Originally on earth.org by MONGABAYAFRICA JULY 15TH 2020
Scraping sounds fill the nights at Mapungubwe, a national park at the confluence of the Limpopo and Shashe rivers, where the borders of Botswana, Zimbabwe and South Africa meet. Families of elephants relentlessly tear the bark off ancient baobab trees, scraping their tusks on the trees and digging deep into their cores to extract the fibrous, moisture-rich interior.
A drive through the national park reveals that dozens of these giant trees have been severely damaged, many left with gaping holes in their trunks. Biotechnician Stephen Khosa of South African National Parks (SANParks) recently completed a survey on baobab (Adansonia digitata) mortality. Of the 501 trees surveyed between 2005 and 2020, he writes in an email, 6% have died. According to a study in the African Journal of Ecology, the typical mortality rate for baobab populations is between 1.1 and 3.7%.
The baobab deaths in Mapungubwe are attributed to elephant damage and other related factors, such as a multi-year drought that started in 2015 and, possibly, groundwater abstraction from mining in the direct vicinity of the park.
However, the true mortality rate could be much higher. There is considerable uncertainty in the survey’s results: Khosa confirmed in an email that “there was a significant monitoring gap in this project between 2009 & 2020.”
Elephants digging into a baobab tree in Mapungubwe National Park, South Africa. Image by Nathalie Bertrams for Mongabay.
A. digitata are resilient trees: the mature baobabs here in the northern parts of Limpopo have an average age of between 300 and 500 years; the oldest specimen in Africa has been dated to 2,500 years. Jens Gebauer, at Germany’s Rhine-Waal University of Applied Sciences, calls it “one of the most impressive plants in coping with drought due to its great ability to store water in its enormous trunks. This allows the baobab to grow in very dry regions and cope with drought and heat.”
The trees can absorb up to 80% of their volume in water, with large trees storing as much as 140,000 liters (37,000 gallons).
Mapungubwe is no ordinary national park. In addition to an abundance of wildlife, it is a UNESCO World Heritage site and a vital archaeological resource, home of the only known San rock art painting of a rhino and one of the best-known pieces of pre-colonial African art, a golden rhino statue. The Kingdom of Mapungubwe (900 to 1300 C.E.) was part of a trade network that stretched all the way to India and China. Ivory and gold from here were traded for porcelain and glass.
The baobabs of Mapungubwe have helped to record the kingdom’s rise and fall. A 1,000-year climatic record of the area was developed by analyzing the carbon isotope values of baobab trees. From this, we know that around 1300, a severe drought destroyed the kingdom’s agricultural base. Mapungubwe was abandoned, and its remarkable civilization shifted north to what is today Zimbabwe.
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While that 14th-century drought was due to a natural fluctuation of rainfall patterns, the present drought is linked to climate change from anthropogenic greenhouse gas emissions and overuse of water resources. Southern Africa has been enduring a severe drought since 2015, heavily affecting its people and wildlife.
A 2018 analysis of the drought, led by Friederike Otto of Oxford University’s Environmental Change Institute, concluded that “the likelihood of an event like the observed 2015–2017 drought has increased by a factor of 3.3 (1.4-6.4). Unlike for other drought analyses in other parts of Africa, this is a very clear result with anthropogenic climate change having significantly increased the likelihood of such a drought to occur.”
Corli Wigley-Coetsee, an ecologist at SANParks’ Savanna and Arid Research Unit, says the Limpopo River’s water resources are overallocated and underprotected: next to diamond mining operations and open-cast and underground coal mining, at least 23 prospecting licenses for coal mining have been granted near the national park, some in the buffer zone, exacerbating water scarcity in the park.
She also points out that in the ecological system of the proposed Greater Mapungubwe Transfrontier Conservation Area, borders like the Limpopo River are no longer a barrier to elephants: the river often dries up.
Elephant populations in Botswana and Zimbabwe are under significant pressure from drought, overpopulation and poaching, and are on the move as a result. Botswana alone hosts 130,000 elephants. Many find a safe haven in Mapungubwe National Park.
With their water-rich interiors, baobab trees are part of the park’s attraction to elephants. The natural process of elephants digging into these trees doesn’t usually cause lasting damage. Baobabs have a unique ability among trees to recover their bark and tissue, says David Baum from the University of Wisconsin-Madison, who has studied the trees for more than 30 years. “Baobabs have coexisted with elephants for millions of years, which probably explains why they have evolved such a remarkable ability for regrowth,” he says.
Baobab trees have evolved to tolerate occasional elephant damage and benefit from elephants eating their fruit and dispersing the seed, Baum says. But at times of severe water shortage, when elephants exploit the trees too heavily, a baobab will eventually collapse. Some simply re-sprout. But if the structural damage is too severe, the tree can die.
According to South African baobab ecologist Diana Mayne, research suggests that lack of precipitation, climate extremes and weather fluctuations most negatively affect baobabs even when they’re not being hollowed out by elephants. “Baobabs are vulnerable to drought-induced embolism, similar to an embolism from a thrombosis or heart attack in humans,” she says.
Elephants are complex, sentient, intelligent and emotional beings responding to human-induced changes in their environment. Hennie Lötter, from the University of Johannesburg’s Department of Philosophy, an expert in the ethics of elephant conservation, says humans have a distinct moral obligation to guarantee their flourishing. In a recent paper, he writes, “We have conquered about 90% of elephant habitats and in the process we have reduced their numbers tremendously compared to the large numbers of elephants alive merely 200 years ago.”
Temperatures in Southern Africa could rise by 5-6°C (9-10.8°F) by the end of the century due to global greenhouse emissions, according to the Intergovernmental Panel on Climate Change. Severe droughts will be a regular part of the region’s future, affecting both baobabs and elephants.
Elephants no longer have room to maneuver: they are trapped between climate change, habitat destruction and poaching. For Lötter, safeguarding the space for them to flourish is bound up in the health of the wider ecosystems of Southern Africa and beyond. “We can safeguard elephant flourishing only if we simultaneously guarantee the well-being of the other members of the global biosphere,” he says, “and the healthy functioning of the global biosphere itself.”