The highest biomass production is in the northeast, especially in dense woodlands in Zambezi, Kavango West and Ohangwena. The savannas of the Karstveld on and around the hills in the Tsumeb–Grootfontein–Otavi area also produce substantial biomass. Plant productivity declines southwards and westwards as one might expect with decreasing average rainfall (figures 3.07 and 6.10).

Other characteristics of plant productivity are also evident. Very little grows in saline soils, such as those west of Etosha Pan. Plant productivity is also low in the densely populated Cuvelai drainage basin north of Etosha Pan; here, woodlands have been mostly cleared and the area consists of saline grasslands, oshana watercourses and vegetation grazed short by the high density of livestock. Similar degradation and low plant productivity is apparent around the town of Rundu and along the Okavango River and the road southwest of Rundu.

There are also distinct differences in plant productivity between vegetation types. For example, biomass production changes abruptly between Northeastern Kalahari Woodland and the Cuvelai, and between the Southern Kalahari and Karas Dwarf Shrubland boundaries, mainly due to soil differences (compare figures 5.01 and 6.02). Black areas on the map show where terrestrial plant production is absent (large saltpans) or areas that remain flooded for extended periods, such as dams, perennial rivers or areas of the Zambezi floodplains.

Measured as the coefficient of variation, this map shows the degree (expressed as a percentage) to which plant productivity fluctuates from 'normal' or average. Variation is lowest at opposite extremes of productivity: in the northeastern woodlands where productivity is relatively high every year and in the Namib Desert where productivity is relatively low, even when there is rain. The greatest variation in plant productivity from season to season is along the western escarpment, the southern areas of Namibia and in the Central Kalahari and Southern Kalahari vegetation types in the southeast. Throughout Namibia, the production of grass cover is more variable than that of cover produced by trees and shrubs because the growth of grass is more dependent on recent rainfall than that of woody plants. For this reason, grassland areas show more variability than adjacent areas of woodland.

This graph provides an example of the variation in grass growth on a farm in Erongo Region where plant production is highly variable. The standing crop of grass measured at the end of each season varied 15 fold from less than 60 kilograms per hectare in the driest 2015/16 season to more than 900 kilograms per hectare in 2010/11 when rainfall was plentiful. This illustrates the tremendous variability that grazing animals and farmers must cope with from season to season. Browsers, which feed on shrubs and trees, are also challenged during poor rainfall seasons when deciduous trees and shrubs are leafless for a longer period during the dry season. Herbivore carrying capacity (i.e. the land's ability to support herbivores) is therefore not constant, but varies from year to year. Farmers thus need to be prepared to respond to low production seasons in a timely fashion by selling stock, moving animals to areas with better grazing or providing feed to animals.