As a result, some trees end up being less than two metres tall, which is far shorter than their normal height.
Two Madikwe elephant bulls. Photograph Jan Venter
By tracking changes in 3,500 trees across 13 dominant tree species over nearly two decades (in 2000 to 2001 and again in 2019), the study showed how the elephants and meso (medium-size) browsers gradually reshaped the architecture of trees in the 75 000-hectare Madikwe Game Reserve. The research provides vital evidence to support adaptive, science-based management of fenced savanna reserves.
The article is entitled ‘Long-term effects of an elephant-dominated browser community on the architecture of trees in a fenced reserve’
Dietre Stols and Dr Lucie Thel, the first authors of the article
“As elephant populations increase in fenced reserves, managers face difficult choices to maintain ecological balance, hence this study was undertaken to provide the rigorous, long-term data needed to guide sustainable conservation actions,” says MSc student Dietre Stols from the Department of Conservation Management at the University. He and Dr Lucie Thel, also from the Department of Conservation Management, are the first authors of the article.
“We used historical data from woody vegetation monitoring conducted at Madikwe in 2000 to 2001, and we gathered data again in 2019 in the reserve, which has an increasing elephant population (from 250 in 1990 to 1600 today),” says Thel. “We could compare this with the adjacent elephant-free Barokologadi Communal Property.”
One of the co-authors of the paper is Professor Jan Venter, also from the Department of Conservation Management, who explains: “A primary concern is the evidence of structural degradation in certain woody species exposed to long-term elephant impact. The fact that 80% are under two metres in height, which can be half the normal height for some species, suggests that repeated elephant browsing may prevent certain trees from reaching reproductive maturity.
“Height reduction in tree species creates what we call a ‘browsing trap’, where vegetation is continually exposed to both elephants and smaller browsers, potentially compromising the regeneration of tall species, such as marula while promoting shrub-like growth forms that are readily accessible to impala and kudu,” Stols adds.
“If we look at impala, their numbers increased in Madikwe Game Reserve over the study period, and they are known to browse on seedlings and saplings, restricting their growth into taller trees. Their presence is likely to have contributed to the greater proportion of smaller trees within the reserve, alongside the elephant impacts.”
Prof Venter adds: “This can potentially lead to long-term population declines or local extirpations of trees that need to be large to reproduce, such as the Marula. From observation, ten years ago there were quite a few large marula trees on Madikwe and most are dead now.”
“What the study offers is more precise information as to what to monitor in ecosystems where the architecture and type of modification of trees is a critical indicator of change, in addition to the effect on or disappearance of specific iconic trees,” adds co-author Professor Herve Fritz from Mandela University’s Sustainability Research Unit and REHABS International Research Laboratory.
“The concern is that there are signs at Madikwe that we are getting close to a serious change in the ecosystem.”
This brings us to the 85 elephants that died on Madikwe during the drought last year. Some argue that if you let nature take its course and a number of elephants die when the habitat deteriorates, then the ecosystem will, in time, restore balance.
“The problem with this is an ethical issue,” says Prof Venter. “When you are dealing with the confined system of a fenced reserve, where the elephants cannot migrate as they would have done historically, it is morally questionable to allow them to starve to death.”
“The hard truth,” continues Prof Venter, “is that the 85 elephants that died last year don’t even make a dent in the elephant population at Madikwe where there are too many for the reserve. Hunting is definitely not an option. Ethics and politics aside you cannot control this number of elephants with hunting.
Contraception will help and translocation to far larger areas with low elephant densities is an option, but it is a major operation that is also limited to how long elephants can remain in the transport truck – generally limited to a distance of ±1000kms.”
Expanding protected areas is often flagged as a solution, adds Prof Venter, explaining that since 30 years ago, Madikwe and the Pilanesberg Game Reserve planned to connect the two reserves and create a wildlife area of over 200 000-hectares, but they have only achieved a ±7000-hectare expansion as they came up against various issues such as landowners who didn’t want to sell and communities who could not agree to combine.
Several reserves, including Madikwe were established in the 1990s and are reaching 40 years old now. Most introduced the Big Five and Madikwe brought in ±250 elephants. In 1995, the government put a moratorium on elephant culling. Madikwe’s large founder population grew and it now faces an acute ecological crisis caused by decades of indecision on elephant management.
“Madikwe offers a strong example of what can happen in other enclosed protected areas if populations and ecosystems are not carefully managed,” says Prof Fritz. “The evidence from this research provides some ecological foundation for urgent, science‑based management decisions with targeted interventions to prevent further habitat collapse and animal suffering.”