Whether or not the absence of trees causes flooding or water shortages, is a question that persists perhaps because it produces overly generalized answers that fit easily into existing preconceptions. It also fits easily into policy frameworks and stories that paint the world in black and white. Depending on the latest scientific publication, newspaper headlines can proclaim trees to be a menace that is advancing the desert – or failing to regulate floods. But single scientific studies generally only address fragments of a larger puzzle, and few if any experts endorse the one-size-fits all approach that the media implies (Nambiar 2006).
These kinds of generalizations also support rigid land use policies, and conveniently eliminate nuances that can be better addressed with a more flexible place-based approach which is necessary to manage an ecosystem. The tremendous interest in payments for watershed services is driven in part by the popular appeal of this generalized model, in which the flow of water that links upstream practices to downstream consequences also provides scientific justification for a market-based approach to conservation. As an added benefit, payments for watershed services would also contribute to poverty alleviation in marginal upper watershed areas. In practice, there are often trade-offs between meeting these diverse objectives, and implementation is never as elegant as the model.
A set of ICRAF (2006) policy briefs that synthesize two decades of research in this field, assert that what matters is not the presence or absence of trees but the types of tree and where they are located. Also of importance, is what happens to land after forests are removed (Bruijnzeel, 2007). These factors all have implications for the amount of water trees consume, and the extent to which they control erosion. It is also important to keep in mind the pathways of water and sediment flow, some of which have created today’s fertile land. Rivers may be muddy because of landslides, erosion of banks during peak flows, or sediment from roads and paths – rather than due to open fields.
Mosaics of mixed land use – combining forestry, agroforestry and upland cropping – are typical of traditional upper watershed systems and can support denser populations than forested areas. However, they generally don’t fit into the discrete classifications found in land use policies, in which land is designated for either forested or agricultural use. As a result, farmers are often excluded from access to traditionally used land areas causing conflict with states.
Controversies about forest and water relationships are deeply rooted, going back at least as far as the late 1800s during the promotion of settlement to the arid American west. Following what had been a wet period, Ferdinand Hayden claimed that, if trees were planted across the
Under this historical context, scientists can no longer play the role of disinterested bystanders. Instead, they need to engage interactively with the public and be aware of the potential uses of their findings in the policy arena. According to Jasanoff (2007), interactive engagement by scientists can help the public think critically about science and bring a healthy skepticism to its claims – instead of accepting it as an arbitrary set of well-established facts. As with climate change, greater public appreciation of the scientific process can help reduce manipulation of the facts in the policy arena, where scientific uncertainty is often cited as justification for arbitrary or delayed decisions.
Given the inherent uncertainties of watershed processes – particularly in the context of highly diverse upland environments, participatory processes are essential for assessing the science and establishing policy-relevant facts. Place-based assessments can also support more nuanced messages that enable mutual learning and more flexible approaches to management. As a more interactive approach to communication, this mutual learning can help broaden the frame of reference for decision-making and enable consideration of trade-offs between the various kinds of ecosystem services and the multiple ways they support human well-being.
References, further information, and new resources are listed below the jump.
References and further information
ICRAF policy briefs:
Rumley, R. and C. Ong (2006). The right tree for a dry place. Synthesis 1
van Noordwijk, M., B. Verbist, et al. (2006). Muddy Rivers – Lack of Trees? Synthesis 2
Swallow, B. and R. Rumley (2006). Rooting Policy in Science. Synthesis 3
Rumley, R., C. Muthuri, et al. (2006). More Trees with Less Water
Other sources:
Bradshaw, C. J. A., N. S. Sodhi, et al. (2007). Global evidence that deforestation amplifies flood risk and severity in the developing world. (abstract/subscription required for access to article) Global Change Biology 13.
Bruijnzeel,
Bruijnzeel, L.A., van Dijk A.I.J.M., van Noordwijk M., Chappell N.A. and Schellekens J. 2007 Tropical deforestation, people and flooding: A recent global analysis claiming that tropical deforestation amplifies flood risk and severity proves less than solid.
Brock, K. and E. Harrison (2006). Linking research, policy and livelihoods: challenges and contradictions (pdf).Brief
Eckl, E. 2007. Words that work — and don’t — to dispell myths and counter lies –blog post on Water Words that Work – a blog about water related communication.
FAO-CIFOR. Forests and Floods: Drowning in Fiction or Thriving on Facts? (FAO-CIFOR, Bangkok-Bogor, 2005).
Fay, C. and G. Michon (2003). Redressing forestry hegemony – Where a forestry regulatory framework is best replaced by an agrarian one (pdf). Rural Livelihoods, Forests and Biodiversity,
Funtowicz, S. (2006). Why knowledge assessment? Interfaces between Science and Society. Â. Guimarães Pereira, S. G. Guedes Vaz and S. Tognetti.
Hays, S. P. (1959). Conservation and the Gospel of Efficiency. The Progressive Conservation Movement, 1890-1920.
Jasanoff, S. (2007). Lecture given to Science Communication Consortium,
Kaimowitz, D. (2004). Useful Myths and Intractable Truths: The Politics of the Link between Forests and Water in Central America (abstract). Forests-Water-People in the Humid Tropics.
MA (2003). Ecosystems and Human Well-being: A Framework for Assessment.
Nambiar, S. (2006). Responsibility of scientists for balanced communication. (pdf) Forests in the landscape for wood production and environmental care.
Van Noordwijk, M , Poulsen, JG , Ericksen, PJ, 2004. Quantifying off-site effects of land use change: filters, flows and fallacies Agriculture, Ecosystems & Environment 104: 19-34
Woodhouse, C. A., S. T. Gray and D. M. Meko (2006). Updated streamflow reconstructions for the Upper Colorado River Basin. Water Resources Research 42(W05415):doi:10.1029/2005WR004455.
Worster, D. (2001). A River Running West: The LIfe of John Wesley Powell.
New Resources
Bond,
Porras,
UN FAO (2007). The State of Food and Agriculture: Paying farmers for environmental services
WatershedMarkets.org – Resources from IIED on markets for watershed services, including several new case studies.
World Bank (2007). World Development 2008: Agriculture for Development.
ICRAF, Global Scoping Study on Compensation for Ecosystems Services, Working paper series:
WP No. 32 Swallow-2007-Compensation-and-Rewards-Environmental-Services
WP No. 33 Poats-2007-Latin-American-Regional-Workshop-Report-Compensation
WP No. 34 Raju-2007-Asia Regional Workshop on Compensation-Ecosystem Services
WP No. 35 Ochieng-2007-African-Regional-Workshop-on-Compensation-Ecosystem
WP No. 36 Iftikhar-2007-Exploring the inter-linkages- Environmental-Services
WP No. 37 van-Noordwijk-2007-Criteria-and-indicators-for-environmental-service
WP No. 38 Swallow-2007-Conditions-Effective-Mechanisms-Environmental-Services
WP No. 39 Bracer-2007-Organization-and-Governance-for-Fostering-Pro-Poor
WP No. 40 Scherr-2007-How-important-will-differen- type- of Compensation-reward
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