Biodiversity characterization at landscape level using geospatial modelling technique

Abstract

Geospatial presentation of habitat status has become a key issue for planning conservation. Biodiversity characters of the habitat provide the basis of prioritizing the sites in conservation effort. Since India is identified as one of the 12-mega biodiversity countries in the world, this task is of great significance. In India, biogeographers have long since recognized North-East India as one of the most diverse regions with respect to flora and fauna. Since historic times, human interventions had started influencing the landuse and landcover of this region. Deforestation is mainly attributed to shifting cultivation and commercial logging of timber. This has resulted in fragmentation of the landscape. Landscape fragmentation and degradation have been identified as fundamental reasons for biodiversity loss. The paper uses landscape ecological principles for biodiversity characterization. Satellite remote sensing data have been used for characterization of the landscape and stratification for ground inventory. A geographic information system has been used to spatially model the disturbance regimes and to integrate the ground based nonspatial data with the spatial characters of the landscape. The vegetation types and landuse of Meghalaya have been mapped using Indian remote sensing (IRS) time series data. The various parameters (viz. patch shape, patch size, number of patches, porosity, fragmentation and juxtaposition) have been analyzed on the most recent landcover map to spatially present the disturbance regimes. A spatial model incorporating ground based biodiversity attributes of the landscape elements, landuse change patterns, disturbance regimes of the landscape and terrain complexity have been used to delineate the spatial pattern of biological richness. This has been achieved using the landscape analysis package (LAP) developed at the Indian Institute of Remote Sensing. Habitat evaluation using ground based data and their spatial organization have been found to provide reliable information on the biodiversity distribution pattern. The present approach for prioritizing the biodiversity rich sites have the advantage of integrating spatial, non-spatial information and horizontal relationships. The information is finally presented in space and time. This approach will facilitate conservation prioritization, systematic inventory and continuous monitoring.

Introduction

India is known for its genetic and species richness in a wide variety of ecological zones. Increasing human intervention and excessive exploitation of resources have resulted in great changes and provide alarming signals of accelerated biodiversity loss. The conventional species level approach for biodiversity management has major limitations, and a major change in understanding the priorities of biological conservation and management (Kempf, 1993) has resulted in a policy shift from conservation of single species to their habitats. The management of habitats through interactive network of species at landscape level is considered important (Orians, 1993, Edwards et al., 1994). Study of the landscape at patch level is an appealing ecological basis for understanding these processes (Wu and Loucks, 1996). Landscape ecology seeks to understand the ecological functions of larger areas and hypothesizes that spatial arrangement of ecosystems, habitats or communities has ecological implications (Romme and Knight, 1982, Tuner, 1987). Landscape analyses at broad spatial scale is becoming increasingly important for biodiversity conservation. Fragmentation of ecological units have been well documented at landscape level using patch size, shape, abundance and forest matrix characteristics (Forman and Godron, 1986, Lehmkuhl and Ruggiero, 1991, Ripple et al., 1991, Skole and Tucker, 1993, Shirish and Roy, 1997). Ecosystem degradation and patch characteristics are found to be associated with the degree of spatial fragmentation (Ludeke et al., 1990, Mertens and Lambin, 1997, Roy et al., 1997). Characterization of habitats, their configuration and fragmentation, on the other hand provide reliable information on biodiversity distribution patterns. Hence, habitat characterization at the landscape level is a major issue for investigation by landscape ecologists.

The site specific studies use theoretical principles in conservation biology which are often inadequately tested in the field. These principles are being used as a framework to guide management plans, with obvious limitations of being applicable in the spatial context (Abbott, 1980). Application of landscape ecological principles for prioritizing the biodiversity rich sites has the advantage of integrating spatial information, non-spatial information and horizontal relationships in space and time. The landscape approach for biodiversity characterization also addresses some of the limitations of ground based point inventory.

Recent developments in satellite remote sensing and a geographic information system (GIS) coupled with user oriented computer programs allow us to use landscape ecological principles for biodiversity characterization at landscape level more efficiently (Roy et al., 1999). The present study hypothesizes biological richness at landscape level as a function of habitat, biogeographical setting, disturbance regime and environmental complexity (Fig. 1). The paper presents an approach for biodiversity characterization at landscape level using geospatial techniques. The approach has been validated in one of the biologically rich sites of North-East India — Meghalaya. Remote sensing data has been used primarily to stratify habitats, vegetation types, landuse and their association. The stratumwise ground data have provided properties of the habitats. Environmental complexity can be spatially estimated based on terrain and climate variability. The surrogate parameters determining the phytodiversity have been taken into consideration for geospatial modelling of biodiversity characterization at landscape level.