The mvule (Milicia excelsa) is a giant of a tree, up to 50 meters (165 feet) tall, with a trunk 6 m (20 ft) around. To collect seeds from such a large tree, climbers work in a team of three, explains Sebastain Walaita, curator at the Tooro Botanical Gardens in Uganda.

Spacing themselves out evenly around the trunk they climb in tandem upwards using a system of ropes, harnesses and spurs. Once in the crown, the climbers separate, moving along the branches and stashing the mature seeds into their collection bags before descending back to the ground.

Walaita first learned high tree climbing for seed collection more than 25 years ago at a course organized by the Danish nonprofit DANIDA Forest Seed Center and has been honing his skills ever since. Over the years, he has trained a cadre of Ugandan botanists at Tooro, who can now safely collect seeds from even the most difficult trees, he says, improving their ability to propagate native species.

“It’s a passion,” Walaita says.

Collecting native tree seeds for restoration

Under the African Forest Landscape Restoration Initiative, or AFR100, governments across the continent have committed to restoring 100 million hectares (247 million acres) of land by 2030.

There’s a growing awareness amongst conservationists that it’s best to replant areas with native species for biodiversity. In addition, an alarming number of tree species are now threatened with extinction, including in Africa; globally, one in three tree species is at risk of extinction, according to a recent Global Tree Assessment by the global wildlife conservation authority IUCN. Many of the native seedlings for restoration, as well as for conservation projects to safeguard the genetic diversity of rare species, rely on seeds collected in the wild.

Yet, there are many challenges when it comes to propagating native tree seedlings. One is that wild seeds can be difficult to access, particularly when the trees are tall. If seed collectors don’t have the skills or equipment to climb the trees, they are confined to collecting seeds within easy reach, Walaita says, such as on the forest floor or from smaller trees.

That leads to a number of problems, he says. Most of the seeds on the ground are past peak maturity and may not germinate. They could also harbor eggs or fungus, problems that might not be immediately apparent but can decimate a collection. Or, in the dense forest, it can be difficult to know exactly where a seed came from.

To get the best seeds, collectors need to ascend. Trees come in different shapes and sizes, so Walaita uses — and teaches — a variety of techniques. In one of the most versatile, the climber secures a rope and harness, then “walks” up the trunk using boots equipped with small spurs, somewhat like an ice climber ascending a frozen waterfall. On trees with thinner bark, they use smaller spikes to minimize damage, Walaita says. Once in the crown, the climbers can move laterally using their ropes, even crossing over to other trees without descending.

One of the biggest obstacles to tree climbing is fear, according to Walaita. He says he tries to train climbers when they are about 18-20 years old, before the “fear factor” sets in.

“People think when you climb up there, it’s highly risky. You are not secure, and all those things come into play,” he says. But climbing with proper equipment and training makes things much safer, Walaita adds, in terms of falling and other dangers.

Once, nearly 40 m (131 ft) up a Eucalyptus grandis, Walaita says, he came face-to-face with a 4-meter-long (13-foot-long) cobra. Using his ropes — called lifelines — he was able to swing out of the snake’s way, dangle in midair, and then descend to the ground. He’s also had climbers stung by bees or falling sick while up a tree, but the rope system allowed them to be rescued safely.

In September 2024, Walaita and other Ugandan trainers took their climbing and seed collection skills to Côte d’Ivoire, under a Darwin Initiative project aimed at growing native tree species for reforestation, a project led by the Center for International Forestry Research and World Agroforestry (CIFOR-ICRAF) in partnership with the Botanic Gardens Conservation International (BGCI) and the National Floristic Center (CNF in French) in Côte d’Ivoire.

In the past, reforestation efforts focused on non-native species like teak, says Konan Yao, a researcher at CNF. Now, there’s a much greater awareness about the value of using native species in reforestation. At present, Ivorian botanists usually harvest native tree seeds using ladders, which require them to sometimes chop off branches, potentially compromising future seed production and injuring the tree. It’s also riskier for climbers. As the demand for native seedlings grows, seed collectors need safer and more sustainable ways to harvest seeds, Yao says.

During an 11-day workshop, Walaita and fellow Ugandan Paul Obbi trained Ivorian botanists on high tree climbing. These skills will allow them to harvest seeds safely, without damaging mother trees, which is especially important for threatened species found in Ivorian forests.

“We are really very grateful for Darwin [Initiative funding], because they bought very good equipment, and those guys really benefited from it,” Walaita says.

The right seeds at the right time

Of course, tree climbing is only one of the skills needed to collect seeds for conservation. It’s also important to choose the right trees and harvest seeds at the right time, Walaita says.

A ‘mother tree’ should demonstrate a certain resilience; ideally it is an older tree that has proved its adaptation to the environment and produces healthy seed, he explains. Mother trees should also be spaced far enough apart to ensure that collectors are capturing a broad spectrum of genetic diversity. Walaita says it’s also important that seeds are collected when they are at the optimum level of maturity — too young and they won’t germinate, too old and they may be infested with pests or diseases.

Alex Hudson, plant conservation manager with BGCI, says there still needs to be more promotion of native species in reforestation. Right now, many tree planting and restoration projects are focused on carbon sequestration, often depending on exotic species.

That’s partially because the seedling supply chain is far more developed for exotic species, Hudson says. Seedlings for commercial tree species and popular exotics are produced en masse and widely available. The propagation of native species is more difficult, both because collecting the seeds is challenging for many species and there isn’t as much knowledge on how to successfully propagate from seeds.

“You’re often talking about going into wild environments where it’s just not as easy to get to,” Hudson says. “I think all of the skills needed to do that well, [there’s] a big gap.”

To promote the use of native species in restoration, BGCI is now leading a project called the Global Biodiversity Standard, which will offer companies a way to evaluate and certify reforestation projects, to show they have been beneficial for biodiversity. Tooro Botanic Gardens was one of six organizations involved in testing the standard. BGCI is also partnering with CIFOR-IFRAC on another project aimed at improving the native seed supply chain in a number of African nations, including in Uganda, where Tooro Botanical Gardens will be involved.

Banner image: A botanist scales a Tieghemella heckelii in Yapo-Abbé Forest, Côte d’Ivoire, during a training session by Sebastain Walaita. Image by Gilberte Koffi / CIFOR-ICRAF.

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