Rapid Ecosystem Change at the Southern Limit of the Canadian Arctic, Torngat Mountains National Park

Shallow subtidal marine benthic communities of Nachvak Fjord, Nunatsiavut, Labrador: A glimpse into species composition and drivers of their distribution

Marine fjords along the northern Labrador coast of Arctic Canada are influenced by freshwater, nutrients, and sediment inputs from ice fields and rivers. These ecosystems, further shaped by both Atlantic and Arctic water masses, are important habitats for fishes, marine mammals, seabirds, and marine invertebrates and are vital to the Labrador Inuit who have long depended on these areas for sustenance. Despite their ecological and socio-cultural importance, these marine ecosystems remain largely understudied. Here we conducted the first quantitative underwater scuba surveys, down to 12 m, of the nearshore marine ecology of Nachvak Fjord, which is surrounded by Torngat Mountains National Park located in Nunatsiavut, the Indigenous lands claim region of northeastern Canada. Our goal was to provide the Nunatsiavut Government with a baseline of the composition and environmental influences on the subtidal community in this isolated region as they work towards the creation of an Indigenous-led National Marine Conservation Area that includes Nachvak Fjord. We identified four major benthic habitat types: (1) boulders (2) rocks with sediment, (3) sediment with rocks, and (4) unconsolidated sediments, including sand, gravel, and cobble. Biogenic cover (e.g., kelp, coralline algae, and sediment) explained much of the variability in megabenthic invertebrate community structure. The kelp species Alaria esculenta, Saccharina latissima, and Laminaria solidungula dominated the boulder habitat outside of the fjord covering 35%, 13%, and 11% of the sea floor, respectively. In contrast, the middle and inner portions of the fjord were devoid of kelp and dominated by encrusting coralline algae. More diverse megabenthic invertebrate assemblages were detected within the fjord compared to the periphery. Fish assemblages were depauperate overall with the shorthorn sculpin, Myoxocephalus scorpius, and the Greenland cod, Gadus ogac, dominating total fish biomass contributing 64% and 30%, respectively. Understanding the composition and environmental influences within this fjord ecosystem not only contributes towards the protection of this ecological and culturally important region but serves as a baseline in a rapidly changing climatic region.

Scientists' warning of the impacts of climate change on mountains

Mountains are highly diverse in areal extent, geological and climatic context, ecosystems and human activity. As such, mountain environments worldwide are particularly sensitive to the effects of anthropogenic climate change (global warming) as a result of their unique heat balance properties and the presence of climatically-sensitive snow, ice, permafrost and ecosystems. Consequently, mountain systems-in particular cryospheric ones-are currently undergoing unprecedented changes in the Anthropocene. This study identifies and discusses four of the major properties of mountains upon which anthropogenic climate change can impact, and indeed is already doing so. These properties are: the changing mountain cryosphere of glaciers and permafrost; mountain hazards and risk; mountain ecosystems and their services; and mountain communities and infrastructure. It is notable that changes in these different mountain properties do not follow a predictable trajectory of evolution in response to anthropogenic climate change. This demonstrates that different elements of mountain systems exhibit different sensitivities to forcing. The interconnections between these different properties highlight that mountains should be considered as integrated biophysical systems, of which human activity is part. Interrelationships between these mountain properties are discussed through a model of mountain socio-biophysical systems, which provides a framework for examining climate impacts and vulnerabilities. Managing the risks associated with ongoing climate change in mountains requires an integrated approach to climate change impacts monitoring and management.

Fire disturbance promotes biodiversity of plants, lichens and birds in the Siberian subarctic tundra

Fire shapes the world's terrestrial ecosystems and has been influencing biodiversity patterns for millennia. Anthropogenic drivers alter fire regimes. Wildfires can amplify changes in the structure, biodiversity and functioning of the fast-warming tundra ecosystem. However, there is little evidence available, how these fires affect species diversity and community composition of tundra ecosystems over the long term. We studied long-term fire effects on community composition and diversity at different trophic levels of the food web in the subarctic tundra of Western Siberia. In a space-for-time approach we compared three large fire scars (>44, 28 and 12 years old) to unburnt controls. We found that diversity (measured as species richness, Shannon index and evenness) of vascular and non-vascular plants and birds was strongly affected by fire, with the greatest species richness of plants and birds for the intermediate-age fire scar (28 years). Species composition of plants and birds still differed from that of the control >44 years after fire. Increased deciduous shrub cover was related to species richness of all plants in a hump-shaped manner. The proportion of southern (taiga) bird species was highest in the oldest fire scar, which had the highest shrub cover. We conclude that tundra fires have long-term legacies with regard to species diversity and community composition. They may also increase landscape-scale species richness and facilitate range expansions of more southerly distributed species to the subarctic tundra ecosystem.