National Scale land use Change Modeling - Issues and Applications
Ks Rajan and Ryosuke Shibasaki
IIS, Univ. of Tokyo, 7-22-1, Roppongi, Minato-Ku Tokyo 106, Japan
Tel : (81)-3-3402-6231 Fax: (81)-3-3479-2762
E-mail: rajan@shunji.iis.u-tokyo.ac.jp
Abstract
Land use/cover modeling requires a variety of data, ranging from basic physical information to socio-economic data to existing land use patterns. The scale, resolution and the type of data like spatial, temporal or statistical data, needs to be known for the proper usage of these datasets in modeling approaches. The scarcityof finer datasets leads to various assumptions and simplifications in the approach. Also, it has to be noted that a data with less number of classes, leads to the error of the assumption of homogeneity with the given class. The paper presented here will discuss the issues that arose in developing a national scale land use model by the authors for Thailand.
Introduction
Natural forces have always had an influence in the shaping of the earth's surface. Material flows and energy transfers have operated at global, regional and local scales, resulting in both gradual and catastrophic transformations of the biosphere, atmosphere, lihosphere and hydrosphere. However, and cover changes have been the most drastic of all changes and also its interaction with the other global systems/cycles is of prime importance in studies on global its interaction with the other global system/cycles is of prime importance in studies on global change research. Land use/cover is continuously changing, both under the influence of humans and nature resulting in various kinds of impacts on the ecosystem. These impacts at local, regional and global levels have the potential to significantly affect the sustainability of the world agricultural systems and the forest systems. To understand the impacts on the ecosystem, we need to understand the mechanisms of the processes involved. The most important factor in the modification of the land cover and its conversion is the human use component. Changes in the land cover cannot be understood without a better knowledge of the land use changes that drive them and their links to human causes.
The linkages between the human and biophysical causes or drivers to land management and land cover are not sufficiently understood. This arises from the complexity in dealing with the considerable variations in the drivers, use and cover at the local, national and regional levels. At present, many of the global and sub-global analyses and studies capture the broad sectoral trends based on the changes in some of the macro variables, like population, socio-economic trends, etc. The modeling at a national level is more complex than to generate a global picture, while local case studies pose a separate set of problems. They not only do not link well with either the regional or global scale models, but also identify an entirely different set of driving variables than the global scale models. The transformations in the land cover, occurring on the large scale will lead to large scale changes in the "global environment". These changes are complex and require different scales of analysis.
Issues in Modeling
Modeling approaches vary according to the objective of the studies and the type of data available. Models may be deterministic or stochastic in nature; macroscopic or microscopic in extent; evaluation models or optimization models. The modeling approaches also depend upon the type of study carried out in understanding the different aspects of the changes that are taking place. These may be a purely descriptive study leading to a cause-effect type of taking place. These may be a purely descriptive study leading to a cause-effect type of explanation of the changes; or a statistical study with the objective for a probabilistic model at a macro-scale; or just monitoring of changes (with the use of remote sensing technologies) at a
spatial and temporal scale. With advances in computing speed and the evolution of better GIS systems, the possibility of combining some of the approaches on a single platform is becoming possible.
