Welcome to the mysterious world of cloud forests. You might say they’re enchanted: swirled in mist and fog in the high mountains, chilly and dewy and mossy. Even though many of them are in tropical or subtropical countries, they’re not necessarily jungles: they could be temperate rainforests, evergreens, or even deciduous forests like you might find in the eastern United States. They’re the birthplace of wild coffee. And they’re old… very old. They used to overflow the lowlands of the tropics centuries ago, but when the last ice age ended, they withdrew up the mountains in search of cooler environments. Now, they’re a source of water for tropical dams and the people they support.
Cloud forests, and why they’re cloudy
There are very few places that can match cloud forests’ ancient preference for cool, humid environments. Those that do exist are often at high altitudes, and, as you might expect, they have constant cloud cover. Since there’s less sunlight, less water evaporates from the ground, and from plant leaves in cloud forests. Instead, water from fog collects on the leaves (called ‘cloud stripping’). From there, it drips down to the ground and into the soil.
Cloud forests supply 50% of the water to tropical dams. That’s water for energy generation, drinking, and much more.
Normally, forests lose quite a bit of water to evaporation. But not cloud forests: they collect more than they lose. And that’s why they’re so useful for tropical dams.
Tropical dams and water supply
All that water has to go somewhere. Forests filter and release water to groundwater and rivers, and in the tropics and sub-tropics, many of these rivers are dammed. So a large proportion of cloud forests end up in tropical dam watersheds – but these watersheds are often huge, which means the forests are actually a tiny part of the total area. But they’re much wetter than other areas of the watershed, with more rainfall. And there are even suggestions that forests attract rain.
Cloud forests are a source of water for tropical dams and the people they support.
The surface water balance of an area tells you how much water is flowing in and out of a system. So, because cloud forests are so good at cloud stripping, the water they collect makes up almost 50% of the surface water balance of tropical dam watersheds, even though they only cover 4.4% of their land area. That’s water that’s critical for clean energy, drinking, and other uses. And that’s why cloud forests are just a little magical.
- Dams