The forest elephants of the Congo Basin are critically endangered and face extinction. They live in Africa’s largest forest, extending over the continent’s west and central regions. Large populations are found in Gabon and the Republic of Congo and smaller groups in Cameroon, the Central African Republic, the Democratic Republic of Congo, Equatorial Guinea, Côte d'Ivoire, Liberia, Ghana, Sierra Leone and Nigeria. But ivory poaching means their numbers have plummeted by 86% over the past three decades. The sharp reduction of their population has a knock-on effect on the Congo Basin forest itself. This is because African forest elephants are the rainforest’s gardeners. They disperse more plant species than any other animal, regenerating and reshaping plant communities. Read more: Cameroon's Baka people say they are part of the forest: that's why they look after it I’m a conservation scientist and part of a research team of international and Cameroonian scientists who set out to examine how forest elephants interact with West African ebony trees. We wanted to know if the decline of elephants had negative, cascading effects on other Congo Basin forest species. We focused on ebony because it was known to be a food for elephants and its wood is prized for numerous uses.The research team set up tree plots and experiments in forests with and without elephants (often lost due to hunting). We used hidden cameras to record which animals ate ebony fruit and how ebony seeds enclosed in dung grew into seedlings. Our lead researcher, Vincent Deblauwe, spent years in the field conducting these experiments and even built a custom camera trap to observe ebony pollinators for the first time in the canopy.We also collected ebony seeds from within elephant dung, manually planted them, and carefully monitored germination rates and seedling survival. Additionally, the project developed cloning propagation methods to support future replanting of ebony trees and ebony plantations. Our research found that forest elephants, a different and smaller species than savannah elephants, are tightly linked to ebony’s life cycle. The impact of elephantsThese little four-tonne elephants support ebony reproduction in at least two ways.Distance matters: Elephants move the ebony seeds quite far away from the parent tree. This reduces the risk of ebony trees growing close together and inbreeding. Inbreeding weakens the genetics and lowers their chances of being resilient and adaptable to future environmental change. Dung as armour: Elephants consume ebony fruits whole and the pulp is digested from around the seeds before they poop them out intact. We found digestion did not help the ebony seeds germinate. However, being encased in dung protected the seeds from rodents that eat and kill the seeds. This greatly improved the seeds’ chances of survival and germinating. Read more: DRC's plan for the world's largest tropical forest reserve would be good for the planet: can it succeed? Our research found that there are nearly 70% fewer small (younger) ebony trees in the areas where elephants have disappeared. Most adult ebony trees alive today were dispersed by elephants decades ago because ebony is a slow growing wood that can take 50 years to begin reproducing, and 60 to 200 years to fully grow.Our conclusion is that it is not certain that ebony trees in the Congo Basin will be able to survive naturally without the help of elephants. Both elephants and rare ebony lie at the heart of the national heritage of Cameroon. By safeguarding elephants, Cameroon can protect the long-term viability of sustainably managed ebony and other valuable timbers. A wake-up call for Central African forestsThe West African ebony tree (Diospyros crassiflora) can grow up to 25 metres tall. It is a culturally iconic and economically valuable tree prized for its deep black heartwood. Ebony has been used for centuries to make carvings, piano keys and guitars due to its special harmonics. Our research found that no other animals in the Congo Basin are able to disperse the ebony tree’s seeds in the same way. This has left a functional gap in the forest – one that current conservation strategies too often overlook. Forest elephants have been poached out of two-thirds of the ebony trees’ natural habitat so most of the Congo Basin’s adult ebony trees are in elephant-free areas. This means they won’t be able to get any help from elephants in dispersing or concealing their seeds within dung. Read more: Nigeria risks losing all its forest elephants – what we found when we went looking for them It’s not only the future of ebony that’s at stake. Other large-seeded trees may also rely on elephants to move their seeds. Elephant declines could be quietly reshaping forests in ways scientists are only beginning to uncover. The takeaway is clear: plant-animal interactions are not a luxury add-on to conservation plans; they’re foundational to keeping forests functioning.What needs to happen nextThere are already many efforts to protect elephants and the processes they drive. Sadly, these seem insufficient to date. The most urgent conservation action is halting the killing of elephants for ivory. Reducing illegal logging of ebony trees is also important. Both of these can be accomplished by better education with local residents about the ecological and economic importance of elephants and ebony, and improved enforcement of existing poaching and logging regulations.Another important step is monitoring less charismatic tree species that also depend on elephants. Similar plant-animal relationships and the species and services they provide might be at risk. Read more: Eyes in the sky and on the ground are helping forest conservation in Cameroon Our project increases international research partnerships with Cameroon’s domestic experts and attracted expertise and funding for local institutions. For example, this research project provided education and capacity-building for Cameroonian researchers and practitioners, growing national expertise in biodiversity management.Finally, African forest elephants don’t just live in the Congo Basin’s rainforests – they shape them. Increased poaching of elephants for ivory not only threatens the ebony tree – forest elephant declines can ripple through forest structure, biodiversity, and carbon storage.This work was part of the Congo Basin Institute at UCLA and was largely funded by Taylor Guitars, which uses ebony for their instruments. They have invested nearly a decade in ebony research and conservation.Matthew Scott Luskin receives funding from NASA, ARC, and the National Geographic Society.