Alison J. Gilbert

Estimation of Distance-Decay Functions to Account for Substitution and Spatial Heterogeneity in Stated Preference Research

In a site-selection choice experiment various hypotheses are tested related to spatial heterogeneity in willingness to pay (WTP) for environmental improvements. Spatial heterogeneity is measured through distance-decay effects, substitute sites inside and outside the experiment’s choice set, and spatial trend variables. We demonstrate that distance-decay functions differ between users and nonusers and across study sites. Also the distance to substitutes outside the choice set explains spatial variation in WTP. We show that further extending the model with spatial trend variables reveals additional spatial heterogeneity in choices. Accounting for spatial heterogeneity patterns results in significantly different WTP estimates for environmental improvements. (JEL Q25, Q51)

Spatial Economic–Hydroecological Modelling and Evaluation of Land Use Impacts in the Vecht Wetlands Area

Wetlands provide many important goods and services to human societies, and generate nonuse values as well. Wetlands are also very sensitive ecosystems that are subject to much stress from human activities. Reducing the stress on wetlands requires a spatial matching between physical planning, hydrological and ecological processes, and economic activities. Spatially integrated modelling and evaluation can support this. The present study has developed a triple layer model that integrates information and concepts from social and natural sciences to address the analysis and evaluation of land-use scenarios for a wetlands area in the Netherlands, the Vecht area. This is the floodplain of river Vecht, located in the centre of the Netherlands. The study has resulted in a set of linked spatial hydrological, ecological and economic models, formulated at the level of grids and polders. The main activities incorporated in the system of models are housing, infrastructure, agriculture, recreation and nature conservation. The formulation of alternative development scenarios is dominated by land use and land cover options that are consistent with the stimulation of agriculture, nature or recreation. Two aggregate performance indicators have been constructed from model output, namely net present value of changes and environmental quality. The spatial characteristics of these indicators are retained in a spatial evaluation that ranks scenarios.