Prof Rudi van Aarde, a leading African conservationist, died on 22 July 2023 after a heart attack. He is survived by his collaborator and wife of 11 years, Camilla Nørgaard. His is a legacy of innovative and practical conservation. In 1998, he founded the Conservation Ecology Research Unit (CERU) at the University of Pretoria and led this group with significant impact until his death. 
 
Rudi was born on 21 September 1951 in Modimolle, called Nylstroom at the time, in Limpopo Province. He completed all his undergraduate and postgraduate degrees at the University of Pretoria, completing the PhD in 1984. His PhD training was in mammalian reproductive hormones under the supervision of the late Prof John Skinner. Before being appointed as a senior lecturer at the University of Pretoria in 1986, he had several visits to European research groups. He formally retired from the University of Pretoria in 2017 but remained research active on a postretirement contract until the end. At Pretoria, his research excellence was recognised with outstanding academic achiever awards from 2000 to 2011. He was actively involved in several science organisations in various leadership positions, notably the Zoological Society of South Africa, the Southern African Wildlife Management Association, the Royal Society of South Africa and the South African Scientific Committee for Antarctic Research.

His early work was on Marion Island and the French Kerguelen Islands. The environmental challenges on these islands were (and are) invasive mammals. Rudi’s earlier work on the population dynamics of invasive house cats on Marion Island laid the foundation for an eradication programme, and his career took a practical turn when he became involved in designing and implementing a plan to remove these house cats from Marion. The project's success is documented in Bester et al. [1]; the cats were all gone by 1991. This first experience of practical focus on real-world conservation founded in solid science was to become a pattern for much of Rudi’s career.

In the early 1990s, Rudi started working on dune forest communities in northern KwaZulu-Natal to design a restoration programme for a dune mining operation in this sensitive area. The success and longevity of this restoration programme have not only resulted in significant biodiversity gains for these erstwhile mining areas, but it made a significant contribution to the science of restoration ecology. To this day, the rehabilitated dune forests are a testament to Rudi’s vision for practical conservation outcomes.
 
By the mid-1990s, Rudi was transitioning from endocrinology studies to conservation, partly triggered by elephant-related research in a small reserve in northern KwaZulu-Natal. He met Prof Stuart Pimm at a conference in Budapest in 1995, and he invited him to visit South Africa the following year. This was the start of a 30-year friendship and collaboration. Rudi felt that studies of elephant reproduction were unlikely to give answers to what was perceived as the problem of too many elephants in Kruger National Park. Until shortly before, an average of about 500 elephants a year were culled to keep numbers at some level expert opinion deemed “right.” The kill was hugely controversial. Might putting elephants on contraceptives solve the perceived problem?

Rudi answered that contraception was a bad idea and involved massive disruption to the individual elephants and their social behaviour. Stuart’s concern was how many elephants would need to be treated to slow the population growth. Together they worked on papers to calculate the answer: it was in the thousands, making the approach impractical for large populations such as Kruger’s [2].

The solution for Kruger, Rudi argued, was to remove the fence between it and the adjacent Limpopo National Park in Mozambique and close some of the many artificial waterholes. Those actions were bitterly contested but eventually prevailed.

A quarter century of elephant studies followed. Few people have seen as much of Southern Africa as Rudi, and indeed no one has photographed so many elephants - see some of his award-winning photos. He had a unique breadth of experience of the African landscape that took him from Addo in the south to Etosha in the west, Zambia and Malawi in the North and Mozambique in the east. Hundreds of thousands of kilometres of roads indeed, and time to think about elephants and conservation at the broadest scales.  

The outcome was his classic “mega parks for metapopulations” [3] — a view that elephants need room to roam. Isolated populations cannot flourish and can do harm when imprisoned behind fences and other barriers.

Since retirement, CERU meetings were often at Rudi and Camilla’s home. A lovely garden setting conducive to talking and vigorously debating all that we learned from the many trips and adventures, with dogs on laps for added company. 

Rudi trained a generation of young African conservation professionals (126 postgraduate students and postdocs, to be exact), and many of them have gone on to have a significant impact on conservation in southern Africa. He brought several of his international networks to Pretoria, notably Stuart’s, and the subsequent collaboration (and social events!) between postgraduates from different parts of the world cemented lifelong networks for many of the CERU alumni. Prof Barend Erasmus, the current Dean of the Faculty of Natural and Agricultural Sciences, vividly remembers Rudi in full swing in teaching third-year ecology; Rudi’s own experience, passion for and commitment to conservation made for paradigm-shifting lectures.

In the last few months, a central event was his book outlining his vision for elephant conservation and, indeed, that of the larger African ecosystem.  As so much of his work was supported by the International Fund for Animal Welfare, Rudi completed it but did not see a physical copy. “Let Elephants Roam” will appear in the New Year. It is an appropriate legacy for his commitment to conservation. 

Acknowledgements:
Prof Stuart Pimm and Prof Barend Erasmus

References:
[1] Bester, M.N., Bloomer, J.P., Van Aarde, R.J., Erasmus, B.H., Van Rensburg, P.J.J., Skinner, J.D., Howell, P.G. and Naude, T.W., 2002. A review of the successful eradication of feral cats from sub-Antarctic Marion Island, Southern Indian Ocean. South African Journal of Wildlife

]2] Whyte, I., van Aarde, R. and Pimm, S.L., 1998, May. Managing the elephants of Kruger national park. In Animal Conservation (Vol. 1, No. 2, pp. 77-83). Cambridge University Press.

[3] Van Aarde, R.J. and Jackson, T.P., 2007. Megaparks for metapopulations: addressing the causes of locally high elephant numbers in southern Africa. Biological Conservation, 134(3), pp.289-297.