Veld Rehabilitation

This month has been particularly hands-on in the field for the Conservation Team.

We started our biggest veld rehabilitation project for the year, Grewia thinning, in an effort to combat bush encroachment in the open areas of Ingwelala.

Bush encroachment is an increase in the woody plant densities in an ecosystem, causing the equilibrium to shift unfavourably towards woody plants (trees and shrubs) as opposed to herbaceous plants (grasses and forbs). This results in the decrease in the health and density of the herbaceous layer, and impacts animals and visibility. This can actively be seen in multiple areas on Ingwelala, where previously open areas have become overgrown with shrubs.

It is important that we combat bush encroachment as best we can, because if left to continue indefinitely, it could result in: (1) the total loss of the herbaceous layer in those areas, (2) the loss of a prominent food source for multiple species, (3) the inability for those species to gain access to favourable grazing, and/or (4) it can deplete the moisture content in the soil through woody plant densities being too high for the soil to cope with. This not only affects the ecosystems at hand, but the animals dependent on them as well.

On Ingwelala, we have targeted 8 different sites for the clearing of Grewias, where bush encroachment has changed the entire look of the habitat. This totals an area of about 250 hectares across the reserve, which we hope to clear in the upcoming 3 years.

Bush encroachment by different Grewia species on the previously open areas of Serengeti Plains

Grewias, or raisin bushes, are native woody species that are generally considered to be shrubs. We have four major species on Ingwelala: Grewia bicolor (White raisin), Grewia monticola (Grey raisin), Grewia flavescens (Sandpaper raisin) and Grewia flava (Velvet raisin). There are also cross-pollinated plants from G. bicolor and G. monticola that have begun to pop up as well. Although Grewias are naturally occurring in this habitat, they are considered to be one of the biggest threats to open, arid and semi-arid habitats in terms of bush encroachment because of their unpalatability and quick growth rates. Certainly, on Ingwelala, Grewia species have completely over-grown in the open areas, and a thinning of these areas has been long overdue.

Over a period of 9 days, we selectively targeted Grewia species on Buffelsbed, which were cut and then immediately treated with a high salt and oil solution, and a blue colourant, to prevent coppicing in the spring. This involved using a 3-wheeler clearing machine, 2-3 staff walking behind moving cut materials away from the stumps, and 3 staff treating the cut stumps behind the clearing crew. The blue colourant will fade, and simply acts as a marker for which stumps have been treated and which have not, to avoid missing stumps or treating the same ones twice. The large, rough tyres and the weight of the machine also assisted with simulating the movement of a buffalo herd moving through the open areas - churning up the soil and compacting cut branches over the soil to act as brush packing material.

The 3-wheeler used to clear Grewias | The 50 hectare area cleared over 9 days

The clearing went incredibly well and we are pleased with the immediate results. Only time will tell how successful the clearing has been, though, because potential re-growth will only begin to surface in the spring. That being said, we are already noticing more grazers enjoying the areas that have been cleared, and as the cut plants die down, the area will become more open with time. For now, it will still look a bit overgrown and “blue” - but this will not last long.

We will slowly be clearing the debris out of the area and transfer any extra brush packing material to other sites that need it to make sure that we can cover as much ground as possible with this project. We will be monitoring the progress of the clearing and brush packing efforts in the coming months, and hopefully continue the project on other targeted areas in the future.

A massive thank you to the Ingwelala community, the Conservation Team and Bush Clearing Solutions for making this possible. We look forward to monitoring the progress!

by Tess Woollgar. Images courtesy of Tess Woollgar.