The scientific evidence is clear — elephants are affecting biodiversity in the Kruger National Park


Jeremy Midgley, Op-Ed / The Daily Maverick

Date Published

See link for photos & audio of article. 

There is no doubt that present African elephant populations and distributions are a fraction of what they were a few hundred years ago. Therefore, given this decline, any suggestions that elephant populations are too high in areas where they are still extant, such as the Kruger National Park (KNP), need to be carefully and scientifically argued.

In an article in Daily Maverick, the journalist Don Pinnock has now presented a perspective suggesting that it is a myth that there are too many elephants in the Kruger National Park. In its place he has promoted the Goldilocks myth… elephant numbers are just right. He avoided any references to the large amount of research showing that high elephant densities reduce trees and biodiversity. Pinnock should have at least presented the data for both sides of the argument. 

He declared that we will never know what historical elephant numbers were and that science is unable to specify elephant carrying capacities. But there are chances to reconstruct the past using scientific tools — including archaeology, isotopes, pollen and modelling. Setting carrying capacities for elephants and biodiversity is tough, but within scientific reach.

However, we know from studies of over-grazing that the limit to the long-term survival of all of biodiversity is long before the last blade of grass is eaten and before the population growth of the herbivores involved is in decline. This over-browsed/grazed state is neither the carrying capacity for elephants nor biodiversity.

Pinnock’s response seems to have been motivated by an article I co-authored. To set the record straight, I have been interested in both the positive and negative impacts of elephants, as far as trees are concerned.

For instance, we showed that elephants are crucial in the dispersal of several savanna plant species. The importance of fruits being eaten by elephants is not due to the acid in elephant stomachs, as suggested by Pinnock, but due to their being chewed by elephants.

In other words, elephants cannot be substituted by other animals to effectively crack the fruits of marula, lala palm, torchwoods and other large-seeded hard fruits. The question then is not whether to have elephants, but how many.

Elephant bulls push over trees, not for feeding, but as part of male behaviour. We have also shown that elephants and fire can together damage and kill stems much larger than either could do alone; elephants damage the bark to let the fire in.

We showed that elephants are presently rendering common widespread tree species, such as the lala palm, sterile in KNP. This is because elephants break the stems which keep these plants too small and too short to produce flowers and fruits, and this occurs on a vast geographic scale.

These tree species are still present as short resprouters, but in an evolutionary sense, if they continue to remain sterile, they are not there…  they are the living dead. Being kept in a short, sterile state will have consequences for animals that depend on their flowers (eg pollinators), fruits (eg dispersers, seed-eaters) and on large stems (eg for nests) and for the evolution and dispersal of these plant species themselves.

The point here is that the situation for trees and biodiversity dependent on the reproductive products of these trees is worse than it seems.

Pinnock cited research showing that elephant populations did not increase during droughts. Did he mean they did not decrease? The paper he cited, and others clearly show that elephant distributions are dependent on water. Since managers have increased water availability to elephants, this likely implies there are more elephants now than ever historically.  

Pinnock cited a paper that showed that heterogeneity of KNP, as measured by Landsat, has not decreased over the last 30 years and therefore it cannot be argued that elephants are trashing KNP. This is surprising because much research has shown high rates of elephant damage to trees. 

Landsat is a rather coarse scale (30m x 30m scale) and so it remains to be seen whether trees broken by elephants but still present in the landscape, will be detectable at this scale.

What then should elephant densities be? One perspective is to attempt to determine what precolonial elephant densities were. To begin to answer this question, we considered a broad spectrum of archaeological and ecological evidence.

We argued that archaeological evidence of mass elephant kills, widespread elephant hunting technology including large spears, bows and pits as well as elephant poison use and trading and the presence of ivory artefacts together suggest an important role for people in limiting elephant densities.

We also used a tree perspective, such as considering the population ecology of long-lived baobabs. They are declining in KNP (few births, many deaths, documented elephant damage) and often now only occur on steep slopes that are inaccessible to elephants. The lack of baobab recruits, the presence of only large old individuals and individuals on steep slopes could be evidence that there were fewer elephants historically, and that this allowed baobabs to be more widespread and to recruit. 

Our paper is a beginning to synthesise diverse information on precolonial elephant densities and suggests that they were not as high as presently at KNP. Pinnock simply dismissed our effort as being dependent “on personal opinion formed through experiences, anecdotes, numbers, rates of growth, limited visual impressions and hearsay”.

Elephants are important and sentient animals. This makes any discussion about their management difficult and thus the debate about elephant numbers in KNP should be based on the best data available, not heated discussions.

Pinnock’s use of descriptions such as “shrill complaints”, “rippled with elephants”, “mountains of meat” does not help to keep the temperature down.

Prof Jeremy Midgley is Emeritus Professor in the Department of Biological Sciences at the University of Cape Town.