Tropical regions are some of the most biodiverse parts of our planet, but are also the least known, least resourced, and often most vulnerable to human impact.

Not only are many plants threatened with extinction, but also as many as one-fifth of all plant species may still be unknown to science. Baseline work to describe these, determine their distributions, and estimate their risk of extinction, is crucial: we can’t protect something until we know it exists, where it is found, and the threats it faces.

The world’s botanic gardens – combining expert scientists with rich, verified collections of living and preserved plant specimens and strong international relationships – are uniquely placed to carry out this work. Working with colleagues around the world, RBGE researchers describe an average of around 60 species new to science each year – that’s more than one every week!

Assessing threat

We played a key role in 2021’s Global Tree Assessment, coordinated by Botanic Gardens Conservation International. The assessment found that, of the world’s c. 58,500 tree species, 142 are already extinct and a further 30% are threatened. Working with researchers across the world, RBGE continues to work to determine the conservation status of important groups including the tropical tree family Sapotaceae, all the world’s conifers, and many rhodendrons.

Long-term relationships between institutions and individuals are vital to protecting plant biodiversity. Working with an international team including Biodiversity International, Malaysia, and APFORGIS, a regional assessment of vulnerability for socio-economically important tree species was recently generated, which enabled us to pinpoint specific areas of natural forest in Malaysia and Indonesia as hotspots for conservation.

Describing species

Turning to the understorey, we also specialise in the tropical plant groups Begonia, Solanum, Gesneriaceae (African violet family) and Zingiberaceae (ginger family). Working with Dr Abdulrokhman Kartonegoro of the Indonesian Institute of Sciences, RBGE’s Dr Hannah Atkins revised the species-rich genus Cyrtandra in Sulawesi, Indonesia. Published – with fully open access – in Edinburgh Journal of Botany, their revision documents 39 species, including four new to science, and over 40% threatened with extinction.

Tackling deforestation

One of the most pressing threats to tropical forests is felling for plantations of crops such as oil palm and rubber. In Southeast Asia, the expansion of rubber (Hevea brasiliensis) plantations at the expense of natural tropical forest increases carbon emissions and has negative impacts on biodiversity. Despite increasing global demand, price fluctuations and a lack of regulation also make it a risky crop for the smallholders who make up the majority of rubber growers.

Dr Antje Ahrends and Dr Yunxia Wang’s work aims to tackle a lack of data on where rubber is grown, whether these areas are suitable for long-term production, and the impacts on forest cover, biodiversity and livelihoods. Working with colleagues at the Kunming Institute of Botany, they use cutting-edge earth observation technologies, modelling, and interviews to map rubber planting and associated forest loss at high resolution, and to understand the present and future environmental suitability of land for rubber and the economic risks to local farmers.

Their work suggests that over half of new rubber plantations are situated in areas where environmental risks (including storms and typhoons, drought or poor soils) may cause low yields or plantation failure. Their predictive models will help discourage future forest conversion to rubber plantations where livelihood gains would be low, underpin policy interventions and support certification schemes.

Raising the profile of grasslands

But it’s not only forests that are under threat. Tropical savannas and grasslands can be equally biodiverse and important for human livelihoods, carbon sequestration and other vital ecosystem services. Dr Caroline Lehmann leads a team studying the grasslands and savannas of tropical Africa. Her cross-disciplinary work in Madagascar is providing urgent insights into how grasslands are maintained, and how they may respond to climate change, with impacts for livelihoods and food security. We ignore these vital ecosystems at our peril.

Find out more about RBGE's other pioneering biodiversity conservation programmes around the world.