Small geese have a large impact on Arctic ecosystems

In the remote and harsh Arctic environment, a significant ecological shift is occurring. New research led by Matteo Petit Bon from the Quinney College of Natural Resources is shedding light on the complex dynamics of the Arctic ecosystem.

The researchers delved into the impacts of two dominant herbivores, geese and reindeer. The study was particularly focused on Svalbard, a high-tundra archipelago located between mainland Norway and the North Pole. 

“Given the current rates of climate change, with associated shifts in herbivore population densities, understanding the role of different herbivores in ecosystem functioning is critical for predicting ecosystem responses,” explained the study authors. 

Svalbard reindeer 

Svalbard reindeer, known for their docility and sedentary nature, have been indigenous to these islands for millennia. However, by 1900, due to extensive hunting by miners and trappers, the reindeer population was nearly extinguished. Only a few isolated populations survived. 

The subsequent legal protection by the Norwegian government facilitated a remarkable recovery, with current numbers exceeding 20,000.

Barnacle geese 

Barnacle geese, which migrate to Svalbard, have experienced a population boom. Their numbers have surged from less than 3,000 in 1960 to over 40,000 today, benefiting from conservation efforts in their overwintering habitat in Scotland. 

These geese play a crucial role in the Arctic ecosystem during their temporary stay, capitalizing on the nutrient-rich vegetation and continuous daylight to breed.

Impact on ecosystems

Both reindeer and geese significantly alter the vegetation composition in Svalbard. Their feeding habits, along with natural fertilization and soil compaction through trampling, have direct and indirect effects on the plant life. 

This interaction has far-reaching consequences for the ecosystem’s response to the rapidly changing Arctic climate, which is warming faster than most other regions.

Altering the landscape 

Geese, although smaller and temporary residents, have a more pronounced impact compared to the larger, more dispersed reindeer. 

The concentrated grazing by geese has led to a significant reduction in plant biomass, with a fivefold decrease in grass biomass in goose-grazed areas between 2008 and 2018. This finding suggests that the geese’s feeding habits are altering the landscape more drastically than the reindeer.

Key insights

Experimental studies confirmed that the geese are more impactful. Removing reindeer from certain areas showed little effect on ecosystem health, whereas excluding geese led to noticeable improvements in vegetation and soil conditions. This indicates that geese, despite their size and temporary presence, exert a more substantial influence on the ecosystem.

“Although both herbivores were key drivers of ecosystem structure and function, the control exerted by geese in their main habitat (wet tundra) was much more pronounced than that exerted by reindeer in their main habitat (moist-to-dry tundra),” wrote the study authors. 

“Importantly, these herbivore effects are scale dependent, because geese are more spatially concentrated and thereby affect a smaller portion of the tundra landscape compared to reindeer. Our results highlight the substantial heterogeneity in how herbivores shape tundra vegetation and ecosystem processes, with implications for ongoing environmental change.”

Study implications

The research is pivotal in understanding the evolving dynamics of Arctic ecosystems. It provides crucial insights into how changing herbivore populations might affect these fragile environments, especially in the context of climate change. 

The study helps to improve predictions about the potential mitigation or amplification of climate change impacts due to shifts in these herbivore populations.

The study is published in the Journal of Ecology.

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