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Experimental climate change weakens the insurance effect of biodiversity
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Ecosystems are simultaneously affected by biodiversity loss and climate change, but we know little about how these factors interact. We predicted that climate warming and CO2-enrichment should strengthen trophic cascades by reducing the relative efficiency of predation-resistant herbivores, if herbivore consumption rate trades off with predation resistance. This weakens the insurance effect of herbivore diversity. We tested this prediction using experimental ocean warming and acidification in seagrass mesocosms. Metaanalyses of published experiments first indicated that consumption rate trades off with predation resistance. The experiment then showed that three common herbivores together controlled macroalgae and facilitated seagrass dominance, regardless of climate change. When the predation-vulnerable herbivore was excluded in normal conditions, the two resistant herbivores maintained top-down control. Under warming, however, increased algal growth outstripped control by herbivores and the system became algal-dominated. Consequently, climate change can reduce the relative efficiency of resistant herbivores and weaken the insurance effect of biodiversity.
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Exponential Decline of Deep-Sea Ecosystem Functioning Linked to Benthic Biodiversity Loss
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Here, we present a global-scale study based on 116 deep-sea sites that relates benthic biodiversity to several independent indicators of ecosystem functioning and efficiency. We show that deep-sea ecosystem functioning is exponentially related to deep-sea biodiversity and that ecosystem efficiency is also exponentially linked to functional biodiversity. These results suggest that a higher biodiversity supports higher rates of ecosystem processes and an increased efficiency with which these processes are performed. The exponential relationships presented here, being consistent across a wide range of deep-sea ecosystems, suggest that mutually positive functional interactions (ecological facilitation) can be common in the largest biome of our biosphere.Conclusions: Our results suggest that a biodiversity loss in deep-sea ecosystems might be associated with exponential reductions of their functions. Because the deep sea plays a key role in ecological and biogeochemical processes at a global scale, this study provides scientific evidence that the conservation of deep-sea biodiversity is a priority for a sustainable functioning of the worlds’ oceans.
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Faustian bargains? Restoration realities in the context of biodiversity offset policies
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The science and practice of ecological restoration are increasingly being called upon to compensate for the loss of biodiversity values caused by development projects. Biodiversity offsetting—compensating for losses of biodiversity at an impact site by generating ecologically equivalent gains elsewhere—therefore places substantial faith in the ability of restoration to recover lost biodiversity. Furthermore, the increase in offset-led restoration multiplies the consequences of failure to restore, since the promise of effective restoration may increase the chance that damage to biodiversity is permitted. But what evidence exists that restoration science and practice can reliably, or even feasibly, achieve the goal of ‘no net loss’ of biodiversity, and under what circumstances are successes and failures more likely? Using recent reviews of the restoration ecology literature, we examine the effectiveness of restoration as an approach for offsetting biodiversity loss, and conclude that many of the expectations set by current offset policy for ecological restoration remain unsupported by evidence. We introduce a conceptual model that illustrates three factors that limit the technical success of offsets: time lags, uncertainty and measurability of the value being offset. These factors can be managed to some extent through sound offset policy design that incorporates active adaptive management, time discounting, explicit accounting for uncertainty, and biodiversity banking. Nevertheless, the domain within which restoration can deliver ‘no net loss’ offsets remains small. A narrowing of the gap between the expectations set by offset policies and the practice of offsetting is urgently required and we urge the development of stronger links between restoration ecologists and those who make policies that are reliant upon restoration science. Keywords:Compensatory habitat - Conservation policy - Mitigation banking - Environmental risk - No net loss - Restoration success
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Climate change and tropical biodiversity: a new focus
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Considerable efforts are focused on the consequences of climate change for tropical rainforests. However, potentially the greatest threats to tropical biodiversity (synergistic interactions between climatic changes and human land use) remain understudied. Key concerns are that aridification could increase the accessibility of previously non-arable or remote lands, elevate fire impacts and exacerbate ecological effects of habitat disturbance. The growing climatic change literature often fails to appreciate that, in coming decades, climate–land use interac- tions might be at least as important as abiotic changes per se for the fate of tropical biodiversity. In this review, we argue that protected area expansion along key ecological gradients, regulation of human-lit fires, strategic forest–carbon financing and re-evaluations of agricultural and biofuel subsidies could ameliorate some of these synergistic threats.
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Schuette, Scott
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