Hesperian Health Guides
Forests and Health
Contents
Forests and water
Some people believe trees attract rain and hold water close to the ground. Others believe trees use more water than they make available, and that they compete with crops. Depending on the kinds of trees, where they grow, and other conditions, both of these beliefs can be true.
Rich forest soils and deep tree roots act as filters for water. When pesticides, heavy metals, and other toxic chemicals pollute surface water and groundwater, forests help filter them out. The filtered water feeds our wells, streams, and lakes, and keeps our watersheds and the people who live there healthy. Without forests to protect water sources, there is less safe water for drinking and bathing. For all of these reasons, it is usually best to leave trees standing rather than cut them down, especially if your water is clean and abundant.
But some kinds of trees, especially trees that grow fast and are not native to the area, may use up water resources. For farmers and others who want to protect water resources, it is important to notice how different types of trees affect the water, and to make careful decisions about what trees to plant.
Forests and weather
Forests have important effects on the weather and the climate (the weather in a place over a long period of time). They help make weather less extreme by making warm air cooler and wetter, and making cold air warmer and drier. Trees protect houses and crops from strong winds and hot sun, and provide shelter from strong rains. On a larger scale, forests fight global warming by absorbing toxic pollution. This helps keep the climate of the entire planet milder and the air and water healthier. When we lose large areas of forest, the threat of natural disasters such as hurricanes, droughts, and heat waves is increased.
Forests prevent erosion and reduce flooding
By adding leaves to the soil, providing shade for plants that grow beneath the trees, and holding soil in place with their roots, trees prevent erosion and reduce flooding. They slow rainwater and spread it across the ground, so it will sink into the soil rather than run off.
When forests are cleared, soil washes into rivers and streams. When storms come, the soil is no longer able to absorb and hold the rainwater. Instead, the water flows faster across the land, causing floods. Keeping trees and forests standing is an important way to protect the natural flow of water through the watershed. (See the activity “What rain does to bare soil.”)
Forest diversity and health
In a forest, it is easy to see the web of life because a healthy forest contains many different kinds of plants and animals. This diversity of life protects people’s health in many ways. Bees and other insects that live in trees pollinate crops so they flower and produce fruit. Wasps and ants eat insects that attack crops. Bats and birds eat mosquitoes that spread malaria, yellow fever, and other diseases. Other forest animals keep rats, fleas, flies, and ticks under control by hunting them or competing with them, and prevent them from spreading disease.
When human settlements are built in or close to degraded forests, the number and variety of animals are reduced because their sources of shelter and food become less plentiful and less diverse. Also, the animals that remain are forced to live in closer contact with people. This leads to a greater possibility that animal diseases will be passed to people. By maintaining enough forest to support a variety of plants and animals, we protect human health.
Forests, food, fuel, and medicine
Forests contain a large variety of fruits, nuts, seeds, roots, insects, and animals that serve as food and medicine for people. When forests are degraded, it often results in hunger, malnutrition, and illness. People who depend on these resources must find other ways to survive. When foods and medicines from the forest are lost, the knowledge of how to prepare and use them is also lost. In this way, the loss of forests leads to the loss of important knowledge and traditions.
In places where resources are scarce, people sometimes feel forced to choose between keeping forests standing and cutting down trees to plant crops for food. But even for farmers who clear the forest to plant crops, keeping some trees is important. In areas where farming competes with forests, it is important to try to keep a balance between them.
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| Carrying heavy loads over long distances can cause headaches, backaches and, especially in children, damage to the spine. |
Women’s burden
Women and children often do the hard work of collecting and carrying wood for fuel. The burden of this work over many years can lead to health problems. As forests are destroyed, people must travel longer distances to collect wood. This gives them less time to do other necessary work and to go to school.
Women and children may also face physical and sexual violence when they travel to collect wood. Because of this, in some places women and girls go in groups to collect firewood during daylight hours. By planting and maintaining good firewood trees close to home, the people who collect wood can stay safe and healthy.