As the global population surges, dams have been increasingly adopted as a way to keep up with skyrocketing demands for water and energy. To date, there are more than 50,000 large dams in around 165 countries; another 300–350 are currently under construction.
Despite our growing reliance on dams, we still have much to learn about how they work. The degradation of forests and other ecosystems has often being linked to reservoir degradation, which reduces dam performance. However, the real value of natural ecosystems on the effectiveness of dams has rarely been quantified.
As fast-developing nations like Brazil, Colombia, Ecuador, Sudan, Cambodia and China continue to expand dam building, our need to better understand the role of nature in maintaining and improving dam environmental performance has never been more pressing.
I have spent much of the last decade trying to understand the contribution of cloud forests to dam effectiveness. During this time, I’ve found that while cloud forests only cover 5% of the watersheds that contribute water to tropical dams, they filter around 50% of the available surface water that flows to those dams.
In the tropics, cloud forests are multifunctional ecosystems that offer a variety of ecosystem services such as carbon sequestration, biodiversity and scenic beauty. They are also essential sources of fresh water for villages and cities downstream.
I began my research at King’s College London during the FIESTA project (Fog Interception for the Enhancement of Stream Flow in Tropical Areas), an international effort between Vrije University of Amsterdam, King’s College London and Costa Rican and Latin American counterparts. The project combined five years of field work, hydrological and meteorological monitoring, modeling and laboratory experimentation in order to explore the hydrological impacts of the conversion of cloud forest to livestock pasture.
My role in this project was to support Dr. Mark Mulligan, one of the lead researchers, in controlling a series of fog interception experiments in a “cloud chamber” located in a lab at King’s College London. We were trying to identify the capacity of cloud forest vegetation to capture fog under different wind speeds and fog intensities.
The information we learned in the cloud chamber, combined with field work, was used to estimate the volume of cloud water interception carried out by tropical cloud forests. The FIESTA project developed a model which is now used intensively within CI’s eco-hydrology program. For example, we recently used it to determine the best site for the relocation of Gramalote, a town dashed to pieces in 2010 during the wettest La Niña event over a century in Colombia.
After three and a half years of work, I built what is currently the most complete georeferenced dam census available for tropical areas, which maps about 20,000 dams of various sizes. (The previous global georeferenced assessment only included around 7,000 dams globally.) I then used the database and recently developed cloud forest maps to estimate the extent of cloud forests within the watersheds of tropical dams and the amount of surface water available in those areas.
My recent paper on this work has just been published in the international journal of Ecosystem Services. I see this is an important opportunity to demonstrate to dam operators, watershed managers, businesses and policymakers how cloud forest protection and restoration is viable and can be very cost-effective.
According to the Industrial Info Resources, the global energy sector is worth more than US$ 5 trillion annually. One-fifth of this is supplied by hydropower, whose performance is likely to be highly impacted by the degradation of watersheds. Therefore, since cloud forests filter half the water that is entering downstream dams, cloud forest conservation can be a low cost but very high reward opportunity to help improve the effectiveness of tropical dams.
So how can we do this? One way cloud forests can be protected for their freshwater benefits is through Payment for Watershed Services (PWS) schemes.
In many mountainous cloud forest regions, poverty forces farmers to turn to water degrading activities, such as converting cloud forests into cattle pasture. With money collected from downstream service users — including the private sector — and often with national and multilateral support, PWS schemes compensate poor farmers for switching to cloud forest protection and/or restoration. Through methods like these, protection of critical cloud forests could potentially contribute to the reduction of poverty across the tropical mountains.
In collaboration with our field offices, we are piloting these ideas in countries like Colombia, where working with dam companies I have demonstrated that there is an opportunity to generate more energy through the protection of critical cloud forests.
I believe that CI is meant to lead the world toward a green infrastructure paradigm that puts nature at the center of sustainable development. As new green energy opportunities expand around the world, it seems to me that the smart conservation of cloud forests can be a truly viable solution which — aside from improving dam performance — can ensure the survival of some of the planet’s most biodiversity-rich ecosystems and the communities who depend on them.
Leonardo Sáenz is CI’s director of eco-hydrology. He would like to dedicate this blog to the memory of Dr. Fred Scatena, who “helped us advance our understanding of these beautiful ecosystems and of their important services to people.” He is also grateful to the Challenge Program on Water and Food (CPWF) and its focal project for the Andes, which has helped to improve understanding of the most pressing water challenges in the region and of the role of benefit-sharing mechanisms, including the public and private sectors, in order to tackle them more effectively.