Island-based catchment—The Taiwan example

Rapid economic and industrial development in Taiwan over the past five decades has elevated the islands standing and earned it a place in the group known as the Four Small Dragons of Asia. Such growth, however, has been at the expense of the environment. There are currently nearly 23 million people juggling for space on the small island of 35,873 km². Aggravating the matter further, the central mountain ranges and hills take up 73.6% of the land area with some 156 peaks surpassing 3,000 m. As a result, most people live in coastal plains which amount to only 9,490 km². Pressure to move people inland has led to road construction and deforestation, both of which have contributed to an already high denudation rate of topsoil. As a consequence of this, thirteen rivers in Taiwan are now ranked among the top 20 worldwide in terms of sediment yield. Aside from this, the frequency of both floods and droughts increased prior to 1990, perhaps because of deforestation and global warming. Fortunately, the new conservation-orientated forest management policy of 1991 has alleviated the problem, somewhat, and the occurrence of floods and droughts has since decreased. The problem of water shortage, however, has worsened because of the warming trend in atmospheric temperature. Damming may ameliorate the water shortage problem but may affect the shoreline stability, as well as the ecology and water quality in the estuaries. Furthermore, these detrimental effects may go far beyond the estuaries, and even fisheries on the continental shelves may be affected.     

Conservation Opportunities for Securing In-Stream Flows in the Platte River Basin: A Case Study Drawing on Casper,Wyoming’s MunicipalWater Strategy

The Platte River Basin consists of tributaries largely in Wyoming, Colorado and Western Nebraska, with the main stem in Central Nebraska. Critical wildlife habitat on the main stem requires additional in-stream flows. The watershed is one hosting multiple resources, a variety of users, and managed by an array of state and federal agencies. This study proposes a basis for securing in-stream flows for the Platte River. Candidate water supply mechanisms are suggested based on the way in which Casper, Wyoming secured water for its municipal needs. Canal lining is compared to a dam project, increasing reservoir storage, and purchasing water rights, with consideration also made for water pricing to reduce municipal use. Comparisons are based on economic efficiency, potential water conservation, and property rights criteria. Canal lining, coupled with demand management, is shown to conserve water best, given the set of efficiency and cost criteria for in-stream flow enhancement. The approach offers an opportunity to organize the water supply choice context in a transboundary watershed when quantitative information is limited.     

Modeling the Suitability of Potential Wetland Mitigation Sites with a Geographic Information System

Wetland mitigation is frequently required to compensate for unavoidable impacts to wetlands. Site conditions and landscape context are critical factors influencing the functions that created wetlands perform. We developed a spatial model and used a geographic information system (GIS) to identify suitable locations for wetland mitigation sites. The model used six variables to characterize site conditions: hydrology, soils, historic condition, vegetation cover, adjacent vegetation, and land use. For each variable, a set of suitability scores was developed that indicated the wetland establishment potential for different variable states. Composite suitability scores for individual points on the landscape were determined from the weighted geometric mean of suitability scores for each variable at each point. These composite scores were grouped into five classes and mapped as a wetland mitigation suitability surface with a GIS. Sites with high suitability scores were further evaluated using information on the feasibility of site modification and project cost. This modeling approach could be adapted by planners for use in identifying the suitability of locations as wetland mitigation sites at any site or region.     

Perspectives on the nature and definition of ecological regions

Among environmental managers, recognition of the importance of integrating management activities across agencies and programs that have different responsibilities for the same geographic areas has created an awareness of the need for a common hierarchical framework of ecological regions (ecoregions) to implement the strategy. Responding to this need in the United States, nine federal agencies have signed a memorandum of understanding on the subject of developing a common framework of ecoregions. However, considerable disagreement over how to define ecoregions and confusion over the strengths and limitations of existing frameworks stand in the way of achieving this goal. This paper presents some perspectives on the nature and definition of ecoregions related to this confusion and provides a brief overview of the weight of evidence approach to mapping ecoregions, using an example initiated by the US Environmental Protection Agency. To effectively implement ecosystem assessment, management, and research at local, regional, and national levels, research is needed to increase our understanding of ecoregions. We must find ways to illustrate the nature of ecoregion boundaries and the variability of characteristics within ecoregions as they relate to management issues. Research must also be conducted on comparing existing frameworks and developing indices of ecological integrity to effectively evaluate their usefulness.     

Graduated driver licensing and safer driving

Graduated Driver Licensing (GDL) inserts between the leaner permit and full licensure an intermediate or "provisional" license that allows novices to drive unsupervised but subject to provisions intended to reduce the risks that accompany entry into highway traffic. Introduction of GDL has been followed by lowered accident rates, resulting from both limiting exposure of novices to unsafe situations and by helping them to deal with them more safely. Sources of safer driving include extended learning, early intervention, contingent advancement, and multistage instruction. To extend the learning process, most GDL systems lengthen the duration of the learner phase and require a specified level of adult-supervised driving. Results indicate that extended learning can reduce accidents substantially if well structured and highly controlled. Early intervention with novice traffic violators have shown both a general deterrent effect upon novice violators facing suspension and a specific effect upon those who have experienced it. Making advancement to full licensure contingent upon a violation-free record when driving on the provisional license has also evidenced a reduction in accidents and violations during that phase of licensure. Multistage instruction attempts development of advanced skills only after novices have had a chance to master more basic skills. Although this element of GDL has yet to be evaluated, research indicates crash reduction is possible in situations where it does not increase exposure to risk. While the various elements of GDL have demonstrated potential benefit in enhancing the safety of novice drivers, considerable improvement in the nature and enforcement of GDL requirements is needed to realize that potential.     

Effects of static vs. tidal hydrology on pollutant transformation in wetland sediments

This work addressed effects of hydrology on biogeochemical processes relevant to pollutant chemical transformation in wetland sediments. Microcosms were designed to impose three hydrologic conditions on salt marsh sediments: (i) drained-oxidized redox potenial (Eh); (ii) flooded-reduced Eh and, (iii) diurnal tide-oscillating Eh. The test chemicals were N- and/or S-heterocycles (NSHs) including quinoxaline (1,4-benzodiazine), 2-methylquinoxaline(2-methyl-1,4-benzodiazine), 2,3-dimethylquinoxalinen (2,3-dimethyl-1,4-benzodiazine), phenazine (2,3,5,6-dibenzo-1,4-diazine), acridine (2,3,5,6-dibenzopyridine), dibenzothiophene (2,3,5-dibenzothiophene), phenothiazine (dibenzo-1,4-thiazine), and phenanthridine (2,3-benzoisoquinoline). Biogeochemical processes reflected the hydrologic conditions in ways analogous to field settings, e.g., Eh characteristics were drastically different: static (flooded and drained) systems had reduced (mu = -428 mV +/- 57) and oxidized (mu = +73 mV +/- 32) values, respectively, with no evidence of periodic variation while the tidal systems exhibited regularly oscillating Eh (amplitudes 40-250 mV). Sediment trace gases also corresponded to the Eh, with the major species detected being CO2 and H2O (drained, tidal) vs. CO2 + H2O + sulfides + methane (flooded). The NSH transformation rates were different in each hydrologic regime and decreased as follows: tidal > or = drained > flooded. These results indicated that there were subtle differences in NSH processing in drained and tidal systems, but both of these systems transformed NSHs faster and to lower levels than flooded sediments. These data suggest that in situ remediation options that preserve wetland integrity and tidal hydrology can be as or more effective than static conditions that obtain in approaches such as impoundment and excavation-upland placement.     

Aggregating the benefits of environmental improvements: distance-decay functions for use and non-use values

One of the main problems in using environmental cost-benefit analysis is deciding on the relevant population: whose benefits should we count? This is important since aggregate benefits depend on both per-person benefit and the number of beneficiaries. Yet this latter term is often hard to evaluate. Distance-decay functions are one way of addressing this problem. In this paper, we present estimates of distance-decay functions for a particular environmental improvement, namely a reduction in low flow problems on the River Mimram in Southern England. We do this both for users and non-users, in the context of a contingent valuation study of the benefits of improving low flow conditions. We test whether distance-decay effects for mean Willingness to Pay are stronger for a single environmental good (the River Mimram, in this case) than for a more inclusive set (here, all rivers in Thames region which suffer from low flow problems). Finally, we explore the impact on part-whole bias, in terms of the relationship between WTP for an individual site and WTP for a more inclusive group of sites, of allowing for distance-decay effects.     

Importance of Sediment–Water Interactions in Coeur d’Alene Lake,Idaho, USA: Management Implications

A field study at Coeur dAlene Lake, Idaho, USA, was conducted between October 1998 and August 2001 to examine the potential importance of sediment–water interactions on contaminant transport and to provide the first direct measurements of the benthic flux of dissolved solutes of environmental concern in this lake. Because of potential ecological effects, dissolved zinc and orthophosphate were the solutes of primary interest. Results from deployments of an in situ flux chamber indicated that benthic fluxes of dissolved Zn and orthophosphate were comparable in magnitude to riverine inputs. Tracer analyses and benthic-community metrics provided evidence that solute benthic flux were diffusion-controlled at the flux-chamber deployment sites. That is, effects of biomixing (or bioturbation) and ground-water interactions did not strongly influence benthic flux. Remediation efforts in the river might not produce desired water-quality effects in the lake because imposed shifts in concentration gradients near the sediment–water interface would generate a benthic feedback response. Therefore, development of water-quality models to justify remediation strategies requires consideration of contaminant flux between the water column and underlying sediment in basins that have been affected by long-term (decadal) anthropogenic activities.