Not only will competition within the arctic fox populations increase, competition with other species will increase as well. "Ecosystems alterations can profoundly affect species occurrence and distribution thereby influencing trophic and/or competitive interactions. arctic foxes have been fully protected in Fennoscandia following their drastic decline in the early 19th century, and their lack of recovery has been hypothesized to result from increased interspecific competition with red foxes that have colonized the arctic fox's range" (Hamel et al., 2013 p 114). The encroachment of these foxes is already being observed in more southern areas. As the tundra warms they will continue to move further north. Far superior at hunting then the arctic fox, the Red Fox would become the dominant predator. Not only would the Red Foxes consume the arctic Foxes' food, but have also been known to prey upon young arctic foxes. They have even been seen preying on fully-grown arctic foxes as well. .
The main diet of the arctic fox is lemmings. Lemmings are known to have large fluctuations in populations that tend to occur in cycles. However, there is increasing evidence showing climate change altering these cycles, leading to instability in the sizes of populations. Lemmings tend to forage below ground in a space between the snow and frozen ground. Warmer weather creates wet snow, which leads to a collapse in these under-snow areas, thus the lemmings burrows disappear. If winters continue to grow shorter and warmer, it is certain that the lemming population cycles will be altered, leading to an overall decline in the lemming population. This decline is surely to affect the arctic fox population. Many argue that a decrease in lemming population would not gravely change arctic fox numbers. They claim that other species may begin to live in this habitat. However, the increased encroachment of the Red Fox will most likely overshadow these benefits.