Drylands cover more than 40% of the Earth's land surface and support over two billion people. These ecosystems provide essential ecosystem services, sustain biodiversity, support food production and pastoral livelihoods, and play an important role in global biogeochemical and climate systems. However, many drylands are increasingly affected by interacting pressures including climate change, land degradation, biodiversity loss, unsustainable land use and resource extraction, leading to declining ecosystem resilience and increasing risks of ecological transition. Therefore, developing integrated tools for assessing and monitoring dryland ecosystems represents a high research priority.
Recent advances in Earth Observation (EO), including long-term satellite archives, hyperspectral sensors, SAR, LiDAR, UAVs and Artificial Intelligence (AI), are transforming our ability to understand dryland dynamics across spatial and temporal scales. These approaches are enabling improved monitoring of vegetation change, ecosystem functioning, degradation processes, restoration outcomes, biodiversity patterns and ecosystem resilience.
Particular attention is being given to the development of EO-based indicators of land degradation, ecosystem condition, ecological integrity, resilience loss and recovery. Emerging EO approaches are also improving our ability to monitor important dryland transition processes such as woody vegetation encroachment, or alterations in vegetation spatial patterns, all modifying the structure and functioning of rangelands, savannahs and shrublands across large regions of the world, with important consequences for ecosystem resilience, biodiversity, fire regimes, ecosystem services and pastoral livelihoods.
The increasing availability of very-high-resolution imagery and hyperspectral datasets is also creating new opportunities for monitoring key but often overlooked dryland components such as biological soil crusts (BSCs), whose influence on soil stability, nutrient cycling, hydrology and ecosystem functioning makes them critical indicators of dryland health, degradation status and ecosystem resilience.