Forest

A forest is a huge area filled with many trees.

Scientists use many different ways to define a forest. Some look at how many trees grow close together. Others look at how tall the trees are. The Food and Agriculture Organization (FAO) uses specific rules. They say a forest must be more than 0.5 hectares. The trees must be higher than 5 meters. They also need a canopy cover of more than 10 percent.

This canopy is the top layer of leaves and branches. Forests are the largest land ecosystems on our planet. In 2020, they covered about 31 percent of the Earth's land. This is about 4.06 billion hectares.

Forests work in many different ways depending on where they are. They form different biomes based on the climate and rain.

Tropical moist forests grow near the Equator. Boreal forests grow in cold, subarctic climates. Temperate forests grow in the middle latitudes. Trees can even change how much rain falls. In the Amazon, trees release water from their leaves. This happens in anticipation of seasonal rains. This process can trigger the wet season two to three months early. If trees are removed, the land might change into a dry savanna. This happens if tree cover drops below 40 to 45 percent.

Forests have been part of Earth for a very long time. The first forests appeared about 390 million years ago. This was during the Middle Devonian period. A plant called Archaeopteris was one of the first tree-like plants. It could grow to be 20 meters tall.

These plants were deciduous, meaning they dropped their leaves. The fallen leaves created soil and shade on the forest floor. This helped create a home for early freshwater fish. The word forest has a long history too. It comes from the Old French word for a vast expanse of trees. Long ago, it was even used as a legal term for hunting grounds.

There are many important facts about how much life forests hold. Forests contain 80 percent of the Earth's plant biomass. Biomass is the total weight of all living plant matter.

Much of this weight is found underground in root systems. The world's forests hold about 606 gigatonnes of living biomass. They also hold 59 gigatonnes of dead wood. Most of the forest land is in large patches. About 80 percent of forests are larger than 1 million hectares. However, 20 percent of forests are in small patches. Some of these patches are less than 1,000 hectares.

Forests and humans are closely linked in many ways. People use forests for wood, beef, soy, and palm oil. This use can lead to deforestation. Deforestation is when humans cut or burn trees to make farms.

This has changed many places over time. In Europe, forest land dropped from 80 percent to 34 percent over 2,000 years. In the eastern United States, only 0.1 percent of land stayed undisturbed. Forests also help people by providing ecosystem services. They can be beautiful places for tourists to visit. They can even affect how healthy people feel. We must care for them to keep the planet healthy.