The COVID-19 pandemic has raised many concerns among Indigenous communities about virus transmission risks from wild food, particularly migratory birds. Snow geese contribute significantly to food security in Indigenous contexts, which is precarious in many communities. The risk to goose hunters is very unlikely as coronaviruses found in birds are from different genera than that of SARS-CoV -2, the etiologic agent responsible for COVID-19. Nevertheless, little is currently known about the host tropism range of SARS-CoV-2. To address the concerns raised by Northern communities, we captured 500 snow geese in May 2020 at their stopover along the St Lawrence estuary. We took oropharyngeal and cloacal samples before releasing the birds. All samples were tested for SARS-CoV-2 within one week and were found to be PCR-negative, allowing us to communicate rapidly with Northern communities. The current pandemic has shown that the importance of understanding animals as potential viral reservoirs, and that a better understanding of these viruses will better prepare us for future spillover events. This project demonstrates that researchers can be quickly and efficiently mobilized to respond to concerns from Indigenous communities.

Changes in mass, extent, duration, and physical properties of snow are key elements for studying associated climate change feedbacks in northern regions. In this study, we analyzed snowpack physical properties along a ‘mega’ transect from 47°N to 83°N (4,000 km) in northeastern Canada, which includes marked transitions between ecozones from boreal forest to subarctic and arctic ecosystems. Our unique dataset of 391 detailed snowpits acquired over the last 20 years, complemented with snow data from weather stations, shows that snowpack properties such as snow water equivalent, snow depth, density, grain size and basal depth hoar fraction (DHF) are strongly linked to vegetation type. Based on these results, we propose an updated classification of snow types in three classes: boreal forest snow (47–58°N), tundra snow (58–74°N) and polar desert snow (74–83°N), which is more appropriate to the study area than the general north hemisphere classification commonly used. We also show that shrub presence along the transect contributes to a significant increase in DHF development which contributes most strongly to the thermal insulation properties of the snowpack. Overall, our analysis suggests that snow–vegetation interactions have a positive feedback effect on warming at northern latitudes.

The startling warming of the Arctic is driving important environmental changes, but vegetation responses have been spatially heterogeneous and difficult to predict. In this context, establishing new ecological baselines and initiating monitoring schemes are essential. We conducted systematic plot-based surveys in the polar desert surrounding Alert (Nunavut, Canada). We aimed at (1) identifying distinct plant communities, (2) characterizing community attributes, including diversity and abundance, as well as environmental variables associated with each community, and (3) establishing a georeferenced baseline with permanent field markers allowing robust resurveying. We used hierarchical clustering to categorize cover values of vascular plant species, cryptogams, and ground substrates from 1,320 quadrats (1 m² each) surveyed in 264 vegetation plots. Five plant communities were identified, with one community associated with each of the barren and mesic habitats, and three communities associated with wetlands. The mean biotic covers were generally higher at Alert (13–98%) compared to other polar deserts in the Canadian Arctic Archipelago. A total of 250 quadrats from 50 vegetation plots were permanently marked, and a database describing all plots is available online. This study improves our understanding of High-Arctic plant communities and establishes an important vegetation monitoring reference at the northernmost permanently inhabited settlement on Earth.

This study examines the Holocene evolution of an inland subarctic permafrost peatland located on the north bank of Wiyâshâkimî Lake (Nunavik, northeastern Canada). The analysis of plant macrofossils allowed us to reconstruct the succession of the trophic conditions of a palsa and a filled thermokarst pond. The accumulation of organic matter began at around 6290 cal. y BP. The evolution of the site then followed three stages: a pond (6290–5790 cal. y BP), a minerotrophic peatland (5790–4350 cal. y BP) and an ombrotrophic peatland (from 4350 cal. y BP). The establishment of permafrost caused a palsa to form at around 170 cal. y BP, which corresponds to the coldest period of the Little Ice Age in northeastern Canada. A subsequent degradation of the palsa and the formation of a thermokarst pond were induced by the climate warming that began at the turn of the 20th century. The analysis of plant macrofossils from an adjacent filled thermokarst pond indicated three phases of development over a short 450-year period: subaquatic, minerotrophic, and ombrotrophic phases. When combined with previous studies of filled thermokarst ponds in northern Québec, this result indicates that ponds are rapidly filling in with vegetation and acting as carbon sinks.

Numerous temperate peatlands are currently experiencing an accelerated process of woody encroachment. Such encroachment may have harmful impacts on peatland biodiversity and functions. Our objective was to investigate the recent history of woody encroachment in a temperate bog using plant macrofossil, testate amoeba, aerial photograph analyses, and plant inventories. We also explored some plausible triggering drivers of the phenomenon and its impacts on plant richness, composition, and beta diversity. We showed that the recent woody encroachment was mainly associated with the native Betula populifolia and the exotic Frangula alnus. It began in the 1960s at the bog margins following a decrease in the water table and recurrent fire events, both likely associated with agricultural activities in the surrounding catchment. We found an increase in species richness with tree cover and basal area, but no effect of tree encroachment on beta diversity. Still, we found a significant compositional turnover from light-demanding bog specialists to terrestrial, exotic or ruderal species with tree basal area. It seems unlikely that the bog will naturally come back to its previous unforested state on a human life's timescale as the observed changes are related to regional factors rather than in situ disturbance.

Arctic fox (Vulpes lagopus) and its tundra habitat are a unique system for the study of rabies virus epidemics. Contrary to theoretical calculations reporting a critical density (K_T) of approximately 1 fox/km² for rabies endemicity, arctic rabies persists at densities below this. The calculation of K_T = 1 fox/km² assumes uniform fox density across the landscape and unrestricted mixing between susceptible and infected foxes. We hypothesize that spatial heterogeneity arising from resource distribution or social structure may result in regions where rabies is endemic, even though average fox densities at the regional or landscape-level are below K_T. To expand upon the limited body of research surrounding arctic rabies persistence, we examine arctic rabies via a two-patch structure. We find that arctic rabies can persist in heterogeneous landscapes where the mean carrying capacity is below the threshold carrying capacity required for endemicity in homogeneous landscapes. Rabies endemicity in low-carrying capacity regions within heterogeneous landscapes is further facilitated by high transmission rates, potentially due to non-breeding foxes (i.e. floaters), and when between-patch movement is restricted to latent and infected foxes. Our results suggest that rabies may persist in heterogeneous landscapes when the mean carrying capacity is as low as 0.25 foxes/km².

Increased snow cover and attenuation of light due to shrub expansion can lead to changes in the quantity and nutritional quality of food resources for migratory caribou (Rangifer tarandus). To determine how vegetation is affected by snow accumulation and shade, we conducted an experiment that simulated the light and snow conditions created by increased shrub cover at Deception Bay (Nunavik, Canada), within the summer range of the Rivière-aux-Feuilles caribou herd. We estimated the foliar biomass of two major components of the caribou diet (Betula glandulosa and Carex spp.). We also harvested foliar tissue to conduct chemical composition analyses (nitrogen, fibre, total phenolics). Experimental light attenuation was found to increase the nitrogen concentrations in B. glandulosa and Carex spp. throughout the growing season. Phenolic concentration in B. glandulosa decreased in early summer but was otherwise consistent in response to light attenuation and increased snow cover. Increased snow cover combined with ambient light had a positive effect on the foliar biomass of B. glandulosa. Increased snow cover and shade caused by shrub densification may therefore increase forage quantity and quality for caribou. We suggest investigating the effects of shrub expansion on other components of the caribou diet, such as lichens and forbs.

The Great Whale River in subarctic Quebec, Canada, is one of the main freshwater inflows to Hudson Bay. This region is experiencing rapid climate change, with pronounced impacts on the cryosphere, and ongoing socio-economic development that may accelerate with future road and shipping links. This review integrates information available to date on the Great Whale River ecosystem, which we define as the river and its watershed, its source lakes and streams, and the river mouth environment and beyond the shoreline in southeastern Hudson Bay. Our aim was to define the current state of this ecosystem as a baseline for ongoing observations, with emphasis on (1) the distribution of water masses, optical characteristics, freshwater discharge, and ice cover; (2) concentrations and fluxes of carbon, nutrients, and contaminants; (3) abundance, production and diversity of the organisms associated with the sea ice ecosystem; (4) plankton abundance, biomass, production, and assemblages; (5) benthic abundance and diversity; (6) fish abundance, diversity and population dynamics; (7) marine mammal biology; and (8) global change impacts on freshwater and marine habitats. This synthesis provides a first step towards the integrated management of the Great Whale River ecosystem, and for similar freshwater-marine systems in the subarctic region.

The Arctic has warmed significantly over the past decades. However, the evolution of Arctic climate during the Holocene remains to be clarified in more detail, and regional factors controlling aquatic ecosystem evolution need to be better defined to grasp the sensitivity of lakes to rapid environmental change. Nettilling Lake was studied for changes in sedimentary diatom assemblages over the last 5 000 years. Lake water pH was reconstructed by applying a diatom-based lake water pH inference model. We hypothesized that the changes in diatom assemblages were driven by variations in lake water transparency and attendant water turbidity associated with the input of fine suspended solids from glacial meltwaters. Reduced underwater light resulted in greater abundance of planktonic over benthic taxa from ca. 5 000 to 3 000 yrs. cal. BP, followed by less turbid conditions and proliferation of benthic taxa during regional cooling. The lake water was slightly alkaline throughout the Holocene, ranging between pH 7.1 and 7.7. Our results support the notion that hydrological processes, dependent on climate variations, have a first-order influence on the regulation of the lake water pH through glacial meltwater inputs, which will likely continue to control the lake's long-term chemical and biological evolution.

Several recent dendrochronological, macrofossil and palynological studies have surveyed modern spruce forests at multiple locations in the Nain region of coastal Nunatsiavut (north-central Labrador) in order to reconstruct past forest composition, growth rates, species diversity and harvesting patterns. The present paper synthesizes original and previously collected data to evaluate the extent to which the dynamics of the region's spruce forests over the past five centuries have been related to anthropogenic impacts. In three key case studies, Picea growth release events demonstrate multiple isolated forest disturbances prior to the late 19th century. In general, these events correspond to the local human settlement history rather than to regional climatic trends, suggesting that ongoing human impacts on the forest extend as far back as the 17th century. Disturbance regimes accelerated by ca 1875 and afterward in all of the study sites. This increase in forest disturbance corresponds to increased demands for wood triggered by socioeconomic changes experienced by the region's Inuit and Settler communities. Ongoing surveys demonstrate the presence of markers of human exploitation of forests throughout the study region, and especially in coastal locations, suggesting that anthropogenic impacts are in fact generalised and not limited to specific areas of recent settlement.

Numerical simulations were carried out based on a conceptual cryohydrogeological model of a permafrost mound near Umiujaq, Nunavik (Québec), Canada, to assess the impacts of climate warming and changes in surface conditions on permafrost degradation. The 2D model includes groundwater flow, advective-conductive heat transport, phase change and latent heat. Changes in surface conditions which are characteristic of the site were represented empirically in the model by applying spatially- and temporally-variable ground surface temperatures derived from linear regressions between monitored surface and air temperatures. After reaching a transient steady-state condition close to present-day conditions, the simulations were then extended to 2100 under hypothetical climate warming scenarios and using imposed changes in surface conditions consistent with observed on-site evolution. The simulations show that the development of a thermokarst pond and shrubification respectively induce ground warming of up to 0.5°C and 1.5°C, upward migration of the permafrost base by up to 2 and 4 m, and a decrease in the lateral permafrost extent of 1 and 7 m, relative to a reference case without changes in surface conditions. Feedback from permafrost degradation which drives changes in ground surface conditions should be included in future numerical modelling of permafrost dynamics.

We present the longest tree-ring chronology to date in northeastern North America (2233 years; 227 BCE – 2005 CE), resulting from several research projects conducted at the subarctic treeline in northern Quebec. This raw chronology of tree-ring width includes 464 black spruce (Picea mariana (Mill.) B.S.P.) shrubs (krummholz) growing in wetlands and preserved within peatlands. An indexed series of 152 erect black spruce trees that have lived in wetlands is also presented, covering the period 216 BCE to 1619 CE. We compared these chronologies to a tree-ring series including 116 black spruce trees and krummholz having grown on well-drained lichen woodlands over the period 1304–2000 CE. These chronologies highlight the major climatic periods of the last two millennia. Floating chronologies dating from 2500 to 3500 years ago were also developed from trees preserved in frozen peat. Growth rings from this period are much wider than those of the last 2233 years, suggesting warm climatic conditions and permafrost-free peatlands during the transition from mid- to late Holocene. The three subarctic chronologies presented here underscore the relevance and usefulness of tree growth rings and growth forms as ecological tools to assess the influence of climate on subarctic ecosystems.

We investigated the sensitivity to vegetation cover type of active (PALSAR) and passive (SMAP) freeze/thaw (F/T) classification. We also used F/T classification from high-resolution PALSAR data (30 m) to follow the evolution of frozen and thawed soil states obtained from an adaptive algorithm with low-resolution SMAP data (36 km). We used PALSAR and SMAP scenes acquired from June 2015 to January 2017 over the Tursujuq National Park (Umiujaq, Quebec, Canada). A new F/T algorithm with a specific reference threshold under each vegetation type (shrub, grass, lichen, wetland, and bare land) is proposed to classify PALSAR pixels. The validation of the PALSAR F/T classification with soil temperature at ∼5 cm depth revealed a greater overall accuracy (> 80%), with horizontal transmitted and vertical received (HV) thresholds. The PALSAR F/T classification shows that a SMAP pixel is classified as frozen when more than 50% of its area is frozen at the surface. We confirmed the sensitivity to vegetation cover type of passive and active F/T classification with L-band sensor.