#1 - Valuing Indirect Ecosystem Services: the Case of Tropical Watersheds
(posted 10/12/00)
Brooks Kaiser and James Roumasset
Mitigating the harmful effects of development projects and industries (negative environmentalism) is inadequate, especially in resource-dependent economies whose resources are at risk from other forces. While positive environmentalism includes conservation projects, the non-market benefits of such projects are difficult to evaluate. This paper provides and illustrates a method for evaluating the indirect, watershed benefits of a tropical forest, without resorting to survey -methods. The conservation of trees prevents a reapportionment from groundwater recharge to runoff that would otherwise occur. The value of the water saved is then valued at the shadow prices obtained from an optimizing model. An illustration of the model shows that watershed conservation projects may have very high payoffs, even before assessing existence values and other forest amenities.
Introduction
The sub-field of development and the environment enriches both environmental economics and development economics. Environmental economics has evolved primarily in industrialized countries and is heavily pollution-based (i.e. oriented to "P-issues"). Developing countries are relatively more dependent on natural resources; accordingly, the sub-discipline is more resource-based ("R-issue" oriented). In particular, natural resources are more prominently featured in the circular-flow description of the economy. This means in turn that conventional methods of project evaluation and measuring economic indicators such as NNP, which often overlook natural capital, are more seriously flawed in developing countries. Finally, interactions and system-based analysis are important - interactions between the environmental resource system and interactions within the resources system.1
Sustainable development in resource-dependent economies may require more than the "negative- environmentalism" of rejecting development projects that fail an environmental impact assessment. Environmental degradation may be occurring for many reasons besides development projects and "positive environmentalism" including environment-enhancing projects may be appropriate.
Forests and forested watersheds are of particular interest among developing countries, whose governments are said to "often look to their forests as a standing asset that can be liquidated to solve financial problems (Abromovitz, 1998)." Many in the environmental movement, on the other hand, see forest preservation as a moral imperative that should be exempted from hard-nosed economic analysis. A third perspective, that conservation may be consistent with economic efficiency, is hampered by the difficulties of measuring the non-market benefits of conservation. This paper develops and illustrates a methodology for evaluating forest conservation projects, more specifically the contribution that the forest makes to the water balance between run-off and groundwater recharge.
1See Opschoor et. al. (2000) especially the volume introduction.
(posted 11/28/03)
Brooks A. Kaiser, Wetinee Matsathit, Basharat A. Pitafi, and James A. Roumasset
This paper revisits the problem of an underpriced and overexploited groundwater resource. Like other renewable resources, an aquifer replenishes itself over time via recharge from rain percolation. Not only is the aquifer vulnerable to simple overdrafting, but recharge quantities are also determined by forest quality. Healthy multi-tiered forests hold more water in place to increase recharge than bare soil with a single canopied forest cover. Forest quality therefore affects water quantity, and decisions regarding forest conservation expenditures must incorporate this physical relationship, as well as the economic usage of the groundwater resource. In this paper, we provide an analytical framework for evaluating the groundwater benefits of watershed conservation when without such conservation damage to the watershed occurs and brings about partial recharge loss. We consider both the case of a certain and immediate loss and the case of a probable and future loss. We illustrate the framework for the case of the Pearl Harbor aquifer on Oahu where we estimate the benefits of both conservation and improved water management and contrast these with the benefits of efficiency pricing without conservation.
(posted 12/02/03)
Albert S. Kim and Rong Yuan
A simple model to evaluate hydrodynamic cake resistance due to filtered aggregates has been developed. An aggregate is treated as a hydrodynamically equivalent solid core with a porous shell. Creeping flow past a swarm of the composite spheres has been solved using the Stokes equation and Brinkman's extension of Darcy's law. The dimensionless drag force exerted on a composite sphere in the swarm is analytically determined by four parameters, i.e., radius of the solid core, thickness of the porous shell, permeability of the aggregate, and occupancy fraction defined in this study. In certain limiting cases, the final expression, represented as ., converges to pre-existing analytic solutions for an isolated (i) impermeable, (ii) uniformly porous, and (iii) composite sphere, and a swarm of (iv) impermeable, and (v) uniformly porous spheres. This expression is then used to predict the specific resistance of aggregate cake formed on membrane surfaces.
Keywords: Aggregation; Fractal Aggregate; Cake Resistance; Cell model; Settling velocity