Projects

Causes and Consequences of Savanna Tree Cover Change

The structure and productivity of savannas has undergone major transitions over the past century, with widespread increases in the cover of small trees and shrubs recorded for sites across the world. Rapid increases in cover have occurred throughout southern Africa, some starting in the late 1800's, and are referred to locally as "bush encroachment". Recent studies show that "bush encroachment" has occurred rapidly in many areas over the past decades in South Africa. At the same time, the abundance of tall trees has been declining in certain, particularly in protected areas where elephants occur. These changes have importance consequences for biodiversity and ecosystem services. Many theories have been proposed to explain these changes, but robust evidence to support them is lacking. Altered fire regimes, overgrazing, declining abundance of browsing, and increased concentrations of atmospheric CO2 have all been proposed as drivers of "bush encroachment“. Evidence supporting the importance of each is limited and often site-specific, while interactive effects have rarely been considered. Critical evidence that is lacking from almost all studies is that of changes in the population dynamics of dominant woody species. This is also a critical gap of knowledge for understanding the decline of tall trees, and the long-term impacts of altered elephant populations. This project aims to provide the long-term demographic data needed to determine past and current changes in the tree layer of savannas. Such data is also critical for modelling future changes. The project is currently implemented at 10 sites in the central lowveld region of South Africa.

NEMO: North-Eastern Mountain Observatories

Mountains are globally recognized as areas where global climate change is having the greatest impact. In the north-eastern parts of South Africa the Soutpansberg and Drakensberg Escarpment form a stark contrast to the generally flat landscapes, extending from around 400m up to nearly 2000m above sea level. This creates strong gradients in climate, soils and ecosystems, and these mountains harbour a high diversity of plant and animal species. Many of these are restricted to the peaks, and are likely to experience shifts in their distributions in response to global climate change, long before the biota of the savannas below. This project aims to detect the impacts of global climate change on montane ecosystems at selected sites. Currently, the focus is on detecting shifts in the boundaries of biomes (particularly grassland to savanna or thicket) and the herbaceous plant diversity of montane grasslands.

The Phalaborwa Land Use Laboratory

The land surrounding the town of Phalaborwa (Limpopo Province) contains a variety of land uses and land management styles, many characteristic of the major land uses of the semi-arid savannas throughout southern Africa. These include large protected areas (the Kruger National Park and the adjacent "Association of Private Nature Reserves"), game farms, rural rangelands (including large areas of small-scale cultivation) and mines. Phalaborwa therefore provides an excellent location to study the effects of land use on biodiversity and ecosystem services, as well as the interactive effects of land use, global climate change and rising atmospheric CO2. This project currently involves assembling a range of base-line surveys for indicators of ecoystem-level biodiversity (including herbaceous and woody plant, dung beetle and bird diversity, and mammal, heptofauna and amphibian species richness). Annual data for selected ecosystem services variables (specifically net primary productivity and secondary productivity) are steadily accumulating.

The Letaba River Hydrological Observatory

A long-term project to study the impacts of land use and climate on the hydrology of the lower reaches of a perennial river, within a semi-arid savanna catchment. The study site covers a stretch of the Letaba River just upstream of the Kruger National Park, including local catchments in both a rural agricultural and conservation area. While much research has been done on the effect of land use and management on hydrology, this has mostly been done in source areas, i.e. high altitude areas where rainfall is greatly exceeds evapotranspiration, and water runs of the landscape and into rivers. But many rivers actually lose water further along their course, as they flow down into more arid areas. What is the effect of land use and management in these areas? Could appropriate land management lead to a reduction in water loss from large rivers, and significantly improve the supply of fresh water downstream? The first phase of this project, initiated in 2014, investigates these questions. All the key components of the hydrological cycle are being quantified, in order to determine whether signficant losses of water occur from the Letaba River, to groundwater and / or through evapotranspiration in the riparian zone. The three-year project will form the basis of long-term data collection and research at this site, giving rise to a genuine hydrological observatory. SAEON intends to maintain all the instrumentation deployed and continue with data collection well beyond the initial three years, and add new projects, instruments and data in the future. This will allow for a better understanding of interactive effects of land use and climate, and provide the type of long-term data needed to detect, and predict, the impacts of climatic change on freshwater resources.

Intensive Monitoring of the Lower Olifants River

The Olifants River is one of the most degraded rivers in the country, with numerous sources of pollution from mining, agriculture and settlements, and numerous dams within its catchment. As the river flows into the Lowveld, it receives some additional pollution but also also flows through extensive protected areas before entering Mozambique. In 2009, the Node established 10 monitoring sites on the lower Olifants River and its main tributaries, in order to better monitor pollution inputs, and study the response of water quality and aquatic biodiversity to these. Surveys of macro-invertebrate and fish composition are used as integrative indicators of water quality and aquatic biodiversity. The specific aims are to: - to determine if a widely used monitoring methods (SASS) can be used to detect large pollution events, - detect trends of changes in water quality on seasonal and annual time scales and - provide long-term data on both aquatic communities and key water quality variables, at the same sites.

Changing Distributions

Global change has already began to alter the distribution of many species in the northern Hemisphere. While such changes are also beginning to occur in Africa, we have little knowledge or this, due to the scarity of suitable that data that reliably indicate a change in distribution, and a lack of accurate models that can indicate which species are most likely to expand or retreat. This project involves surveys to establish the current distribution of selected species that are likely to change their distribution significantly in response to changing climate over the coming decades. Surveys have been conducted in selected areas on the edges of the current distribution of these species. Due to the potential impact of temperature changes, most of the surveys for this project have been conducted at high altitude sites on the peaks of the Drakensberg Escarpment.