Forest and forestry

Forest and forestry

A plant community consisting predominantly of trees and other woody vegetation, growing closely together, is a forest. Forests cover about one-fourth of the land area on Earth. The trees can be large and densely packed, as they are in the coastal forests of the Pacific Northwest, or they can be relatively small and sparsely scattered, as they are in the dry tropical forests of sub-Saharan Africa.

Forests are complex ecosystems that also include soils and decaying organic matter, fungi and bacteria, herbs and shrubs, vines and lichens, ferns and mosses, insects and spiders, reptiles and amphibians, birds and mammals, and many other organisms. All of these components constitute an intricate web with many interconnections. See Forest ecosystem

Forests have important functions, such as cleansing the air, moderating the climate, filtering water, cycling nutrients, providing habitat, and performing a number of other vital environmental services. They also supply a variety of valuable products ranging from pharmaceuticals and greenery to lumber and paper products.

Forest types

There are many ways to classify forests, as by (1) location (for example, temperate zone forests, tropical zone forests); (2) ownership (for example, public forests, private forests); (3) age or origin (for example, old-growth forests, second-growth forests, plantation forests); (4) important species (such as Douglas-fir forests, redwood forests); (5) economic and social importance (for example, commercial forests, noncommercial forests, urban forests, wilderness); (6) wood properties (for example, hardwood forests, softwood forests); (7) botanical makeup (for example, broadleaf forests, evergreen forests); or (8) a combination of features (such as moist temperate coniferous forests, dry tropical deciduous forests). The last approach tends to be the most descriptive because it often integrates several dominant characteristics related to climate, geography, and botanical features.

Some examples of the major forest types are: Northern coniferous forests which span the cold, northern latitudes of Canada and Europe; Temperate mixed forests which occupy the eastern United States, southeastern Canada, central Europe, Japan, and East Asia, and parts of the Southern Hemisphere in Chile, Argentina, Australia, and New Zealand; Temperate rainforests which are situated along moist, coastal regions of the Pacific Northwest, southern Chile, southeastern Australia, and Tasmania; Tropical rainforests which are found in the equatorial regions of Central and South America (for example, Costa Rica, Brazil, and Ecuador); on the west coast of Africa (for example, Congo, Ivory Coast, and Nigeria); and Southeast Asia (for example, Thailand, Malaysia, and Indonesia); Dry forests which occur in the southwestern United States, the Mediterranean region, sub-Saharan Africa, and semiarid regions of Mexico, India, and Central and South America; and mountain forests which are characteristic of mountainous regions throughout the world.


Although forests take a variety of forms, they have several features in common that allow them to develop in their respective environments. Forests generally contain a broad array of species, each of which is well adapted to the environmental conditions of the region. This biodiversity and adaptability help the forests cope with natural (and in some cases human-caused) forces of destruction, including wildfire, windstorms, floods, and pests. This built-in resiliency also allows the periodic extraction of wood and other products without jeopardizing the long-term health and productivity of the ecosystems—provided such harvesting operations are performed with care. Forests are dynamic—they are constantly changing at both landscape and smaller scales of resolution. This natural propensity to change and develop over time is called forest succession. Forests have a mitigating influence on the environment. This characteristic not only facilitates their own survival and development but also moderates the surrounding climate.

Ecological processes and hydrologic cycle

Forests play a vital role in ecological processes. From a global perspective, they help convert carbon dioxide in the atmosphere to oxygen, thereby facilitating life for aerobic organisms. Forests can also capture, store, convert, and recycle a variety of nutrients such as nitrogen, phosphorus, and sulfur. Forests also play a critical role in the hydrologic cycle. Finally, forests play a crucial ecological role in the habitat that they provide for countless organisms. See Ecological succession

Forestry and forest management

The Society of American Foresters defines forestry as the science, the art, and the practice of managing and using for human benefit the natural resources that occur on and in association with forest lands. Natural resources have traditionally entailed major commodities such as wood, forage, water, wildlife, and recreation. However, the concept of forestry has expanded to encompass consideration of the entire forest ecosystem, ranging from mushrooms to landscapes. The practice of forestry requires in-depth knowledge of the complex biological nature of the forest. It also requires an understanding of geology and soils, climate and weather, fish and wildlife, forest growth and development, and social and economic factors. Foresters, wildlife managers, park rangers, and other natural resource specialists are trained in biology, physics, chemistry, mathematics, statistics, computer science, communications, economics, and sociology.

Silviculture is the art, science, and practice of controlling the establishment, composition, and growth of a forest. It entails the use of both natural and induced processes to foster forest development. For example, reforestation of a harvested or burned-over area can be accomplished by natural seeding from nearby trees or by planting seedlings. See Reforestation

Laws and policies

The management of forest land in the United States is regulated by numerous laws and policies. Federal agencies must comply with laws such as the National Forest Management Act (1976), the Forest and Rangeland Renewable Resources Planning Act (1974), and the National Environmental Policy Act (1969). Other public and private forest landowners generally must comply with state regulations or guidelines designed to promote sound forest stewardship in their respective regions. Policy makers in government, industry, environmental organizations, and the private sector strive to balance the multitude of interests surrounding forest resources. Input from the public as well as resource managers and specialists is a crucial ingredient in the process.

Utilization of forest resources

Forests are often focused on particular uses. For example, plantation forests are generally designed to produce wood and fiber products. Conversely, public forests are increasingly devoted to nonconsumptive purposes such as the preservation of biodiversity, natural conditions, and scenic vistas. However, all forests can provide multiple benefits, including harvestable products, watershed protection, recreation opportunities, wildlife habitat, and ecological services. See Forest genetics

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
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