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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

Higher than expected prevalence of dementia in South African urban black population
2010-09-22

 Prof. Malan Heyns and Mr Rikus van der Poel

Pilot research done by University of the Free State (UFS) indicates that the prevalence of dementia, of which Alzheimer’s disease is only one of the causes, is considerably higher than initially estimated. Clinical tests are now underway to confirm these preliminary findings.

To date it has been incorrectly assumed that dementia is less prevalent among urban black communities. This assumption is strongly disputed by the findings of the current study, which indicates a preliminary prevalence rate of approximately 6% for adults aged 65 years and older in this population group. Previous estimates for Southern Africa have been set at around 2,1%.

The research by the Unit for Professional Training and Services in the Behavioural Sciences (UNIBS) at the UFS and Alzheimer’s South Africa is part of the International 10/66 Dementia Research Group’s (10/66 DRG) initiative to establish the prevalence of dementia worldwide.

Mr Rikus van der Poel, coordinator of the local study, and Prof. Malan Heyns, Principal Investigator, say worldwide 66% of people with dementia live in low and middle income countries. It is expected that it will rise to more than 70% by 2040, and the socio-economic impact of dementia will increase accordingly within this period. 21 September marks World Alzheimer’s Day, and this year the focus is on the global economic impact of dementia. Currently, the world wide cost of dementia exceeds 1% of the total global GDP. If the global cost associated with dementia care was a company, it would be larger than Exxon-Mobil or Wal-Mart.

The researchers also say that of great concern is the fact that South Africa’s public healthcare system is essentially geared toward addressing primary healthcare needs, such as HIV/Aids and tuberculosis. The adult prevalence rate of HIV was 18,1% in 2007. According to UNAIDS figures more than 5,7 million people in South Africa are living with HIV/Aids, with an estimated annual mortality of 300 000. In many instances the deceased are young parents, with the result that the burden of childcare falls back on the elderly, and in many cases elderly grandparents suffering from dementia are left without children to take care of them. “These are but a few reasons that highlight the need for advocacy and awareness regarding dementia and care giving in a growing and increasingly urbanized population,” they say.

Low and middle income countries often lack epidemiological data to provide representative estimates of the regional prevalence of dementia. In general, epidemiological studies are challenging and expensive, especially in multi-cultural environments where the application of research protocols relies heavily on accurate language translations and successfully negotiated community access. Despite these challenges, the local researchers are keen to support advocacy and have joined the international effort to establish the prevalence of dementia through the 10/66 DRG.

The 10/66 DRG is a collective of researchers carrying out population-based research into dementia, non-communicable diseases and ageing in low and middle income countries. 10/66 refers to the two-thirds (66%) of people with dementia living in low and middle income countries, and the 10% or less of population-based research that has been carried out in those regions.

Since its inception in 1998, the 10/66 DRG has conducted population based surveys in 14 catchment areas in ten low and middle income countries, with a specific focus on the prevalence and impact of dementia. South Africa is one of seven LAMICs (low and medium income countries) where new studies have been conducted recently, the others being Puerto Rico, Peru, Mexico, Argentina, China and India.

Mr Van der Poel says participating researchers endeavour to conduct cross-sectional, comprehensive, one-phase surveys of all residents aged 65 and older within a geographically defined area. All centres share the same core minimum dataset with cross-culturally validated assessments (dementia diagnosis and subtypes, mental disorders, physical health, anthropometry, demographics, extensive non-communicable risk factor questionnaires, disability/functioning, health service utilization and caregiver strain).

The local pilot study, funded by Alzheimer’s South Africa, was rolled out through an existing community partnership, the Mangaung University of the Free State Community Partnership Programme (MUCPP).

According to Mr Van der Poel and Prof. Heyns, valuable insights have been gained into the myriad factors at play in establishing an epidemiological research project. The local community has responded positively and the pilot phase in and of itself has managed to promote awareness of the condition. The study has also managed to identify traditional and culture-specific views of dementia and dementia care. In addition, existing community-based networks are being strengthened, since part of the protocol will include the training and development of family caregivers within the local community in Mangaung.

“Like most developing economies, the South African population will experience continued urbanization during the next two decades, along with increased life expectancy. Community-based and residential care facilities for dementia are few and far between and government spending will in all probability continue to address the high demands associated with primary healthcare needs. These are only some of the reasons why epidemiological and related research is an important tool for assisting lobbyists, advocates and policymakers in promoting better care for those affected by dementia.”

Media Release
Issued by: Mangaliso Radebe
Assistant Director: Media Liaison
Tel: 051 401 2828
Cell: 078 460 3320
E-mail: radebemt@ufs.ac.za  
21 September 2010

 

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