Photo: Pos Raj Adhikari
The assumption that more trees equals more water (which has inspired most forests and water policy) is based on incorrect understanding of the hydrological cycle in forest ecosystems, according to the FAO. FAO’s forestry paper 155 ‘Forests and Water’ published in 2008 stated in its executive summary that the forest ecosystem is in fact a major user of water. Tree canopies reduce groundwater and stream flow, through interception of precipitation; and evaporation and transpiration from foliage. It further stated that as both natural and human-established forests use more water than most replacement land cover (including agriculture and grazing), there is no question that even partial forest removal increases downstream water yields. It was probably the first time that a debate about a contentious subject as the role of forests in regulating or enhancing stream flow, which has continued throughout history, has now been explained with the help of science.
It has already been five years since the revelation; nevertheless, it went unnoticed in the mainstream environmental field. It must be stressed that forests are very important source of timber and fuel wood. Forests maintain greenery and help maintain forest ecosystems as well as natural habitat for wildlife and thereby support biodiversity. Forests are equally important to capture carbon. But its role in regulating stream flow and conserving water has been extended far beyond. In fact, the debate about forest – water relationship has continued since the Roman era. Romans who championed the skills of solving the problem of water supply to the people of Rome by developing aqueducts circa 312 BC, were already debating about how forest are important in reducing floods and preserving water sources.
The story goes something like this. Romans required huge quantities of timber for mining, and heating, as well as for construction and the production of iron and other metals. As a result, forests were depleted particularly in the Mediterranean basin which had been largely denuded by the beginning of the Common Era. About the same time, the Romans suffered frequent floods and droughts. Since forests were being cut to meet the timber and wood demand, the fluctuating water level in the streams and rivers were thought to be the result of deforestation in the hills.
The debate continued and efforts to protect forests as well as deforestation went on throughout the history in Europe. Louis VI of France issued an ordinance in 1215 with regard to forest and water. Swiss communities began establishing protected forests in 1342. Many protected forests had been established by the 16th century. With industrial revolution in the 18th century, demand for timber increased and so did deforestation as well as the effort to protect forests. Increased events of floods in the streams and rivers in France, Austria, and Italy were considered a result of deforestation in the Alps. Series of articles published attracted the attention of the then rulers, who made rules for forest protection.
The story in North America was not different. The new European settlers cut vast tracts of forests to establish farms in order to supply food and timber to Europe. Floods events here were also attributed to deforestation and legal measures were taken to protect forests. After a two decade long debate, the state of New York established national forests in 1891. But critics began asking for scientific basis behind the logic of protecting forests to reduce floods. Critics asked the reasons for occurrence of floods before the settlers arrived and cut forests. Scientific research in the first half of the 20th century gave enough ground to argue against the belief about the role of forests in controlling floods and regulating dry season flow. However, the environmental conference held in Stockholm in 1972 and subsequent publication of the book Losing Ground brought forth the theory of Himalayan Degradation, which once again bolstered the preconceived belief about deforestation and increased floods. With all the investments in protecting the forests (which has been quite successful), floods and droughts continue to impact our lives. Finally, with the FAO revelation of 2008, we can be assured of how much to expect from forests in maintaining water flow.
It is a challenge for people living in the present day to reflect on the debate that has gone on for over two millennia and pause to take note of the happenings today. The FAO’s revelation is important and provides us with critical lessons to consider as we wrestle with the importance of protecting our own critical watersheds in Nepal. Pine trees (Khote salla) growing in the abandoned terraces and slopes in the eastern Nepal (seen in the picture above) is perhaps signalling a different message than what has been made to believe. The fact is that Khote salla grows in dry places and not that they make places dry. The spread of pines in Panchthar district perhaps indicates that the hills and mountains in the eastern parts of Nepal have gone dry. We have seen that old springs have disappeared for years. One of the reasons for this is the impacts of repeated earthquakes since 1988 together with the expansion of network of rural roads across the mountains that have diverted the runoff filling the groundwater aquifer. Change in temperature and rainfall, if it has occurred significantly, would not have impacted water sources to the extent as has been seen in the area.
The lesson is that when systems begin to collapse or change from one system to the next, the fallout is often visible even in the most unexpected places for everyone to see and perhaps be sorry for being unmoved by the writing on the wall. Spreading khote salla is perhaps telling a similar story about changing hydrological regime in the area.
Until next time