The “boring” grassland biome?

Map: SANBI

When you look at a map of the vegetation of South Africa, the right half of the map is nearly dominated by one particular biome – grasslands.

The grassland biome covers nearly a third of South Africa’s land area (339 237km²).

Grasslands might bring up rolling images of boredom for some people (they support few to no trees, from afar they seem to support only grasses, and they look brown and boring in the winter).

I’ll explain why this should not be the case.

Despite its somewhat uniform appearance, the grassland biome has particularly high plant species diversity in South Africa, second only to the famous fynbos biome. More about species diversity later.

Animal life is spread liberally throughout the biome in the form of birds, mammals, reptiles, and butterflies – it is also the preferred habitat for South Africa’s national bird, the blue crane (Anthropoides paradiseus).

Ecosystem services – the benefits humans get from nature – are really where grasslands shine. The biggest river systems in the country are born in this biome and nearly 50% of the catchments’ water purifying ‘kidneys’ (i.e. wetlands) are found here.

Further still, beneath the carpet of greenery, gold, diamonds, uranium, and other minerals, but mostly coal can be found. Economic gifts, but arguably an environmental curse.

 

Sketchy understanding

 

 

University of Pretoria MSc student Annerine Myburgh carrying out fieldwork with colleague Mpilo Khumalo.

In 2014 a Department of Environment, Forestry and Fisheries Committee on Land and Mineral Resources reported that 40% of the biome had already been irreversibly modified, 60% of remaining grassland was threatened, and less than 3% was under formal protection.

Despite conservation concerns around the biome, relatively little is known about plant diversity – i.e. how many species there are in the whole biome.

A deeper understanding of the biome’s diversity is also sketchy: we do not know how many species there are per unit area (alpha diversity) and also how species change when we move from one site to another (beta diversity).

University of Pretoria’s Prof Michelle Greve is an expert at understanding the driving forces behind the diversity and distribution of species, at both large and small spatial scales in the grassland biome.

Her expertise led her to apply for SANBI Foundational Biodiversity Information Programme (FBIP) Small Grant funding to shed light on the yet unknown structure of grassland diversity.

 

Alpha, beta diversity

 

According to Prof Greve, this knowledge is crucial for decision-making and has implications for how much diversity is lost if a certain vegetation patch is destroyed, and also how unique that diversity is.

Prof Greve explains how the destruction of high alpha or high beta diversity vegetation can have different results for conservation, highlighting the importance of a nuanced understanding:

“If you have high beta diversity (i.e. species change a lot as you move from one area to another), then, if you destroy one area, the species in that area may not be conserved elsewhere.

This is in contrast with an area that has high alpha diversity (i.e. high species richness in one area) but has low beta diversity. In this scenario, destroying some of the natural vegetation will result in the loss of many species. Still, these species will be conserved elsewhere because species composition is very similar amongst sites.”

Annerine Myburgh (25), Prof Greve’s MSc student on the project, showed that grasslands have both high alpha and beta diversity. So, if a patch of grassland is lost due to e.g. agriculture or mining one not only loses many species, but one might not find the same species in adjacent or other areas.

The implications for conservation are clear: it is not enough to conserve just one area, you need to conserve multiple areas if you want to conserve grassland diversity.

 

EIAs

 

Environmental Impact Assessments (EIA); the process that often stands between the behemoth mining industry and untouched grassland biome, is enhanced by the findings.

“When conducting EIAs to assess diversity within an area to decide on potential land uses (e.g. mining, agriculture), it is not sufficient when doing EIAs to survey only a small area; instead you need to survey extensively across a landscape to get an idea of what species are in an area,” says Prof Greve.

There is much at stake in the grassland biome of South Africa. The biome’s riches clothed in its modest appearance leave it vulnerable to exploitation.

The unique patterns of species diversity have been uncovered by Prof Greve and her team, but will this knowledge find its way into the EIA process?

For now, we know that the grassland biome is a lot more than a boring landscape.

The FBIP is funded by the Department of Science and Innovation (DSI) and jointly managed by SANBI and the National Research Foundation (NRF).