Over 50,000 ants have stumbled into traps in the ground and thus into the hands of Kate Parr, who has been looking at how fire affects biodiversity in the Kruger National Park (KNP). Microscopic examination of this multitude of ants has revealed 169 species – an astonishing amount of biodiversity when you consider that Kruger is estimated to have only 122 species of mammals, 109 species of reptiles and 55 fish species.
It is also more than double the number of ant species found when ants were initially surveyed in the 1960s. It might seem that 169 species is a lot, but Kate says, “The total number of species I found is probably still only about half of the estimated total number of ants species in the whole of Kruger!”
The new research on ants is taking place in one of Kruger’s oldest experiments – the Experimental Burn Plots. Fire is known to affect how the trees and grass in savanna ecosystems interact, and to induce changes in biodiversity.
For the last 50 years, land has been set aside in the Experimental Burn Plots and subjected to controlled burning at different time intervals and times of the year to see what changes occur.
The burn plots provided an ideal location for Kate to investigate how fire was affecting biodiversity - not the more commonly considered trees and grasses, but the busy little ants that prey on other species, eat greenery and scavenge on anything dead.
Kate says, “Ants can be used as indicators of landscape health and ecosystem condition. They are relatively easy to sample, get sufficient numbers of, and they are relatively easy to identify.”
One ant may not weigh much, but the combined weight of all the ants in all the colonies is considerable. With different species of ants performing different roles in the ecosystem, their combined effect helps keep the savanna system functioning. Sampling from six different fire treatments in the burn plots allowed Kate to gain an idea of how fire affects ant biodiversity.
She says, “Ants were very resistant to fire”, with the major finding being that differences in the ant communities existed mostly between sections that had not been burnt for a very long time and those that were burnt regularly. This held true regardless of the frequency or timing of the burns that were applied to the burnt plots.
Some species of ant were only found on plots that had not been burnt for a long time, but Kate suggests that these species are also likely to occur in habitats that have more woody vegetation, such as along rivers.
“My results indicate that at least for ants, there may not be a need for a diverse range of fire regimes to be applied. This idea needs testing for a range of other organisms now.”
The timing and frequency of fires has long been a hot topic amongst savanna ecologists, and this ant’s perspective may help future scientists to decide how much fire is necessary to maintain biodiversity in an ecosystem.