Indices of connectivity are critical means for moving from qualitative to (semi-)quantitative evaluations of material (e.g., water, sediment and nutrients) transfer across the building blocks of a terrestrial system. In geomorphology, compared to closely related disciplines like ecology and hydrology, the development of indices has only recently started and as such presents opportunities and challenges that merit attention. In this paper, we review existing indices of sediment connectivity and suggest potential avenues of development for meeting current basic and applied research needs. Specifically, we focus on terrestrial geomorphic systems dominated by processes that are driven by hydro-meteorological forcing, neglecting seismically triggered events, karstic systems and environments controlled by eolian processes. We begin by setting a conceptual framework that combines external forcings (drivers) and system (intrinsic) structural and functional properties relevant to sediment connectivity. This framework guides our review of response variables suitable for sediment connectivity indices. In particular, we consider three sample applications concerned with sediment connectivity in: (i) soil studies at the plot scale, (ii) bedload transport at the reach scale, and (iii) sediment budgets at the catchment scale. In relation to the set of response variables identified, we consider data availability and issues of data acquisition for use in indices of sediment connectivity. We classify currently available indices in raster based, object or network based, and indices based on effective catchment area. Virtually all existing indices address the degree of static, structural connectivity only, with limited attention for process-based, functional connectivity counterparts.

Soil erosion is the primary process driving land degradation. Using multiple scales of management to minimize soil erosion is crucial to achieve land degradation neutrality targets within the Sustainable Development Goals agenda. Land management (LM) influences both onsite and off-site erosion on the event-scale and over the long-term. However, each LM differs in effectiveness depending on the temporal scale considered. In order to understand how LM effects internal and external catchment dynamics, we apply LandSoil, a physically based landscape evolution model, to evaluate 7 LM scenarios over long-(30 years) and short-terms (event scale). LM scenarios included changes in land use and/or landscape structure. Under current LM, mean surface soil erosion was ~ 0.69 ± 39•10 -3 m over 30 years. In contrast, a single extreme event (435 mm/24h) in January resulted in ~ 0.62 ± 3•10 -3 m loss and ~ 0.04 ± 2•10 -3 m if it occurred in October. Heterogeneous patterns of erosion and deposition developed after 30 years, whereas extreme events dominantly showed soil loss and high catchment connectivity. Effectiveness of LM in erosion mitigation and sediment trapping differed according to temporal and spatial scales for each scenario. We concluded that multiple temporal and spatial scales must be incorporated in order to adaptively manage land degradation and meet neutrality targets.

Soil resources are important for the socioeconomic development of the Mediterranean area. Their durability may be threatened because of intense erosion processes that result in severe degradation in the field (on‐site effects) and downstream degradation (off‐site effects). Based on the literature and results obtained during several research projects, this paper presents the main lessons and challenges dealing with Mediterranean soil resources under global change. After a review of the main drivers of Mediterranean soil erosion and the main impacts of water erosion processes, the paper highlights that the nature and intensity of active erosion processes are as diverse as the mosaic of the Mediterranean landscape. It then discusses the expected evolution of Mediterranean soil resources under global change and illustrates the prevalent influences of land use (partly depending on climatic constraints) on the evolution of erosion risk and soil vulnerability. Finally, it details some main challenges for the future of Mediterranean soil resources dealing with a better knowledge of factors and processes involved in soil erosion, a better evaluation of soil vulnerability through a combined quantitative and qualitative soil erosion approach, and the need for a site‐specific conservation strategy for Mediterranean soil resources. Copyright © 2017 John Wiley & Sons, Ltd.

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Increased soil erosion, pressure on agricultural land, and climate change highlight the need for new management methods to mitigate soil loss. Management strategies should utilize comparable data sets of long‐term soil erosion monitoring across multiple environments. Adaptive soil erosion management in regions with intense precipitation requires an understanding of inter‐annual variability in sediment yield (SY) at regional scales. Here, a novel approach is proposed for analysing regional SY. We aimed to (i) investigate factors controlling inter‐ and intra‐annual SY, (ii) combine seasonality and time compression analyses to explore SY variability and (iii) discuss management implications for different Mediterranean environments. Continuous SY measurements totalling 104 years for eight small catchments were used to describe SY variability, which ranged from 0 to 271 t/ha/year and 0 to 116 t/ha/month. Maximum SY occurs in spring to summer for catchments with oceanic climates, while semi‐arid or dry summer climates experience SY minimums. We identified three time compression patterns at each time scale. Time compression was most intense for catchments with minimum SY in spring to summer. Low time compression was linked to very high soil loss, low run‐off and sediment production thresholds, and high connectivity. Reforestation, grassland and terracing changed SY magnitudes and time compression, but failed to reduce SY for large storm events. Periods with a high probability of high SY were identified using a combination of intra‐annual SY variability, seasonality analysis, and time compression analysis. Focusing management practices on monthly flow events, which account for the majority of SY, will optimise returns in Mediterranean catchments.

Using concepts of connectivity in challenges regarding land and water management (flooding, erosion, nutrient leaching, landslides) can only be fully harnessed if knowledge is communicated well between scientists and stakeholders. Proper communication requires prior understanding of end‐users' perception of connectivity as a useful framework. Therefore, we analysed (a) perceptions of ‘connectivity’ for stakeholders involved in water and land management across Europe, (b) potential for stakeholders to apply connectivity‐related measures in their management decisions, (c) stakeholders' biggest challenges in water and land management, and (d) stakeholders' expectations for future connectivity research agendas. We studied 85 questionnaires from 19 countries using a grounded theory approach. One third of stakeholders understood connectivity in its scientific context, whereas 39% perceived connectivity indirectly through their personal experiences (e.g., water and sediment fluxes and erosion). Half of stakeholders' perceived links and challenges were related to availability of data and methods, communication, and institutions or policy, whereas others believed they were related to water quality and quantity, soil erosion and quality, and climate change. Half of the stakeholders considered connectivity management important, and one third showed high interest in managing connectivity. Adopting connectivity into management is hindered by institutional‐ and policy‐based management limitations, insufficient data and methods, and ineffective knowledge transfer. Explicitly considering heterogeneity of stakeholder perceptions is required for projects regarding management of connectivity at European, national, and local scales.

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