What Goes In Must Come Out: The Surprising Science of Arctic Nutrient Cycling
May 23, 2025
Arctic Herbivores Drive Soil Health: New Research from UVic and Partners
A new international study with contributions from UVic geography professor Dr. Noémie Boulanger-Lapointe reveals how herbivores play a critical role in shaping soil fertility in Arctic tundra ecosystems. Working with collaborators in Iceland and across continental Europe, the team explored how different herbivore species—geese, sheep, and reindeer—contribute to nutrient cycling and overall ecosystem health. Their findings, recently published in The Science of the Total Environment, offer vital insight into the dynamics of Arctic soil systems in the face of rapid climate and land-use change.
Fieldwork in a Changing Arctic
Tundra ecosystems rely on herbivore waste for nutrient cycling, but variations in faecal nutrient content between species and over time are poorly understood due to costly traditional wet-lab analyses. Instead of relying on old approaches, this new research studied faeces through the development a NIRS-based model to estimate nutrient levels in herbivore waste. By scanning light reflections from just 191 samples, they could accurately predict the chemical makeup of over 300 droppings from sheep, reindeer, and geese. This innovative approach made it possible to monitor nutrient cycling across vast landscapes—at a fraction of the cost.
The researchers studied sites dominated by three different herbivores in Iceland: feral reindeer, domestic free-ranging sheep, and pink-footed geese. These animals represent different grazing behaviours and ecological histories. Sheep are actively managed, reindeer are once-introduced animals that now run feral, and geese are migratory birds that are only present from mid-June to mid-September.
Each site was studied intensively during the Arctic summer. By analyzing nitrogen, phosphorus, and carbon levels—essential elements for plant and microbial growth—the team was able to estimate the contribution of each herbivore to ecosystem nutrient cycling.
Goose Droppings Pack the Biggest Nutrient Punch
Although all three herbivores added nutrients to the tundra soil, the team found that geese contributed disportionately to the nutrient pools of Icelandic rangelands due to their high defecation rate and large population.
Raindeer and sheep had more similar nutrient concentrations and stoichiometry than geese, as was expected from researchers due to the mammals similar size and digestive systems. However, contrary to initial hypotheses, geese has the lowest N and P levels among the three species, while sheep had the highest. One possible explanation for this unexpected ranking is that sheep in Iceland are domestic, and thus are kept indoors and receive supplemental feeding throughout the winter, leading to higher nutrient reserves during the summer months. By comparison geese, who arrive in Iceland after long migrations, experience a period of nutrient depletion as they recover from the stress of travel.
The study also showed that nutrient contributions from herbivores decline significantly over the course of the growing season, likely due to decreases in plant quality and quantity as the summer progresses.
A Climate-Sensitive System
The implications of this work are especially relevant in a warming world. As Arctic temperatures rise and human influence grows, the makeup of herbivore communities is shifting. These changes can alter the way nutrients move through the ecosystem, potentially impacting everything from plant diversity to greenhouse gas emissions. Understanding the ecological roles of herbivores is becoming increasingly important for conservation and land management. This study offers a foundation for future research into how biodiversity, animal behaviour, and nutrient cycling interact to shape northern ecosystems.
Dr. Boulanger-Lapointe and her colleagues hope their findings will help inform sustainable land use strategies that consider the vital, yet often overlooked, role of animals in ecosystem health.
