22 March is World Water Day 2014. To celebrate the day, RECOFTC is launching its new report Forests and water: A synthesis of the contemporary science and its relevance for community forestry in the Asia–Pacific region. The report aims to shed light on the relationships between forests and water in both temperate and tropical regions. However, it finds that there is a “popular narrative” that often runs counter to the consensus views of the forest hydrology scientific community.

Regan Suzuki Pairojmahakij, Program Officer with RECOFTC, reflects on some of the discussions and reactions that have ensued through the development of the report.

Photo credit: J. Broadhead, FAO 

Recently, I was thrown off balance. I learned that the brontosaurus never existed. The archetypal dinosaur of my elementary school books has since been found to be an imposter – a trick of science due to the mistaken (or fraudulent) assembly of skeletal remains belonging to entirely different dinosaur species more than a century ago. And yet, the impact of this knowledge reverberated a bit more sharply than would be justified by a simple correction of fact. How is it possible that this cornerstone of our imagined prehistoric world never existed?

A comparable disruption of commonly held belief has been occurring within my own sphere in community forestry.  The popular belief in question is that of the ‘sponge theory’ whereby forests have long been credited with ‘regulating’ hydrological systems – capturing water during rainy seasons and gradually releasing this throughout dry seasons. The sponge theory may well be supported in the very specific geo-physical context (namely the Swiss Alps) in which it originated, but is increasingly being seen to have less validity, if not downright detrimental land management implications, in regions such as humid tropics and sub tropics. Popular media and policy-makers throughout the region continue to embrace the sponge theory as a deeply held axiom and its resulting influence on public opinion has been profound. Propounded everywhere from school text books to newspaper headlines – forests, or the lack of them, have been associated with flooding, with the existence (or otherwise) of springs, and even local-level rainfall events. And these popular beliefs seem to be nowhere more closely held than by foresters themselves.

“Much folklore and many myths remain about the role of land use and its relation to hydrology, and these hinder rational decision-making. This is particularly true in relation to forestry, agroforestry and hydrology: claims by enthusiastic agroforesters and foresters are often not supportable. The perception that forests are always necessarily ‘good’ for the environment and water resources has, however, become so deeply ingrained in our collective psyches that it is usually accepted unthinkingly. The view is routinely reinforced by the media and is all-pervasive…” (Prof. Ian Calder, 2005)

 When RECOFTC decided to engage in issues related to water, for which a respected forester and hydrologist was tasked to produce a report on community forestry and implications for water management, Forests and water: A synthesis of the contemporary science and its relevance for community forestry in the Asia–Pacific region, few here were prepared for some of the results. As a community forestry capacity development organization, an exploration of community forestry and its presumed contributions to improved water regulation and access seemed innocuous as a topic.  And yet, it very quickly became a rabbit hole in which our epistemological machinery was suddenly laid bare with unsettling results. The pervasive sponge theory, not only may not be relevant to the geo-hydrology of this region, but may be the complete opposite of what good science suggests. Institutional consensus has led us to grudging agreement that there is a body of science that argues that forests, and particularly afforestation, may reduce ground and water flows (although this needs to be nuanced as dry season and total annual flows). However, this continues to be viewed as a one part of the evidence. The truth however, as pointed out in Gilmour’s report, is that barring several very specific and justified exceptions, there is no compelling scientific evidence contesting this.

The key findings of the report, simplified considerably, with relevance for community forestry and the regional forestry sector, are as follows:

• Both natural and plantation forests managed by communities can produce hydrological benefits, but these are mainly locally specific, i.e., felt mainly on-site or nearby rather than far downstream. In absolute terms, hydrological benefits of forests are less than popularly believed.

• Trees produce biomass by using water for growth processes. Generally, trees that are fast growing and produce a lot of biomass use a lot of water, thereby reducing both total annual as well as dry season flows.

• Community forests in the Asia-Pacific region tend to commence in most cases with degraded lands that have lost their water storage capacity due to reduced infiltration rates. As forests are planted or restored, water yields can be expected to decline further and remain low for decades.

• In small catchments and for small rainfall events, forests have a limited capacity to regulate stream flows. For large catchments and particularly for large rainfall events, forests have limited demonstrated capacity to regulate stream flows compared with other well-managed vegetation types. [1]

• Increases in peak (flood) flow as a result of clearing forests are observable for small to medium size rainfall events in relatively small catchments. The major determinants of large scale flooding at all catchment scales are: rainfall amount and intensity, antecedent rainfall and catchment geomorphology—not vegetation type.

• Community forests normally occur in a landscape mosaic of agricultural, grazing and forest land of different tenure—not all of it community managed. Management of community forests can contribute to these wider objectives, but the hydrological impacts of individual treatments at local levels will be diluted as the catchment size increases. 

What are we to take from this? The overarching lesson to be learned is the fallible and iterative nature of knowledge and the means by which we come to conclusions about the world. Related, is the often logic-defying strength of our conviction in certain axioms. It can be surprisingly difficult to wrestle beliefs out of the popular domain once embedded (in fact, science knew that the brontosaurus was wrong all the way back in 1971 – it has taken more than 30 years for this revision to gain ground in the popular imagination). For the field of community forestry, failing to conduct our work through employing the most current and rigorous science puts vulnerable communities and ecosystems at risk. If the sponge theory does not apply here, we have an obligation to consider alternatives and support communities in making the best land use management decisions on the basis of the best knowledge and models we have available.