• Energy Research
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Shrub encroachment influences several ecosystem services in drylands worldwide. Yet, commonly used strategies to reduce encroachment show a low medium-term success, calling for a better understanding of its causes. Previous works identified multiple drivers responsible for this phenomenon, including anthropogenic and environmental causes. However, the relative effect of climate, topography and edaphic factors on shrub encroachment is not fully understood nor has been properly quantified in Mediterranean Basin drylands. Also, understanding how these drivers lead to changes in plant communities' functional traits associated to shrub encroachment is crucial, considering traits influence ecosystem processes and associated ecosystem services. Here, we studied the understory of a Mediterranean dryland ecosystem composed of savanna-like Holm-oak woodlands, along a regional climatic gradient. We specifically assessed (i) how climatic, topographic and edaphic factors influence understory relative shrub cover (RSC) and (ii) their direct and indirect effects (via RSC) on plant functional traits. We studied the mean and diversity of 12 functional traits related to plant regeneration, establishment, and dispersal, at the community-level. We found that, under similar low-intensity land use, topographic and edaphic factors, namely slope variations and soil C:N ratio, were the most important predictors of shrub encroachment, determining communities' functional characteristics. Climate, namely summer precipitation, had a much lesser influence. Our model explained 52% of the variation in relative shrub cover. Climate had a stronger effect on a set of functional traits weakly involved in shrub encroachment, related to flowering and dispersal strategies. We show that shrub encroachment is largely predicted by topo-edaphic factors in Mediterranean drylands subject to conventional low-intensity land use. Hence, management strategies to reduce encroachment need to take these drivers into account for efficient forecasting and higher cost-effectiveness. Our results suggest that climate change might not greatly impact shrub encroachment in the Mediterranean Basin, but may affect functional structure and reduce functional diversity of plant communities, thus affecting ecosystem functioning.

The Arctic is experiencing rapid warming, and resultant sea ice losses represent a serious threat to ice-associated species in the region. This study explored the distribution and abundance of the 3 Arctic resident whale species: narwhals, bowhead and white whales, in the marginal ice zone and into the sea ice north of the Svalbard Archipelago. Line-transect surveys were conducted using a combination of helicopter-based and ship-based efforts in August 2015. Twenty-six sightings, involving 27 bowhead whales and 58 narwhals, occurred along the helicopter transects, while no whales were recorded along ship transects. No white whales were observed during these surveys. After correcting for surface availability, distance sampling produced abundance estimates of 343 (CV = 0.488) bowhead whales and 837 (CV = 0.501) narwhals within the 52919 km2 study area. Bowhead whales were predominantly seen close to the ice-edge, whereas narwhals were located deeper into the ice. To contextualize these results within the broader Svalbard cetacean community, all whale sightings from the Norwegian Polar Instituteís Svalbard Marine Mammal Sighting Data Base, from the period of the survey, were mapped to compare general distributions. These opportunistic sightings included numerous cetacean species, especially seasonally occurring ones. However, white whales dominated in terms of the numbers of individuals reported. Our results suggest little spatial overlap between seasonally occurring whales and the 3 Arctic resident whales. Bowhead whales and narwhals were tightly associated with sea ice, and white whales were tightly coastal. In contrast, the seasonally occurring species were found over the shelf and along its edges.

Half the population of China live in coastal zones where 70% of large cities are also located. Intensive human activities pose significant environmental and ecological hazards to these cities that are already vulnerable to natural hazards and climate change. The sustainable development of coastal cities is thus both a national and international issue. Rongcheng is a typical coastal city in east China. It is a national marine ranch demonstration area that is subjected to multi-stressors from human activities and climate change. The dominant economic sectors include aquaculture and fisheries, agriculture, shipping and tourism. A multitude of resulting pressures come mainly from intensified human activities, such as intensive aquaculture, overfishing, industrial pollutants, agricultural runoff, land reclamation and port expansion. In addition, Rongcheng is also facing exogenic pressures from extreme climate events such as intensified storms, storm surges, droughts and sea ice. A growing awareness of these problems brought together a trans-disciplinary group from local government, research institutions, local practitioners and coastal representatives to jointly explore and co-design adaptive coastal management options. In this transdisciplinary study, a social-ecological analysis based on a combination of the Systems Approach Framework and the Drivers-Pressures-States-Impacts-Responses framework was used to analyze and formulate an adaptive management plan for the sustainability of Rongcheng. More than 40 stakeholders including government, companies, civil society and institutions participated in the study through questionnaires and on-site meetings. A statistical analysis of the results identified urgent issues impeding the sustainable development of Rongcheng. The issues identified were poorly regulated aquaculture, loss of shoreline, and the decline of seagrass and cultural heritage. The study identified management options and measures, some of which were adopted by the local government in a co-designed management plan. The measures included upgrading of aquaculture industry, habitat conservation and restoration, and the development of cultural tourism. Another outcome was the increased knowledge exchange between stakeholders to inform management, policy, and decision making, as well as raised awareness of vulnerability to natural hazards and climate change. The success of this case study provides a reference for the adaptive management of other coastal cities and their sustainable development in a changing climate.

Metal accumulation by Juncus maritimus and the effect this plant might have on the physico-chemical composition of sediments, from Douro river estuary (NW Portugal), were investigated through one year of plant's life. The contents of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined (by atomic absorption spectrophotometry) in sediments, rhizosediments (those among plant roots and rhizomes) and different tissues of J. maritimus. Two estuarine sites with different characteristics were studied, one a sandy sediment with relatively low organic matter content, the other a muddy site. The role of the plant seemed to be markedly dependent on the sediment composition. At the sandy site, significant variations throughout the year (a decrease from winter to summer and an increase in autumn) either in rhizosediment and sediment or in J. maritimus roots were only observed in Cd and Cu levels. These variations were the same in both compartments, probably caused by tidal water movements and the activity of the plant. At the muddy site, variations throughout the year were observed for all studied elements but Pb. Changes in the Cd and Zn contents of roots were opposite to those in the rhizosediment (uptake of Cd and Zn by J. maritimus roots in summer may have caused a decrease in rhizosediment levels). Fe and Mn showed similar patterns of variation in both roots and rhizosediment (contents significantly increasing in summer). Higher contents of Fe and Mn in roots in summer could be related to changes in mass, higher availability of the elements, or accumulation at the surface of the root in (hydr)oxides forms. For the remaining elements no significant correlations between rhizosediment and roots variations were observed, indicating that their uptake and release by roots were not based on single exchanges with the sediment. J. maritimus showed capacity to accumulate Cu, Zn and particularly Cd, thus appearing to be useful for the phytostabilization of these metals.

AbstractElectrocution on power lines is an important human‐related cause of bird mortality and an important conservation issue worldwide. Besides impacts on bird populations, electrocutions cause power outages, resulting in damage to power line network integrity. However, there is a general lack of knowledge on the risk of bird electrocution, especially in developing countries. Generating information over large scales without resorting to local mortality data can be useful for the development of regional management strategies, particularly in countries where electrocution is poorly documented. Here, we developed a framework to model the risk of bird electrocution as an interaction between the species‐specific exposure to power lines (pole density within a species distribution range) and susceptibility (morphological and behavioral traits associated with electrocution hazards). We applied this framework to Brazil, identifying 283 species that face a risk of electrocution, of which 38 were classified as higher risk, mostly raptors (76%). The Pantanal (a large wetland biome) concentrates the greatest cumulative susceptibility due to the high number of species vulnerable to electrocution (i.e. large species using power lines for perching or nesting), while the Atlantic Forest region has a higher risk for electrocution, due to the spatial overlap between the presence of vulnerable species and high exposure to power lines. Furthermore, our study identified spatial patterns of bird electrocution, highlighting priority areas for electrocution susceptibility and electrocution risk to be further investigated, and where measures to mitigate bird electrocutions should be applied on new and existing power lines. Our framework allows a preliminary assessment aimed at identifying areas of higher risk of electrocution, to highlight species vulnerable to this threat and to improve power line routing. This approach can be replicated to other understudied areas of the world where the same information is available.

AbstractParapatry is a biogeographical term used to refer to organisms whose ranges do not overlap, but are immediately adjacent to each other; they only co‐occur – if at all – in a narrow contact zone. Often there are no environmental barriers in the contact zones, hence competitive interaction is usually advocated as the factor that modulates species distribution ranges. Even though the effects of climate change on species distribution have been widely studied, few studies have explored these effects on the biogeographical relationships between closely related, parapatric, species. We modelled environmental favourability for three parapatric hare species in Europe – Lepus granatensis, L. europaeus and L. timidus – using ecogeographical variables and projected the models into the future according to the IPCC A2 emissions scenario. Favourabilities for present and future scenarios were combined using fuzzy logic with the following aims: (i) to determine the biogeographical relationships between hare species in parapatry, that is L. granatensis/L. europaeus and L. europaeus/L. timidus and (ii) to assess the effects of climate change on each species as well as on their interspecific interactions. In their contact area L. granatensis achieved higher favourability values than L. europaeus, suggesting that if both species have a similar population status, the former species may have some advantages over the latter if competitive relationships are established. Climate change had the most striking effect on the distribution of L. timidus, especially when interspecific interactions with L. europaeus were taken into account, which may compromise the co‐existence of L. timidus. The results of this study are relevant not only for understanding the distribution patterns of the hares studied and the effects of climate change on these patterns, but also for improving the general application of species distribution models to the prediction of the effects of climate change on biodiversity.

Global climate change accentuates the seasonal and interannual irregularity of temperature and precipitation of the Mediterranean climate. The consequences of this variability on wheat production are felt on its development cycle and productivity, making the production chain of this crop vulnerable to the occurrence of years with abnormal distributions of precipitation and with extreme temperatures. Adaptation strategies like irrigation or fertilization can help to cope with the negative impacts of climate uncertainty. This study evaluated the effects of water regime and nitrogen (N) fertilization techniques on wheat production in southern Portugal based on the results of three trials conducted in two agricultural years (2016/2017 and 2017/2018) with contrasting climate conditions. Phenology and yield were evaluated by comparing water regimes (R1, full irrigation; R2, supplemental irrigation at four stages: start of stem extension, booting, anthesis, grain filling; R0, rainfed (in 2017/2018)) and N fertilization splitting/timing and type (conventional and enhanced efficiency fertilizers (EEFs): controlled-release N, stabilized with nitrification inhibitor, and stabilized with urease inhibitor). Significant effects of water regime on grain yield were obtained in 2016/2017, a year with extreme aridity and high water requirements felt from the tillering stage, in the trial with conventional fertilizers. In 2017/2018, when a beneficial seasonal rainfall distribution occurred, water regime did not influence grain yield, pointing to the feasibility of supplementary irrigation to maximize water productivity. Nitrogen fertilization influenced yield and its components, with the highest values of grain yield being obtained with conventional fertilizer. Regardless of the possible effects on grain quality, the use of EEF did not prove to have an indisputable effect on wheat yield in the conditions under which the trials were conducted. Comparison of the results in the two years accentuates the need to continue the evaluation of the influence of agronomic management in wheat production in the context of adaptation to the climatic uncertainty in Mediterranean regions.