How Midnight Sun Affects the Environment


A beautiful Alaskan sunset

Long daylight hours benefit Alaska’s plants because plants generally begin making food through photosynthesis as soon as the sun rises, and they continue until sunset. Warmth from the sun also helps, until temperatures reach into the high 80s, which is not uncommon in Interior Alaska. Then photosynthesis actually decreases.

Parts of Alaska such as the Tanana Valley between Fairbanks and Delta and the Matanuska Valley near Anchorage are famous for their production of gigantic vegetables. Among the largest vegetables have been a 138 pound cabbage from Wasilla, and 18.9-pound carrot from Palmer, and a 1,287 pound pumpkin from Nikiski on the Kenai Peninsula.

Studies have shown some interesting effects of midnight sun on plants in Alaska. In 1960 a forester measured seasonal growth of white spruce in Interior Alaska at the same times that another forester measured growth of white spruce in Massachusetts. Over the course of the year, the studies showed that trees at both locations produced the same amount of wood. The Alaskan trees just did it in half the time required by those in Massachusetts.

Alaska is famous, or infamous, for its biting insects, including mosquitoes, black flies, and no-see-ums. The abundance of standing water provides breeding habitats, but long daylight hours also benefit insects a great deal. When the sun shines for most of the day, the ground stays constantly warm rather than cooling at night, so insect development can proceed uninterrupted by low nighttime temperatures.

These masses of insects in turn benefit many birds that nest in northern Alaska, enabling parents to find food nearly 24 hours a day and providing juicy packages of protein to feed their hungry chicks. Insect-eating chicks grow faster and fledge sooner than similar-sized species nesting farther south, and females of some species such as hoary redpolls, snow buntings, and northern wheatears lay more eggs than their southern counterparts. Apparently long daylight enables the females to find food to provide the extra energy to lay more eggs, and allows both parents to gather enough food to feed larger families.

Long summer daylight also benefits Alaska’s fish. Studies of arctic grayling, which feed by sight, show that they feed 24 hours a day during June and July in Interior Alaska. They cease feeding later in the year only during darkness.

Arctic mammals may also benefit from increased daylight. Animals that feed by sight have more hours in which to feed. Highly nutritious, fast-growing vegetation benefits grazing animals such as caribou, which need to develop good body condition in summer to survive harsh northern winters and be fit enough to reproduce in the spring.

Benefits of the midnight sun and long hours of daylight are seldom lost on Alaska’s human residents and visitors. There are few other places in the world where one can work all day and still have time after dinner to climb a mountain or catch a salmon—to raft a river, hike past a glacier, and picnic at sunset all within a single day. Those who appreciate solitude in nature can venture out after midnight or for a 3:30 A.M. sunrise and be rewarded with close looks at wildlife, which are more active during these early morning hours.