Why are Arctic food webs especially vulnerable when one important species decreases in number?

Arctic food webs are particularly vulnerable to the decline of an important species primarily due to the low species diversity and relative simplicity of polar ecosystems. Unlike complex tropical or temperate environments, Arctic ecosystems often feature species that play dominant roles in trophic dynamics, meaning the loss or significant reduction of one species can trigger dramatic, destabilizing effects throughout the entire food chain.1

This vulnerability is characterized by:

• Lack of Complexity: Because there are fewer species, there are fewer alternative food sources or redundant ecological roles. When a key species—such as the lemming—declines, its predators (e.g., Arctic foxes, snowy owls) may face immediate reproductive failure or population collapse because they lack sufficient alternative prey.12
• Trophic Cascades: The removal of a keystone species or a major predator can cause a trophic cascade, where reciprocal changes in predator and prey populations lead to widespread shifts in ecosystem structure and nutrient cycling.3
• Biological Limitations: Many Arctic animals live near their biological limits, making them highly sensitive to environmental fluctuations and imbalances in predator-prey relationships.1

Ultimately, the simplicity of these webs means that the stability of the entire community often depends on the presence of specific, dominant species.1