The 59th annual congress of the Grassland Society of Southern Africa (GSSA) took place in July in somewhat chilly conditions at the Gariep Forever Resort in the Free State. It was a hybrid event for the third consecutive year, which means that delegates could attend in person or virtually be part of the conversation that cantered on South Africa’s grassland and rangeland ecology.
Prior to the congress, a research skills workshop, steered by Dr Justin du Toit, production scientist at the Grootfontein Agricultural Development Institute, offered participants the opportunity to learn more about artificial intelligence (AI) and how to use it responsibly in data analysis, writing, and research. On the last day of this year’s event, a Policy and Practice workshop was facilitated, shining the spotlight on woody range-expanding species in Southern Africa’s mountain areas (trends, predictions, and mitigations).
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The sessions at this year’s congress covered detailed presentations relating to climate change and carbon, biodiversity and conservation, rangeland and fire ecology, and communal rangelands. While most of the focus was on rangelands (grasslands, savannas and the Karoo), a session on cultivated pastures and feeding ecology also addressed more intensive production systems.
Climate change tops the list
Susanne Vetter, associate professor in the Department of Botany at Rhodes University, gave a presidential address to welcome the delegates at this year’s congress. During her presentation, she reported on research on climate change and fire in the Kalahari where wet seasons result in high grass biomass that can lead to large wildfires. At the gala dinner and awards ceremony, she received the award for best presentation.
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The first keynote speaker was Prof Guy Midgley, researcher and acting director of the School for Climate Studies at Stellenbosch University, who tackled the controversial topic of climate change and carbon dioxide (CO₂). A large chunk of bush encroachment, he said, is driven by carbon, and grazing lands are being lost due to endemic invasive (woody) bush encroachment because of the vast amount of CO₂ in the atmosphere.
He addressed soil carbon in arid ecosystems and the role it plays in global carbon storage, emphasising the fact that better land use and rangeland restoration can make a limited but important contribution to absorbing carbon from the atmosphere. He also shared preliminary data showing how resting and restoring degraded veld can act as a carbon sink.
In support of grazing
During his keynote address on rangeland ecology and management, Richard Fynn, associate professor at the University of Botswana, said conventional rotational grazing tends to put livestock into camps where the grass has already grown and lost its nutritional value. This leads to poor animal performance and selective grazing, with both reducing veld condition. Soil nutrient availability peaks for a few months after the first rains, followed by a period of root growth, and grasses need a full season’s rest to recover from grazing and take advantage of this entire period, not just part of it, to take up nutrients and then to grow their roots.
Talking about the ambiguity of grazing intensity and providing a novel index for quantifying this metric to address conflicting outcomes of grazing systems comparisons, Prof Urs Kreuter from Texas A&M University said that much effort has gone into comparing the effectiveness of continuous versus rotational grazing. Yet it is not a simple binary.
He and his PhD students have developed an index that measures different dimensions of a producer’s grazing management, including grazing intensity, rest, and stocking rate. They found that there was a huge variety of practices, and to evaluate their effects on animal performance and veld condition, one needs to include these different metrics rather than do a simple comparison of continuous versus rotation.
Invaders and encroachment
In terms of dealing with invasive species, Liam Cogill, a PhD student at Stellenbosch University, broached the subject of satellite remote sensing to measure the water-use impact of invasive alien trees in the grasslands of Southern Africa. He touched on one of the questions currently in the spotlight, namely whether acacia species in the Karoo have a bigger environmental impact than wattle.
During the policy and practice workshop, William Bond, emeritus professor in Biological Sciences at the University of Cape Town, talked about bush encroachment in Southern African mountain areas. He also addressed the question of why the upland grasslands are tree-less. At this year’s award ceremony, he received the Prestige Award, a rare honour (last awarded in 2015), which recognises scientists whose work has made a significant impact on range and forage science and/or practices.
Another presentation at the policy and practice workshop that gave much food for thought was delivered by Brian van Wilgen, emeritus professor at the Centre for Invasion Biology at Stellenbosch University. He took a closer look at legislation governing the management of invasive alien woody plants in South Africa, what is regarded as acceptable changes in the environment, and how decisions will be taken as to which plant species are deemed acceptable or unacceptable in South Africa. – Carin Venter, Plaas Media
For more information regarding the GSSA, send an email to Minette van Lingen, society administrator, at info@grassland.org.za or visit www.grassland.org.za.
