Panel-based assessment of ecosystem condition as a platform for adaptive and knowledge driven management.

Ecosystems are subjected to increasing exposure to multiple anthropogenic drivers. This has led to the development of national and international accounting systems describing the condition of ecosystems, often based on few, highly aggregated indicators. Such accounting systems would benefit from a stronger theoretical and empirical underpinning of ecosystem dynamics. Operational tools for ecosystem management require understanding of natural ecosystem dynamics, consideration of uncertainty at all levels, means for quantifying driver-response relationships behind observed and anticipated future trajectories of change, and an efficient and transparent synthesis to inform knowledge-driven decision processes. There is hence a gap between highly aggregated indicator-based accounting tools and the need for explicit understanding and assessment of the links between multiple drivers and ecosystem condition as a foundation for informed and adaptive ecosystem management. We describe here an approach termed PAEC (Panel-based Assessment of Ecosystem Condition) for combining quantitative and qualitative elements of evidence and uncertainties into an integrated assessment of ecosystem condition at spatial scales relevant to management and monitoring. The PAEC protocol is founded on explicit predictions, termed phenomena, of how components of ecosystem structure and functions are changing as a result of acting drivers. The protocol tests these predictions with observations and combines these tests to assess the change in the condition of the ecosystem as a whole. PAEC includes explicit, quantitative or qualitative, assessments of uncertainty at different levels and integrates these in the final assessment. As proofs-of-concept we summarize the application of the PAEC protocol to a marine and a terrestrial ecosystem in Norway.

Comparative molecular analyses of Eimeria Schneider (Apicomplexa: Eimeriidae) species from rock ptarmigan in Iceland, Svalbard-Norway, and Japan.

The rock ptarmigan (Lagopus muta) has a Holarctic breeding distribution and is found in arctic and sub-arctic regions. Isolated populations and glacial relicts occur in alpine areas south of the main range, like the Pyrenees in Europe, the Pamir mountains in Central Asia, and the Japanese Alps. In recent decades considerable effort has been made to clarify parasite infections in the rock ptarmigan. Seven Eimeria spp. have been reported parasitizing rock ptarmigan. Two of those species, E. uekii and E. raichoi parasitizing rock ptarmigan (L. m. japonica) in Japan, have been identified genetically. Here we compare partial sequences of nuclear (18S rRNA) and mitochondrial (COI) genes and we detail the morphology of sporulated oocysts of E. uekii and E. raichoi from Japan, E. muta and E. rjupa, from the rock ptarmigan (L. m. islandorum) in Iceland, and two undescribed eimerian morphotypes, Eimeria sp. A, and Eimeria sp. B, from rock ptarmigan (L. m. hyperborea) in Norway (Svalbard in the Norwegian Archipelago). Two morphotypes, ellipsoidal and spheroidal, are recognized for each of the three host subspecies. Our phylogenetic analysis suggests that the ellipsoidal oocyst types, E. uekii, E. muta, and Eimeria sp. A (Svalbard-Norway) are identical and infects rock ptarmigan in Japan, Iceland, and Svalbard-Norway, respectively. Eimeria uekii was first described in Japan in 1981 so that E. muta, described in Iceland in 2007, and Eimeria sp. A in Svalbard-Norway are junior synonyms of E. uekii. Also, phylogenetic analysis shows that the spheroidal oocyst types, E. rjupa and Eimeria sp. B (Svalbard-Norway), are identical, indicating that rock ptarmigan in Iceland and Svalbard-Norway are infected by the same Eimeria species and differ from E. raichoi in Japan.

Adaptation to the High-Arctic island environment despite long-term reduced genetic variation in Svalbard reindeer.

Typically much smaller in number than their mainland counterparts, island populations are ideal systems to investigate genetic threats to small populations. The Svalbard reindeer (Rangifer tarandus platyrhynchus) is an endemic subspecies that colonized the Svalbard archipelago ca. 6,000-8,000 years ago and now shows numerous physiological and morphological adaptations to its arctic habitat. Here, we report a de-novo chromosome-level assembly for Svalbard reindeer and analyze 133 reindeer genomes spanning Svalbard and most of the species' Holarctic range, to examine the genomic consequences of long-term isolation and small population size in this insular subspecies. Empirical data, demographic reconstructions, and forward simulations show that long-term isolation and high inbreeding levels may have facilitated the reduction of highly deleterious-and to a lesser extent, moderately deleterious-variation. Our study indicates that long-term reduced genetic diversity did not preclude local adaptation to the High Arctic, suggesting that even severely bottlenecked populations can retain evolutionary potential.

Iterative model predictions for wildlife populations impacted by rapid climate change.

To improve understanding and management of the consequences of current rapid environmental change, ecologists advocate using long-term monitoring data series to generate iterative near-term predictions of ecosystem responses. This approach allows scientific evidence to increase rapidly and management strategies to be tailored simultaneously. Iterative near-term forecasting may therefore be particularly useful for adaptive monitoring of ecosystems subjected to rapid climate change. Here, we show how to implement near-term forecasting in the case of a harvested population of rock ptarmigan in high-arctic Svalbard, a region subjected to the largest and most rapid climate change on Earth. We fitted state-space models to ptarmigan counts from point transect distance sampling during 2005-2019 and developed two types of predictions: (1) explanatory predictions to quantify the effect of potential drivers of ptarmigan population dynamics, and (2) anticipatory predictions to assess the ability of candidate models of increasing complexity to forecast next-year population density. Based on the explanatory predictions, we found that a recent increasing trend in the Svalbard rock ptarmigan population can be attributed to major changes in winter climate. Currently, a strong positive effect of increasing average winter temperature on ptarmigan population growth outweighs the negative impacts of other manifestations of climate change such as rain-on-snow events. Moreover, the ptarmigan population may compensate for current harvest levels. Based on the anticipatory predictions, the near-term forecasting ability of the models improved nonlinearly with the length of the time series, but yielded good forecasts even based on a short time series. The inclusion of ecological predictors improved forecasts of sharp changes in next-year population density, demonstrating the value of ecosystem-based monitoring. Overall, our study illustrates the power of integrating near-term forecasting in monitoring systems to aid understanding and management of wildlife populations exposed to rapid climate change. We provide recommendations for how to improve this approach.

The neglected season: Warmer autumns counteract harsher winters and promote population growth in Arctic reindeer.

Arctic ungulates are experiencing the most rapid climate warming on Earth. While concerns have been raised that more frequent icing events may cause die-offs, and earlier springs may generate a trophic mismatch in phenology, the effects of warming autumns have been largely neglected. We used 25 years of individual-based data from a growing population of wild Svalbard reindeer, to test how warmer autumns enhance population growth. Delayed plant senescence had no effect, but a six-week delay in snow-onset (the observed data range) was estimated to increase late winter body mass by 10%. Because average late winter body mass explains 90% of the variation in population growth rates, such a delay in winter-onset would enable a population growth of r = 0.20, sufficient to counteract all but the most extreme icing events. This study provides novel mechanistic insights into the consequences of climate change for Arctic herbivores, highlighting the positive impact of warming autumns on population viability, offsetting the impacts of harsher winters. Thus, the future for Arctic herbivores facing climate change may be brighter than the prevailing view.

High Arctic ecosystem states: Conceptual models of vegetation change to guide long-term monitoring and research.

Vegetation change has consequences for terrestrial ecosystem structure and functioning and may involve climate feedbacks. Hence, when monitoring ecosystem states and changes thereof, the vegetation is often a primary monitoring target. Here, we summarize current understanding of vegetation change in the High Arctic-the World's most rapidly warming region-in the context of ecosystem monitoring. To foster development of deployable monitoring strategies, we categorize different kinds of drivers (disturbances or stresses) of vegetation change either as pulse (i.e. drivers that occur as sudden and short events, though their effects may be long lasting) or press (i.e. drivers where change in conditions remains in place for a prolonged period, or slowly increases in pressure). To account for the great heterogeneity in vegetation responses to climate change and other drivers, we stress the need for increased use of ecosystem-specific conceptual models to guide monitoring and ecological studies in the Arctic. We discuss a conceptual model with three hypothesized alternative vegetation states characterized by mosses, herbaceous plants, and bare ground patches, respectively. We use moss-graminoid tundra of Svalbard as a case study to discuss the documented and potential impacts of different drivers on the possible transitions between those states. Our current understanding points to likely additive effects of herbivores and a warming climate, driving this ecosystem from a moss-dominated state with cool soils, shallow active layer and slow nutrient cycling to an ecosystem with warmer soil, deeper permafrost thaw, and faster nutrient cycling. Herbaceous-dominated vegetation and (patchy) bare ground would present two states in response to those drivers. Conceptual models are an operational tool to focus monitoring efforts towards management needs and identify the most pressing scientific questions. We promote greater use of conceptual models in conjunction with a state-and-transition framework in monitoring to ensure fit for purpose approaches. Defined expectations of the focal systems' responses to different drivers also facilitate linking local and regional monitoring efforts to international initiatives, such as the Circumpolar Biodiversity Monitoring Program.

Sea ice loss increases genetic isolation in a high Arctic ungulate metapopulation.

Sea ice loss may have dramatic consequences for population connectivity, extinction-colonization dynamics, and even the persistence of Arctic species subject to climate change. This is of particular concern in face of additional anthropogenic stressors, such as overexploitation. In this study, we assess the population-genetic implications of diminishing sea ice cover in the endemic, high Arctic Svalbard reindeer (Rangifer tarandus platyrhynchus) by analyzing the interactive effects of landscape barriers and reintroductions (following harvest-induced extirpations) on their metapopulation genetic structure. We genotyped 411 wild reindeer from 25 sampling sites throughout the entire subspecies' range at 19 microsatellite loci. Bayesian clustering analysis showed a genetic structure composed of eight populations, of which two were admixed. Overall population genetic differentiation was high (mean FST  = 0.21). Genetic diversity was low (allelic richness [AR] = 2.07-2.58; observed heterozygosity = 0.23-0.43) and declined toward the outer distribution range, where populations showed significant levels of inbreeding. Coalescent estimates of effective population sizes and migration rates revealed strong evolutionary source-sink dynamics with the central population as the main source. The population genetic structure was best explained by a landscape genetics model combining strong isolation by glaciers and open water, and high connectivity by dispersal across winter sea ice. However, the observed patterns of natural isolation were strongly modified by the signature of past harvest-induced extirpations, subsequent reintroductions, and recent lack of sea ice. These results suggest that past and current anthropogenic drivers of metapopulation dynamics may have interactive effects on large-scale ecological and evolutionary processes. Continued loss of sea ice as a dispersal corridor within and between island systems is expected to increase the genetic isolation of populations, and thus threaten the evolutionary potential and persistence of Arctic wildlife.

Temporal trend of mercury in relation to feeding habits and food availability in arctic foxes (Vulpes lagopus) from Svalbard, Norway.

We investigated the temporal trend of mercury (Hg) in arctic foxes from Svalbard, Norway sampled in the period 1997-2014 (n = 109, from 11 trapping seasons). We used linear models to investigate the effect of trapping season, feeding habits (δ13C), food availability from marine and terrestrial ecosystems (reindeer carcasses and sea ice cover), sex, age and body condition on liver total Hg (THg) levels. Liver THg levels increased in arctic foxes with 7.2% (95% CI: 2.3, 9.6) per year when the concentrations were adjusted for variation of δ13C, sea ice cover, and reindeer carcasses, whereas the raw annual trend was 3.5% (CI: -0.11, 7.2). However, the THg levels in arctic foxes from Svalbard are still lower than other marine mammals. We also demonstrate that arctic fox terrestrial food consumption is important for lowering the overall THg levels in this species.

Emission Changes Dwarf the Influence of Feeding Habits on Temporal Trends of Per- and Polyfluoroalkyl Substances in Two Arctic Top Predators.

We monitored concentrations of per- and polyfluoroalkyl substances (PFASs) in relation to climate-associated changes in feeding habits and food availability in polar bears (Ursus maritimus) and arctic foxes (Vulpes lagopus) (192 plasma and 113 liver samples, respectively) sampled from Svalbard, Norway, during 1997-2014. PFASs concentrations became greater with increasing dietary trophic level, as bears and foxes consumed more marine as opposed to terrestrial food, and as the availability of sea ice habitat increased. Long-chained perfluoroalkyl carboxylates (PFCAs) in arctic foxes decreased with availability of reindeer carcasses. The ∼9-14% yearly decline of C6-8 perfluoroalkyl sulfonates (PFSAs) following the cease in C6-8 PFSA precursor production in 2001 indicates that the peak exposure was mainly a result of atmospheric transport of the volatile precursors. However, the stable PFSA concentrations since 2009-2010 suggest that Svalbard biota is still exposed to ocean-transported PFSAs. Long-chain ocean-transported PFCAs increased 2-4% per year and the increase in C12-14 PFCAs in polar bears tended to level off since ∼2009. Emerging short-chain PFASs showed no temporal changes. Climate-related changes in feeding habits and food availability moderately affected PFAS trends. Our results indicate that PFAS concentrations in polar bears and arctic foxes are mainly affected by emissions.

Climate change impacts on wildlife in a High Arctic archipelago - Svalbard, Norway.

The Arctic is warming more rapidly than other region on the planet, and the northern Barents Sea, including the Svalbard Archipelago, is experiencing the fastest temperature increases within the circumpolar Arctic, along with the highest rate of sea ice loss. These physical changes are affecting a broad array of resident Arctic organisms as well as some migrants that occupy the region seasonally. Herein, evidence of climate change impacts on terrestrial and marine wildlife in Svalbard is reviewed, with a focus on bird and mammal species. In the terrestrial ecosystem, increased winter air temperatures and concomitant increases in the frequency of 'rain-on-snow' events are one of the most important facets of climate change with respect to impacts on flora and fauna. Winter rain creates ice that blocks access to food for herbivores and synchronizes the population dynamics of the herbivore-predator guild. In the marine ecosystem, increases in sea temperature and reductions in sea ice are influencing the entire food web. These changes are affecting the foraging and breeding ecology of most marine birds and mammals and are associated with an increase in abundance of several temperate fish, seabird and marine mammal species. Our review indicates that even though a few species are benefiting from a warming climate, most Arctic endemic species in Svalbard are experiencing negative consequences induced by the warming environment. Our review emphasizes the tight relationships between the marine and terrestrial ecosystems in this High Arctic archipelago. Detecting changes in trophic relationships within and between these ecosystems requires long-term (multidecadal) demographic, population- and ecosystem-based monitoring, the results of which are necessary to set appropriate conservation priorities in relation to climate warming.

Levels and temporal trends of persistent organic pollutants (POPs) in arctic foxes (Vulpes lagopus) from Svalbard in relation to dietary habits and food availability.

Temporal trends of persistent organic pollutants (POPs) in arctic foxes (Vulpes lagopus) from Svalbard, Norway, were investigated in relation to feeding habits and seasonal food availability. Arctic foxes from Svalbard forage in both marine and terrestrial ecosystems and the availability of their food items are impacted by climatic variability. Concentrations of polychlorinated biphenyls (PCBs), organochlorinated pesticides (OCPs) and brominated flame retardants (polybrominated diphenyl ethers [PBDEs] and hexabromocyclododecane [HBCDD]) were analyzed in the liver of 141 arctic foxes collected between 1997 and 2013. Stable carbon isotope values (δ13C) were used as a proxy for feeding on marine versus terrestrial prey. The annual number of recovered reindeer carcasses and sea ice cover were used as proxies for climate influenced food availability (reindeers, seals). Linear models revealed that concentrations of PCBs, chlordanes, p,p'-DDE, mirex and PBDEs decreased 4-11% per year, while no trends were observed for hexachlorobenzene (HCB) or ß-hexachlorocyclohexane (ß-HCH). Positive relationships between POP concentrations and δ13C indicate that concentrations of all compounds increase with increasing marine dietary input. Increasing reindeer mortality was related to lower HCB concentrations in the foxes based on the linear models. This suggests that concentrations of HCB in arctic foxes may be influenced by high mortality levels of Svalbard reindeer. Further, ß-HCH concentrations showed a positive association with sea ice cover. These results in addition to the strong effect of δ13C on all POP concentrations suggest that climate-related changes in arctic fox diet are likely to influence contaminant concentrations in arctic foxes from Svalbard.

Climate events synchronize the dynamics of a resident vertebrate community in the high Arctic.

Recently accumulated evidence has documented a climate impact on the demography and dynamics of single species, yet the impact at the community level is poorly understood. Here, we show that in Svalbard in the high Arctic, extreme weather events synchronize population fluctuations across an entire community of resident vertebrate herbivores and cause lagged correlations with the secondary consumer, the arctic fox. This synchronization is mainly driven by heavy rain on snow that encapsulates the vegetation in ice and blocks winter forage availability for herbivores. Thus, indirect and bottom-up climate forcing drives the population dynamics across all overwintering vertebrates. Icing is predicted to become more frequent in the circumpolar Arctic and may therefore strongly affect terrestrial ecosystem characteristics.