The iconic savannas of Africa have been found to be under greater threat than rainforests, a ground-breaking study has revealed.
Africa’s sprawling savanna ecosystems, defined as areas that receive between 300 and 1,500 millimetres of rain each year, are home to well-known, charismatic species such as giraffes, rhinos and elephants, and are at the heart of Africa’s wildlife tourism. However, a new study published recently in Biodiversity Conservation has found that 75% of the continent’s large-scale, intact grasslands have been lost.
“These savannas conjure up visions of vast open plains. The reality is that from an original area a third larger than the continental United States, only 25 percent remains,” said co-author Stuart Pimm from Duke University.
While routine global assessments are carried out on tropical rainforest ecosystems to determine the rate of habitat loss, with the Brazilian Amazon being assessed every month, similar studies on dry woodlands and savannas are few. This new study has shown that, shockingly, a smaller proportion of grassland habitats are left than tropical rainforests, of which only 30% remain.
High-resolution satellite imagery
Exacerbated by a greatly increasing human population across much of the continent, Africa’s vital savanna ecosystem is currently experiencing widespread destruction and loss as a result of ever-expanding agriculture and urbanisation.
Researchers used high-resolution satellite imagery to measure the extent of Africa’s savanna, enabling them to paint a more accurate picture of how much of this critical habitat remains.
“Based on our fieldwork, we knew that most of the information out there from low-resolution satellite-based studies was wrong,” explained lead author Jason Riggio of Duke University’s Nicholas School of the Environment. “Existing global maps are quite coarse and show large areas of African woodlands as being intact. Only by utilising very high-resolution imagery were we able to identify many of these areas as being riddled with small fields and extensive, if small, human settlements.”
The study took a ‘lion’s view’ in order to determine how much intact savanna remains, focusing on habitat that is healthy enough to support the continent’s top predator, the African lion.
“If areas retain lions, the continent’s top predator, they are likely to be reasonably intact ecosystems,” the scientists explained in their paper. “By considering the size of savanna Africa from the lion’s perspective, we can assess how much of it remains in large, relatively intact areas, not yet heavily modified by human influence. Clearly, smaller areas will still support less complete sets of species.”
The results of the study indicate that just 3.3 million square kilometres of savanna capable of containing African lions remains, with this vital habitat vanishing at an alarming rate.
Decline of Africa’s top predator
Lion populations have suffered a dramatic and unprecedented decline in the last few decades, with numbers decreasing from around 100,000 individuals just fifty years ago to as few as 32,000 today, a worrying decline of 68%.
In addition to declines as a result of degradation and loss of its savanna habitat, the African lion, currently listed as Vulnerable on the IUCN Red List of Threatened Species, faces a whole host of other threats. Legal hunting, poaching and human-wildlife conflict are all taking their toll on this iconic species, and there are concerns that lions are being killed to fuel the Chinese traditional medicine market as an alternative to tiger bones.
The recent study found that 24,000 African lions, a disconcerting 75% of the total remaining population, are located in just ten separate strongholds. All of these strongholds are in eastern and southern Africa, with Tanzania alone housing 40% of the global population.
Worryingly, researchers found that approximately 6,000 African lions exist in populations which may not be viable in the long term, and the study also produced evidence of local extinctions of lions, even in protected areas.
“There is evidence of strong declines and even extirpation of lions in some range countries. Especially in West and Central Africa, declines have been dramatic and conservation measures are urgent,” said the researchers. “While lions are protected in some of the lion areas, in many they are not, and in others they are hunted.”
A lack of lions in West Africa’s national parks is of particular concern to conservationists, with the region housing just 525 individuals. West African lions are considered by some to be a separate subspecies, Panthera leo senegalensis, and recent genetic studies have indicated that this population may actually be more closely related to the Asiatic lion than to other African lions.
“This research is a major step in helping prioritise funding strategies for saving big cats,” said co-author Luke Dollar of National Geographic’s Big Cats Initiative (BCI), which helped fund the study. “The research will help us better identify areas in which we can make a difference.”
“Giving these lions something of a fighting chance will require substantial increases in effort,” added co-author Andrew Jackson from Duke University. “The next 10 years are decisive for [West Africa], not just for lions but for biodiversity, since lions are indicators of ecosystem health.”
Read more on these stories at Mongabay.com – Africa’s great savannahs may be more endangered than the world’s rainforests and Lion population falls 68 percent in 50 years.
Learn more about lions on ARKive.
Find out about species found in Africa on ARKive.
Kathryn Pintus, ARKive Text Author