The Arctic, at the northernmost part of the Earth, is a region of extreme cold, vast ice sheets, and a year divided into periods of continuous daylight and unending night. Despite these challenging conditions, the region supports a surprising abundance of specially adapted life. Organisms from microscopic plankton to the largest predators are all interconnected within an ecosystem tuned to its physical setting.
The Physical Arctic Environment
The Arctic’s physical environment is shaped by three dominant, interconnected components. First among these is sea ice, the frozen seawater that blankets much of the Arctic Ocean. This ice is not a static feature; it expands dramatically in the winter and retreats during the summer. This floating platform is a habitat, providing a surface for animals to travel, hunt, and rest, while its movement influences the distribution and behavior of marine life.
Beneath the tundra landscapes of the Arctic’s terrestrial areas lies another element: permafrost. This is ground that remains frozen for at least two consecutive years, a layer of soil, rock, and ice that can extend hundreds of meters deep. Permafrost acts as a foundation for the treeless plains, locking vast amounts of organic material and water into a frozen state. Its presence dictates the flow of water on the surface, creating the wetlands and shallow lakes that dot the landscape during the brief summer melt.
Completing the trio of defining physical characteristics are the extreme light cycles. Due to the Earth’s tilt, the Arctic experiences seasons of continuous daylight, known as the “midnight sun,” and periods of prolonged darkness, called the polar night. These dramatic shifts in sunlight have a profound impact on the region’s energy and temperature. The long, dark winters bring intense cold, while the summer offers a brief but intense period of 24-hour sunlight that fuels a burst of life.
Survival Strategies of Arctic Life
Surviving the intense cold requires specialized physiological traits for animals. Polar bears and seals, for instance, are insulated by thick layers of blubber, while animals like the Arctic fox and caribou possess coats of hollow hair that trap air, creating an insulating barrier. The polar bear also has black skin under its transparent fur to better absorb the sun’s heat.
Camouflage is another widespread survival strategy, tied directly to the snow and ice-covered landscape. The Arctic fox and the ptarmigan (a type of grouse) undergo seasonal changes in coat color, sporting pure white fur or plumage in the winter to blend in with the snow and brown or grey coats in the summer to match the thawed tundra. This ability to remain unseen is important for predators trying to ambush prey and for prey avoiding detection.
Many species undertake long-distance migrations to cope with the dramatic seasonal shifts. Caribou herds travel vast distances between their wintering grounds in the boreal forests and their summer calving grounds on the open tundra, following the availability of food. Similarly, many whale species, such as bowhead and beluga, move into Arctic waters during the summer to feed in the highly productive seas before retreating to warmer waters for the winter.
Arctic flora is also highly adapted. To survive the short growing season and harsh winds, most plants are low-growing, forming mats and cushions close to the ground where temperatures are slightly warmer. Many species have dark-hued leaves and stems to absorb more solar radiation, and some have fine hairs that help trap heat. Their life cycles are accelerated, with rapid flowering and seed production compressed into the few frost-free weeks of the midnight sun.
The Arctic Food Web
The Arctic food web begins in the nutrient-rich marine environment. At the base are phytoplankton, microscopic marine algae that bloom in large numbers during the sunlit summer months. Just as important is the ice algae, which grows on the underside of sea ice, providing a source of food even before the major phytoplankton blooms begin.
Feeding on this algae are tiny animals called zooplankton, including small crustaceans like krill. These organisms, in turn, become the primary food source for a variety of other species. The Arctic cod is a fish species that thrives in the cold waters by consuming vast quantities of zooplankton. As a linchpin species, it connects the lower levels of the food web to the larger predators.
The next level of the food web includes marine mammals such as seals. Ringed and bearded seals, for example, feed extensively on Arctic cod and crustaceans to build fat reserves. These seals then become the primary prey for the ecosystem’s apex predator, the polar bear. Polar bears are adapted to hunt on the sea ice, waiting for seals to surface at breathing holes, while in the open water, orcas are another top predator.
While the marine food web is dominant, a simpler terrestrial food web also exists. This web is based on lichens, mosses, and low-lying shrubs that can survive on the tundra. These plants are the main food source for herbivores like caribou and muskoxen. These large grazers are, in turn, preyed upon by Arctic wolves, which are adapted to hunt in packs across the vast, open landscapes.
Pressures on the Arctic Ecosystem
Climate change is the most profound pressure on the Arctic ecosystem, causing the region to warm at a rate nearly double the global average. This warming has led to a rapid decline in the extent and thickness of summer sea ice. The loss of this platform directly impacts the hunting grounds for polar bears and the habitat for seals, which rely on the ice for resting and raising their pups.
The warming climate is also causing permafrost to thaw. As the frozen ground melts, it destabilizes the landscape, impacting everything from plant roots to the infrastructure of human settlements. The thawing process also releases vast amounts of stored carbon and methane, greenhouse gases that can further accelerate global warming.
Direct human activities are introducing new stressors. Reduced sea ice has opened previously impassable shipping routes, increasing vessel traffic through sensitive marine habitats. This brings risks of oil spills, underwater noise pollution that can interfere with marine mammal communication, and the introduction of non-native species. Furthermore, the growing demand for resources is driving increased exploration for oil, gas, and minerals, which can lead to habitat destruction and pollution.