A third of plant species in tropical Africa are threatened with extinction, a new study suggests. Plants are crucial to many ecosystems and life in general, providing food and oxygen, as well as being the source of myriad materials and medicines. However, human activities including logging, mining and agriculture pose a major threat.
While the extinction risk of animals around the world has been well studied, the risk facing many plants remains unclear: 86% of mammal species have been assessed by the International Union for Conservation of Nature (IUCN) for its Red List, compared with only 8% of plant species. Now experts say they have come up with a rapid approach to give a preliminary classification.
“Our approach can help to prioritise either species or regions on which proper IUCN Red Listing should focus,” said Dr Gilles Dauby of the French National Research Institute for Sustainable Development and a co-author of the research. He said the list was recognised as an authoritative source, and was crucial to planning projects that could affect the environment.
The new study is the latest to throw the plight of plants into the spotlight. Earlier this year, scientists completed the most thorough analysis to date of plant extinctions, finding that 571 species had been wiped out since the start of the industrial revolution – a figure they say is likely to be an underestimate.
Writing in the journal Science Advances, Dauby and colleagues report how they focused on two IUCN Red List criteria – one relating to population size reduction and the other to habitat decline – to develop a computer algorithm to automatically classify the conservation status of plants.
The team presented the algorithm with a recently compiled database of the distribution of more than 20,000 plant species across tropical Africa, together with data on threats such as croplands and cities, and predicted mining activities.
The Red List process also involves such data, which is examined manually for each species, and includes input from experts for each species and region – a process that is more meticulous, but far more expensive and time-consuming.
The authors say their algorithm classified 17% of the plant species in tropical Africa as likely to be under threat and 14% as potentially threatened – a total of almost 7,000 species. These species are largely concentrated in the rainforests of western Africa and the Ethiopian highlands.
If mapped on to the IUCN Red List categories, these species would all be “threatened with extinction” – falling into categories ranging from vulnerable to critically endangered. That means almost a third of the plant species examined might be threatened by extinction, a proportion expected to hold even if all tropical African species are considered.
“There is an extra 38% of species which we assess are geographically restricted, so they are rare, but for which no obvious threats for the moment are identified,” said Dauby. “If the human pressure increases, which is very likely in most parts of tropical Africa, they will be likely threatened in the very near future.”
The researchers say their approach is not designed to replace the Red List assessment, but could be used for a rapid, preliminary estimate of extinction risk as it is cheaper and faster – assessing more than 20,000 species in under seven hours.
The IUCN told the Guardian it welcomed the new approach. But Dr William Hawthorne of the University of Oxford described the new study’s conclusion that a third of tropical African species are potentially threatened as somewhat alarmist.
“What is really needed in the face of all this general alarm call is more locally focused studies based on new data and a big initiative to do more and more thorough botanical surveying,” he said.