Before we learn more about the world’s forests, let’s think about the place on which these forests grow. What do we call this place? If you guessed Earth, you are correct! We know that Earth spins on its axis and revolves around the Sun. The area near the Equator is closest to the Sun. Earth is warmest near the Equator and coolest near the North Pole and the South Pole. The distance from the Equator, along with other factors, influence what kind of forests grow in particular areas on Earth (Figure 1).

At higher elevations, the climate is cooler (Figure 2). The top level of any ocean is called sea level. The height of the land above sea level is called its elevation.

Across Earth, different areas receive different amounts of precipitation. Plants need water to survive and have adapted over time to live with varying amounts of precipitation. Some plants, such as those in tropical rain forests, need a lot of water to survive. Other plants, like those in deserts, have adapted to conserve the water they receive. Therefore, they need much less water. Drier areas have fewer plants and trees. Some areas have no plants or trees at all.

The three things that we have just explored are latitude, elevation, and precipitation. These three things influence the type of forest that grows naturally in a particular area on Earth (Figure 3).

Different types of forests are found across the planet. In one area, a forest may be dry with little vegetation. In another, a forest may contain large trees that grow quickly because of high precipitation and fertile soil. Different types of forests exist because they grow under different climates. These different climates result in different ecological zones, or ecozones (Figure 4). Another reason different types of forests exist is that human activities have changed some of the forests. These activities include actions such as felling or planting trees.

Natural events can change Earth’s forests. For example, forests may change as a result of hurricanes and typhoons. Earth’s forests are also being changed by something else. It was this influence that FAO was most interested in understanding. What influence did the scientists want to understand?

If you guessed humans, you are correct! FAO wanted to understand how forests are changing as a result of human activity. To study the influence of humans on forests, the scientists classified the world’s forests into two categories (Table 1).

Combining the natural and planted forest categories, the world’s forests cover a little less than 4 billion hectares (Figure 8 and Figure 9).

This is about 31 percent of Earth’s land surface. Of these forested hectares, 54 percent are in the following countries: Brazil, Canada, China, the Russian Federation, and the United States of America. Most of the world’s forests are in natural forest area (Figure 10 and Figure 11).

In the past 25 years worldwide, the amount of area that makes up the world’s forests has slightly declined (Figure 12 and Figure 13). Even though the amount of forest has decreased, the rate of forest loss has been reduced by over 50 percent. Between the periods 1990-2000 and 2010-2015, the annual loss went from 7.3 million hectares per year to 3.3 million hectares per year.

In 1990, the world’s forests covered 4128 million hectares. By 2015, 129 million hectares of forest land had been lost. This is a change from 31.6 percent of the world’s land area in 1990 to 30.6 percent in 2015. This loss is equal to an area about the size of South Africa. Most forest area was lost in the tropical ecozone, and most of this loss was in South America and Africa (Figure 14).

The percentage of forest area in each country varies (Figure 15). For countries that have a small percentage of their total area in forests, forest loss might be more noticeable.

Natural forests decrease when forests are lost to other land uses. For example, trees may be felled to plant food crops or to build roads and buildings (Figure 16).

Constructing roads and buildings is not the only way that trees and forests are lost. Trees and forests can also be lost to insects and other threats, such as invasive fungi, forest fires, or hurricanes and typhoons.

Between 1990 and 2015, most of the world’s natural forest area loss took place in the tropical ecozones (see Figure 4). In the temperate ecozones, natural forest area has been increasing since 1990. The boreal and subtropical ecozones have had little change in forest area over the same 25 years.

FAO is interested in how the amount of natural and planted forests on our planet has changed. Recall that natural forests are forests with native tree species and little evidence of human activities. FAO discovered that natural forests have been declining in area, and planted forests have increased in area (Figure 17 and Figure 18). Planted forest area increased 105 million hectares between 1990 and 2015, about 4.2 million hectares per year.

Planted forests made up 7 percent of the world’s forests in 2015. FAO scientists expect that planted forests will increase in area, particularly in the boreal ecozone (see Figure 4).

Another way scientists understand the amount of forest land in an area is to compare it with the number of people living in the area. This can be done within a community, a country, a continent, or across our planet. The calculated figure is called per capita, meaning the amount of something per person. Consider the 25 years between 1990 and 2015. During that time, the world’s population increased by 2.1 billion people, and over 100 million hectares of forest land were lost. The amount of forest land per person, therefore, has decreased over the past 25 years (Figure 19).

Although the world’s natural forest area has declined in area over the past 25 years, 93 percent of the world’s forests are still natural. Regardless of whether a forest has grown naturally or has been planted, people worldwide gain important benefits from their forests.

FAO has classified the world’s forests into two categories: natural forests and planted forests. If you live in an urban area, however, you might have a third kind of forest nearby. The trees in this forest may have germinated and grown without human assistance, or the trees may have been planted. Usually, the trees in this kind of forest are surrounded by grass and other landscaped areas or even roads and buildings. According to FAO, these forests may include individual trees or groups of trees. This kind of forest is called an urban forest, and it is often found as a part of urban parks (Figure 20).

Urban forests provide many of the same benefits as natural forests. Some urban forests, for example, are found along rivers and provide a place for rivers to flood during high rainfall. Urban forests and parks provide beautiful places for people to walk, play, picnic, and rest. Urban forests also provide homes for wildlife, reduce erosion into urban waterways, and help keep urban areas cooler in hot weather.