Dryland cities are important locations for human–environmental interactions and differ in many key characteristics from cities in wetter environments. Defined by chronic water deficit, these cities face challenges that include securing essential resources, reducing vulnerability to hazards and conserving threatened species. The resilience of dryland cities depends on interactions across the entire urban continuum, from urban cores and suburban areas to teleconnected zones and wildland–urban interfaces. Resilience solutions must enhance the well-being of residents and institutions while fostering adaptive capacity throughout the urban continuum. Key axes of solutions include hydrologic integration, including stormwater capture and reuse, nature-based solutions, including expanding urban tree cover for cooling and health benefits, and landscape sustainability, including the incorporation of spatial heterogeneity into planning and development. Addressing the large uncertainties in ensuring more resilient cities requires convergence research, the integration of theoretically driven science that brings researchers and stakeholders together to identify problems, solutions and opportunities for action. While convergence approaches look to address pressing scientific uncertainties, they also are inherently place-based and address compelling case studies to understand system dynamics and improve decision-making and land management. New research is needed to address the trade-offs resulting from decision-making and urban management activities, to meet the needs of diverse stakeholders and to ensure that policies do not marginalize underserved communities. By leveraging innovative technologies, sustainable practices and community involvement, dryland cities can overcome the challenges posed by chronic water limitations and thrive in their diverse environments.

Unconsolidated soils typically develop a physical surface crust after wetting and drying. We reproduced this process in the laboratory by wetting with fog and simulated rain on fallow agricultural soils from 26 locations, representing 15 soil types from Pinal County, Arizona. Through correlative analyses, we found that carbonate content was a strong predictor of physical crust strength with fog (p < 0.0001, R2 = 0.48) and rain (p = 0.004, R2 = 0.30). Clay content increased crust strength (p = 0.04) but was not a useful predictor. Our results extend the current understanding of the soil crusting process by highlighting the preeminence of carbonate cementation in desert agricultural soils. Consequently, we identify carbonate as a pragmatic tool for estimating crust strength, a surrogate measure of a soil’s potential to produce fugitive dust, which can help prioritize interventions to curb airborne dust in arid lands.

The last half of the previous century has seen an explosion in publications on biocrusts, communities of eukaryotic and prokaryotic organisms inhabiting the uppermost surface of predominantly dryland soils. Much of the early work emanated from the western United States, yet there have been few attempts to document the breadth of this work and its contribution to our understanding of the ecosystem roles of biocrusts. We used a structured literature search to extract the 868 publications on biocrusts published between January 1900 and July 2024, and explored the trends in publications in 12 subject areas over that time. We found that almost half of the 868 publications focussed on the ecological and physiological effects of biocrusts and that more recent research explored emerging fields such as restoration, monitoring and climate change impacts. Five authors comprised about 10% of all authors on these publications, and 5.5% of publications had 10 or more authors. The number of authors per publication tended to increase over time. We identified three main periods of research ranging from basic ecology and exploration of ecological mechanisms pre-2000 to biocrust function, physiology and climatic drivers up to 2020. The post-2020 period was characterized by a greater emphasis on molecular approaches, restoration and climate change impacts. Our literature review identifies knowledge gaps associated with the need for more trained taxonomists, and greater education on biocrust ecology and function. Potential developments in biocrust research include a greater use and recognition of biocrust species traits, the establishment of a dedicated international biocrust society, and the development of a global research and monitoring network to coordinate methods and provide a framework to answer critical knowledge gaps.

Composed of poikilohydric organisms, biocrusts have the ability to survive during periods of drought, making them particularly important in arid and semi-arid areas. However, despite recent research into climate change, the limits of this tolerance to desiccation and the effects of increased water availability, are not very well known. Our objectives were to analyze the effect of prolonged droughts on the cover and metabolism of various crust types, as well as the effect of increased precipitation. Five types of crusts representative of hypothetic successional stages were studied (Physical, Incipient, Cyanobacteria, Squamarina and Lepraria). Two representative areas were selected for each crust type. Nine plots were established in each area, delimited by a 10-cm-diameter ring, and distributed in sets of three plots. In each set, three treatments were applied (control, watering and rain exclusion), and changes in cover, CO2 fluxes and chlorophyll a fluorescence were analyzed. Rain exclusion led to cover losses due to respiration, although this effect differed among successional stages. However, increased precipitation did not increase biocrust cover, because both photosynthesis and respiration rates increased. Chlorophyll a fluorescence was higher in lichens; under watering, it was not different from the control but decreased under rain exclusion.

Land degradation is reducing biodiversity and crop yields, and exacerbating the impacts of climate change, throughout the world. Monitoring land degradation is required to determine the effectiveness of land management and restoration practices, and to track progress toward reaching land degradation neutrality (LDN). It is also needed to target investments where they are most needed, and will have the greatest impact. The most useful indicators of land degradation vary among soils and climates. The United Nations Convention to Combat Desertification (UNCCD) selected three widely accepted land degradation indicators for LDN: land cover, net primary production (NPP) and soil carbon stocks. In addition to non-universal relevance, the use of these indicators has been limited by data availability, especially for carbon. This article presents an alternative monitoring framework based on the definition and ranking of states in a degradation hierarchy. Unique classifications can be defined for different regions and even different landscapes allowing, for example, perennial cropland to be ranked above a highly degraded grassland. The article concludes with an invitation to discuss the potential value of this approach and how it could be practically implemented at landscape to global scales. The ultimate objective is to support decision-making information at the local levels at which land degradation is addressed through improved management and restoration while providing the information necessary for reporting on progress toward meeting goals.

Reconstructing Quaternary-timescale environmental change in drylands provides insights into styles and rates of change in response to direct insolation forcing and variations in global temperature, ice volume and sea level. Changes to the relatively inhospitable environments presented by drylands are also central to debates about the migration and adaptability of hominin species. This review outlines approaches used for reconstructing past environments, which use dated sequences of environmental proxies – the properties of physical sediments, chemical precipitates and biological materials. In addition, climate model simulations can explore responses to known climatic forcing factors. Advances in both approaches remain situated within conceptual frameworks about dryland responses to: (i) cyclical changes in the Earth’s orbit around the sun, either mediated via the global cryosphere during glacial–interglacial cycles (~100 ka periodicity during the last ~0.9 Ma), or mediated via the response of the global monsoon with ~23 ka periodicity (precession) and (ii) millennial-scale climatic shifts, which are thought to originate outside drylands, within the North Atlantic.

In this review, three examples are outlined to demonstrate areas of emerging consensus and remaining contradictions: (1) speleothem and tufa growth records that span hundreds of thousands of years (ka), (2) conditions at the last glacial maximum (LGM) and (3) proxies recording millennial-scale events. Precessional-scale forcing of the monsoon is not always observed, with apparent mediating roles from glacial boundary conditions in parts of the northern hemisphere (NH) and from interglacial boundary conditions in parts of the southern hemisphere (SH). The LGM in drylands was initially conceptualised as experiencing pluvial (wet) conditions, which shifted to a glacial aridity paradigm, and is again shifting to a pattern of global heterogeneity, in which some drylands were wetter-than-present and others drier. However, there remain contradictions between environmental proxies and model simulations, and spatial heterogeneity is observed within many drylands. Dryland proxies that record millennial-scale events demonstrate clearly the importance of climatic teleconnections across the globe in influencing dryland hydroclimate. The records of Quaternary dryland change across a range of timescales get used alongside simulations of ecosystem response through time, hominin habitat and even hominin physiology to better understand likely hominin dispersals through dryland regions.

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.

African dryland farming systems integrate crop and livestock production. In these systems, cropland and livestock productivities are intricately connected to support livelihoods of pastoral and agropastoral communities inhabiting African drylands. However, achieving sustainable increases in crop and livestock production under the prevailing conditions of low external inputs, soil degradation and climate variability and vulnerability to climate change, remains a great challenge in African drylands. Thus, to address these inherent challenges and achieve food security in the region, there is a need to adopt sustainable agricultural systems and practices. Pasture cropping, a no-tillage system where annual cereal crops are sown into perennial pastures during their dormant stage, has great potential to diversify African dryland farming systems and enhance overall cropland productivity. This can be linked to its contribution to increased perennial vegetation cover that protects the soil from agents of erosion, improving soil structure and soil hydrological properties, accumulation of organic matter, reducing N leaching, promoting C sequestration and weed control. Despite its great potential, pasture cropping in African drylands is still at its infancy stage. This review examines the potential of pasture cropping as a sustainable agricultural production system in African drylands. Specifically, we describe its salient features, benefits and challenges and explore its applicability to the environmental and socio-economic conditions of African drylands. Pasture cropping shows promise for improving agricultural productivity and sustainability in the African drylands. However, to achieve its full potential, significant adaptations are needed to tailor the system to match prevailing local socio-economic and environmental conditions, including climate and local adaptation, species selection, socio-economic constraints and economic viability among farming communities.

Groundwater is a critical support system for agriculture, domestic and industrial consumption in India, but escalating depletion and climatic stresses underscore the need for scientifically robust groundwater potential zone (GWPZ) mapping. In response to the aggravating water security issues in India, this study presents a critical and systematic-methodical review of research articles focused on GWPZ mapping. The primary goal of this research is to integrate input parameters, modeling techniques and validation methods to produce an evidence-based framework for selecting appropriate and effective GWPZ mapping strategies. Six prominent thematic categories – topography, geology, hydrology, climate, land cover and aquifer properties – seem to be inevitably predominant in different physiographic zones. Methodological tendencies suggest a shift from conventional Multi-Criteria Decision-Making models, that is, Analytical Hierarchy Process and Frequency Ratio, toward sophisticated machine learning techniques like Random Forests, Support Vector Machine and Extreme Gradient Boosting. Validation practices are dominated by a high incidence of receiver operating characteristic curve analysis and area under the curve metrics, with occasional addition of precision, recall, F1-score and root mean square error. Across the studies reviewed, field-derived data, well yield, groundwater depth, aquifer thickness and resistivity surveys remain critical for ground-truthing model results. Our view is that even though Indian GWPZ research has taken significant methodological strides, regional data heterogeneity, aquifer complexity and climatic variability issues continue to pose a key challenge in GWPZ mapping. We suggest future strategies involving high-resolution datasets, three-dimensional subsurface modeling, climate-resilient algorithms and more diversified validation frameworks. Through this critical synthesis, the article presents an integrated guide to support planners select cost-effective mapping techniques, inform policymakers on strategic investments and data collection priorities and direct researchers toward the most critical scientific gaps in India’s increasingly dynamic hydro-environmental context.

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.

How do succession and the microhabitat interact to shape the mosaic of biocrust types in the Tabernas Desert (semi-arid Southeast Spain)? We hypothesize that succession (in human time scales) occurs only where the habitat allows it and can regress. Reviewing results from an extensive body of research conducted at the Tabernas region, we aimed (i) to show that crust types can be considered successional stages, (ii) to propose a succession model. We used two approaches: (a) direct, in situ monitoring of three sites (13, 17 and 11 years) and examination of unaltered micro-profiles of biocrusted soil; and (b) indirect assessment, by reviewing functional properties (e.g., ecohydrology, soil loss, physical–chemical properties, microbiota and gas exchange) of biocrust types hypothetically considered successional stages. Although differences among communities in these functions do not necessarily imply species replacement, they were consistent with the hypothetical successional order and the evidence of replacement from the direct approaches. Succession occurs at various speeds across space because it is controlled by habitat. Therefore, it is mainly observable in favourable habitats where the biocrust was altered, or in ecotones. We propose a succession model, including microclimatic controls, two early cyanobacterial stages and two later lichen stages, showing the regressive paths.