When you hear the word “forest,” what comes to mind? Many people think first of trees. These people are correct, but only partly correct. Trees, of course, are the foundation of a forest. An area without trees is not a forest at all. However, a forest is much more than trees. In addition to trees, forests include many other living and non-living parts. The living parts include other plants like shrubs, vines, grasses, flowers, mosses, and algae. Living parts also include animals like insects, mammals, birds, fish, reptiles, and amphibians (Figure 1, Figure 2, and Figure 3). Fungi and bacteria, which have characteristics of both plants and animals, are also in forests (Figure 4). Nonliving parts of forests include soil, water, rocks, and minerals.

All of the living parts of a forest interact with each other and with the nonliving parts. These living and nonliving parts create a complex community known as an ecosystem. Forest ecosystems help sustain the lives of everything on Earth.

Forests play a role in moving nutrients from on living things, such as the soil, to living organisms and back. Forests store and release gases such as carbon dioxide, nitrogen, and oxygen. Forests store elements such as carbon and molecular compounds such as water, and provide a way for these elements and compounds to move into, throughout, and out of the ecosystem (Figure 5).

Forests contain a diversity of life. This diversity of life is called biodiversity. In most forests, you will find a wide diversity of plants and animals. These plants and animals live together and keep the ecosystem in balance over time.

A diversity of plants and animals, however, is just one kind of biodiversity. Biodiversity can be found within the same genus or species of a plant or animal (Figure 7). One tree of the same species may grow taller or one deer may run faster than another. These differences may give one plant or animal an advantage over another.

Primary forests are a type of natural forest. Primary forests contain native tree species. In primary forests, human activities are not noticeable and the forest’s ecological processes are not widely disturbed. Primary forests help conserve the diversity of animal and plant species and protect natural ecosystems (Figure 8).

In 2015, 33 percent of the world’s forests were primary forests. These forests covered 1.3 billion hectares, and half of these forests were in the tropical ecozone. Look at Figure 9 and Figure 10. Which continent had the highest amount of primary forest hectares in 2015? Which continent had the highest percentage of primary forest area as a percentage of its total forest area?

Between 1990 and 2015, the amount of primary forest has been changing on each of the world’s continents. What patterns do you observe in Figure 11?

Some forests are managed to protect biodiversity. This type of forest management occurs in 13 percent of the world’s forests (Figure 12 and Figure 13). These forests cover 524 million hectares. Worldwide, the amount of forest land set aside to protect biodiversity has slightly increased since 1990.

The United States of America and Brazil have set aside the largest areas of forested hectares to protect biodiversity. Venezuela and Mexico, however, have reported the largest percentage of their forested land area set aside and managed for biodiversity. Over half of Venezuela’s forests are set aside to protect biodiversity.

Governments sometimes protect forests by giving them a special legal status. When a forest area is protected legally, it must be managed according to the law that established the area. Usually, these laws protect the area from human
activities that might change the forest’s natural character. Worldwide, 651 million hectares of forest are found within protected areas (Figure 14 and Figure 15).

Seventeen percent of the world’s forests are legally protected from damaging human activities. Worldwide since 1990, the number of hectares in protected areas has increased by 200 million. Of these additional 200 million hectares, 143 million hectares are in the tropical ecozone (Figure 16).

What is one element that your body shares with the rest of Earth’s living things? If you guessed carbon, you are correct! Carbon is one of Earth’s 118 elements. Carbon is needed for the growth, survival, and reproduction of living things. Carbon can form bonds with other elements to create compounds. One carbon compound you may have heard about is carbon dioxide. Carbon dioxide is a compound formed from carbon and oxygen atoms.

Carbon moves throughout Earth and Earth’s atmosphere in a cycle. This movement is called the carbon cycle (Figure 17). When the carbon cycle is balanced, Earth’s living systems are more likely to remain in healthy balance as well. One of the ways that the carbon cycle becomes unbalanced is when too much carbon goes into the atmosphere in the form of carbon dioxide. As the carbon cycle becomes unbalanced, Earth’s climate responds by changing over time.

When Earth’s carbon is cycled, a balanced percentage of Earth’s carbon remains on Earth. This carbon is stored in living things such as trees, forests, animals, and the remains of living things, as well as nonliving things like soil, freshwater, and oceans. Forests and forest soils store a large amount of the world’s carbon.

FAO has estimated the amount of carbon being stored in the world’s forests as 296 gigatonnes (Gt). One Gt is equal to 1 billion tonnes. One tonne is equal to 1 000 kilograms, or 2,205 pounds. This estimate includes carbon stored in vegetation above and below the ground. The forests of South America and west and central Africa store about 120 tonnes of carbon per hectare (Figure 18 and Figure 19). Worldwide, in comparison, forests store an average of 73 tonnes of carbon per hectare.

Over the past 25 years, the amount of carbon stored by forests has decreased by almost 11 Gt. This decrease is mostly due to felling trees and replacing forests with crops and human settlements. Sometimes, forests are not completely destroyed. However, when forests are degraded but not destroyed, they still store less carbon than healthy forests.

Have you ever heard the term “ecosystem services”? Can you imagine what ecosystem services might be?

Ecosystem services are provided by healthy forests and other healthy ecosystems. Ecosystem services are valued by people, even if people do not always think about where these services come from. Examples of ecosystem services include (Figures 21 to 23):
• Clean air
• Clean water
• Beautiful landscapes
• Healthy soil
• Wildlife habitat
• Places for outdoor recreation

Ecosystem services are important because they provide goods and services that are vital to human health and quality of life. Ecosystem services are called “public goods” because they are available to everyone, such as clean air. Carbon storage, which you read about in the previous section, is an ecosystem service. Soil and water protection are two important ecosystem services that you will learn about in the next section.

FAO is interested in learning whether people living in different cultures value their forests for ecosystem services. FAO is interested in how nearby forests support local culture and how forests are used for spiritual renewal. Since 1990, more of the world’s forests are being managed for ecosystem services, and cultural and spiritual values (Figure 24 to Figure 26).

Soil and water protection are two ecosystem services. These two particular ecosystem services are vital to human health. Where would we be without healthy soil? Can you imagine a world where the soil could not support crops, trees, and other plant life? Life as we know it depends on healthy soil.

A forest floor is covered with a layer of decaying leaves, sticks, and trees, or litter. As litter decays over time, it creates a layer of soil that is protected from heavy rainfall by the forest canopy (Figure 28). Without forest cover, the rich top level of soil is easily worn away by rain and wind (Figure 29). Tree roots and the roots of other plants also help hold the soil in place. Forested areas reduce the impact of heavy rains because trees slow down the flow of rainwater. When rainfall is slowed, less soil erosion occurs. When rainfall falls on forest litter, the litter slows the runoff and reduces soil
erosion into streams. In a healthy forest, rainfall seeps through the leaf litter to the soil beneath. Forest soils filter out sediment and pollutants that might be in water before the water flows into streams and rivers.

Clean water is another of Earth’s most important natural resources. All of our planet’s organisms need water. Some small amounts of water may come to Earth from outside of our atmosphere, such as from meteors. Practically speaking, however, water found on Earth is our water supply today and into the future. The water you drink today was on Earth even before the dinosaurs lived!

Water moves from Earth’s atmosphere, to its surface and underground, and then back to the atmosphere in a continuous cycle. See Figure 5 for an illustration of the water cycle.

Just over 70 percent of Earth’s surface is covered by water. Of this surface area, 97.5 percent is saltwater. Saltwater is found in oceans, bays, and other coastal areas. Take a look at a globe or a map of Earth. You will see for yourself just how much saltwater is found on our planet. The remaining 2.5 percent of Earth’s water is freshwater. Humans must have clean freshwater to live (Figure 30).

Worldwide, about one-third of forests are managed for soil and water protection (Figure 31 and Figure 32). In the last 25 years, about 117 million more hectares of forest area have been designated for soil and water protection (Figure 33).

Forests provide a wide variety of benefits. You have just learned about the ecosystem services provided by healthy forests. You may already know about the wood products that
forests provide. FAO has noted that “wood is a part of almost everyone’s life.” The list of wood products used by people includes wood fuel (wood used for cooking fires or for heating), construction material, furniture, paper, pencils, baseball bats, and fence posts (Figures 34, 35, and 36). Look around you and see if you can identify products made from wood.

Roundwood is used for non-fuel purposes. Roundwood is felled in its natural state, with or without bark (Figure 37). After being harvested, roundwood is either left in its round state or is cut into sheets, squares, or other forms. Roundwood may also be crushed into small pieces called pulp, which is then used to make paper products.

Close to 1.2 billion hectares of forest land are managed for wood production worldwide, and the amount of wood removals is increasing (Figure 38). In 2011, about 3 billion cubic meters of wood were removed from forests worldwide
(Figure 39).

Worldwide, woodfuel is used for about half of total wood removals from forests. Most woodfuel worldwide is removed from forests in countries with lower income levels. In these low-income countries, about 93 percent of wood removals
are for woodfuel.

Forests also provide non-wood products that people buy and use. Examples of non-wood products include food and food additives, such as edible nuts, mushrooms, fruits, herbs, spices, aromatic plants, and game animals (Figure 40).

Other non-wood products include fibers used in construction, furniture, clothing, or utensils. Non-wood products also include resins, gums, and plant and animal products used for medicinal, cosmetic, or cultural purposes. Non-wood removals provide a livelihood for many people and provide income for industries that use these products (Figure 41).

The Republic of Korea, Portugal, the Czech Republic, and Tunisia all reported a high value for their non-wood forest products in 2010 (Figure 42).