(Posted 13th November 2024)
(Courtesy of African Elephant News and Colorado State University, Phys.org)
Habitat loss and poaching have driven dramatic declines in African elephants, but it is challenging to measure their numbers and monitor changes across the entire continent. A new study has analyzed 53 years of population survey data and found large-scale declines in most populations of both species of African elephants.
From 1964–2016, forest elephant populations decreased on average by 90%, and savanna elephant populations fell on average by 70%. In combination, populations declined by 77% on average. The study compiled survey data from 475 sites in 37 countries, making it the most comprehensive assessment of African elephants to date.
Declines were not uniform across the continent, with some populations disappearing completely and others showing rapid growth. Colorado State University Professor George Wittemyer, one of the architects of the study and chair of the scientific board of Save the Elephants, said that identifying success stories where elephant populations are stable or increasing could help with their conservation.
“The context and the solutions at different sites can be quite different, but there are examples where people are effectively managing and protecting these populations,” Wittemyer said. “It helps to have a contextually relevant model for elephant conservation, and we’ve got that in a lot of different places.”
The study, “Survey based inference of continental African elephant decline,” published in Proceedings of the National Academy of Sciences, modeled site-level elephant density rather than numbers because the survey area was not constant over time for most survey sites. A clear trend toward smaller populations emerged.
“This paper shows the scale of the declines and how widespread they are across the continent,” Wittemyer said. “It shines a light on how quickly even something as big and noticeable as elephants can just disappear.”
Not Simple Arithmetic
Elephants may be big and noticeable, but counting them is complicated and resource intensive. Surveys of savanna elephants are done by spotters in planes, and forest elephants must be counted on foot. Drones aren’t yet capable of the long flights over remote areas necessary to survey elephants, and processing drone imagery is also resource intensive.
“We were really happy to bring all of that data together and leverage it, given the effort and care taken to collect it,” Wittemyer said.
As elephant populations declined, some protected spaces were condensed and survey borders changed. To compensate for shrinking survey areas and gaps in data, the study authors had to use places with good information to estimate population change for nearby places with less information. They looked at site-based trends to get a picture of the overall distribution of trends.
“The strength of our approach is that we were able to infer these trends, even in places where the data were extremely poor, in a way that allowed the results from each survey site to be compared,” said co-author Charles Edwards, a research scientist with CEscape consultancy services.
“Understanding how and where trends are different across the range of a species is arguably more important for their conservation than an overall change in abundance, which may only reflect change in the largest populations. It’s not a metric of the number of elephants left on the continent,” Wittemyer added. “It’s an assessment of how each population is doing, and they’re generally not doing great.”
Shifting Distribution
However, elephants are thriving in parts of southern Africa, particularly in Botswana, where populations have been protected and sustainably managed.
The authors said that the study’s comprehensive assessment of the status of African elephants is fundamental to management decisions like knowing where to invest limited funding and capabilities to best protect elephants.
“The overall story is one of decline, but we’re focusing on long-term stability of the species,” Wittemyer said. “I think we can do that in a bunch of places, but not all places.”
Co-authors of the study are Kathleen Gobush (University of Washington), Fiona Maisels (Wildlife Conservation Society and University of Stirling), Dave Balfour (Nelson Mandela University) and Russell Taylor (WWF Namibia).
