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Remote
REMOTE SENSING AND GIS APPLICATIONS
FOR MAPPING AND SPATIAL MODELLING OF INVASIVE SPECIES
Chudamani Joshi *" *, Jan de Leeuw?, Iris C. van Duren?
" Department of Natural Resources, International Institute for Geo-information Science and Earth Observation (ITC),
P. O. Box 6, Hengelosestraat 99, 7500 AA, Enschede, The Netherlands - (joshi, leeuw, vanduren) G itc.nl
^ Ministry of Forest and Soil Conservation, Department of Plant Resources, Thapathali, Kathmandu, Nepal
KEY WORDS: Review, Biological invasions, GIS and remote sensing, Mapping techniques, Canopy cover classification
ABSTRACT:
Biological invasions form a major threat to the sustainable provision of ecosystem products and services, both in man-made and
natural ecosystems. Increasingly, efforts are made to avoid invasions or eradicate or control established invaders. It has long been
recognized that remote sensing (RS) and geographical information system (GIS) could contribute to this, for instance through
mapping actual invader distribution or areas at risk of invasion. Potentially GIS could also be used as a synthesising tool for
management of interventions aiming at invasive species control. This paper reviews the application of remote sensing and GIS in
mapping the actual and predicting the potential distribution of invasive species. Distinction is made into four categories of invasive
species based on whether they appear in and dominate the ecosystem canopy or not. We argue that the possibility to apply RS to map
invaders differs between these categories. Our review summarizes RS techniques applied in here and outlines the potential of new RS
techniques. It also demonstrates that RS has so far been applied predominantly to canopy dominant species. This contrasts with
ecological databases revealing that the large majority of invasive species do not dominate the canopy. The mapping of these invaders
received little attention so far. In this paper we will review various possibilities to map non-canopy invader species. The paper also
reviews techniques used to map the risk of invasion for areas not invaded so far.
1. INTRODUCTION view, multispectral data, multitemporal coverage and cost
effectiveness (Stoms & Estes, 1993; Soule & Kohm, 1989; Van
Invasive species are a current focus of interest of ecologists, der Meer et al., 2002). It is now widely applied on collecting
biological conservationists and natural resources managers due and processing data. It has proved to be a practical approach to
to their rapid spread, threat to biodiversity and damage to ^ study complex geographic terrain types and diverse inaccessible
ecosystems. Invasions may alter hydrology, nutrient ecosystems. It provides a wide range of sensor systems
accumulation and cycling, and carbon sequestration on including aerial photographs, airborne multi-spectral scanners,
grasslands (Polley et al., 1997). The global extent and rapid satellite imagery, low and high spatial and spectral resolution
increase in invasive species is homogenising the world's flora and ground based spectrometer measurements.
and fauna (Mooney & Hobbs, 2000) and is recognized as a
primary cause of global biodiversity loss (Czech & Krausman, ^ Remote sensing technology has many attributes that would be
1997; Wilcove & Chen, 1998). Bio-invasion may bé considered beneficial to detecting, mapping and monitoring invaders.
as a significant component on global change and one of the Spatial heterogeneity complicates the study of seasonal and
major causes of species extinction (Drake et al., 1989). long-term trends of biological invasion. Remote sensing,
: however, with its broad view has the potential to deliver the
This article attempts to provide a review of several studies that relevant information. Satellite imagery is available for most of
assess the utility of remote sensing (RS), or remote sensing the world since 1972. The multidate nature of satellite imagery
coupled with geographical information system (GIS), in permits monitoring dynamic features of landscape and thus
mapping and modelling the distribution of invasive species. The provides a means to detect major land cover changes and
term invasive species is also more or less synonymously quantify the rates of change.
referred to as aliens, barriers, naturalized species, invaders,
pests, colonisers, weeds, immigrants, exotics, advantives, ^ Integrated GIS and remote sensing have already successfully
neophytes, xenophytes, introduced species or transformers been applied to map the distribution of several plant and animal
(Heywood, 1989; Richardson et al., 2000). These terms come species, their ecosystems, landscapes, bio-climatic conditions
from studies having different view points on the problem but in and factors facilitating invasions ((Stow et al., 1989, 2000; Los
the context of this paper they should be considered as similar. et al., 2002; Haltuch et al., 2000; McCormick, 1999; Rowlinson
et al., 1999). An increasing number of publications (Graph 1) is
1.1 Application of RS and GIS techniques in mapping dealing with the application of remote sensing and GIS in the
biological invasions data collection and analysis of invasive animal and plant
species, their abundance, distribution, mapping, modelling and
Remote sensing technology has received considerable interest in factors influencing their distribution.
the field of biological invasion in the recent years. It is a tool :
offering well-documented advantages including a synoptic
* Corresponding author
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