The Boundary Waters Canoe Area Wilderness (BWCAW or BWCA), is a 1,090,000-acre (4,400 km2) wilderness area within the Superior National Forest in northeastern Minnesota (United States) under the administration of the U.S. Forest Service. A mixture of northwoods, forests, glacial lakes and streams, it is a popular destination for both canoeing and fishing on its many lakes and is one of the most visited wildernesses in the United States.
The lakes of the BWCAW are located in depressions formed by differential erosion of the tilted layers of the Canadian Shield. For the past two million years, massive sheets of ice have repeatedly scoured the landscape. The last glacial period ended with the retreat of the Laurentide Ice Sheet from the Boundary Waters about 17,000 years ago. The resulting depressions in the landscape later filled with water, becoming the lakes of today.
Many varieties of Precambrian bedrock are exposed including: granite, basalt, greenstone, gneiss, as well as metamorphic rocks derived from volcanic and sedimentary rocks. Greenstone of the Superior craton located near Ely, Minnesota, is up to 2.7 billion years old. Igneous rocks of the Duluth Complex comprise the bedrock of the eastern Boundary Waters. Ancient microfossils have been found in the banded iron formations of the Gunflint Chert.
The Boundary Waters area is within the Laurentian Mixed Forest Province (commonly called the “North Woods”), a transitional zone between the boreal forest to the north and the temperate hardwood forest to the south that contains characteristics of each. Trees found within the wilderness area include conifers such as red pine, eastern white pine, jack pine, balsam fir, white spruce, black spruce, and white-cedar, as well as deciduous birch, aspen, ash, and maple. Blueberries and raspberries can be found in cleared areas. The BWCAW is estimated to contain 455,000 acres (1,840 km2) of old growth forest, woods that may have burned but have never been logged. Before fire suppression efforts began during the 20th century, forest fires were a natural part of the Boundary Waters ecosystem, with recurrence intervals of 30 to 300 years in most areas.
On July 4, 1999, a powerful wind storm, or derecho, swept across Minnesota, central Ontario, and southern Quebec. Winds as high as 100 miles per hour (160 km/h) knocked down millions of trees, affecting about 370,000 acres (1,500 km2) within the BWCAW and injuring 60 people. This event became known officially as the Boundary Waters – Canadian derecho, commonly referred to as “the Boundary Waters blowdown”. Although campsites and portages were quickly cleared after the storm, an increased risk of wildfire due to the large number of downed trees became a concern. The U.S. Forest Service undertook a schedule of prescribed burns to reduce the forest fuel load in the event of a wildfire.
The first major wildfire within the blowdown area occurred in August 2005, burning 1,335 acres (5.40 km2) between Alpine Lake and Seagull Lake in the northeastern BWCAW. In 2006, two fires at Cavity Lake and Turtle Lake burned more than 30,000 acres (120 km2). In May 2007, the Ham Lake Fire started near the location of the Cavity Lake fire, eventually covering 76,000 acres (310 km2) in Minnesota and Ontario and becoming the most extensive wildfire in Minnesota in 90 years. In 2011, the Pagami Creek Fire ultimately grew to over 92,000 acres (370 km2), spreading beyond the wilderness boundary to threaten homes and businesses. Smoke from the Pagami Creek Fire drifted east and south as far as the Upper Peninsula of Michigan, Ontario, Chicago, Poland, Ukraine, and Russia.
Animals found in the BWCAW include deer, moose, beaver, timber wolves, black bears, bobcats, bald eagles, peregrine falcons and loons. It is within the range of the largest population of wolves in the contiguous United States, as well as an unknown number of Canada lynx. It has also been identified by the American Bird Conservancy as a globally important bird habitat.
Woodland caribou once inhabited the region but have disappeared due to predation by wolves, encroachment by deer, and the effects of a brainworm parasite carried by deer which is harmful to both caribou and moose populations. Very rare sightings have been reported in nearby areas.