Emergent vulnerability to climate-driven disturbances in European forests

Forest disturbance regimes are expected to intensify as Earth’s climate changes. Quantifying forest vulnerability to disturbances and understanding the underlying mechanisms is crucial to develop mitigation and adaptation strategies. However, observational evidence is largely missing at regional to continental scales. Here, we quantify the vulnerability of European forests to fires, windthrows and insect outbreaks during the period 1979–2018 by integrating machine learning with disturbance data and satellite products. We show that about 33.4 billion tonnes of forest biomass could be seriously affected by these disturbances, with higher relative losses when exposed to windthrows (40%) and fires (34%) compared to insect outbreaks (26%). The spatial pattern in vulnerability is strongly controlled by the interplay between forest characteristics and background climate. Hotspot regions for vulnerability are located at the borders of the climate envelope, in both southern and northern Europe. There is a clear trend in overall forest vulnerability that is driven by a warming-induced reduction in plant defence mechanisms to insect outbreaks, especially at high latitudes.

Local was best: sourcing tree seed for future climates

As climate change accelerates, foresters are looking to ever warmer climates to secure sources of climatically adapted tree seed with which to establish healthy and productive plantations. However, as seed procurement areas approach jurisdictional boundaries (states, provinces, nations), across which seed and seed transfer systems are not typically shared, innovative approaches are required to identify those plantation areas for which suitable domestic provenances will be lacking, and areas in neighbouring jurisdictions with matching warmer, future climates that could fill domestic seed supply gaps. We describe a straightforward, climate envelope approach to locate these areas, using British Columbia (BC), Canada, and the Pacific Northwest (PNW) USA to illustrate the analysis. We find that 21% of BC’s ecosystems (seed zones) will be at moderate or high risk of lacking adapted domestic provenances for plantation establishment by 2040. Importantly, however, we find large areas in the PNW that should be able to fill most of BC’s domestic seed supply gaps. Spatial analyses of this type will inform seed suppliers, managers and policymakers where alternative seed procurement arrangements are needed and underscore the operational and policy barriers to acquiring seed from warmer jurisdictions. More broadly they also highlight the need for inter-jurisdictional cooperation in matters pertaining to resource management.

Rise of the rare biosphere

Ocean ecosystems are changing, and the climate envelope paradigm predicts a steady shift, approximately poleward, of species ranges. The Gulf of Maine presents a test case of this paradigm, as temperatures have warmed extremely rapidly. Some species have shifted northeastward, matching predictions. Others—namely harmful algal species like Pseudo-nitzschia australis and Karenia mikimotoi—do not appear to have followed climate trajectories, arriving as surprises in the Gulf of Maine. Rare-biosphere dynamics offer one possible ecological lens for understanding and predicting this type of surprise. Rare species in the plankton, possibly more so than southerly ones, may provide management challenges in the future. Improved monitoring and broader coordination of monitoring of the rare biosphere could help develop early warning systems for harmful and toxic algae. A better theoretical understanding of rare biosphere dynamics is also needed. A challenge for the next cohort of ecosystem projections is to predict the newly emerging harmful species of the type that catch us by surprise.

Roles of hostplant availability and quality for the distribution and climate change response of a dietary specialist herbivore

Species distributions are recognized to be driven by abiotic factors, but the importance of biotic interactions that provide critical resources is less well understood, especially with respect to variation in critical resource quality. Disentangling the relative importance of these factors – abiotic environment, presence of critical resources and their quality-may be critical to predicting species response to climate change. We used species distribution models (SDMs) to address these questions for the western monarch butterfly (Danaus plexippus), a species that obligately feeds upon plants in the genus Asclepias, and for which hostplant quality in this region varies among species by an order of magnitude. We modeled the distribution of 24 Asclepias species to develop and compare three monarch distribution models with increasing levels of ecological complexity: (i) a null model using only environmental factors (a climate envelope model), (ii) a model using environmental factors and Asclepias spp. distribution, (iii) and a model using environmental factors and Asclepias spp. distribution weighted by hostplant quality assessed through a greenhouse bioassays of larval performance. Asclepias models predicted that half of the Asclepias spp. will both expand their ranges and shift their distribution towards higher latitudes while half will contract within the study region. Our performance analysis of monarch models revealed that the climate envelope model was the poorest performing. Adding hostplant distribution produced the best performing model, while accounting for hostplant quality did not improved model performance. The climate envelope model estimated more restrictive contemporary and future monarch ranges compared to both hostplants models. Although all three models predicted future monarch range expansions, the projected future distributions varied among models. The climate envelope model predicted range expansions along the Pacific coast and contractions inland while hostplants models predicted range expansions in both of these regions and, as a result, estimated 14 and19% increases in distribution relative to the climate envelope model, respectively. These results suggest that information on biotic interactions that provide critical resources is needed to predict future species distributions, but that variation in the quality of those critical resources may be of secondary importance.

Climate adaptation of listed buildings: an interaction between design, regulations and energy efficiency

Energy retrofitting of listed buildings requires a rethink as it is economically and technically complicated to retrofit. The Technische Universität Berlin has 47 buildings with a total net floor area above 500.000 m2 in its central campus, and 60% of them are listed. In Germany, optimizing the energy efficiency of such buildings has not to fulfill the requirements of the energy efficiency regulations. On the one hand, this situation is not corresponding to the national objectives regarding climate adaptation. On the other hand, they have to be retrofitted because of issues like poor energy efficiency and user comfort, and not privileged with special regulations. However, instead of changing the regulations, it is possible to solve the problem by changing the way of thinking. In this regard, rather than retrofitting such buildings directly, a new approach has been developed where the surrounding climatic conditions are optimized. Hereby, a simulation-based concept has been developed with an external transparent envelope. This “climate envelope” creates an intermediate space between outdoor and indoor, where through controlled air movement and passive solar gains, the balance in seasonal energy efficiency can be kept economically without any implementation on the buildings according to the building thermal and CFD simulations. This overall approach activates the yet not exploited capacity of energy savings by listed buildings using intelligent design and saves up to 30% more of primary energy.

Increased Suitability of Poleward Climate for a Tropical Butterfly (Euripus nyctelius) (Lepidoptera: Nymphalidae) Accompanies its Successful Range Expansion

Distribution shifts are a common response in butterflies to a warming climate. Hong Kong has documented records of several new butterfly species in recent decades, comprising a high proportion of tropical species, some of which have successfully established. In this study, we examined possible drivers for the establishment of Euripus nyctelius Doubleday (Lepidoptera: Nymphalidae) by studying its thermal physiology and modeling current climate and future distributions projected by species distribution modeling (SDM). We found that E. nyctelius adults have a significantly higher critical thermal minimum than its local temperate relative, Hestina assimilis Linnaeus (Lepidoptera: Nymphalidae), suggesting a possible physiological constraint that may have been lifted with recent warming. SDMs provide further evidence that a shifting climate envelope may have improved the climate suitability for E. nyctelius in Hong Kong and South China—however, we cannot rule out the role of other drivers potentially influencing or driving range expansion, habitat change in particular. Conclusive attribution of warming-driven impacts for most tropical species is difficult or not possible due to a lack of historical or long-term data. Tropical insects will require a significant advancement in efforts to monitor species and populations across countries if we are to conclusively document climate-driven shifts in species distributions and manage the consequences of such species redistribution. Nevertheless, the warming climate and subsequent increased climatic suitability for tropical species in poleward areas, as shown here, is likely to result in future species redistribution events in subtropical and temperate ecosystems.

Declines of the globally threatened Rudd’s Lark Heteromirafra ruddi in one of its last remaining strongholds

SummaryRudd’s Lark Heteromirafra ruddi is a globally threatened species endemic to eastern South Africa’s highland grasslands, where climate envelope modelling has predicted a dramatic reduction in its already small and fragmented distribution. Here we assess recent changes in one of its last strongholds, the Wakkerstroom grasslands. We assessed changes in Rudd’s Lark population and habitat condition over 12 years, within a core section of an area intensively surveyed in 2002–2004. Our 2016 survey found lower absolute numbers of Rudd’s Larks (five transects with Rudd’s Lark present compared to nine in 2002; nine individuals compared to 32), as well as a lower probability of encounter. Transects with shorter grass and higher altitude had a higher probability of Rudd’s Larks occurrence, consistent with findings in 2002. Point locations where Rudd’s Larks were recorded had shorter grass, higher forb cover and more bare ground cover, and tended to be at higher altitudes than random locations in the surrounding grassland. Remotely-sensed fire data showed that late-season fires, which pose a threat to Rudd’s Lark nestling survival, are generally uncommon. Field observations indicated that seven transects (of which two previously contained Rudd’s Lark) that had previously been grassland had been converted to intensive crop production. While Rudd’s Lark may be affected by direct loss of grassland habitat through conversion to crops, the species has also declined within remaining grassland habitat. The drivers of decline remain unclear but this recent observed local decline of Rudd’s Lark in the immediate Wakkerstroom area supports the species’ recent IUCN uplisting to globally ‘Endangered’, given that its previous downlisting was based on habitat requirements and breeding success from this area.