2 October 2024
The dark matter of botany
Revealing the extent of plant diversity currently unknown to science
Did you know that there could be over 60,000 species of plant not yet known to science?
That’s about ten times the number of known mammal species on Earth – and we don’t know what or where they are. This great unknown is the ‘dark matter’ of botany, and finding these species is a priority for science, conservation and the future of our planet.
The State of the World’s Plants and Fungi 2023 report revealed that three-quarters of undescribed plant species may currently be threatened with extinction, and knowing their identity and their distribution would allow us to put measures in place to protect them. The burning question that remains, though, is how do we find these species?
Making the unknowns known
To answer this question, scientists at both Kew and partner institutions have put together a computer model to map the ‘botanical countries’ (often corresponding to political countries, or regions within them) that they predict are home to the highest numbers of undocumented species.
The model ranks regions in terms of the predicted number of undescribed and unmapped species. Undescribed species are those that are not yet known to the scientific community, whereas the unmapped species are those we know exist, but lack information about all the regions where they occur.
How can we predict what we do not know?
In both cases, our team of scientists looked back in time at how quickly species have been documented across the world and predicted a trend into the future of how much we have left to describe.
The team also considered the characteristics of the landscape and the plants themselves – tropical areas are more likely to contain new species, and plants that are used by humans are more likely to have already been documented.
The result: a list of 33 plant biodiversity ‘darkspots’, mostly clustered in Asia and South America. Of these, Colombia, New Guinea and China South-Central have the highest combined density of undocumented and unmapped species.
Hotspots and darkspots
Armed with this list of underexplored regions, the scientists compared their findings with a list of important regions for conservation – the global ‘biodiversity hotspots’.
There are 36 biodiversity hotspots across the globe – regions with rich and unique flora and fauna that are under threat from habitat loss. These are current priorities for conservationists but could be biased toward regions where fieldwork is easier to organise, and more species have been documented there as a result. We need to cement these hotspots with more complete global biodiversity knowledge that we do not yet possess.
As it turns out, all but one of the darkspots identified by the team overlapped with a biodiversity hotspot. The odd one out was New Guinea: the island with the largest number of plant species in the world, two-thirds of which are found nowhere else.
Brazil North, which encompasses the Amazon, is another region with vast numbers of unique species, and only narrowly missed out on making the list of darkspots. It, too, is not considered a hotspot.
New Guinea and Brazil North are not classed as hotspots because they are not ‘threatened’ enough – that is, they have not (yet) lost over 70% of their native vegetation. The importance of that ‘yet’ cannot be understated, as these regions are under rapidly growing threat from species overexploitation and deforestation. Their classification as darkspots will help prioritise research to further support the essential conservation work that we so urgently need.
Where could our priorities lie?
This list of darkspots tells us where in the world scientists should focus their efforts to document more species. This begs the question of where amongst these regions strategic government investment could make the most difference in expanding our knowledge, so that we can prioritise conservation needs.
It might make sense to begin in the countries with the most undocumented species, because there are more to find!
However, regions with many undocumented species might already have lots of scientific resources and efforts to document them, so it’s also important to consider the existing capacity for collecting new specimens in each country, as well as how threatened those species might be.
The team explored different scenarios re-prioritising the darkspots according to current environmental protections and socioeconomic factors (for example, higher national income indicates that there exist more resources to collect and document new species).
Areas that are prioritised under both these scenarios are those that need scientific effort the most – they do not currently have the resources to collect and describe new species, and their existing flora is not protected.
Six areas were identified as potential priorities – Colombia, Myanmar, New Guinea, Peru, Philippines and Turkey – which could become the primary focus of global collection efforts and new conservation schemes.
Influencing the future
The six global priority regions are a good starting point for botanists to document some of the vast number of plants unknown to science. The 2030 Declaration on Scientific Plant and Fungal Collecting includes a commitment to use evidence-based collection strategies – using this darkspot analysis and others to inform where future collection work takes place.
The resulting new knowledge will not only benefit the scientific community – it has implications for global environmental protection and can be passed to decision-makers on the world stage.
They could then identify new priorities for conservation, for instance by designating Protected Areas to safeguard the species that live there. Such analyses can also inform policy at the UN Conference of the Parties (COP) on biological diversity, the 16th meeting of which (COP16) is taking place in Colombia in October 2024, where Kew scientists will be presenting and discussing this work with policymakers from all over the world.
Alongside new frameworks like the Kunming-Montreal Global Biodiversity Framework, the darkspots analysis and the 2030 Declaration highlight the importance of Indigenous and local communities in biodiversity knowledge and conservation. While 'undiscovered’ species may not be known to science, they are often known and used by the people who live amongst them.
Local communities should be involved in collections and biodiversity conservation, whether that’s through the sharing of benefits from the work, or the development of new research, training and collection infrastructure.
With botanists across the world targeting their efforts more efficiently than in the past, we will be one step closer to filling the most critical gaps in our botanical knowledge, allowing us to better conserve and protect the beautiful breadth of plant species that live on this planet.
“Just as our early ancestors needed to know what grows where for their own survival, so plants and fungi need us to know where they grow — to enable us to safeguard their continued existence for generations to come.”
Alexandre Antonelli, Director of Science, RBG Kew
