Mzuzu is renowned for its unique climate in Malawi, and the people of Mzuzu believe our trees contribute significantly to the distinct weather patterns we enjoy here. But is Mzuzu green because the climate allows it, or is the climate favorable because we are surrounded by forests? Today, as we eagerly await the rains, we will explore how trees regulate rain. Or, in the words of permaculture expert Andrew Millison, “How Trees Make Water.”
The Tree as a Giant Net
Imagine a tree as a giant net, with an extensive surface area to capture what’s in the air. Regardless of rainfall, a tree captures atmospheric moisture and nutrients. The air’s humidity condenses on the tree’s surfaces, and water drops from the leaves, bringing moisture to the soil and surrounding root area. This harvested humidity accounts for a significant portion of the total precipitation a forest receives.
Trees and Rainfall
When it rains, each raindrop is fragmented upon contact with the tree, creating a fine mist. The tree’s intricate structure, with grooves on leaves and bark acting like small gutters, directs water to the ground, where the already spongy soil (thanks to leaf litter) absorbs it. Trees absorb a lot of water – 50% of a tree’s mass is water, stored both above and below ground. Thus, a forest can be visualized as a standing lake.
Trees as Rainmakers
Trees contribute to the water cycle through processes like evaporation and evapotranspiration, sending water upwards. As trees release humidity, small particles like pollen and fungi spores, abundant in forests, are lifted by the vapor. These particles, at the right place and time, facilitate raindrop formation.
Clouds formed over large water bodies move inland, encountering forest air rich in water vapor and particles. This is when rain occurs.
The Drought and Flood Cycle
Forests store water, induce rainfall, and moderate its flow. When it rains, the canopy slows the rain’s descent, the soil absorbs it, and the roots drink. Any excess water flows downhill. A forest moderates this flow – or fails to when it is absent.
Deforestation disrupts this system. Barren lands receive less rain, as there are no trees to convert rolling clouds into rain, leading to drought. Conversely, in the absence of trees to moderate flow, rain rushes down bare hillsides, causing floods.
The drought and flood cycle is a global issue. In Malawi, we’ve begun to experience it, but there’s hope for reversal. The first step is acknowledging the protective role of forests. The second, following immediately, involves taking every possible action to safeguard our forests. Standing against deforestation is crucial for our protection and that of future generations.
