Conservation | Boabab Populations in the OmusatiJuly 3, 2015
Camping in KhaudumJuly 9, 2015
Ecology field course for young environment leaders
Gobabeb Training and Research Internship Programme
Dr Theo Wassenaar
The Desert Science, Research and Training Programme is the 2013 version of Gobabeb’s popular GTRIP (Gobabeb Training and Research Internship Programme) course for postgraduate Namibians. DeSeRT focuses on a unique and diverse part of the central Namib- the triangle formed by the confluence of the Khan and Swakop rivers. This area, known for its high biodiversity and scenic attractiveness, is also the location of the new Husab Uranium Mine. The aim is to understand the potential ecological impacts of this mine, and contribute to the debate on how to mitigate and/or restore such impacts. Cammy Ndaitwah, Elise Nghalipo and Ndapewa Iipinge studies aspects of the ecology of the arid ecosystem. Highlights of their studies, which were supported by Go Green Fund and Swakop Uranium, are detailed below.
The recovery of biological soil crust in response to rehabilitation
Biological soil crust (BSC) is a cohesive organic layer on the surface of the soil, created by fog-adapted organisms such as hypolithic (“below the rock”) cyanobacteria (called HLC) and lichens that bind soil particles together, aid water retention and dispersion, and fix atmospheric nitrogen. HLC are easily disturbed and often destroyed during recreational mineral exploration off-road driving. The study established the baseline, but also found that the recovery of HLC after disturbance takes many years. No evidence was found that raking (the currently preferred rehabilitation method) increased the rate of recovery. A site that was disturbed 43 years ago also has no yet recovered HLC cover similar to the adjacent undisturbed areas. But a lot is not yet known. Different rehabilitation techniques- raking, sweeping, watering and so on – may have different outcomes. In addition, severity of disturbance, frequency of disturbance, and external climatic factors, may all impact the recovery rate of HLC and BSC in general, and therefore need to be studied in more detail.
Correlates of the health of plants, as a baseline for a future monitoring programme
Desert plants are components of biodiversity and, through providing habitat and food to other organisms, also functional elements that affect overall biodiversity. Plants naturally experience many stressors, such as dust, that lead to physiological stress from which they can recover, but a long-term stressor may cause the death of a plant and eventually affect the fortunes of the whole population. Dust occurs naturally in arid zones, but mining activities generate excessive amounts of dust. This project was therefore designed to establish standardised techniques of measurement and baseline values for plant health and stress (general plant health, growth rate, reproductive health and physiological stress of Welwitschia, pencil bush and dollar bush) relative to the location of Husab Mine.
An ancillary investigation also showed that the amount of dust currently on plants increases significantly closer to the mine and closer to roads. More importantly, the physiological health of Welwitschia plants was significantly lower when covered with road dust than without it, confirming the negative effect of dust on plants and highlighting the importance of understanding this impact at the physiological level. Questions for further study relate to the rate of change in health status, the critical stress levels at which plants start dying, the relative magnitude of stress caused by mine dust (vs other natural stressors) and the population-level effect of stress on reproduction and mortality rates. This study achieved its primary aim of providing the baseline data and standardised techniques for a long-term monitoring programme, assisting the company to detect and mitigate the impacts of dust on the natural environment.
The Husab sand lizard’s ecology, spatial distribution and behaviour, and potential for impacts by mining
Impacts on species with restricted ranges are an important aspect of the overall impacts of mining on the Namib’s biodiversity. Although there are many invertebrate and vertebrate endemics with extremely small ranges in the central Namib, the Husab sand lizard (Pedioplanis husabensis) which occurs near the Khan and Swakop rivers, is a good example of such an organism that is also in potential conflict with mining. Previous studies have shown that the Husab sand lizard may be a habitat specialist, preferring light-colored rocky substrates. Extreme habitat specialisation such as this could partly explain its small range and furthermore restricts the management of impacts. However, previous studies focused on only a small part of its known range. The current study, part of a larger set of projects on the topic and on the species, added more sites and more observations of its habitat preference. Different from previous studies, which found that the species was confined to rock, half of the observed lizards were found on sand, while 43% were found on rocks and 7% on gravel. The study also confirmed that the species avoids dark-colored substrates and prefers surface temperatures between 40 and 49’C. The current study also showed a clear preference of the lizards for low vegetation (grass and shrub) cover. Similar to previous studies, the lizards were mostly active from 10:00 am to 12:00 pm every day.
Overall the findings from this study suggest that the behaviour and habitat preference of the species is more general than originally suspected, allowing more options for managing potential impacts on the species from mining and exploration activities.
What will happen in future
The DeSeRT Programme will continue, albeit under an old acronym. GTRIP will continue the theme of ecological restortaion of arid areas, but focus exclusively on understanding the nature of disturbance to and the factors that affect the recovery of soil surface ecosystems (including HLC). To improve efficiency of supervision and training, the future course will concentrate on areas surrounding Gobabeb.