Drones are being used to help save the critically endangered Clanwilliam cedar in the Western Cape

Not too far in the future, a specialised tree-planting drone will fly over the rugged mountains of the Cederberg in the Western Cape, firing seedpods into the ground with precision to help give the region’s namesake — the rare Clanwilliam cedar tree — a fighting chance of survival.  

The ancient Clanwilliam cedar (Widdringtonia cedarbergensis) is only found in the Cederberg. In 2013, it was listed as critically endangered on the International Union for Conservation of Nature’s Red List of Plants. 

The long-lived species is on the brink of extinction after decades of unsustainable harvesting for their “beautiful, long-lasting, fragrant timber” and from frequent veld fires, according to the South African National Biodiversity Institute. Only an estimated 13 000 individual trees remain in the wild.

AirSeed Cedar project 

The AirSeed Cedar project, a long-term project, will use a single drone with a seedpod delivery system designed for it. 

Jonathan Dawe, business development executive at AirSeed, an ecological restoration company, said much work had been done in the past to prevent the Clanwilliam cedar from going extinct and there were still a number of ongoing initiatives. 

“AirSeed has developed cutting-edge technology that allows targeted seed distribution using drones, reducing the physical and logistical barriers of restoration in dangerous or difficult terrain.

“To allow distribution by drone, the seeds are encased in specially designed seedpods, which are customised for the needs of the species and allow the seed to escape predation until they experience appropriate conditions for germination and growth.”

Seedpods allow for accurate and geotagged delivery to facilitate monitoring, reduce wastage, and increase the emergence success, survival and growth of the species. 

“With this technology, seeds of the Clanwilliam cedar can be delivered to the right place, at the right time, and in volumes that will allow for successful recruitment events.” 

Recruitment is the process in which seeds establish in an area and grow into new mature individuals.

The restoration of the Clanwilliam cedar stands out as a “logical application” of AirSeed’s technology, because it will enable access to microsites that are difficult or impossible to reach otherwise, he said.

“In addition, the relatively low availability of Clanwilliam cedar seeds makes it an excellent candidate for seed-based restoration (rather than seedlings); this significantly reduces the cost of a restoration programme and further demonstrates the efficacy of the use for AirSeed’s approach.”

The project is still at a relatively early stage and nursery and field trials are underway. “It is expected that the project will continue for many years to come.” 

AirSeed’s mission, Dawe said, is to plant 100 million trees a year by 2024 and restore lost biodiversity across the world.

Remnants of the Ice Age

According to CapeNature, cedar trees date back to the last Ice Age, 300 to 255 million years ago, when the landscape was much colder. 

“The cedar trees are under tremendous pressure due to climate change that results in more frequent fires and less rainfall,” it said. “Fire is devastating to these trees as they do not resprout after being burned and die. Lower rainfall reduces natural germination of seeds and survival of seedlings.”

Conservation efforts to increase their numbers got underway in 1805 when forest rangers realised that harvesting of the cedar wood was reducing numbers. 

“Collecting and distribution of seeds and planting of seedlings have taken on various forms,” it said. “Annually, volunteers from the Cederberg communities and surrounding areas assist to plant cedar tree seedlings to increase the number of cedar trees in the mountain.”

The Clanwilliam cedar, Dawe said, is important for conservation because of its cultural significance, the role it plays as a charismatic species for conservation of the general area, and its ecological role as one of the only tree species in its habitat. “We don’t know what will happen if the species goes extinct,” he said. 

Passion project

The AirSeed Cedar project is the brainchild of Dawie Burger, a farmer and conservationist from the farm Driehoek, who moved to the Cederberg – part of the Cape Floral Kingdom – 14 years ago. Over the past decade, he has witnessed the precipitous decline of the fragile species.

“We had a really big fire in 2016; it took a lot of cedars out. Normally, you would look up to these mountains and would really see the cedar trees but in the last 10 years you can really see the big effect that these fires have had. 

“You have to look carefully up these mountains and rock cliffs to really see a cedar tree now … It’s hard to see fires coming through here and you smell the cedars burning and you know here goes another few cedars. 

“There’s one site here that I know, one of these cedars up there is 400 years old and just to see that cedar tree, it looks like a real archive full of history and character. The ones we see now are the ones the fires struggle to get to.”

For now, the work is about finding the “winning recipe” for when the seed must germinate through the seedpods. The thought of the tree’s potential extinction is unthinkable, he said. 

“If these cedars are out of the Cederberg, that’s such a big piece of our cultural history ripped apart. I can just not think of driving to the Cederberg and there’s no cedar tree in sight anymore … I really want to do everything possible to really help these cedars and see if, as humans, we can make a difference.”

Beneficial rodents

The aim is not to create big forests that fires would obliterate, he said. “The first years are to basically concentrate on these islands where the fires struggle to get to – just to disperse more seeds and then get into the wetter areas, the protected areas and into the rock crevasses where it doesn’t get the scorching summer sun.”

The Cape spiny mouse disperses the seeds that come into effect. “There are just too few rodents moving seeds around into those proper good spots – we want to mimic what the spiny mouse is doing. It buries the seeds but either it’s killed or it forgets where it puts the seeds and that’s how they germinate. But we want more of that on better spots for these trees. The trees take between 14 to 18 years then they will start producing seedpods of their own.”

Joseph White, a postdoctoral researcher at Wits University’s school of Animal, Plant and Environmental Sciences, said the Cape spiny mouse, together with the Cape gerbil, are responsible for the seed dispersal of about 300 species that have large nut-like fruits, including the Clanwilliam cedar.

White’s research, together with that of colleagues, has shown how the large, wingless nuts of the cedar are “scatter hoarded”, or buried for later consumption by the rodents, but this dispersal process is not working in many areas because adult plants are too scarce. 

“Seeds on the ground in fynbos, without being buried underground in some way, are going to be burnt and incinerated so basically dispersal is not exactly going to happen without something like the Cape spiny mouse,” he said. 

“… They get them into a safe place, where they’re not going to be incinerated by fire, not going to be available to the other rodents that don’t disperse and just eat them … so the seeds are essentially reliant on them to be hidden away.”

There’s a concern that changes in fire regimes, “which is part of what’s been a problem with the cedar trees”, would also be affecting the rodents and changing the whole plant community in general.

“The cedar is an umbrella species, similar to rhinos, where you have a species that becomes the focus. The cedar is an amazing plant, it’s really charismatic, and the area is named after it, but hopefully the future of the project will be restoring some of the other large, nut-bearing plants, to take a bit of the weight off the cedar trees.”

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