By Malee Oot
Like other large carnivores around the world, Africa’s lions are disappearing. Lions once wandered practically the entire African continent, absent only from the Sahara Desert and the tropical forests of the Congo Basin — but today, the cats roam only about 8% of their historic range. Over the last two decades, Africa’s lion population is estimated to have decreased by 43%. The bulk of the continent’s lions now live in just six stronghold countries in eastern and southern Africa. One of the primary threats to wild cats is contact with people – and according to a new study, climate change may exacerbate the potential for human-wildlife conflict in several critical lion areas in eastern Africa.
Published in the journal Conservation Biology, the study assessed the impact rising temperatures will have on the distribution of the vector-borne disease trypanosomiasis in eastern Africa – and the potential implications for humans, livestock, and lions.
Spread primarily by tsetse flies, trypanosomiasis is present in 37 African countries, an area equivalent to about one-third of the continent – putting nearly 60 million people at risk for the disease commonly referred to as sleeping sickness. But, the disease doesn’t only affect humans. Animal trypanosomiasis has a devastating impact on African livestock. Every year, the disease is responsible for killing nearly three million cattle in Africa, making trypanosomiasis one of the primary constraints to successful livestock production in affected regions.
Temperature affects both the development rate of the Trypanosoma parasites and the geographic distribution of the disease’s primary vector – tsetse flies. Rising global temperatures are predicted to alter the range of trypanosomiasis in Africa, ultimately changing land-use patterns and potentially intensifying the human-wildlife conflict in areas critical for wildlife.
Led by Dr. Neil Carter of Boise State University’s Human-Environment Systems Research Center, the authors of the study explored the potential impact climate-induced variation in the range of the Trypanosoma parasite could have on regional lion populations. Using two climate projection models – an emissions scenario assuming business-as-usual and another assuming some moderate climate change mitigation – the authors predict shifts in the geographic range of the Trypanosoma parasite expected to occur by 2050.
Under both climate scenarios, the geographic range of the Trypanosoma parasite is expected to expand in East Africa over the next three decades. However, while the cumulative area affected by trypanosomiasis is projected to increase in the region, the Trypanosoma parasite will also simultaneously disappear from places it has previously occurred — including some of East Africa’s key lion hotspots.
In lion strongholds like Niassa National Reserve in Mozambique and Zambia’s Luangwa Valley, the authors point out that the presence of the Trypanosoma parasite has historically limited the encroachment of humans and livestock, which has helped to preserve lion populations.
Using the grimmer, business-as-usual climate scenario, the findings indicate that the range of the Trypanosoma parasite could shrink in 45% of the region’s recognized and prospective lion areas. For instance, the research suggests the parasite could potentially disappear from as much as 48% of Mozambique’s Niassa National Reserve and 61% of Tanzania’s Selous Game Reserve, one of the continent’s oldest and largest protected areas. According to the research findings, if the cats are evenly spread across eastern Africa’s lion areas, the predicted disappearance of the Trypanosoma parasite by could impact 19% of the region’s lions, about 6,500 cats.
These projections have significant implications for lion conservation in eastern Africa – and for the species as a whole.
A recent study of 47 different lion populations spread over sub-Saharan Africa documented a sobering pattern of decline. Lion populations are dwindling across the continent, with the exception of four countries in southern Africa – Botswana, Namibia, South Africa, and Zimbabwe. The lions of West and Central Africa – a distinct sub-species more closely related to the Asiatic lions of India’s Gujarat state – are perilously close to extinction. Most of the region’s remaining 400 cats are found in a single protected area — the transboundary W-Arly-Pendjari Complex, which spreads into Benin, Burkina Faso, and Niger. According to the same study, the outlook could ultimately become bleak for some of East Africa’s longest enduring lion populations too – and protected areas in southern Africa could emerge as the most iconic strongholds for the continent’s remaining cats.
Contact with humans – and livestock – is one of the key factors driving the decline of lion populations across the continent – especially in East Africa. Livestock predation can be a significant economic burden, especially for pastoralists living adjacent to wildlife-rich protected areas – and can result in lethal acts of retaliation against lions. Outside established protected areas, the preemptive and retaliatory killing of lions has been determined to be the main threat to the cats. One study conducted in community conservancies north of Kenya’s Maasai Mara National Reserve even found human-wildlife conflict played a more significant role in lion survival than environmental factors.
Incidences of retaliatory lion killing adjacent to high-profile protected areas are well documented. Roving lions have been speared and poisoned outside Nairobi National Park, on the outskirts of Kenya’s capital. Research conducted in northern Tanzania’s Maasai Steppe, the region harboring Tarangire National Park, found that even though three different predators – lions, leopards, and spotted hyenas – were responsible for the bulk of livestock losses, lions were most vulnerable to retaliatory killings. In Botswana, the government suspended lion hunting in 2007 due to concerns about dwindling populations as a result of human-wildlife conflict around protected areas, including the Khutse Game Reserve and the Kgalagadi Trans-frontier Park.
Rising temperatures and climactic shifts mean humans, livestock and lions will have to find new ways to coexist in the coming decades, before it’s too late for Africa’s most iconic cats.