Climate change is rapidly altering Arctic ecosystems, with significant consequences for species dependent on seasonal food availability. In her PhD, Samantha Paige Huset Dwinnell investigates how Svalbard reindeer respond to climate-driven shifts in vegetation and weather, revealing mechanisms that link environmental change to population growth.
In the High Arctic archipelago of Svalbard, climate change is reshaping ecosystems at an unprecedented pace. A new doctoral thesis by Samantha Paige Huset Dwinnell investigates how Svalbard reindeer (Rangifer tarandus ssp platyrhynchus) respond to climate-driven changes in food availability, particularly during the critical autumn and early winter seasons.
Over the past 26 years, the reindeer population in Nordenskiöld Land has increased 3.5-fold. Huset Dwinnell’s research links this growth to increased plant biomass resulting from warmer summers and extended growing seasons. Her findings suggest that reindeer are not only benefiting from these changes but are also exhibiting flexible foraging behaviors that may support resilience in a rapidly changing environment.
“This work begins to uncover the mechanisms linking climate to population-level consequences,” Huset Dwinnell says.
“High-Arctic reindeer have benefited from vegetation responses to warming and exhibit flexible foraging, likely enabling adaptive responses to rapid environmental changes.”
GPS tracking and measurements
Huset Dwinnell’s study builds on 30 years of individual-based monitoring of Svalbard reindeer, combining GPS tracking, body condition measurements, and field observations with experimental plant studies.
She analyzed how reindeer use different habitats across seasons and assessed the nutritional value of above- and belowground plant parts. In one experiment, she manipulated soil moisture to simulate increased precipitation and observed species-specific effects on plant senescence.
Key findings
Increased biomass supports population growth: Warmer summers have led to an 86% increase in grass biomass. Despite a tripling of reindeer numbers, grazing pressure remains low because animals selectively feed on high-biomass patches.
Autumn foraging has fitness benefits: Reindeer that used marsh habitats during brief warm spells in autumn and early winter were up to 5 kg heavier in spring. This weight gain is associated with improved reproductive success and survival.
Behavioral plasticity in foraging: Reindeer adapt their foraging strategies based on seasonal conditions. In warm autumns, they dig for roots; in colder years, they consume frozen green foliage. These behaviors reflect dynamic responses to changing food accessibility.
Soil moisture affects plant senescence: Experimental waterlogging delayed senescence in grasses but accelerated it in dwarf shrubs. This could shift the nutritional landscape for reindeer as precipitation patterns change.
“Access to belowground food resources may be of increasing importance as warmer autumns continue,” Huset Dwinnell notes, “but the nutritional benefits remain unknown.”
More than food quality
Huset Dwinnell’s research highlights the importance of understanding how climate change affects not just food quantity, but also the timing and accessibility of nutrition. While Svalbard reindeer currently appear to be “climate winners,” ongoing warming may challenge their adaptive capacity.
“This resilience may persist as long as warming remains within their adaptive thresholds,” she concludes, “but continued Arctic warming could challenge these benefits.”