Interventions can boost rangeland recovery

Given the recurrent erratic rainfall activities and the continued pressure on rangelands, the shifts in plant and grass succession stages will take longer than desired, unless there are human interventions to facilitate the natural processes of rangeland revegetation.

According to Agribank’s technical advisor for livestock and rangeland, Erastus Ngaruka, one such practice is to re-introduce the valuable grasses by re-seeding.

This practice can be undertaken at various scales, in backyard gardens, planting fields, camps or grazing areas.

Ngaruka said the productive potential of Namibian rangelands has been compromised, especially in communal areas, due to degradation. The main forms of rangeland degradation are bush encroachment and soil erosion.

These two forms of degradation are a consequence of improper rangeland utilisation practices such as overgrazing, land clearing and soil mining practices, among others.

He said rangelands offer direct or indirect support to all forms of life and are the cheapest source of food for livestock. Humans also derive food, medicine, and construction materials, among others, from the rangeland.

“This is an indication that there is huge demand and competition for rangeland resources, thus putting them under immense pressure to produce or continue to provide such services,” Ngaruka explained.

Contributing factors

Ngaruka said rangeland productivity is influenced by a combination of factors, including rainfall, soil condition, seed availability and utilisation, among others.

“For example, overgrazing reduces the density and the competitive ability of grasses, thus promoting the undesired opportunistic plants, such as the woody encroachers and other weeds, to inhabit the grazing areas.”

Ngaruka said competition exists not only between grass and the woody plants, but also between grass plants themselves.

Selective grazing where only one grass species is targeted has also led to the disappearance of the most valuable grass species, leaving the undesired grasses to dominate rangelands.

Threats to grass species

Annual grasses have short life cycles, grow and live during the rainy season and die off.

Regrowth of annual grasses from the seed occurs in the next rainy season, whereas perennial grasses live for more than one season, stay dormant during winter and re-grow from the same stump and seed in the next season.

“Therefore, grazing animals would depend on perennial grasses during the winter/dry season.”

Over the years, the most valuable perennial grasses have been disappearing from many grazing areas, Ngaruka said.

Lately, the common drought-tolerant Silky bushman grass and Gemsbok tail, which could save animals during dry periods, are slowly losing dominance to annual grasses, especially in grassland areas.

“From the previous rainy season, there has been an abundance of grasses in some grazing areas that were carried over to the current season. This is not optimal rangeland recovery yet.”

Recover rangeland

Rangeland recovery occurs in three basic succession stages, namely pioneer, sub-climax and climax, which are distinguished by the type and species of grass observed. The pioneer is the lower-ranked stage, with grasses having little grazing value compared to the climax stage, which is characterised by the presence of the most valuable grass species.

“Currently, most rangelands, especially those that are overcrowded and are under continuous grazing, will remain in the pioneer stage for a long period," Ngaruka explained.

The grasses that are in abundance are the annual type of grasses, with a short life cycle only available during the rainy season.

These annual grasses have taken over large parts of grazing areas in the central, eastern and northern regions and will disappear in July/August, leaving most of the grazing areas bare.

“Apart from grazing value, perennial grasses also protect the soil. They stabilise and shield the soil from the adverse impact of rainfall, wind and extreme temperatures.”