Species diversity maps < Comparing geographic data from different sources > Analysis of point data

4.4.3 — Comparing geographic data from different sources

Most information on species distributions is published as text or simple line drawings on maps. In most cases, scale or projection are missing, which is a severe impediment for transfer into GIS-formats. Especially for birds, distribution maps of varying scale and quality form an integral part of most field guides and handbooks. The general problem of such distribution maps is summarised by K. Kaufmann: "Most bird cartography takes what might be called a 'broad brush' approach", and he concludes:

"such a map is comforting because it looks so absolute. But it is also invariably misleading [...] compiling perfect range maps is not just difficult, it's literally impossible" (Introduction by K. Kaufmann to Price et al. 1995).

The only way to overcome this problem is a raster approach, i.e. covering whole regions with a defined counting protocol within a well-defined geographical grid. Impressive raster data sets exist for certain groups and regions, providing population numbers with high spatial resolution (e.g European birds: Hagemeijer & Blair 1997). However, maintenance of such data sets is expensive, and up to now they are available only for some well-monitored regions.

Tab. 4.13: Examples of major development projects within ecologically sensitive areas. Some of the projects have undergone extensive environmental assessment (Chad-Cameroon), others are still in the planning phase (Ebro). Tab. 4.13: Beispiele wichtiger Entwicklungsprojekte in ökologisch sensiblen Gebieten. Einige der Projekte sind bereits begutachtet worden (Umweltverträglichkeitsprüfung) (Tschad-Kamerun), andere sind noch in der Planungsphase (Ebro).
Name Type Protection Important for Project
Alaskan oil fields Arctic tundra National park Terrestrial mammals (caribou) Oil extraction
Ebro water deviation (Spain) Wetlands, various Various Ramsar-sites Waterbirds, fishes Irrigation
Mindo (Ecuador) Tropical moist forest Important Bird Area (IBA), protected forest Birds Oil pipeline
Mühlenberger Loch (Germany) Wetland: freshwater mud flat National, European, Ramsar Waterbirds Industrial development (factory)
Chad-Cameroon (Africa) Various None African mammals, birds, fishes Oil fields at Doba (Chad) Pipeline to Cameroon
Baku oil fields (Caspian sea) Steppe, wetland complexes None Terrestrial mammals, birds, fishes Oil extraction
Three Gorges (China) River, wetland complexes None Waterbirds (Siberian crane), fishes Dam

Once entered into a GIS, maps from different sources and with different projections can be compared. An example is provided by the distribution map of the monk seal Monachus monachus (Figure A2.17, and references therein), or the overlay of two general distribution maps for Vanellus gregarius (Figure A2.49). The differences are considerable, and illustrate several problems of mapping:

Basically, these two concepts reflect the difference between "Expected Area" and "Area of Occupancy", respectively.

The "African mammal database" (Institute of Applied Ecology 1998) is among the few GIS map sources based on well-defined data sources and models, including probability analysis of habitat suitability (see Figure A2.14, and Institute for Applied Ecology 1998). However, even this valuable data set has to be complemented constantly by fresh data, which might come from a wide variety of sources, including checklists for countries, provinces or sites. An example is the distribution map of the oryx (Oryx dammah) shown in Figure A2.7. It already shows a historical distribution, as the species is now considered to be "Extinct in the Wild" (EW), according to the IUCN Red List 2000 (Hilton-Taylor 2000). However, historic distributions are very important information. This is particularly relevant for migratory species, many of which have been widespread throughout huge ranges, but have become continuously reduced since historic times — an example is presented in Figure A2.11, showing the shrinking range of the Mongolian gazelle Procapra gutturosa. In many cases, such reduced ranges are confused with "natural distributions", and the omission of older data sets leads to a constantly shifting baseline of conservation goals. In addition, these data are necessary for species rehabilitation and re-introduction plans, which will be made much more efficient by using GIS technologies.

Species diversity maps < Comparing geographic data from different sources > Analysis of point data

This document should be quoted as part of the publication "Riede, K. (2001): The Global Register of Migratory Species ­ Database, GIS Maps and Threat Analysis. Münster (Landwirtschaftsverlag), 400 pp." + CD

 by Klaus Riede