No abstract

Over the past 3.5 million years, there have been several intervals when climate conditions were warmer than during the preindustrial Holocene. Although past intervals of warming were forced differently than future anthropogenic change, such periods can provide insights into potential future climate impacts and ecosystem feedbacks, especially over centennial-to-millennial timescales that are often not covered by climate model simulations. Our observation-based synthesis of the understanding of past intervals with temperatures within the range of projected future warming suggests that there is a low risk of runaway greenhouse gas feedbacks for global warming of no more than 2 °C. However, substantial regional environmental impacts can occur. A global average warming of 1-2 °C with strong polar amplification has, in the past, been accompanied by significant shifts in climate zones and the spatial distribution of land and ocean ecosystems. Sustained warming at this level has also led to substantial reductions of the Greenland and Antarctic ice sheets, with sea-level increases of at least several metres on millennial timescales. Comparison of palaeo observations with climate model results suggests that, due to the lack of certain feedback processes, model-based climate projections may underestimate long-term warming in response to future radiative forcing by as much as a factor of two, and thus may also underestimate centennial-to-millennial-scale sea-level rise.

In disaster risk management (DRM), an emerging shift has been noted from broad-scale, top-down assessments toward more participatory, community-based, bottom-up approaches. Arguably, nonscientist local stakeholders have always played an important role in knowledge risk management and resilience building within a hydrological context, such as flood response and drought alleviation. However, rapidly developing information and communication technologies such as the Internet, smartphones, and social media have already demonstrated their sizeable potential to make knowledge creation more multidirectional, decentralized, diverse, and inclusive. Combined with technologies for robust and low-cost sensor networks, a ‘citizen science’ approach has recently emerged as a promising direction in the provision of extensive, real-time information for risk management. Such projects work best when there is community buy-in, when their purpose(s) are clearly defined at the outset, and when the motivations and skillsets of all participants and stakeholders are well understood. They have great potential to enhance knowledge creation, not only for data collection, but also for analysis or interpretation. In addition, they can serve as a means of educating and empowering communities and stakeholders that are bypassed by more traditional knowledge generation processes. Here, we review the state-of-the-art of citizen science within the context of hydrological risk reduction and resilience building. Particularly when embedded within a polycentric approach toward risk governance, we argue that citizen science could complement more traditional knowledge generation practices, and also enhance innovation, adaptation, multidirectional information provision, risk management, and local resilience building

According to the competitive exclusion principle, species with low competitive abilities should be excluded by more efficient competitors, and yet they generally remain as rare species. Here, we describe the positive and negative spatial association networks of 326 disparate assemblages, showing a general organization pattern that simultaneously supports the primacy of competition and the persistence of rare species. Abundant species monopolize negative associations in about 90% of the assemblages. Contrarily, rare species are mostly involved in positive associations, forming small network modules. Simulations suggest that positive interactions among rare species and microhabitat preferences are the most likely mechanisms underpinning this pattern and rare species persistence. The

SignificanceClimate warming is impacting the cryosphere in high mountain ranges, thereby enhancing the probability for more and larger mass-wasting processes to occur. This tree-ring–based snow avalanche reconstruction in the Indian Himalayas shows an increase in avalanche occurrence and runout distances in recent decades. Statistical modeling suggests that this increase in avalanche activity is linked to contemporaneous climate warming. These findings contradict the intuitive assumption that warming results in less snow, and thus fewer snow avalanches in the region, with major implications for disaster risk management and risk mitigation in a region with steadily increasing human occupation.

Climate, stand structure and local site conditions are potentially important determinants of forest dynamics. Understanding the relative contributions of competition and climate to tree growth is critical to project likely stand development under different climate change scenarios. Further, current competition levels and stand structure may reflect legacies of past forest management. Here, we analyze the effects of climate, site conditions and competition on radial growth in three Scots pine plots located along an altitudinal gradient. These stands are subjected to Mediterranean climate with continental influence, i.e., growth is limited by low winter temperatures and dry summer conditions. Current stand structure and retrospective analyses of radial growth (basal area increment, BAI) were used to model changes in tree growth as a function of competition (CI) and climate at an annual resolution. Negative exponential functions characterized the CI-BAI associations, whereas linear mixed-effects models were used to model BAI and to quantify the growth response to climate of trees under low and high competition. Competition effects on growth were steady over time regardless of the elevation and tree age. High competition levels negatively affected growth, with a proportionally stronger influence in suppressed trees than in dominant trees. Sensitivity of tree growth to climate increased with decreasing competition. Altitudinal gradientrelated growth responses to climate were found only for temperature variables. Specifically, growth at high elevations was mainly limited by low winter temperatures, whilst warm spring enhanced growth at middle elevations and late summer temperatures did it at low elevations. Since growth and its sensitivity to climate is more pronounced in low competition trees, we argue that the past management of the forest overrides site conditions and climate effects through the legacies on stand structure and competition. Pro-active forest management practices should be adopted to reduce the vulnerability of previously managed Scots pine forests currently threatened by the predicted warmer and drier conditions.

Please cite this article as: Bodoque, J.M., Amerigo, M., Díez-Herrero, A., García, J.A., Cortés, B., BallesterosCánovas, J.A., Olcina, J., Improvement of resilience of urban areas by integrating social perception in flash-flood risk management, Journal of Hydrology (2016), doi: http://dx.doi.org/10. 1016/j.jhydrol.2016.02.005 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractIn urban areas prone to flash floods, characterization of social resilience is critical to guarantee the success of emergency management plans. In this study, we present the methodological approach that led to the submission and subsequent approval of the Civil Protection Plan of Navaluenga (Central Spain), in which the first phase was to analyse flood hazard by combining the Hydrological Modelling System (HEC-HMS) and the Iber 2D hydrodynamic model. We then analysed social vulnerability and designed measures to put into practice within the framework of the Civil Protection Plan. At a later phase, we assessed citizens' flash-flood risk perception and level of awareness regarding some key variables of the Civil Protection Plan. To this end, 254 adults representing roughly 12% of the population census were interviewed. Responses were analysed descriptively, comparing awareness regarding preparedness and response actions with the corresponding information 2 and behaviours previously defined in the Civil Protection Plan. In addition, we carried out a latent class cluster analysis aimed at identifying the different groups present among the interviewees. Our results showed that risk perception is low. Specifically, 60.8% of the interviewees showed low risk perception and low awareness (cluster 1);24.4% had high risk perception and low awareness (cluster 2), while the remaining 14.8% presented high long-term risk perception and high awareness (cluster 3).These findings suggest the need for integrating these key variables of social risk perception and local tailored information in emergency management plans, especially in urban areas prone to flash-floods where response times are limited.

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