The Appalachian temperate rainforest, also called the Appalachian cloud forest, is found in the southern Appalachian Mountains of the eastern United States. It is one of the most diverse temperate regions in the world. This rainforest is mainly located in the Southern Appalachian spruce–fir forests between southwestern Virginia and southwestern North Carolina. It has a cool, mild climate with temperatures and rainfall that change a lot depending on elevation. The entire temperate rainforest has an average yearly temperature near 7°C (45°F) and receives more than 140 centimeters (55 inches) of rain each year. Higher mountain peaks can get over 200 centimeters (79 inches) of rain and are often covered in fog.
Because the climate varies at different elevations, the rainforest can support both northern and southern species. Some species had to move south during the Last Ice Age. At higher elevations, the forest is dominated by evergreen spruce and fir trees, while lower areas have deciduous cove forests. The ecosystem includes thousands of plant species, such as epiphytes, orchids, mosses, and ferns. It is also home to many animals and fungi, including endangered and species found only in this area. This region has the highest numbers of mushrooms, salamanders, land snails, and millipedes in the world.
For the last 12,000 years, humans have influenced the rainforest through activities like hunting and farming. These impacts increased after European colonization, which led to changes such as the decline of native populations, changes in land use, and the arrival of non-native species. By the 1880s, industrialization caused serious damage to the forest through mining, logging, and invasive species like chestnut blight and the balsam woolly adelgid. Conservation efforts, such as creating national forests and parks, have helped protect the ecosystem. However, the rainforest still faces challenges like wildfires and climate change.
Definition
To be classified as a rainforest, the area must receive at least 140 cm (55 in) of rainfall each year. A temperate rainforest differs from a tropical rainforest because it has an average yearly temperature between 4 and 12 degrees Celsius (39 and 54 degrees Fahrenheit). Some sources suggest that areas receiving at least 50 inches of rainfall annually may also be considered rainforests. However, the book Temperate and Boreal Rainforests of the World states that temperate rainforests require at least 1,200 mm (47.24 inches) of average annual rainfall. According to Alaback, temperate rainforests must also meet additional conditions: at least 10% of their yearly rainfall should occur during summer months; summers must be cool and often cloudy, with average July temperatures below 16 degrees Celsius (60.8 degrees Fahrenheit); forest fires should be rare and not significantly affect the ecosystem; and the forest must be dense, lush, and have a rich layer of plants growing beneath the trees, as well as plants that grow on other plants, such as epiphytes.
Climate
The Appalachian temperate rainforest has a cool and mild climate that fits the definition of temperate rainforests described by forest ecologist Paul Alaback. Temperature and rainfall change greatly with elevation, and rainforest conditions are often found in spruce–fir forests at higher elevations, though not always. These spruce–fir forests have an average yearly temperature of 6.5 °C (43.7 °F) and an average temperature during the growing season (May–September) of 13.5 °C (56.3 °F). However, this temperature may be slightly cooler than the average for the entire rainforest ecosystem. The area receives more than 140 centimeters (55 inches) of rain each year, has cool summers, occasional snow in winter, and an average yearly temperature near 7 °C (45 °F). Summer rainfall makes up more than 10% of total yearly rainfall, which classifies it as a perhumid temperate rainforest.
Rainfall amounts vary widely across the mountainous region, with the highest rainfall in southwest North Carolina. High-elevation areas with spruce–fir forests receive more than 2,000 millimeters (79 inches) of rain annually, while lower-elevation rainforest areas receive more than 1,525 millimeters (60 inches). This pattern is mainly caused by the movement of southerly winds. When moist air from the Gulf of Mexico and the western Atlantic Ocean rises over the mountains, it creates rainfall. During winter and spring, more rain falls in the southern areas. In summer, weaker upward air movement brings more rain to the highest elevations, and autumn is usually the driest season, with occasional heavy rain from tropical storms.
In addition to rainfall from mountains pushing air upward, cloud cover reduces water loss because of low evapotranspiration. High-elevation forests are covered by clouds on 65% of growth-season days, leading some sources to call the rainforest a cloud forest. Water collected from clouds accounts for 25% to 50% of yearly rainfall, which is a high rate. For comparison, fog in the boreal rainforests of Eastern Canada contributes only 5 to 8% of yearly rainfall. According to a classification proposed by DellaSala, Alaback, Spribille, Wehrden, and Nauman in 2011, high-elevation temperate rainforest areas in Central Appalachia might be considered a southern extension of Appalachian boreal rainforests from Eastern Canada. However, this idea needs more research to confirm.
Locations
The Appalachian temperate rainforest is found in western North Carolina and eastern Tennessee. In western North Carolina, the rainforest includes areas such as Pisgah National Forest, Nantahala National Forest, Gorges State Park, DuPont State Forest, Chatahoochee-Oconee National Forest, and other parts of the Blue Ridge Mountains. The Great Smoky Mountains National Park, which covers parts of North Carolina and Tennessee, is also part of the rainforest. The Appalachian temperate rainforest includes mountains in northern Georgia, such as the Chattahoochee–Oconee National Forest, as well as areas in southwestern Virginia, northwestern South Carolina, and southeastern Kentucky. The wettest place in the Appalachian temperate rainforest is Nantahala National Forest, where some areas receive more than 100 inches of rain each year. This makes Nantahala one of the wettest places in the continental United States, after the Pacific Northwest region.
Ecology
High rainfall, steady temperatures throughout the year, and varied landscapes allow many different types of plants and animals to live in the rainforest. The rainforest has more types of living things than any similar area in temperate regions. For example, over 19,000 species have been found in Great Smoky Mountains National Park. Scientists think the actual number of species may be as high as 100,000 or more. The rainforest is also home to many species that are at risk of disappearing, found only in this area, or protected by law, including plants, fungi, insects, fish, mammals, shellfish, and amphibians.
Red spruce and Fraser fir are the main trees in high mountain areas. In areas above 1,980 meters (6,500 feet), Fraser fir is most common. In areas between 1,675 and 1,890 meters (5,495 to 6,201 feet), red spruce and Fraser fir grow together. In areas between 1,370 and 1,650 meters (4,490 to 5,410 feet), red spruce is most common. Trees like Yellow birch, mountain ash, mountain maple, younger spruce and fir, and shrubs such as raspberry, blackberry, hobblebush, southern mountain cranberries, red elderberry, minniebush, and southern bush honeysuckle grow beneath the main trees. At around 1,200 meters (3,900 feet), the forest changes to include more trees that lose their leaves, such as American beech, maple, birch, and oak. American rhododendron is the main shrub in the leafy forest layer but is rarely found in spruce–fir forests. Eastern skunk cabbage and common juniper are plants that survived after glaciers moved away. The American sycamore (Platanus occidentalis) is found in several places.
In addition to more than 100 types of native trees, 1,400 other flowering plants and 500 species of moss and fern live in the rainforest. These include many wildflowers and orchids that depend on fungi. The rainforest’s high humidity allows plants that grow on other plants to live at greater heights and in greater numbers than anywhere else in the eastern United States. Mosses, ferns, and liverworts have been found as high as 140 feet (43 meters) above the ground. These include common plants like resurrection fern, the rare liverwort Bazzania nudicaulis, and plants that only grow on the ground in other areas, such as Appalachian rockcap fern, rose moss, and narrow-fruited crisp-moss. Vines are also common, especially in leafy forests, with Virginia creeper, poison ivy, and grapevines being the most common.
The rainforest is home to the greatest number of salamanders in the world, with 30 identified species. Some of these are found only in this region, including the black mountain salamander, southern dusky salamander, red-cheeked salamander, and Cheat Mountain salamander. Many salamanders in this area do not have lungs and instead breathe through their skin, so the wet environment of decaying trees and moist leaves helps them survive.
Larger animals in the rainforest include the American black bear, white-tailed deer, wild turkey, and groundhog. Many large animals once lived in the area but were lost due to changes in land use and hunting caused by European settlers. These include bison, elk, mountain lion, gray wolf, red wolf, fisher, river otter, peregrine falcon, and several types of fish. Northern species like the Carolina northern flying squirrel, American red squirrel, and saw-whet owl remain in the area because of the cool climate. Mollusks and millipedes have the highest diversity in the region, with about 150 species of land snails and 230 species of millipedes recorded so far. Scientists believe the actual numbers are much higher. The rainforest is also home to 460 species of arachnids, including the endangered spruce–fir moss spider, which lives nowhere else in the world.
The wet mountain environment supports one of the highest numbers of fungi in the world, including lichens, sac fungi, molds, and mushrooms. Over 2,300 species have been identified in the area, and scientists think the actual number may be as high as 20,000. Of the species found so far, 800 (40%) are lichens.
History
The Appalachian Mountains started forming 460 million years ago when large pieces of Earth’s crust, called tectonic plates, collided. They finished rising around 230 million years ago. During the Last Ice Age, ice covered much of northern North America, but the southern part of the Appalachian Mountains stayed free of ice. This ice-free area became a safe place for species forced to move south. After the ice melted, some species returned north, but many remained in the southern Appalachians. Because temperatures get colder as elevation increases, the varied mountain landscape creates small areas with climates similar to both northern and southern regions. This, along with a stable climate year-round, allows species from both areas to live near each other, contributing to the region’s high biodiversity.
About 12,000 years ago, early Native American groups, called Paleo-Indians, first settled in the Southern Appalachians. They made stone tools from local materials, showing they lived there for a long time. Evidence of homes in the highlands is not found until around 7,500 BCE, but hunting, making tools from flint, processing animal hides, and working with wood were common in the area. During the Archaic period, these groups used more advanced tools like woven fabrics, baskets, and a spear-throwing device called an atlatl. They shifted from relying mostly on hunting and gathering to fishing and growing crops in lowland areas. Human activity helped spread edible plants, such as trees, shrubs, grasses, and climbing plants.
Cultural changes happened faster in the highlands during the Middle Woodland period when agriculture was adopted, though this happened later than in lowland areas because of rough terrain, few people, poor soil, and a short growing season. By around 1000 CE, farming expanded with the use of crops like corn, beans, pumpkins, squash, and tobacco. More complex societies formed around permanent villages in Appalachian river valleys. At the same time, human activity shaped the landscape into a mix of towns, farms, fields, and forests used for hunting and gathering.
When Europeans arrived in the region, Native American populations declined quickly because of European settlers and diseases from Europe. This caused many Native American societies to break down. European trade and exploration brought iron tools, foreign plants and animals, and conflicts with Native Americans. With fewer people, many farmed areas were taken over by forests. After the American Revolution, European settlers moved westward more freely, and Euro-American communities grew. However, groups like the Chickamauga Cherokee resisted, slowing European expansion into the rainforest region until 1790.
Roads were built quickly, and by the early 1800s, the United States controlled the area. Valleys were farmed heavily, but high-elevation areas saw little change in land use, though European animals were introduced. Most industries remained agricultural until the 1880s, when logging and small-scale mining for gold and copper began. During this time, rewards for killing predators led to their near extinction, and species like bison and elk disappeared. Trapping also reduced populations of animals with fur. Most of the Cherokee Nation was forced to move from their homeland to Oklahoma during the Trail of Tears. However, about 9,000 Cherokee people still live in the Qualla Boundary, which is within the rainforest biome.
By the 1880s, Appalachia’s natural resources attracted industrialists and vacationers from the North, who bought land and expanded railroads. While coal is famous in Appalachia, mica mining was more common in rainforest areas, and logging was mostly limited to valleys near rail lines. As outside investors bought more land and railroads grew, large areas of forest were cleared. By the 1900s and 1910s, even the spruce–fir forests on Mount Mitchell—the highest peak in the Appalachian Mountains—were logged.
The early 1900s were very harmful to the rainforest. Animals like wolves, beavers, and mountain lions disappeared, and populations of bears, turkeys, and deer dropped sharply. Invasive species, such as chestnut blight, wild boar, and rainbow trout, were introduced. In 1907, severe flooding of the Monongahela and Ohio Rivers was linked to the clearing of forests upstream. Encouraged by these events and the work of the Appalachian National Park Association (founded in 1899), Congress passed the Weeks Act in 1911 to buy land for federal protection. Starting with the creation of Pisgah National Forest in 1916, much of the rainforest area is now preserved.
Threats
Wildfires are a natural event that has happened in the Southern Appalachian temperate rainforest for thousands of years. They play an important role in the ecosystem. However, after European colonization, efforts to stop wildfires created two major problems: a greater chance of large, dangerous wildfires and a decrease in species that depend on disturbances like fire, such as Table Mountain pine and woodpeckers. After the 2016 Great Smoky Mountains wildfires, the National Park Service began using controlled burns to help species that benefit from fire and to reduce piles of dead wood and brush that could cause dangerous wildfires during droughts. Natural wildfires in the rainforest most often occur in May, when lightning is common in some years.
High peaks in the temperate rainforest have some of the highest air pollution levels in the Eastern United States. A 1999 study found that sulfate and nitrate levels in these areas were 6–20 times higher than in lower elevation sites. This is mainly because pollutants from cars and power plants settle in Appalachian valleys and are trapped by high mountain ridges. However, since this pollution is mostly carried by acid fog, the wettest areas receive the most pollution. This pollution often has a pH below 4.0, sometimes below 3.0, which can harm tree health and cause serious nutrient shortages.
Anthropogenic climate change will likely have many effects on the rainforest, some of which are hard to predict. These effects may be most noticeable in high-elevation spruce–fir forests, which depend on cold temperatures and fog. Changes in cloud patterns or height could disrupt the water supply these forests rely on, forcing them to move uphill until they disappear. However, it is thought that higher elevations might be more resistant to climate change. Climate change is also expected to increase the frequency of wildfires and put more stress on forests, making them more vulnerable to existing threats.
Invasive species have caused major harm to the Appalachian temperate rainforest. Two major events since the early 20th century include the chestnut blight, which was introduced from Asia and killed most American chestnut trees. These trees once made up as much as 25% of hardwood forests but are now critically endangered and nearly gone from their natural range. Another invasive species, the balsam woolly adelgid from Europe, caused widespread death of fraser fir trees on mountaintops. By 1970, fir mortality in Appalachia had increased by 1,600%, killing two-thirds of adult trees. Though some recovery has been seen, such as increased fir numbers in Kuwohi by 2020, scientists warn that climate change could lead to future outbreaks. Kristine Johnson, a supervisory forester at the Great Smoky Mountains National Park, has noted that warmer winters and drier summers might support new adelgid infestations.