Broadleaf forest

A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' Food and Agriculture Organization (FAO) defines a forest as, "Land spanning more than 0.5 hectares with trees higher than 5 meters and a canopy cover of more than 10 percent, or trees able to reach these thresholds ''in situ''. It does not include land that is predominantly under agricultural or urban use." Using this definition, '' Global Forest Resources Assessment 2020'' (FRA 2020) found that forests covered , or approximately 31 percent of the world's land area in 2020.

Forests are the predominant terrestrial ecosystem of Earth, and are found around the globe. More than half of the world's forests are found in only five countries (Brazil, Canada, China, Russia, and the United States). The largest share of forests (45 percent) are in the tropical latitudes, followed by those in the boreal, temperate, and subtropic domains.

Forests account for 75% of the gross primary production of the Earth's biosphere, and contain 80% of the Earth's plant biomass. Net primary production is estimated at 21.9 gigatonnes of biomass per year for tropical forests, 8.1 for temperate forests, and 2.6 for boreal forests.

Forests at different latitudes and elevations, and with different precipitation and evapotranspiration form distinctly different biomes: boreal forests around the North Pole, tropical moist forests and tropical dry forests around the Equator, and temperate forests at the middle latitudes. Areas at higher elevations tend to support forests similar to those at higher latitudes, and the amount of precipitation also affects forest composition.

Almost half the forest area (49 percent) is relatively intact, while 9 percent is found in fragments with little or no connectivity. Tropical rainforests and boreal coniferous forests are the least fragmented, whereas subtropical dry forests and temperate oceanic forests are among the most fragmented. Roughly 80 percent of the world's forest area is found in patches larger than . The remaining 20 percent is located in more than 34 million patches around the world – the vast majority less than in size.

Human society and forests influence each other in both positive and negative ways. Forests provide ecosystem services to humans and serve as tourist attractions. Forests can also affect people's health. Human activities, including unsustainable use of forest resources, can negatively affect forest ecosystems.

Definition

Although the word ''forest'' is commonly used, there is no universally recognised precise definition, with more than 800 definitions of forest used around the world. Although a forest is usually defined by the presence of trees, under many definitions an area completely lacking trees may still be considered a forest if it grew trees in the past, will grow trees in the future, or was legally designated as a forest regardless of vegetation type.

There are three broad categories of definitions of forest in use: administrative, land use, and land cover. Administrative definitions are based primarily upon the legal designations of land, and commonly bear little relationship to its vegetation: land that is legally designated as a forest is defined as such even if no trees are growing on it. Land-use definitions are based on the primary purpose that the land serves. For example, a forest may be defined as any land that is used primarily for production of timber. Under such a land-use definition, cleared roads or infrastructure within an area used for forestry—or areas that have been cleared by harvesting, disease, or fire—are still considered forests, even if they contain no trees. Land-cover definitions define forests based upon the type and density of vegetation growing on the land. Such definitions typically define a forest as an area growing trees above some threshold. These thresholds are typically the number of trees per area (density), the area of ground under the tree canopy (canopy cover) or the section of land that is occupied by the cross-section of tree trunks (basal area). Under such land-cover definitions, an area of land can only be known as forest if it is growing trees. Areas that fail to meet the land-cover definition may be still included while immature trees are present that are expected to meet the definition at maturity.

Under land-use definitions, there is considerable variation on where the cutoff points are between a forest, woodland, and savanna. Under some definitions, to be considered a forest requires very high levels of tree canopy cover, from 60% to 100%, which excludes woodlands and savannas, which have a lower canopy cover. Other definitions consider savannas to be a type of forest, and include all areas with tree canopies over 10%.

Some areas covered with trees are legally defined as agricultural areas, e.g. Norway spruce plantations, under Austrian forest law, when the trees are being grown as Christmas trees and are below a certain height.

Etymology

The word ''forest'' derives from the Old French ''forest'' (also ''forès''), denoting "forest, vast expanse covered by trees"; ''forest'' was first introduced into English as the word denoting wild land set aside for hunting without necessarily having trees on the land. Possibly a borrowing, probably via Frankish or Old High German, of the Medieval Latin , denoting "open wood", Carolingian scribes first used ''foresta'' in the capitularies of Charlemagne, specifically to denote the royal hunting grounds of the king. The word was not endemic to the Romance languages, e.g., native words for ''forest'' in the Romance languages derived from the Latin