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APPLICATION OF GIS TO CONSERVATION ASSESSMENTS AT THE ROYAL BOTANIC GARDENS, KEW
also to locate where a species may occur and has not been collected or even for the reintroduction
of a species.
A revision of the Leguminosae of Madagascar (Du Puy et al. 2001) has provided the basis for
applying GIS to the investigation of ecological parameters which determine the extent of
species distributions. The revision produced a database of Papilionoid Legumes in Madagascar,
giving the co-ordinates of each collection locality, which could be used to make a point
distribution map. The species distribution map was then compared with other map layers in
the system, such as altitude, substrate, climate or vegetation type and the results gave much
greater precision of altitudinal ranges, substrate preferences (both difficult to determine
accurately in the field, leading to inaccurate data on specimen labels) and data on other
ecological parameters which dictate the distribution patterns of the species.
This data on ecological parameter preferences of species, combined with map layers, can be
used to predict the full possible distribution of a species, filling in the apparent gaps caused by
under-collection in certain areas: a technique called gap analysis (Scott et al. 1993). Point
distribution maps only show where species have been collected, and not necessarily the whole
range of a species: the points are often concentrated along roads and rivers or other easily
accessible areas. However, by applying this technique, the full distribution of a species can be
predicted from incomplete point distribution maps.
Other techniques have also been developed from this project, and are discussed below.
GIS AND IUCN RATINGS
One of the primary targets agreed under the Global Strategy for Plant Conservation (Anon.
2002) is “A preliminary assessment of the conservation status of all known plant species, at
national regional and international levels” (Target (a) (ii)) – to be achieved by 2010. However,
currently less than 3% of vascular plants have a global conservation status using the IUCN
criteria, and between 2003 and 2004, the number of species evaluated and published was
similar to the number of new species described during that period. The rate at which IUCN
ratings can be assigned and published therefore needs to be dramatically increased if this
target is to be met, and if IUCN ratings are to be of use in conserving plant biodiversity.
GIS can be used as a tool for applying IUCN ratings as certain parameters used in IUCN Red
List criteria can be quickly calculated from databased and georeferenced species. Using
herbarium datasets, scripts have been developed in Avenue (ArcView’s programming language)
to automate the calculation of Extent of Occurrence (EOO), Area of Occupancy (AOO),
estimates of the number of subpopulations as well as the number of collections and number of
unique localities. Willis et al. (2003) used herbarium data in Red List assessments of
Plectranthus from eastern and southern tropical Africa, and describe the GIS techniques used.
Extent of occurrence (EOO)
The spatial distribution (range) of a species can be used in assessing its conservation status, as
a species with a small distribution, or a distribution fragmented in few locations, is likely to be
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