From seeds to forests

When you work with Rainforest Builder, you quickly get used to a certain kind of landscape—the hot, dry scrublands that emerge after large-scale deforestation. These are not easy places to spend time- the sun glares down relentlessly, the soil bakes hard and dusty, and blade-like grasses and vines seem to cross every path you want to walk.

If it’s tough on people, it’s even tougher on trees. In these degraded habitats, intense heat and parched soils make it difficult for tree seeds to germinate, and those that do sprout are often quickly choked by fast-growing invasive weeds. With few mature trees left to supply seeds, these landscapes can remain stuck in a scrub-dominated state for decades, unable to recover naturally.₁

Seeds, however, are among nature’s greatest innovations. Plants have evolved ingenious ways of sending their offspring into the world—floating on the wind, hitching rides on (or in!) animals, even surviving epic ocean journeys. But when only a handful of mother trees remain, the chances of enough seeds arriving to spark regeneration are slim. Nature, in short, needs a helping hand.

That’s where we come in. By planting and caring for thousands of seedlings, we are able to jump-start the natural process of succession. The key is getting the right density of seedlings: enough young trees must be planted to quickly form a canopy that shades out the grasses and weeds. For large-scale projects, this means millions of seedlings—and that raises a daunting question: where do we get all the seeds?

‍Building a Seed-to-Tree Pipeline

As we established our first projects, this was one of the toughest challenges we faced. Thankfully, we had the support of leading experts— both from local West African research institutions, and also from international partners at Kew Royal Botanic Gardens and the Millennium Seed Bank. Together, we were able to design a sustainable seed-to-tree pipeline capable of producing millions of seedlings from dozens of native rainforest species each year.

The pipeline begins with finding the mother trees. Our teams of tree scouts search widely across our project landscapes to find healthy mature individuals of native rainforest species, recording detailed data on their growth forms, fruiting condition and characteristics. Working with local communities is central to this work – not only because of their intimate knowledge of the trees, but also to gain consent from everyone who may use or hold rights to the tree we want to harvest from. Ensuring these local community custodians benefit directly from our projects is also a great way to incentivise the long-term protection of the landscape’s remaining mature trees.

Once permission is secured, a waiting game begins. Not all trees fruit every year, and even when they do, the window for collecting ripe seeds is often narrow. Knowledge of the timing of these windows remains patchy for many West African tree species, and climate change is making things increasingly unpredictable. Our teams collect detailed data to help us track seeding patterns, but there’s no substitute for making regular repeat visits to each tree to ensure we’re in the right place at the right time.

Harvesting seed from rainforest trees is rarely simple. Seeds that fall to the ground can quickly spoil or pick up pests and pathogens, so the best option is to collect them directly from the tree. That usually means climbing—sometimes 40 meters or more into the canopy—to then carefully collect the best seeds from selected fronds. Our trained climbers follow detailed guidelines for sustainable seed collection developed by our Kew collaborators, ensuring the operation has no impact on the health of the parent trees.

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‍Cracking the Code of Seed Survival

Once collected, seeds need careful handling. Some species (the “recalcitrant) lose their viability very quickly after harvest, so the seed must be planted out at once. Others have adaptations for seed dormancy, meaning they can be stored for much longer periods if they are processed and treated correctly. This has been a key focus of our research collaboration with Kew and the Millennium Seed Bank team, who are pioneers in the art of keeping seed viable through drying and cooling to the right levels.₂  Working together, we have developed new field-based techniques that allow us to safely store seed in challenging tropical environments where temperatures are high and electricity supplies unreliable. Our first dedicated “seed hubs” following this blueprint are currently under construction in Ghana and Sierra Leone.

Next comes germination—another challenging puzzle to solve. Once seeds enter dormancy - essentially a biological sleep mode - they typically require some external cue to trigger them to re-awaken and start growing. Some respond to moisture or temperature shifts, others to sunlight or shade. In more extreme cases, some rainforest tree seeds can only germinate after passing through the digestive system of an animal (part of their adaptations to promote dispersal). Obviously, we can’t feed all our seeds to birds and monkeys—so we mimic the process with techniques like scarification(lightly sanding the seed coat) or soaking in weak acid. Each species requires its own tailored treatment, keeping our research teams busy running experiments to discover what works best.

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Restoring rainforests is a complex, multi-layered challenge—but without a functioning seed pipeline as foundation, our forests would never get started. The knowledge shared by our expert partners has been crucial in building a system that works. Some of our earliest restoration sites now have more than two years of growth, and it is a joy to walk in the shade of the growing trees, many already well over head height, and marvel at the transformation from the hot, dry scrubland that was there before. The future really is restorable – it just takes millions of seeds!