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31 October 2021 | Story Elsabé Brits
Grassland

In the vast, flat grasslands of South Africa a host of magnificent plant and animal species flourish, but not all of them are large. Insects and spiders share the landscape, and they are sometimes the uncelebrated heroes of a fragile ecology.

Walking through grasslands one often ignores what is under our feet, but these creatures are vitally important for the wellbeing of any ecosystem.

Grasslands are the dominant vegetation in the central parts of the country, covering most of the Free State and Gauteng and large parts of the North West, Mpumalanga, KwaZulu-Natal and the Eastern Cape, explains Prof Charles Haddad from the Department of Zoology and Entomology in the Faculty of Natural and Agricultural Sciences at the University of the Free State (UFS).

Insects fulfil a myriad of ecosystem functions and deliver crucial services in grasslands. They are the most important group of pollinators, such as bees, flies, and beetles, and are critical to the breakdown of plant and animal waste, especially flies and beetles. They are predators and parasites of other invertebrates, especially spiders, beetles, wasps and flies. The more species in an ecosystem, the greater the number of interacting organisms that can contribute to food webs.

Unfortunately, grasslands are the most threatened biome in South Africa, largely as a consequence of historical agricultural expansion of crop and livestock farming. More recently, urban development, invasive plants and silviculture have impacted on the remaining natural grasslands.

“Little is known about the impact of these activities on terrestrial biodiversity. The presumption is that the destruction and fragmentation of natural grassland reduces the natural vegetation available to indigenous organisms. This creates problems for insects to find suitable plants to feed on, which has a negative impact on their predators and parasites.

“Most anthropogenic influences affect indigenous biodiversity negatively, with very few exceptions. Generally, it is exotic invasive species that benefit the most from disturbance, habitat changes or destruction,” says Prof Haddad.

Spiders

More than 900 species of spiders have been recorded in our grasslands and some 2 300 in the country. Spiders are predators of other invertebrates, especially insects, and play an important role in the natural control of their populations.

They are very resilient to disturbance but are susceptible to chemicals used on crops, the effects of alien plants, and competition with exotic spider species, says Prof Haddad.

Among the interesting spider species one can find in grasslands is a rich diversity of trapdoor spiders, which live in burrows in the ground. Many of them have narrow associations with specific soil types and are often good bioindicators for conservation management.

Some plant-dwelling spiders are uniquely adapted to living on grasses and have slender, pale bodies to camouflage themselves on the stalks of grasses. In contrast, tree-dwelling spiders are often brown with tubercles on their bodies to blend in with the bark of trees to help them ambush their prey, says Prof Haddad.

Termites

Termites are some of the most populous animals on Earth, and the effects they have are most profound in the grasslands. Termites are one of the few animals that can break down cellulose from dead wood and grass. This is made possible through their symbiotic association with tiny microorganisms in their alimentary canal, such as protozoans and bacteria. The microorganisms secrete the enzyme cellulase, which the termites cannot produce themselves, allowing for the breakdown of cellulose in the ingested plant material and the release of the component nutrients for use by the termites. Therefore, these insects play an integral role in the reintroduction of nutrients from the dead plants into the soil.

This enables them to utilise the molecules in the grass that would have otherwise been inaccessible. Their faeces, therefore, contain broken-down nutrients that the roots of plants can absorb.

Many termite species live in underground nests that are great in aerating the soil. Others build large mounds which are extensions of the nests above the soil surface. These mounds, particularly those of the snouted harvester termites, are a familiar feature in most grassland landscapes in the country. These nests and mounds also offer shelter to other organisms, such as spiders, scorpions, lizards, snakes, millipedes, and various insects.

Termites are an important food source for enigmatic animals such as the aardvark and aardwolf, as well as some spiders and beetles, says Prof Haddad. 

Mosquitoes 

Liezl Whitehead, a master’s student in the Department of Zoology and Entomology at the UFS, explains the role of how even mosquitoes are essential.

Mosquitoes are vitally integrated into the ecosystem even as larvae, where they feed on aquatic microorganisms, thereby affecting species interactions and ecosystem dynamics within the aquatic habitat.

Adult mosquitoes feed on nectar as their main food source, and in the process also serve as plant pollinators. Many female mosquitoes do, however, require a blood meal for egg production, where they then transmit a multitude of pathogens. Interestingly, these pathogens play a vital role in the ecosystem, where they help to regulate host population sizes, thereby maintaining the integrity of the ecosystem.

“In recognising the significance of all forms of life, one also realises that mosquitoes play an essential role in the life cycle of numerous other organisms, including protozoans [single-celled microscopic organisms], nematodes [often referred to as roundworms, but they are not closely related to true worms], and mites that depend on mosquitoes for their development and dispersal.

The abundance and widespread nature of mosquitoes contributes to their significant role in the grassland food chain, where the larvae are consumed by countless aquatic organisms, including insects, fish and amphibians. The adults are consumed by a multitude of arthropods and vertebrates, including dragonflies, birds and bats.

“Their elimination from the ecosystem would thereby impact multiple processes within the ecosystem, affecting food webs, pollination and the presence of many other associated organisms,” Whitehead adds. 

A vital food source, urgent protection needed

Prof Liesl van As, Head of the Department of Zoology and Entomology at the UFS says that although the Grassland biome covers an area of 339 237 km2, less than 2% is formally protected. In 2004, the National Spatial Biodiversity Assessment (NSBA) identified the Grassland biome as the most threatened habitat, with more than 30% already irreversibly transformed. A year later, the Grassland Biodiversity Spatial Priority Assessment identified 37% of the land as being important for conservation and suggested that 12% needs to be under formal protection by 2028.

Most of the South African grassland literature refers to the almost 400 plant species, the 34 endemic mammals, and the dozen or so globally threatened bird species, with almost no mention to representatives of the Arthropoda (including spiders, termites and mosquitoes).

Invertebrates are the main components of faunal diversity in grasslands, playing substantial roles in ecosystem processes, including nutrient cycling, pollination, and being a vital food source in food webs (Die een se dood is die ander een se brood).

“These invertebrate communities are heavily dependent on plant diversity and production within a given ecosystem, but for some reason, they don’t get the full recognition and attention compared to the larger animals. Maybe it is because they are not so visible due to their smaller size?

“A visit to www.grasslands.org.za and the Grassland Society of Southern Africa draws our attention towards the fact that although progress has been made in the awareness of the sensitivity of grassland habitats, gaps still exist concerning the biodiversity of the remaining natural fauna. To follow up on this, I am of the opinion that when it comes to invertebrates, such as the spiders, termites and mosquitoes we are now writing about, knowledge and public awareness (citizen science) is contributing to reducing this gap” says Prof Van As.

According to her, in their department, a number of colleagues from Animal Behaviour, Arachnology, Nematology, Applied Agricultural Entomology, Environmental Entomology and Dipterology, to name a few, have been involved in research projects for the past few decades, with a focus on the grassland area, closer to home.  Through their effort and contributions, they are making a scientific difference. 

News Archive

Agriculture must adapt to change
2008-11-28

 

At the launch of "50 years of agriculture" at the UFS were, from the left: Mr Corwyn Botha: Chairman: Agri Business Chamber and Managing Director: Cape Agri Group, Mr Motsepe Matlala, President of NAFU, Mr Hans van der Merwe, Executive Head: Agri SA, Prof. Herman van Schalkwyk: Dean: Faculty of Natural and Agricultural Sciences at the UFS, and Mr Sugar Ramakarane, Head: Department of Agriculture, Free State Province.
Photo: Lacea Loader

 “The biggest factor driving agriculture today is change. Our major challenge is to adapt to this changing environment.” This was stated by Prof. Herman van Schalkwyk, Dean of the Faculty of Natural and Agricultural Sciences at the University of the Free State (UFS) during the recent celebration of the faculty’s “50 years in agriculture”.

Prof. Van Schalkwyk stated that the most important changes include power relationships in supply chains, consumer demand, new products and technology in agriculture, government action and developments in neighbouring states. “At the moment there is very little cooperation between small-scale farmers, small-scale farmers and commercial farmers and farmers and processors. There are also low levels of processing, low levels of value adding and a lack of creative thinking in agriculture," he said.

“This must change – we need comprehensive agricultural support and new business ideas in agriculture. We need better infrastructure, value chain financing and improved institutional support,” he said.

Speaking about agriculture and institutional co-operation in the Free State, Mr Sugar Ramakarane, Chief Director of the Free State Department of Agriculture, said that the UFS plays a vital role in bringing together organised agriculture in the province. “The responsibility of transforming our economy cannot be done by government alone. We need partners like the UFS to assist us with bringing together the two most important stakeholders of the agricultural sector, namely the National Farmers’ Union (NAFU) and Free State Agriculture. You can assist us with harnessing co-operation and providing practical solutions," he said

Mr Ramakarane said that his department is aware of the university’s good work with emerging farmers. “But, I want to encourage the university to help us with skills transfer and the development of the emerging farmers. You can play a vital role in developing a mentorship programme. Yours remains a central and critical role of being torch bearers in guiding the transformation agenda of our country," he said.

In his contribution on the challenges of small scale farmers in South Africa and the role of the university, Mr Motsepe Matlala, President of NAFU, said that unity in organised agriculture and working together with other stakeholders has become even more crucial with regard to the global challenges now faced by the country. “The university should take the lead in guiding all farmers on how to respond to, among others, the global financial turmoil and politics, developments in trade negotiations, food prices, input costs and the availability of energy," he said.

“If the UFS, and more specifically the Faculty of Natural and Agricultural Sciences, is to continue to play a leading role in academia as well as in the production of research that matters to the growth and development of this country, it must adopt an approach that seeks to harness the capacity of everyone in an inclusive manner. The strides already made in this regard must be applauded,” Mr Matlala said.

Speaking on the future challenges in agriculture and the role of universities, Mr Hans van der Merwe, Executive Head of Agri SA said that South Africa has not spent money on agricultural development in a long time. “We must increase our product capacity in the agricultural sector. Universities must focus on cultivating enough expertise and the skills necessary to manage the resources and capacity needed," he said. In his view, South Africa must also focus on technological advancement in agriculture as this has also been neglected in the past. He urged universities to provide best-practice education and to look at international trends in agricultural training. “That is why we should not only focus our attention on South Africa, but on southern Africa,” Mr van der Merwe said.

In conclusion to the day’s programme, Mr Corwyn Botha, Chairperson of the Agricultural Business Chamber, Managing Director of the Cape Agri Group and former Kovsie stated that: “If you want to be an example of leadership, people around you must do better because you are there. A university should evaluate itself in this context. You cannot create solutions to problems with the same attitude in which the problems were created."

Media Release
Issued by: Lacea Loader
Assistant Director: Media Liaison
Tel: 051 401 2584
Cell: 083 645 2454
E-mail: loaderl.stg@ufs.ac.za  
28 November 2008
 

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