Human impacts can induce ecosystems to cross tipping points and hence unexpected and sudden changes in ecosystem services that are difficult or impossible to reverse. The world´s oceans suffer from cumulative anthropogenic pressures like overexploitation and climate change and are especially vulnerable to such regime shifts. Yet an outstanding question is whether regime changes in marine ecosystems are irreversible. Here we first review the evidence for regime shifts in the North Sea ecosystem, one of the heaviest impacted and best studied marine ecosystems in the world. We then used catastrophe theory to show that fishing and warming have caused a previously undetected and potentially irreversible regime shift. Our study emphasizes the combined effects of local and global human impacts in driving significant ecosystem shifts and suggests that adaptation is likely the central avenue forward for maintaining services in the face of global climate change.

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The taxonomic histories of the genus Beta and of section Beta within this genus are summarised. The subdivision of the genus agrees largely with (im)possibilities to produce hybrids. Classification within section Beta has been very variable, with examples of overclassification and severe lumping of taxa. The present study includes a morphometric analysis of variation, research on the patterns of allozyme differentiation, and studies of available herbarium specimens. After a description of the taxonomic criteria used, and after the stabilisation of four Linnaean names through typification, the results of the various studies are combined and used to formulate a revision of Beta section Beta. It is proposed to distinguish three species: B. vulgaris, a large and variable species containing both cultivated and wild materials; B. macrocarpa; and B. patula. B. vulgaris is subdivided into three subspecies: subsp. vulgaris, containing all cultivated materials; subsp. maritima, a large and variable group of plant types; and subsp. adanensis. Further subdivision is considered to be of little or no use. The so-called weed beets are classified as subsp. maritima. A key to the species and subspecies of section Beta is presented. Allozyme studies indicate that the development of self-compatibility and autogamy might have been important in the formation of taxa. Results are also discussed in relation to sampling strategies for gene banks.

Nephrops (Nephrops norvegicus) is an economically valuable target species in the North Sea. Although individual Nephrops populations are scattered, the crustacean is managed regionally by the European Union (EU). The spatial competition for fisheries in the North Sea is growing especially due to expanding offshore wind farms (OWF) and newly implemented marine protected areas (MPA). Moreover, the Brexit affects the availability of EU fishing quotas and adds to the overall uncertainty EU fishers face. We compare landings and catches to scientifically advised quantities and perform an overlap analysis of fishing grounds with current and future OWFs and MPAs. Furthermore, we explore the German Nephrops fleet using high-resolution spatial fishing effort and catch data. Our results confirm earlier studies showing that Nephrops stocks have been fished above scientific advice. Present OWFs and MPAs marginally overlap with Nephrops fishing grounds, whereas German fishing grounds are covered up to 45% in future scenarios. Co-use strategies with OWFs could mitigate the loss of fishing opportunities. Decreased cod quotas due to Brexit and worse stock conditions, lowers Germany's capability to swap Nephrops quotas with the UK. We support the call for a new management strategy of individual Nephrops populations and the promotion of selective fishing gears.