Too many elephants can overwhelm an ecosystem. And yet not enough elephants can have equally damaging impact.
We are driving through Zinave National Park in Mozambique, and our Land Rover has to stop so the team can clear some branches and debris out of the road. The branches are the collateral damage to trees that have been disturbed by elephants — recent arrivals to Zinave from De Beers Group’s Venetia Limpopo Nature Reserve (VLNR) in South Africa.
Our Peace Parks Foundation (PPF) hosts, who co-manage the park with the Mozambique government’s entity responsible for the administration of conservation areas (ANAC, the Portuguese acronym for National Administration for Conservation Areas), are noticeably delighted by the destructive evidence of the elephants’ presence.
Having just come from VLNR, where such elephant-initiated damage was a cause for alarm — enough so that De Beers Group enacted an elephant translocation effort to move 200 elephants out of the VLNR habitat — the lay people in our party are confused: if elephants cause sufficient damage to an ecosystem in one park as to catalyze their removal, why would that kind of damage be celebrated in another?
“Disturbance stimulates diversity,” notes Bernard van Lente, Project Manager at Zinave for PPF and a biologist by training. “Elephants push over trees, break off branches, pull out grass, trample. In a natural system, that is what’s needed. It is a delicate balance — too much leads to destruction, which negatively affects diversity the other way. Venetia Limpopo Nature Reserve has a problem of too many elephants — and we have too few.”
In other words, too many elephants can overwhelm an ecosystem. But, surprisingly, not enough elephants can have an equally damaging impact.
Here in south-central Mozambique’s Inhambane Province, van Lente is looking out across Zinave from a campfire perched above the Save River, from which hippos periodically emerge to take a breath. “There haven’t been elephants in this park for many years,” he says. “And there are ways you can tell: the trees are bigger and bushes are thicker than at a park with elephants. And the grass is higher — lack of elephants causes that look.”
“Elephants are a keystone species,” he adds, “an animal that plays a unique and important role in the way an ecosystem functions and helps to define the entire ecosystem. If that species is removed, no other species would be able to fill its ecological role, which will lead to ecosystem change.”
It’s almost as if elephants play a magical role in an ecosystem, bringing specific characteristics and enormous contributions. Consider:
* Elephants pave highways through densely forested jungles for other species.
This is true for impala, notes van Lente, as well as nyala, kudu, bushbuck and other grazers and browsers. “Even predators will also invariably make use of the pathways created to move around and find prey.”
* Elephants knock over certain trees, giving other flora species a chance at sunlight exposure and, therefore, growth.
“Elephants create gaps in the vegetation of dense woodlands,” adds van Lente. “These gaps help the growth of other plants, which then provide food for different species. And by tearing down high branches of trees such as acacia trees, elephants also create food sources for a multitude of organisms, like borers, ants and others, which in turn attract birds and small predators.”
* Speaking of insects, elephants also create other food sources for tiny organisms — as well as a host of other creatures — via their dung.
“Elephant dung texture and composition is markedly different from other grazer dung. The dung is very rich, and constitutes a source of food for other species,” adds van Lente. “Species include vervet monkeys, ground hornbills, various bird species, banded mongooses, baboons and many insect species. It is also very rich in minerals and fiber, as only about 50% of what elephants eat is digested. Elephant dung is a good fertilizer and important for contributing to nutrient-rich soils.”
* Elephant dung is also essential for dispersing the seeds of certain flora.
“For instance, the Balanite tree (Balanites aegyptiaca) is solely dependent on elephants for its seed dispersal through elephant dung,” notes van Lente. “They can disperse a large amount of intact seeds for great distances.”
* Elephants also eat high grasses, exposing lower grasses to other grazing plains species.
“Generally, they can pull out a whole grass clump, opening a new spot and making other grass/ shoots accessible to smaller grazers, such as oribi and impala,” says van Lente. “Elephants eat a lot, and they process a huge amount of vegetation, which is not happening here [in Zinave] at the moment. Their excretions cause the ground to be more fertile.”
Overall, the contributions elephants make to an ecosystem’s diversity is far-reaching. “You can calculate a habitat’s diversity by the number of actual species it has,” says van Lente. “And, as elephants cause disturbance, disturbance stimulates diversity.”
“Elephants are a keystone species — an animal that plays a unique and important role in the way an ecosystem functions. If that species is removed, no other species would be able to fill its ecological role.”
Bernard van Lente, Project Manager at Zinave National Park in Mozambique
“The idea of a ‘keystone’ in architecture is that it is in a critical position in the arch of a building,” notes Dr. Lori Eggert, professor of biological sciences at the University of Missouri, who specializes in conservation genetics. “If a keystone was removed, the whole thing would collapse.”
“That is a good analogy for a keystone species,” Eggert tells Moving Giants, “because if you were to remove the species, the whole ecosystem could fall apart. A keystone species plays a disproportionate role in a habitat. They may be few in numbers, but they have a big, larger effect — one that plays a role in the ecosystem that is really, well, key.”
Eggert’s purview at the University of Missouri also includes running the Eggert Lab, which uses molecular tools to study wildlife species that are difficult or dangerous to study using traditional methods. On the key role that elephants play, she notes that “they keep the habitat in control.”
“Elephants tend to graze and keep areas open that would become forests if they didn’t,” says Eggert. “They keep the little shrubs from becoming big trees. They keep the land open for other big grazers. Other herbivores are grass eaters, but elephants are browsers. Browsers tend to uproot and eat trees, and thus they keep the trees in control. Other herbivores are generally grass eaters, not browsers. Herbivores, such as zebras, impala — all those species that graze but don’t eat trees — are able to live there,” thanks to elephants.
“Plus, the [tree] species that elephants tend to eat have very large seeds. Those seeds are not going to disperse on their own [over large distances]. Which is why their role in moving and dispersing seeds for plant species is so critical.”
A critical factor that affects not only other animal species but also humans is the curtain that elephants put up against the deadly diseases carried by tsetse flies.
“Tsetse flies tend to live in forest areas,” notes Eggert. “Tsetse flies pass encephalitis. They are not little horseflies — tsetses are big, nasty flies that suck blood. The tsetses live in the forested areas. When elephants keep the trees down, the tsetse flies don’t do as well. So elephants play a role in preventing diseases.”
And it would be hard to dismiss the role that elephants play in the public consciousness. As a unique and beloved species, elephants have a certain tug on the heartstrings that other animals don’t. In this sense, says Eggert, elephants are known as an “umbrella species.”
“An umbrella species is one that, when you protect it,” says Eggert, “you protect the others that are in the same ecosystem and enjoy the protections of that species. Just look at the Thomson’s gazelle. They are a very cute, tiny grazer, but they are not charismatic like the elephant. You’re not going to find people marching on the street to save them.”
Hardly shy, retiring wallflowers, elephants are not afraid to leave their footprints on their delicate ecosystems. And, because elephants are so massive, even their footprints can play a role in that ecosystem. As an example, when forest elephants trudge through a habitat, they leave behind swimming-pool-size homes for at least “61 different microinvertebrate species from nine different orders,” which “appears to be an important part of the lifecycle and food web for many species.”
Though their trunks are not divining rods, elephants can also be a provider of water for other creatures, which is yet another way they serve as a keystone species.
“During the dry season, elephants use their tusks to dig for water,” Frank Pope, CEO of Save the Elephants, tells Moving Giants. “This not only allows the elephants to survive in dry environments and when droughts strike, but also provides water for other animals that share harsh habitats.”
And, sadly, harsh habitats will be only increasingly familiar as climate change starts to take hold on the planet. Interestingly, though, a new research paper posits that the translocation of elephants — such as is occurring in the Moving Giants effort — may help alleviate climate change.
As reported in Moving Giants last month, “Elephants — along with other megaherbivores, such as rhinos and hippos — make subtle but essential atmospheric contributions through their diet and other habits.”
The research, which was published in the Royal Society’s journal "Philosophical Transactions,” notes that “the mega browsers [such as elephants] help to maintain the balance in savanna systems between trees and grasslands, working in synergy with the mega grazers. Without the mega browsers, trees and bushes would take over the grasslands and, without them, grasslands would take over the tree and forest areas.”
And that is important because, “in addition to their role as water-production areas, [grasslands] reflect the sunshine, and therefore reduce solar radiation.”
As charismatic as they are — much more so than poor Thomson’s gazelle — it is important to remember that elephants are much more than an iconic African creature. They are essential guardians of the African bush, and repopulating them can save not only the elephants, but hundreds of other fauna and flora alike.
This feature is a companion piece to Episode 2 of our "Moving Giants" video series, which you can watch below. To see previous episodes in the series, please visit our video hub here.
"Just look at the Thomson’s gazelle. They are a very cute, tiny grazer, but they are not charismatic like the elephant. You’re not going to find people marching on the street to save them.”
Dr. Lori Eggert, professor of biological sciences at the University of Missouri