A key function of forests is the regulation of the hydrological cycle which drives weather patterns and gives us clean water for drinking, agriculture, fisheries, and more. Forests can attract, direct, and even generate rain, in addition to softening the impact of floods and storms. Water is always on the move through transpiration, condensation, and infiltration, all functions to which forests are essential, helping nutrient cycling, maintaining moisture, and sustaining the biosphere.
When trees pull moisture from the ground and return it into the atmosphere through evapotranspiration, they literally generate rain clouds which are then dispersed by winds. Often, these winds are also generated by the forests as air pressure changes when gases are turned into liquids, moving the air. This process is essential for downwind terrains, cooling temperatures, and maintaining vital atmospheric moisture. Scientists have called this a biotic pump, and likened the process to what our hearts do. In this sense, forests could be considered both the heart and the lungs of our world since forests purify the air as a result of photosynthesis.
Forests also condense water. Studies have found that forests, fungi, and other plants emit terpenes which emit ice nuclei that condense water inside clouds and prompt precipitation. Meanwhile, forest canopies act as an interception point slowing down heavy rainfall and softening the impact on soils, avoiding runoff and soil erosion. The network of roots in a forest act as an anchor for the soil and support permeability, helping avoid direct runoff of pollution into our waterways. Without the intervention of trees, unfiltered water entering our waterbodies can create large “dead zones” such as the one found in the Gulf of Mexico/ America.
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