Simulation of land uses through utilitaristic agents embedding environmental quality perception Abstract

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1 Simulation of land uses through utilitaristic agents embedding environmental quality perception Abstract Dominique Prunetti, Alexandre Muzy and Eric Innocenti CNRS LISA Università di Corsica Pasquale Paoli Corti, ID 20250, France {a.muzy, prunetti, Introduction Heterogeneity and continuity of space make economic spatial models of the environment intractable. Experimenting land-uses and land changes (pollutions, constructions, etc.) is ecologically, ethically and economically unfeasible. Alternatively, simulation allows representing digital data of reality and achieving computations to experiment with land-use scenarios. To achieve this goal, the space is discretized through a cellular model. Agent behaviors are abstracted through computational decision making models. To investigate economic land-use changes, MAS/LUCC (Multi-Agent System model of land use / land cover change) models have been introduced by (Parker, Manson et al. 2003). MAS/LUCC models include two key components: A cellular model representing the landscape over which actors make decisions; An agent-based model that describes the decision making architecture of the key actors in the system under study. Such approach is investigated here. This work in progress results from a collaboration between computer scientists and economists. On the one hand, computer engineering is used to build a system-based simulator. In the latter, characteristics and behaviors of the dynamic systems (agents and land) can be changed easily according to model improvements. Agent modular components interact with cell components. Agent perception of the environmental quality is achieved through a local cellular automaton of the cellular model embedded in the agent component. Computational components are designed to account for last researches in object-oriented and discrete-event simulations (Zeigler, Praehofer et al. 2000). On the other hand, classical economics is used to define utility functions of agents (mayor, residents and land owners) influencing land-uses/changes. Decision makings of agents are achieved according to the expected utility of the decision. Different attitudes against environmental quality are taken into account. Our aim is to investigate many strategies of various categories of agents (institution, landowners, homeowners ) facing intense residential development in a framework presenting institutional characteristics similar at real procedures like the Local Master Plan in France. This new approach aims to be coupled with a Geographical Information System to obtain empirical results of land use and land-cover changes. Hence, modeling difficulties of purely analytical framework can be solved. Characteristics of real world (agents heterogeneity, complexity of

2 networks relationship and environmental quality implication on agents welfare) are tackled. Currently, a cellular model interacting with agents is built to experiment the modeling approach. The whole system can be considered as a virtual laboratory. 1. Space and agents characteristics Space is discretized in cells. Agent landowners possess a set of cells. Different numbers of cells are allocated to land owners at the beginning of the simulation using a Gumbel s distribution. Cells have many attributes distributed stochastically. They can be constructible or non constructible. Four types of activities are defined: industrial, commercial, residential and wild. The environmental quality of cells is calculated from agents according to local and neighboring activities. The environmental quality calculation depends on each agent perception. Different values of quality and different neighboring cells can be taken into account for the calculation. Swimming pool, sea sight and garden attributes of constructed cells are considered by residents to evaluate cells values. The tax revenue is calculated according to the cell activity. 2. Agent classes: utility and decision making The institutional framework is represented by the mayor. The latter can be considered as the resultant of all administrative procedures of the Municipal Council. Residents can protest against a constructability decision and vote a new mayor. Landowners can protest against a constructability decision and decide to (do not) sell their cells Mayor At the beginning of the simulation a type of mayor is chosen. Mayors can be more sensible to ecology or economical development. Three relative weights of partial utilities determine his sensibility to: environment, citizen welfare and tax revenue. All partial utilities are calculated according to spatial constructions. Environmental amenities and tax revenue attached to a cell depend on the cell activity. Tax revenue concerns wild, residential, commercial and industrial cells. Environmental amenities (inversely proportional to environmental damages of cell s activity) concern too wild, residential, commercial and industrial cells According to these partial utilities, decisions of the mayor are achieved in two steps: Step 1 Constructability proposal decision At the beginning of the simulation, the mayor decides and proposes (this is not a final decision) the constructability or not of cells. Two kinds of choices are achieved: Cells non constructible which can become constructible: If the number of neighboring cells developed (cells which are not wild) around the wild non constructible cell does not exceed a threshold the cell will not

3 become constructible. The number of neighboring cells can be chosen at the beginning of the simulation. If the number of neighboring cells developed (cells which are not wild) around the wild non constructible cell exceeds a threshold the cell would become constructible. A probability proportional to the number of cells developed in the neighborhood is used. Cells constructible which can become non constructible: As long as the number of neighboring cells developed (cells which are not wild) around the constructible cell does not exceed a threshold the cell would become non constructible. A probability proportional to the number of cells developed in the neighborhood is used. If the number of neighboring cells developed (cells which are not wild) around the constructible cell exceeds a threshold the cell remains constructible. Then, for cells potentially constructible a type of further potential activity is defined by a probability proportional to the number of cells of the same type in the neighborhood. Step 2 Final constructability decision Other economic agents (residents or landowners) are informed of the development project of the mayor. According to the constructability decision the agent decides to protest or not. All the decisions are then transmitted to the mayor who decides of the final affectation of cells. The affectation depends on the utilities obtained in statu quo and change scenarios. Finally, the mayor informs every resident and landowner of the final decision Residents Residents take two kinds of decisions: They chose to protest or not after the mayor constructability decision, They vote once the definitive constructability plan is adopted. Decision 1 Protestation or neutrality This decision is based on a utility function composed of two kinds of partial utilities. These partial utilities are based on environmental preferences. These preferences depend on: - The environmental amenities, which depend on the activities of the neighbourhood of their residence - The characteristics of the wild lands in the neighbourhood, - The relative preferences of the agent. These preferences depend on the value of their h (land size, swimming pool, garden, neighbourhood activities, etc.) Residents can be ecologists or rent-seeker according to the weight accorded to the corresponding partial utilities. Every resident has a protestation threshold stochastically attributed at the beginning of the simulation (high for the majority). The resident takes the decision to protest according to a potential change of characteristic in a cell in his

4 neighbourhood. This decision depends on the difference between the utility in the statu quo scenario and in the construction one. Decision 2 Election decision According to the new land-uses, new kinds of residents are obtained. Agents learn from new activities settled in their neighborhood. The kind changes according to the number of past protestations. If the resident protested for a certain kind of construction, he is more sensible to environmental amenities (the increase being directly and positively linked to the number of past protestations and environmental amenities). Finally, the residents choose a new kind of mayor. The probability to vote an ecologist one is proportional to the importance of environmental amenities for the agent. The probability to vote a mayor more sensible to economic development is proportional to agent s preferences depending on wealth Landowners Landowners can be: traditionalist, ecologists or more sensible to economic development. The agent kind depends on each weight of each kind of partial utility. Each partial utility represents preferences depending on the tradition (the more the land is possessed the more utility the landowner will have), the environmental amenities and is wealth. Using this utility function, landowners can take three decisions: - They choose or not to protest the mayor constructability decision. The mechanism used is the same as residents one. - When they agree the constructability decision they choose to sell or not their cells. They calculate the expected utility in both cases. When they sell, a probability of buyer (residential, commercial or industrial) is calculated. The probability depends on the number of cells of the same kind in the neighborhood. - They vote once the final constructability decision is adopted. The mechanism used is the same as residents one. 3. Simulation description The simulation flowchart in annexe describes the overall simulation sequence: 1) At the initialisation, for every cell, the activity value is attributed stochastically. 2) The mayor inspects every cell and decides a constructability proposal. 3) He informs every resident and landowner of the constructability proposal. 4) Every resident and landowner chooses to protest or not. 5) Every decision is transmitted to the mayor who decides of the final constructability of the cells. 6) Landowners decide to sell or not and choose a buyer. 7) A new land cover is obtained. 8) According to this new land cover and to past protestations new kinds of residents are obtained.

5 9) Election of the new mayor by residents. Improvement perspectives The simulator developed allows investigating new models of land-use and land changes. Complex interactions and choices of agents with their environment are simulated. Only simulating the model can provide us results to understand it. This model simulation aims to increase our knowledge validating or invalidating economic assumptions. Currently, actual data of the environment are collected in a GIS. Finally our model will be tested by connecting the current simulator to a GIS. As the simulator design is modular, only cells and agent characteristics will be updated.

6 Annex: Simulation flowchart Initialise cells activity Define of a constructability proposal Inform residents and landowners of the constructability proposal For every resident (i) and landowner (i) Protest Be neutral Communicate protestations to the mayor Constructible Not constructible Inform landowners (i) of the final decision Do not sell Sell Buyer probability Industrial Commercial Residential New landscape cover New types of résidents Vote of residents (i) Election of the mayor

7 References Parker, D. C., S. M. Manson, et al. (2003). "Multi-Agent System Models for the Simulation of Land-Use and Land-Cover Change: A Review." Annals of the Association of American Geographers 93(2): Zeigler, B. P., H. Praehofer, et al. (2000). Theory of modelling and simulation, Academic Press.

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