Giraffes are one of Africa’s most iconic animals. Towering above the bush with their long necks and gentle gait, they are a favourite among tourists and landowners alike. But what happens when giraffes are introduced to ecosystems where they never naturally occurred?
In our recent study, we explored this very question in the Albany Subtropical Thicket of South Africa’s Eastern Cape. What we found is a sobering reminder that even the most charismatic species can become ecological disruptors—especially during times of stress such as drought.
Thicket Under Pressure
The Albany Subtropical Thicket is unlike its neighbouring fynbos or grassland. Dense, tangled, and largely fire-free, it once formed an impenetrable scrub-forest across much of the Eastern Cape. Centuries of overgrazing and agricultural use have left over 70% of this vegetation degraded. Large canopy trees, once beyond the reach of browsers like kudu and goats, have struggled to recruit new individuals, and many landscapes are now open woodlands rather than closed thicket.
More recently, land use has shifted from livestock farming to wildlife ranching. This has brought opportunities for conservation and ecotourism—but also challenges, as landowners have introduced extralimital (non-native) wildlife species such as giraffes.
Giraffes in a Landscape They Never Knew
Historically, giraffes did not occur in Albany Thicket. Records show no natural populations in this region. Yet today, many private reserves stock them for their appeal to visitors. Unlike kudu or goats, giraffes feed at heights of 2–4 metres—reaching deep into tree canopies that other browsers cannot touch.
For some thicket trees, this is a problem. Species like Boscia oleoides, Pappea capensis, and Schotia afra had escaped the “browse trap” by growing taller than local herbivores could reach. With giraffes present, that refuge disappears.
The Role of Drought
On their own, giraffes may not kill trees outright. In their native savannas, their impact is often minor compared to elephants. But drought changes the equation. During dry years, plants are already struggling with water stress. Add heavy browsing pressure, and mortality can skyrocket.
Between 2016 and 2022, the Eastern Cape experienced one of the longest droughts on record. This provided us with a natural test case: would giraffe browsing make thicket trees more vulnerable?
Our Study: Tracking Boscia oleoides
We focused on Boscia oleoides, a pale-barked canopy tree that is widespread in thicket. Over several months, we surveyed 451 trees across paired properties near KwaNojoli—some stocked with giraffes, others without.
Each tree was scored for canopy condition:
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Canopy volume (was the crown full or sparse?)
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Proportion of leafy branches
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Leaf and branchlet intactness
Healthy trees scored high; dying or dead trees scored low.
What We Found
The results were stark:
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Trees on properties with giraffes were in significantly poorer condition than those on giraffe-free land.
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Mortality rates were 6–12 times higher where giraffes were present. For example, one property with giraffes had almost 30% dead Boscia trees, compared to less than 5% on its neighbouring giraffe-free property.
In other words, the combination of giraffe browsing and drought stress proved devastating.
Why This Matters
Our findings highlight an underappreciated dynamic: megaherbivores can act as catalysts of drought-driven vegetation dieback. Just as insects and pathogens have been shown to amplify drought mortality in forests, giraffes can do the same in thicket systems.
Unlike elephants, giraffes may not physically destroy trees, but by stripping leaves and shoots from drought-stressed canopies, they push plants beyond recovery. And because giraffes are not water-dependent, they remain active browsers throughout droughts, when other animals might move on in search of water.
Managing for the Future
Our findings strongly suggest that giraffes should not be introduced into Albany Subtropical Thicket. This biome did not evolve with giraffes, and the ecological consequences of their browsing are severe, especially under drought.
If landowners feel compelled to stock giraffes for tourism or other reasons, then management must be extremely cautious:
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Keep numbers at the absolute minimum possible.
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Restrict their movement so that the majority of the thicket is protected and sensitive plant species retain safe refuges.
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Prioritise ecosystem integrity over the appeal of charismatic but extralimital species.
Anything less risks further degradation of a biome already under immense pressure from both historical land use and climate change.
Browsing impacts on a large Boscia oleoides tree: A) the long-term browse line driven by native and domestic ungulates, B) the recent browse-line and entire leaf-loss due to giraffe, and C) the zone above the reach of any vertebrate herbivore. Note that this is an exceptionally tall tree in this landscape (~6.5 m), and all other Boscia oleiodes measured were well below giraffe browse height. Photo taken on De Plat on 1 October 2020 by AJ Potts.
A Bigger Picture
This study adds to a growing body of work showing how extralimital species—however beloved—can reshape ecosystems in unexpected ways. The thicket biome is already under immense pressure from centuries of land-use change. With climate change amplifying droughts, the additional pressure of giraffe browsing could tip the balance further.
Protecting thicket into the future will require careful ecological management, balancing tourism appeal with the resilience of this unique and fragile biome.
This work was conducted by Alec Blewett (Nelson Mandela University), Alastair J. Potts (NMU), Robert P. Skelton (University of the Witwatersrand), and Marietjie Landman.
