Scientists believe there are now 73,000 species of tree on Earth — 14 per cent more than previously thought but the complete list remains unfinished business in the plant world.
A study using advanced technology estimates there are 9,200 tree species yet to be discovered but scientists have vowed to complete challenge.
The latest findings have been made using modern developments of techniques first devised by mathematician Alan Turing during the Second World War to crack Nazi code, will help prioritise forest conservation efforts.
The study involved more than 100 scientists and has been published in the Proceedings Of The National Academy Of Sciences. It suggests most of the undiscovered species are likely to be rare, with very low populations and in small areas.
Researchers say the undiscovered species will be especially vulnerable to disruptions caused by humans such as deforestation and climate change.
“These results highlight the vulnerability of global forest biodiversity to anthropogenic changes, particularly land use and climate, because the survival of rare taxa is disproportionately threatened by these pressures,” said University of Michigan forest ecologist Peter Reich, one of two senior authors of the paper
"By establishing a quantitative benchmark, this study could contribute to tree and forest conservation efforts and the future discovery of new trees and associated species in certain parts of the world.”
Researchers combined data from two global data sets, one from the Global Forest Biodiversity Initiative and the other from TreeChange.
The databases yielded a total of 64,100 documented tree species worldwide, similar to a previous study that found about 60,000 tree species on the planet.
After combining the data sets, the researchers estimated the total number of unique tree species, including those yet to be discovered and described by scientists.
The study estimates the total number of tree species on Earth is 73,274, indicating about 9,200 tree species are yet to be discovered.
According to the researchers, their new study uses a more extensive data set and more advanced statistical methods than previous attempts to estimate the planet’s tree diversity.
“Counting the number of tree species worldwide is like a puzzle with pieces spread all over the world,” said Jingjing Liang of Purdue University, co-ordinator of the Global Forest Biodiversity Initiative.
It is thought that around 40 per cent of the undiscovered tree species are likely to be in South America, more than on any other continent.
South America is also the continent with the highest estimated number of rare tree species, about 8,200, and the highest estimated percentage of species found only on that continent, the research suggests.
It has identified the tropical and subtropical moist forests of the Amazon basin, as well as Andean forests at elevations between 1,000 metres and 3,500 metres, as likely hotspots of undiscovered South American tree species.
“Extensive knowledge of tree richness and diversity is key to preserving the stability and functioning of ecosystems,” study lead author Roberto Cazzolla Gatti of the University of Bologna in Italy, said.
Around the world, around two thirds of all already known tree species occur in tropical and subtropical moist forests, which are both species-rich and poorly studied by scientists.
These forests probably hold high numbers of undiscovered tree species, the researchers say.
Previous research has revealed that two in five plant species are at risk of extinction.
