Image caption Until now, there has not been a global list of all the plant species known to science

The inventory of plants known to science worldwide has been cut by more than 600,000 species names.

Many plants have been named more than once, so for the past two years, scientists have been developing an accurate record of the world's plants.

The ongoing study involves UK and US researchers, who expect the final number of recorded species appearing on the Plant List to be closer to 400,000.

The list, to help plant conservation, will be published later this year.

"Without accurate names - authoritatively determined - understanding and communication about global plant life would descend into inefficient chaos," said Stephen Hooper, director of the Royal Botanical Gardens, Kew - one of the organisations involved in the project.

In partnership with the Missouri Botanical Gardens, Kew Gardens have been working on the project, which aims to provide a working list of all plants species in an effort to support plant conservation around the world.

It involves taking records from existing plant databases and producing a single, global inventory that removes duplications and errors - something that is not available at the moment.

The latest developments were outlined during the fourth Global Botanic Gardens Congress, which was held in Dublin in June.

The researchers involved in the Plant List are aware that is not without its own problems.

"It's been a rollercoaster of a project, and the results will be far from perfect but it will be the most comprehensive list to date," said Kew's head of science policy and co-ordination, Eimear Nic Lughadha.

"It will include almost all scientific names at species level that have been published for plants."

However, when the list is published, there will be no coverage of ferns, nor algae, which account for about 10,000 and 30,000 species respectively.

It is hoped that the working list will be accessible via the web in the coming months.