Water and Forests
While trees and forests, like all living things, need water to survive, forests also play an integral role in the water cycle. Forests store and release large amounts of water and provide valuable services to the environment – they can help to maintain stable water flow, keep water clean and prevent erosion. Keep reading to find out the interconnections between forests and water.
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- As water travels through a forest ecosystem, its chemical makeup changes. Soil can filter out dangerous substances and pollutants, making water cleaner.
- Trees hold and recycle a massive amount of water, which is critically important to regional ecosystem processes. This water is held in plant parts, such as leaves and stems, and is returned to the atmosphere by the process of evapo-transpiration (when water vapour escapes from wet surfaces and from plant parts). For example, the Amazon rainforest stores 3 trillion tonnes of water, and releases 20 billion tonnes of this water each day.
- The rainfall created by the release of water vapour from tropical canopies stabilizes local and regional weather patterns and nourishes rivers and seas that are farther inland. Many South American countries depend on regional rainfall in the Amazon rainforest to power their electricity and fuel certain industries.
- Tree roots play an important role in holding together soil and preventing it from being eroded (washed away) by wind or rain. For example, within a century, Ethiopia’s forest cover drastically decreased from 35% to just over 4%. This massive deforestation resulted in desertification of many areas within the country, which has directly contributed to decades of famine.
- Erosion and storm runoff (water that cannot be absorbed by soil) can drag pesticides and other pollutants into lakes and rivers. Having well managed forests near urban areas and farmland can help to reduce erosion and runoff, which helps to keep water clean.
- Increasing forest cover near water sources significantly reduces the cost of water treatment.
- Trees along the sides of rivers can provide shade, which cools the water and creates better conditions for aquatic life. Many countries have created “green stream corridors” to ensure this ecological service is maintained.
- In Mexico, which suffers from water scarcity, a Payment for Environmental Services (PES) program has been put in place by the government to reward people who maintain healthy forests on their land. This incentive is needed because cattle-ranching and/or agriculture, activities which encourage deforestation, are often more profitable for land-owners than keeping forests intact. In 2007, 480,000 hectares of forest were covered by 879 contracts through the program.
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