Namibian environment

The extrapolated distribution ranges that are mapped for some species were based on the following environmental datasets. (More information on methodology used can be found here.)

Many datasets are from: Mendelsohn, J., Jarvis, A., Roberts, C. & Robertson, T. 2002. Atlas of Namibia - a portrait of the land and its people. Ministry of Environment and Tourism, Windhoek. They were released into the public domain upon publication of the Atlas, and may be freely downloaded from here, or here.

Those used by NaBiD are of three main types:

1. CATEGORISED DATASETS - 'normal' maps that display areas of the country that conform to different categories of the parameter being mapped.

Soil type (Atlas 2.20). Many species prefer particular substrates, e.g. more sandy, or more rocky. Note that the Atlas dataset incorrectly categorises the Swakopmund-Walvis Bay dune strip as 'rock outcrop'. It is treated as 'dune sand' here.

Geology (Atlas 2.4). Geology per se is probably not a primary determinant of species distribution, but many secondary results of geology, like topography or soil type, are.

Vegetation types (Atlas 4.2) and Vegetation structure (Atlas 4.4). Two ways of looking at vegetation.

Biomes. Another way of looking at vegetation. This was based on the biome categorisation of Irish (1994). The vegetation types dataset from the Atlas does depict biomes, and the vegetation structure dataset implies them, but there are minor differences. In particular Irish's biome delimitation:

• depicts the northern border of the Succulent Karoo differently.
• maps the Aussenkehr - Noordoewer area as Desert, not Nama Karoo.
• maps the northern (Kaokoveld escarpment) extention of the Nama Karoo much narrower.
• maps the Oponono Plains as part of the Edaphic Nama Karoo of the Etosha Basin, not Savanna.
• maps the Brandberg as a Savanna Outlier - though admittedly it does not fit comfortably there, no viable alternatives present themselves.
• does not map any true Grassland Biome - most Namibian grasslands are considered to be edaphic in origin and to belong to non-grassland biomes.
• does not map any true Forest Biome - what is sometimes called forest in Namibia is at most called woodland elsewhere.

2. SURFACES - continuous datasets that have been extrapolated from point data, e.g. climatic measurements.

We currently use average annual rainfall data derived from the AgMet database. Initiatives are underway to expand this to include other rainfall datasets as well, and also to add other climatic parameters: temperature and incidence of fog are high priorities.

3. BLANKING FILES - are used to exclude particular areas from analysis.

Sea only. Excludes all land areas. Used for marine taxa.

Land only. Excludes all ocean areas. Used for terrestrial taxa. In addition, terrestrial taxa currently have their distributions clipped to display within the borders of Namibia only.