Understanding human vulnerability to climate change: A global perspective on index validation for adaptation planning

Climate change is a severe global threat. Research on climate change and vulnerability to natural hazards has made significant progress over the last decades. Most of the research has been devoted to improving the quality of climate information and hazard data, including exposure to specific phenomena, such as flooding or sea-level rise. Less attention has been given to the assessment of vulnerability and embedded social, economic and historical conditions that foster vulnerability of societies. A number of global vulnerability assessments based on indicators have been developed over the past years. Yet an essential question remains how to validate those assessments at the global scale. This paper examines different options to validate global vulnerability assessments in terms of their internal and external validity, focusing on two global vulnerability indicator systems used in the WorldRiskIndex and the INFORM index. The paper reviews these global index systems as best practices and at the same time presents new analysis and global results that show linkages between the level of vulnerability and disaster outcomes. Both the review and new analysis support each other and help to communicate the validity and the uncertainty of vulnerability assessments. Next to statistical validation methods, we discuss the importance of the appropriate link between indicators, data and the indicandum. We found that mortality per hazard event from floods, drought and storms is 15 times higher for countries ranked as highly vulnerable compared to those classified as low vulnerable. These findings highlight the different starting points of countries in their move towards climate resilient development. Priority should be given not just to those regions that are likely to face more severe climate hazards in the future but also to those confronted with high vulnerability already

Mitochondrial Acclimation Capacities to Ocean Warming and Acidification Are Limited in the Antarctic Nototheniid Fish, Notothenia rossii and Lepidonotothen squamifrons

Antarctic notothenioid fish are characterized by their evolutionary adaptation to the cold, thermostable Southern Ocean, which is associated with unique physiological adaptations to withstand the cold and reduce energetic requirements but also entails limited compensation capacities to environmental change. This study compares the capacities of mitochondrial acclimation to ocean warming and acidification between the Antarctic nototheniid Notothenia rossii and the sub-Antarctic Lepidonotothen squamifrons, which share a similar ecology, but different habitat temperatures. After acclimation of L. squamifrons to 9°C and N. rossii to 7°C (normocapnic/hypercapnic, 0.2 kPa CO2/2000 ppm CO2) for 4-6 weeks, we compared the capacities of their mitochondrial respiratory complexes I (CI) and II (CII), their P/O ratios (phosphorylation efficiency), proton leak capacities and mitochondrial membrane fatty acid compositions. Our results reveal reduced CII respiration rates in warm-acclimated L. squamifrons and cold hypercapnia-acclimated N. rossii. Generally, L. squamifrons displayed a greater ability to increase CI contribution during acute warming and after warm-acclimation than N. rossii. Membrane unsaturation was not altered by warm or hypercapnia-acclimation in both species, but membrane fatty acids of warm-acclimated L. squamifrons were less saturated than in warm normocapnia-/hypercapnia-acclimated N. rossii. Proton leak capacities were not affected by warm or hypercapnia-acclimation of N. rossii. We conclude that an acclimatory response of mitochondrial capacities may include higher thermal plasticity of CI supported by enhanced utilization of anaplerotic substrates (via oxidative decarboxylation reactions) feeding into the citrate cycle. L. squamifrons possesses higher relative CI plasticities than N. rossii, which may facilitate the usage of energy efficient NADH-related substrates under conditions of elevated energy demand, possibly induced by ocean warming and acidification. The observed adjustments of electron transport system complexes with a higher flux through CI under warming and acidification suggest a metabolic acclimation potential of the sub-Antarctic L. squamifrons, but only limited acclimation capacities for N. rossii

Assessing and responding to complex climate change risks

Real-world experience underscores the complexity of interactions among the multiple drivers of climate change risks and of interactions among multiple risks. However, a synthesis of recent climate change assessments and literature shows a holistic framework for assessing such complex climate change risks has not yet been achieved. Clarity is needed regarding perspective, we present three categories of increasingly complex risk that focus on interactions among multiple drivers of risk, as well as multiple risks. A significant innovation is recognition that risk can arise from both potential impacts due to climate change and from responses to climate change. This approach encourages thinking that traverses sectoral and regional boundaries, and that links physical and socio-economic drivers of risk. Advancing assessment of climate change risk in this way is essential for informed decision-making to reduce negative climate change impacts

Thermal acclimation to 10 or 4°C imparts minimal benefit on swimming performance in Atlantic cod (Gadus morhua L.)

Thermal acclimation is frequently cited as a means by which ectothermic animals improve their Darwinian fitness, i.e. the beneficial acclimation hypothesis. As the critical swimming speed (U (crit)) test is often used as a proxy measure of fitness, we acclimated Atlantic cod (Gadus morhua) to 4 and 10 degrees C and then assessed their U (crit) swimming performance at their respective acclimation temperatures and during acute temperature reversal. Because phenotypic differences exist between different populations of cod, we undertook these experiments in two different populations, North Sea cod and North East Arctic cod. Acclimation to 4 or 10 degrees C had a minimal effect on swimming performance or U (crit), however test temperature did, with all groups having a 10-17% higher U (crit) at 10 degrees C. The swimming efficiency was significantly lower in all groups at 4 degrees C arguably due to the compression of the muscle fibre recruitment order. This also led to a reduction in the duration of "kick and glide" swimming at 4 degrees C. No significant differences were seen between the two populations in any of the measured parameters, due possibly to the extended acclimation period. Our data indicate that acclimation imparts little benefit on U (crit) swimming test in Atlantic cod. Further efforts need to identify the functional consequences of the long-term thermal acclimation process

Ultrastructure of pedal muscle as a function of temperature in nacellid limpets

Temperature and mitochondrial plasticity are well studied in fishes, but little is known about this relationship in invertebrates. The effects of habitat temperature on mitochondrial ultrastructure were examined in three con-familial limpets from the Antarctic (Nacella concinna), New Zealand (Cellana ornata), and Singapore (Cellana radiata). The effects of seasonal changes in temperature were also examined in winter and summer C. ornata. Stereological methods showed that limpet pedal myocytes were 1–2 orders of magnitude smaller in diameter (≈3.5 μm) than in vertebrates, and that the diameter did not vary as a function of temperature. Mitochondrial volume density (Vv(mt,f)) was approximately 2–4 times higher in N. concinna (0.024) than in the other species (0.01 and 0.006), which were not significantly different from each other. Mitochondrial cristae surface density (Sv(im,mt)) was significantly lower in summer C. ornata (24.1 ± 0.50 μm2 μm−3) than both winter C. ornata (32.3 ± 0.95 μm2 μm−3) and N. concinna (34.3 ± 4.43 μm2 μm−3). The surface area of mitochondrial cristae per unit fibre volume was significantly higher in N. concinna, due largely to the greater mitochondrial volume density. These results and previous studies indicate that mitochondrial proliferation in the cold is a common, but not universal response by different species from different thermal habitats. Seasonal temperature decreases on the other hand, leading preferentially to an increase in cristae surface density. Stereological measures also showed that energetic reserves, i.e. lipid droplets and glycogen in the pedal muscle changed greatly with season and species. This was most likely related to gametogenesis and spawning