Biological soil crusts (biocrusts) are key components of dryland ecosystems worldwide, contributing to soil stabilization, nutrient cycling and enhancing ecosystem resilience. Despite their ecological importance, biocrusts in the Arabian Peninsula are largely underexplored, with much of the region’s biocrust diversity and functionality remaining undocumented. This review synthesizes current knowledge on biocrusts across the Arabian Peninsula, focusing on their major taxonomic groups (cyanobacteria, fungi, lichens, mosses and algae), their ecological roles and distribution patterns. It also discusses the potential for biocrust restoration through strategies such as cyanobacterial inoculation and passive protection, which could contribute to land degradation and desertification control in the Arabian Peninsula. Our work identifies significant research gaps in biocrust biodiversity, ecophysiology and their role in ecosystem functioning within this region, and calls for more focused research to integrate biocrusts into land management strategies for the Arabian Peninsula.

Islands of fertility, patches of locally enhanced soil conditions, play a key role in increasing productivity in dryland regions. The fertile island effect (FIE) influences a range of variables including nutrient availability, soil moisture and microbial activity. While most examinations of the FIE focus on islands created by perennial plants at local scales, the effect may vary across spatial scales and under cover types including shrubs, grasses and biological soil crusts (biocrusts). This study explored differences in the FIE between soil depths across landforms and patch types for biogeochemical factors (nutrient availability) and biotic properties (microbial community structure, extracellular enzymatic activity). The FIE differed across landforms and soil depths, suggesting that soil geomorphology may play a major role in predicting soil fertility. Additionally, the FIE of enzymatic activity and available nutrients varied by patch type consistently across landforms, suggesting patch-scale processes influencing nutrient availability and acquisition are independent of landscape-scale differences. We show that biocrusts can have an FIE similar to that of shrubs and grasses, an underexplored control of variability and productivity in drylands. These findings necessitate further work to improve our understanding of how ecosystem processes vary across scales to influence patterns of productivity and soil fertility.