Using wastewater in forestry combines water re-use and nutrient recycling. This approach can theoretically address water scarcity, help to maintain tree cover and provide multiple ecosystem services. In addition, forests can filter wastewater, reducing treatment costs. However, using wastewater to irrigate forests also has challenges. First, is it even safe?
That is what was discussed at the event ‘Irrigating Forests with wastewater: Natural and effective water treatment?’ held during the World Water Week 2017 in Stockholm. The event was organized in collaboration between FAO, CIFOR, SIANI, Forest Trends, IUFRO, Focali, The Swedish Forest Agency, SLU, and SIWI. The event discussed the pros and cons of using wastewater for irrigation of trees and highlighted successful cases from South Africa, North Africa and Sweden.
The pros and cons
Wastewater use in forestry and agroforestry has many benefits. Trees sequester carbon, cool terrestrial surfaces, regulate fresh water flows, prevent erosion and maintain soil fertility. In drylands, where water is scarce, wastewater can be used in landscape restoration helping to combat desertification.
“Wastewater has a huge untapped potential for resource recovery and reuse!” – emphasized Akiça Bahri (National Agricultural Institute of Tunisia, INAT). “Imagine if we could use all of the globally generated wastewater to irrigate land, provide fertilizer, biogas as well as electricity?” she continued. In fact, the UN 2017 World Water Development Report was called “Wastewater: The Untapped Resource.”
Even though, some may say that from the financial point of view reusing water in forestry is not as viable as in agriculture, the benefits are much higher if we consider the total economic value of forests with all environmental services they provide.