Groundwater is a vital ecosystem of the global water cycle, hosting unique biodiversity and providing essential services to societies. Despite being the largest unfrozen freshwater resource, in a period of depletion by extraction and pollution, groundwater environments have been repeatedly overlooked in global biodiversity conservation agendas. Disregarding the importance of groundwater as an ecosystem ignores its critical role in preserving surface biomes. To foster timely global conservation of groundwater, we propose elevating the concept of keystone species into the realm of ecosystems, claiming groundwater as a keystone ecosystem that influences the integrity of many dependent ecosystems. Our global analysis shows that over half of land surface areas (52.6%) has a medium‐to‐high interaction with groundwater, reaching up to 74.9% when deserts and high mountains are excluded. We postulate that the intrinsic transboundary features of groundwater are critical for shifting perspectives towards more holistic approaches in aquatic ecology and beyond. Furthermore, we propose eight key themes to develop a science‐policy integrated groundwater conservation agenda. Given ecosystems above and below the ground intersect at many levels, considering groundwater as an essential component of planetary health is pivotal to reduce biodiversity loss and buffer against climate change.

Literature provides only a few examples of contamination of groundwater with microplastics, mainly investigated using a chemical approach. Little importance is given to the hydrogeological processes able to affect the contamination, such as river–groundwater interactions. This study was carried out with two aims. The first aim is the formulation of a method with a high result-to-cost ratio, based on the hydrogeological aspects of the investigated area. Microplastics were extracted from samples through filtration and successively counted and characterized morphologically through analysis of optical microscopy images. The second aim is to evaluate the presence of microplastics in some portions of an alluvial aquifer using this methodology. Microplastics in groundwater showed a higher circularity and Feret diameter than those found in surface waters, indicating that in porous aquifers the transport is likely more influenced by the microplastics’ shape than by their size. The aquifer recharge did not modify the microplastics’ characteristics in groundwater, whereas in surface water the flood wave promoted the resuspension of microplastics with lower circularity. These findings provide new pieces of evidence on the presence and transport of microplastics in both groundwater and surface waters, underlining how the hydrogeological characteristics of the area can be one of the main drivers of microplastics’ contamination.

The interaction between water, energy, and food as the water–energy–food (WEF) nexus has drawn much attention recently to solve upcoming uncertainty in food security. The aim of this study is to investigate the status of the WEF nexus in European countries. It is indicated that the largest nexus studies (among 27 European countries) have been conducted in Spain and Italy. It is confirmed that there is a large number of nexus studies in water-stressed countries while there are few studies on water-abundant countries (Slovakia and Luxembourg). Based on existing research, the majority of nexus studies focused on energy production. It is highlighted that most of the nexus studies were focused on water quantity aspects (rarely related to quality aspects) and energy; however, other resources including land, climate, ecosystem, soil, and environment received little attention. The migration of people as a result of climate change in the WEF nexus is not considered. Moreover, there is a lack of common and standard frameworks for nexus assessment. Therefore, we suggest a standard approach for nexus studies and produce a cross-sectoral and holistic approach for the evaluation of a water (quantity and quality)–energy–food–land–climate (WqEFLC) nexus that takes into consideration the circular economy.

The water–energy–food (WEF) nexus is drawing much attention in scholarly literature as a novel alternative to address complex resources and achieve resource security. The aim of this study is to analyze and review existing nexus studies to investigate the current status of nexus research worldwide. This study used a narrative review approach to provide a comprehensive overview on the WEF nexus using a variety of databases. It is indicated that the majority of studies in Asia and Africa focused on the water–energy–food (WEF) nexus. China and Brazil had the largest nexus research. Based on the existing literature, most of attention has been paid to food production. However, food consumption patterns and dietary change are rarely evaluated, and there is a lack of study on impacts of dietary change on the WEF nexus. Moreover, there is a lack of frameworks for the evaluation of the WEF nexus under dietary change scenarios. The major challenge of the nexus approach is data availability in crop production, which can be solved by using remote sensing data. There is a lack of standard and conceptual frameworks for nexus assessment and, then, an essential need to provide a new holistic and standard approach that be applicable worldwide to increase connections between researchers and decision makers, as well as the applicability of nexus approaches. Future research must couple the development of a holistic standard approach with experimental tests in different areas, involving interdisciplinary research groups able to carry out all the experimental activities, the numerical simulations, and the statistical analyses of climatic time series (in a climate change perspective) indispensable to demonstrate the real benefits of using a WEF-derived nexus approach.

In the Po plain, northern Italy, rivers within agricultural basins display steep summer increases in nitrate (NO₃⁻) concentrations. Flood irrigation in overfertilized, permeable soils may drive such diffuse pollution, facilitating interactions between NO₃⁻-rich groundwater and surface waters. We discuss multiple, indirect evidence of this mechanism in the Adda, Oglio, and Mincio rivers. These rivers drain agricultural soils with elevated nitrogen (N) surpluses, averaging 139, 193, and 136 kg ha⁻¹ in the Adda, Oglio, and Mincio watersheds, respectively. The three rivers cross a transitional area between highly permeable and impermeable soils, where summer NO₃⁻ concentrations may increase by one order of magnitude over short distances (8–20 km). Upstream of this transitional area, a major fraction of the river flow is diverted for flood irrigation, a traditional and widespread irrigation technique for permeable soils. We speculate that diverted water solubilizes soil N excess, recharges the aquifer, and transfers soil N surplus into groundwater, resulting in NO₃⁻ pollution. Groundwater–river interactions were estimated experimentally, via water and NO₃⁻ budgets in 0.3 to 1 m³ s⁻¹ km⁻¹ and in 1500 to 5400 kg NO₃⁻–N day⁻¹. The data suggest a pronounced east–west gradient of groundwater to river diffuse water inputs among the three adjacent basins, reflecting the soil permeability and the width of the river–groundwater interaction zone. Given the large stock of NO₃⁻ in groundwater, management interventions performed at the basin scale and aimed at decreasing N excess will not produce an immediate decrease in river NO₃⁻ pollution.