration efforts it remains at risk of disappearing entirely.
The Great Green Wall of Africa is an initiative launched by the African Union in 2007 to plant vegetation across an 8,000-kilometer stretch spanning the entire width of the continent, involving 20 countries with 8 billion dollars in support. As of reporting, the project has restored 36 million hectares of land and created over 20,000 jobs in Nigeria alone, with a target of restoring 100 million hectares by 2030.
At least 90% of dryland inhabitants live in developing countries where land degradation reduces agricultural productivity and cuts off access to resources. Desertification forces rural populations to abandon land that can no longer support them, driving mass migration to cities. Projections for sub-Saharan Africa show environmental refugees could grow from 14 million in 2010 to nearly 200 million by 2050.
Farmer-Managed Natural Regeneration (FMNR) is a low-cost technique applied since 1980 in Niger that enables native trees to regrow by selectively pruning shrub shoots from existing root systems. The method has helped farmers regenerate approximately 30,000 square kilometers of degraded land in Niger. The Humbo Assisted Regeneration Project in Ethiopia uses the same approach and has received funding from the World Bank's BioCarbon Fund.