Measuring the neighbourhood effect to calibrate land use models

https://doi.org/10.1016/j.compenvurbsys.2013.03.006Get rights and content

Highlights

  • We used modified enrichment factors to measure the neighbourhood effect.

  • Measurements confirm the existence of a neighbourhood effect, especially for urban land uses.

  • Modified enrichment factors can be used to improve the calibration of neighbourhood rules in land use models.

Abstract

Many spatially explicit land use models include the neighbourhood effect as a driver of land use changes. The neighbourhood effect includes the inertia of land uses over time, the conversion from one land use to another, and the attraction or repulsion of surrounding land uses. The neighbourhood effect is expressed in the neighbourhood rules, but calibration of the neighbourhood rules is not straightforward. This paper aims to characterise the neighbourhood effect of observed land use changes and use this information to improve the calibration of land use models. We measured the over- and underrepresentation of land uses in the neighbourhood of observed land use changes using a modified version of the enrichment factor. Enrichment factors of observed land use changes in Germany between 1990 and 2000 indicate that the neighbourhood effect exists. This suggests that it is appropriate to use neighbourhood rules to simulate urban land use changes. Observed enrichment factors were used to calibrate a land use model for Germany from 1990 to 2000 and the obtained neighbourhood rules were validated independently from 2000 to 2006. The results show that both the allocation accuracy and the pattern accuracy of the land use model improved for the calibration period, as well as for the independent validation period. This indicates that enrichment factors can be used to improve the calibration of the neighbourhood rules in land use models.

Introduction

Land use models typically include a combination of drivers to simulate land use changes over time (Poelmans and van Rompay, 2010, Wang et al., 2011), often including the interaction between land uses in space and in time (Irwin and Bockstael, 2002, Verburg et al., 2004b). This spatial and temporal interaction between land uses is known as the neighbourhood effect, which is represented in many land use models by the neighbourhood rules (Hagoort, Geertman, & Ottens, 2008). Examples of land use models that include a neighbourhood effect are LUCIA (Hansen, 2007), Dyna-CLUE (Verburg & Overmars, 2009), and LUMOCAP (Van Delden et al., 2010).

These land use models often exist as generic modelling frameworks, which can be calibrated for a specific case study application. This calibration includes the definition of the shape and parameter values of the neighbourhood rules. However, the calibration of neighbourhood rules is not straightforward. Several automated methods have been developed (Arai and Akiyama, 2004, Jenerette and Wu, 2001, Li and Yeh, 2002, Li and Yeh, 2004, Straatman et al., 2004), but, despite these efforts, Hagoort et al. (2008) observe that the current practice of calibrating neighbourhood rules is predominantly manual. This is inherently subjective, not repeatable and highly dependent on the knowledge and skills of the modeller. One limitation of automated calibration methods is that most methods deal with the allocation of one land use type only and cannot handle the interaction between multiple land uses, while many contemporary CA models represent multiple types of land use changes (Arai and Akiyama, 2004, Van Delden and Hurkens, 2011, Wang et al., 2011). Another drawback of these calibration methods is that model parameters are assessed indirectly from the predictive accuracy of the simulation result: such assessment does not indicate directly which parameters should be changed and in what direction.

The research presented in this paper aimed to measure the neighbourhood effect of observed land use changes and use this information to improve the calibration of land use models. To do this, we measured the over- and underrepresentation of land uses in the neighbourhood of observed land use changes using a modified version of the enrichment factor (Verburg, de Nijs, van Ritsema Eck, Visser, & de Jong, 2004a). First, enrichment factors were measured for observed land use changes to test the existence of the neighbourhood effect. The enrichment factors of the observed land use changes were subsequently used to calibrate the neighbourhood rules in a cellular automata land use model. Two methods were employed to calibrate an application for land use changes in Germany between 1990 and 2000: an automated procedure and a manual procedure. Both methods were validated independently by simulating land use changes in Germany between 2000 and 2006. Calibration and validation results for both methods were compared with results from a null calibration to assess their accuracy.

In the next section we discuss the neighbourhood effect in more detail and how this is reflected in the neighbourhood rules in land use models. Section three presents the methodology for this study, including a description of the land use model, the case study application, and the details of both calibration procedures. Section four presents the simulation results and discusses these in relation to the applied calibration methods. In section five we draw conclusions and provide some directions for further research.

Section snippets

Inertia, conversion, and attraction/repulsion

Existing land use patterns influence future land use patterns in three ways: (1) through the inertia of land uses in a location, (2) through the ease of conversion from one land use to another, and (3) through the attraction or repulsion effects exerted by land uses situated in the neighbourhood of a location. The combined influence of inertia, conversion and the attraction/repulsion effects of existing land uses is known as the neighbourhood effect, which therefore includes the effects of land

Characterization of the neighbourhood effect

Verburg et al. (2004a) introduced the enrichment factor to characterize the neighbourhood effect. The enrichment factor is defined as the over- or underrepresentation of a land use in the neighbourhood of a particular location, relative to the average land use distribution:Fi,l,d=ni,l.d/ni,d|Nl|/|N|where Fi,l,d is the enrichment of land use l on location i at distance d, ni,l,d is the number of cells of land use type l at distance d of location i, ni,d is the total number of cells at distance d

Enrichment factors of observed land use changes

Fig. 4 shows the over- or underrepresentation of land uses in the neighbourhood of residential land and industrial land that appeared in Germany between 1990 and 2000 and between 2000 and 2006 as a function of the distance to the locations of land use changes. The graphs show two separate effects: the value at distance zero in the graphs indicates the conversion effect, while values at distance greater than zero indicate the over- or underrepresentation of land uses in the neighbourhood of

Conclusions

An analysis of observed land use changes indicates that there is a relation between locations of land use change and the land use in their neighbourhood. This was found for all combinations of land uses, and in both the calibration and the validation period, but predominantly for the allocation of urban land uses. Using enrichment factors to calibrate the neighbourhood rules in cellular automata land use models improved model results considerably. This was found in the calibration as well as in

Acknowledgements

We thank the anonymous reviewers for their helpful comments.

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