Academic journal article Theoretical and Empirical Researches in Urban Management

Comparative Assessment between Area Based and Patch Based Gibbs-Martin Diversification Index for Land Use Pattern Analysis

Academic journal article Theoretical and Empirical Researches in Urban Management

Comparative Assessment between Area Based and Patch Based Gibbs-Martin Diversification Index for Land Use Pattern Analysis

Article excerpt

1. INTRODUCTION

It is trivial that land use and land cover change induced either due to urbanization or otherwise will invariably lead to the diversification of land use and land covers. The term land cover refers to the type of feature present on the surface of the earth whereas land use relates to the human activity or economic function associated with a specific piece of land (Lillesand et al 2008). In order to carry out sustainable planning and development in an area, it is highly vital to determine the magnitude of diversification on a spatio-temporal basis. One of the powerful yet methodologically simple index of diversification was proposed by Gibbs and Martin (1962) referred to as the Gibbs-Martin index or G-M index of diversification. The index, which is discussed below has been applied in a diversity of disciplines with considerable success (Bhatia 1965). The index is determined by considering the proportion of the area of the different land use and land cover categories present in an area. As per the index, if an area is comprised of only one land use or land cover, the G-M index will be zero. On the other hand, if the area consists of an infinite number of categories with equal proportion of the area in each category, the G-M index will be equal to 1. If the number of categories increases, the score of the G-M index also increases. For example, for 4 categories, each with 25% areal extent, the G-M index score=0.75, for 5 categories with 20% areal extent of each, G-M index score = 0.8 (Patil 2008). However, the diversification of land use and land cover categories cannot be explained solely by their areal proportion, since this would also be significantly influenced by the number of patches of the different categories present in an area. For example, consider two different situations in which the number of categories is same; say only two with equal areal extent of each i.e. 50% and the total number of patches of both the categories is also same in both the situations; however in the two different situations, the number (or proportion) of the patches of the two categories is different. Consider that in each situation the total number of patches of both the categories is say 20; however, in the first situation, each category has 10 polygons that indicates the occurrence of 50 % proportion of each category, while in the second situation, one category consists of 15 patches and the other 5 patches that results in the proportion of the patches of the two categories as 75:25. The first situation indicates that both the categories are fragmented with equal magnitude while in the second situation, one category is fragmented three times more than the other category. The prevalence of these two kinds of situations is certainly indicative of different magnitudes of diversification of the land use and land cover categories. Therefore, the areal extent of the categories remaining same, the magnitude of diversification will be different, which is influenced by their number of patches.

The Gibbs-Martin index has been widely used in several fields due to the flexibility and reliability of the index such as urbanization pattern analysis, crop diversification and demographic studies. Recently crop diversification analysis has been carried out by Datta (2012) in Hugli district, West Bengal, India, using Gibbs-Martin diversification index. The study provided clear areal differentiation among the crops grown that would subsequently provide an avenue to future planners to establish more economically sustained agricultural system. Crop diversification study was also carried out by Das and Mili (2012) in Dibrugarh district, Assam, India who reported that it is vital to promote crop diversification in the district in order to improve the agricultural sustainability. Gibbs-Martin index of diversification has been used to determine the caste diversification in the Kathmandu Metropolitan area, Nepal (Subedi 2010). The study examined the population dynamics from a socio-geographic perspective by focusing on the concentration of caste/ethnic groups, migration into the city and apparent ethnic diversification. …

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