The middle latitudes of Earth have seasons of weather and a wide diversity of landscapes and vegetation. But not many mid-latitude locations have year-round greenery and distinct seasons, as they do in central Maine.
The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 satellite captured these images centered on the small towns of Howland and West Enfield, Maine, on April 14 and July 15, 2008. Though spring begins on March 20, central Maine was still shedding its blanket of winter snow in mid-April, revealing brown farmland, deciduous forest, and shrubland that struggle to sprout buds in the raw springtime of New England. By July, the landscape is covered in bright green of full growth. (Visit this page to see five more images across the seasons.)
One constant in the images is the green, as Maine has the highest percentage of forest cover in the United States (about 86 percent). Central Maine lies along the transition between northeastern hardwood trees and softwood coniferous species. The area has long been a rich source of lumber, a major supplier for the United States and the world since the 19th century. Logging is still a key industry, supporting thousands of jobs in the state.
Deciduous trees, such as red oak and white ash, appear to line the rivers and streams and the residential areas shown above. But it is the evergreen trees that dominate the forest canopy, particularly spruce, cedar, hemlock, and white pine. Fir trees were once abundant, but many were wiped out in the 1960s and 70s by budworm infestations. These evergreens hold their color throughout the year and cover much of the landscape, even standing above the winter snowfall.
The patchwork of forest has been a boon to research. On a tract southwest of the towns (image lower left), the Howland Research Forest is the site of long-term scientific studies supported by NASA, the National Science Foundation, the U.S. Forest Service, the U.S. Department of Agriculture, and the U.S. Department of Energy. Researchers have observed the effects of acid rain; examined the cycling of nutrients through soils; and continually measured how much carbon dioxide the trees absorb, store, and return to the atmosphere. The Howland Forest is also a key natural laboratory for observing long-term ecosystem changes.
The Penobscot River watershed has been undergoing a renaissance in recent years, as two dams have been removed to restore habitat for salmon, bass, and other fish that have had their passage blocked for nearly two centuries. The Howland Dam (image center, at the confluence) will soon be decommissioned as well, and a fish bypass will be built.
The landscape around West Enfield and Howland is mostly flat and about 70 meters (230 feet) above sea level. The area was buried under rivers of ice during the last Ice Age. Then, when the glaciers retreated, the area was underwater until the landmass bounced back from the weight of the ice cover. Fossil shells and marine clays can still be found amidst the peat soils, glacial tills, bogs, and wetlands.
NASA Earth Observatory images by Robert Simmon and Jesse Allen, using Advanced Land Imager data from the NASA EO-1 team. Caption by Mike Carlowicz.
In British Columbia’s Coast Mountains, some 200 kilometers (125 miles) inland from the Pacific Ocean, rivers and lakes cut tortuous paths through rugged terrain. The peaks and valleys in this region are covered with forest, but the forest has changed over the years due to human use and insect pests, in particular, the mountain pine beetle.