One of Africa鈥檚 last major lion strongholds听has听experienced a significant decline in its genetic diversity since the end of the 19th听century, leaving the animals more vulnerable to future threats.
For the first time, researchers looked at how the genetic diversity of African lions听(笔补苍迟丑别谤补听濒别辞)听has changed over time.听They discovered that the diversity of the population in the听Kavango-Zambezi conservation area, a region that includes parts of Angola, Botswana, Namibia, Zambia and Zimbabwe, has fallen by up to 17 per cent since 1895.
This drop is significant because it took place in an area that is home to one of the continent鈥檚 most important lion populations, says Simon听Dures at the Zoological Society of London, who led the听analysis.听鈥淚t鈥檚 pointing out we听have to听be careful even in these strongholds, not to let them split up into fragments,鈥� he says.
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Less able to adapt
Researchers have known about the shrinking area that lions occupy in Africa, and their falling numbers, but were previously less clear on how well they were doing in their heartlands.
The loss of genetic variation in the Kavango-Zambezi lions reduces their ability to adapt to future changes. The most obvious of these is climate change 鈥� we already know that some African lions are better adapted to live in drier environments, and others in wetter ones. While lions are generally adaptable hunters, changes in prey may impact them too.
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鈥淚f you lose some of those听[lion]听populations, or they鈥檙e not mixing, you鈥檙e going to lose the overall population鈥檚 ability to withstand change. It could be climate听change,听it could be disease. It鈥檚 the ability to withstand the unknown,鈥� says Dures.
The听team was able听to measure the change in genetic diversity over time in part due to a 19th-century British hunter,听. Many of the lions he killed in the听Kavango-Zambezi听area ended up at the Natural History Museum in London.
In total,听Dures听and his team were able to identify 27 relevant old lion samples at the museum. The final number was small because the researchers erred on the side of caution, discounting any samples with an uncertain date and location of collection.
They compared DNA taken from these old specimens with that of 204 lions living in the conservation area today. To compensate for the older data set being much smaller, random groups of 27 lions were taken from the modern data set and compared against the old ones. That process was repeated hundreds of times and the findings didn鈥檛 change.
Removing fences
Stopping the decline in the lions鈥� genetic diversity, and potentially even reversing it, will require political support. The听Kavango-Zambezi conservation area is made up of a series of protected areas and most of it is sparsely populated by humans. But some parts, particularly in Zimbabwe and Zambia, have large swathes of subsistence and cattle farming, which can lead to tensions between farmers and wildlife.
There is political will to protect lions in Botswana because tourism is so important for the country, as evidenced by , says Dures. A key measure will be to remove some of the fencing in the听Kavango-Zambezi听area to create wildlife corridors so lion populations can mix. 鈥淭he main thing is ensuring within this big area that the lion populations are connected,鈥� says听Dures.
Europeans buying Botswana beef are, inadvertently, partly to blame for the fences. Many have been erected to stop the transmission of disease between wild ungulates and cattle, to meet European Union import rules.
Diversity and Distributions
