Pretoria - 4x4 vehicles should be banned from off-road driving in protected areas because of their negative impact on the environment.
Dr Gerhard Nortjé, a soil scientist who received his doctorate in wildlife management at the University of Pretoria this week, said the soil damage by 4x4 vehicles was “underestimated, long-term and mostly irreversible”.
Nortjé suggests that strict legal measures be applied to regulate the use of 4x4 vehicles in protected areas and said sensitive areas, such as wetlands, should be declared “absolute no-go areas”.
“While it may not seem that off-road driving has negative impact on the environment, especially on the soil and vegetation, the risk of damage is real,” said Nortjé.
“It is not an ecologically sustainable practice and should therefore not be allowed.”
Some of the negative impacts of eco-tourism include damage to vegetation, habit destruction and soil erosion.
Nortjé based his research on Makuleke Contractual Park in the north of the Kruger National Park and found SANParks should reconsider its management strategies for off-road driving in its protected areas.
While SANParks recognises the potential damage off-road driving can cause, it does not specifically acknowledge possible soil damage.
Some of SANParks’ guidelines - such as suggesting vehicles do not drive in each other’s tracks - have not been scientifically validated.
Nortjé’s research shows that up to 90 percent of soil damage is caused the first time a vehicle passes over an area.
“Vehicles should be driven in the same tracks when driving off-road as a form of traffic control, and lower tyre pressures should be used,” he said.
His research also showed that wet soil was more prone to damage than dry soil.
Off-road driving causes three types of soil degradation - dense compacting of the subsurface layer because of the vehicle’s wheels, the formation of a dense, thin soil crust under the tracks and soil erosion due to increased run-off from the hard soil crust.
The degradation leads to the soil drying out because of poor water infiltration and increased run-off.
Soil crusting makes plants vulnerable to drought and influences their ability to absorb water because their roots are shallow and poorly developed.
Plants in these areas are nutrient deficient and do not grow well. The degradation of vegetation worsens over time because of a predisposition to further damage.
The negative effects are not limited to the narrow tracks, but have a wider lateral effect on both sides of the tracks.
Nortjé’s results show the need for improved visitor education regarding the impact of off-road driving and legal measures to control this practice.
As wild animals are found in areas with the most nutritious vegetation, that is where predators are also found. These areas experience the highest frequencies of off-road driving because tourists and visitors want to be close to the wildlife.
This means that in game reserves, people often drive on virgin and undisturbed soil.
“Tourists’ ignorance and lack of consideration for the environment - or the soil for that matter - combined with operators’ and land owners’ need to make money is normally the reason for allowing off-road driving,” said Nortjé.
To simulate the effect a fully laden vehicle with tourists has on the soil, Nortjé used a game driving vehicle loaded with 10 sand bags, each weighing 70kg.
Nortjé owns a 4x4 but said he only used it in designated areas.