Plants Under Pressure

Principal Investigator

Dr Neil Brummitt

Project summary

  • Focus: quantifying the threats to plants across the world

The Plants Under Pressure project aims to quantify how threatened plants are across the world.

The question of how threatened plants are is difficult to answer. Despite more than 300 years of scientific discovery, thousands of new species are described every year, and some remote regions of the world remain poorly understood.

Plants are also facing greater risks from habitat loss, invasive species and other factors, meaning an accurate picture of their conservation status remains unknown.

The International Union for the Conservation of Nature (IUCN) Sampled Red List Index for Plants aims to fill this gap by providing a baseline for global plant conservation. This is the first estimate of the extent of the threat to the world's estimated 380,000 species of plants.

The project is a partnership between the Museum, the IUCN, and the Royal Botanical Gardens, Kew.


Five major groups of plants were assessed in the study:

  • bryophytes (mosses and liverworts)
  • pteridophytes (ferns and allied species)
  • gymnosperms (conifers, cycads and related species)
  • monocotyledons (including orchids, bulbs palm trees and the grass family)
  • legumes (the family of peas and beans)

Of the five major groups of plants studied, bryophytes and pteridophytes were assessed at the Museum.

For each group, 1,500 species were randomly selected and assessed against the criteria set out in the IUCN Red List to evaluate their risk of extinction.

Ferns in Costa Rica

Assessing fern species in the rain forests of Costa Rica


Historical records and modern technology are combined to assess the status of each plant species.

Many species of plants have not been extensively studied and records of them are scarce. Some are only found in the scientific paper that first described them and they have no distribution map or population surveys associated with them.

To overcome this, researchers scoured the world's herbaria - collections of dried, preserved plant specimens. Specimen records in this form are numerous:

  • the Museum herbaria contain six million plant specimens
  • the herbaria of the Royal Botanical Gardens, Kew contains seven million plant and fungal specimens

Collection data associated with these specimens shows when and where a plant was collected, spanning hundreds of years of global collecting. This information feeds into the assessment of a species, combined with information from:

  • botanical literature
  • Geographical Information Systems (GIS)
  • satellite images, such as those on Google Earth
  • the expert opinion of scientists who study that species or the area of the world it's from

All these inform the assessment of each species' conservation status and underpin the assignment of an IUCN Red List category.

Threatened species map


Uncover some of the preliminary results and key findings from the Plants Under Pressure Project.

Museum staff

What is the IUCN Red List?

The IUCN Red List evaluates the risk of extinction for any species.

Of the estimated 380,000 species of plants, only about three per cent are currently on the Red List, and the majority of those were assessed because they were already presumed to be under threat.

To create a more representative picture of the conservation state of plants worldwide, the Plants Under Pressure project created a sampled IUCN Red List Index for Plants. This means that not all species of plants were assessed. Instead, a limited set of species was selected to represent each group.

Each species was assigned a category based on the Red List criteria.

  • Least Concern (LC): the taxon is abundant and widespread.
  • Near Threatened (NT): the taxon nearly qualifies in the endangered categories, or will likely quality for them in the near future.
  • Vulnerable (VU): the taxon faces a high risk of extinction in the wild.
  • Endangered (EN): the taxon faces a very high risk of extinction in the wild.
  • Critically Endangered (CR): the taxon faces an extremely high risk of extinction in the wild.
  • Extinct in the Wild (EW): the taxon survives only in cultivation, in captivity or as a naturalised population well outside its past range.
  • Extinct (EX): when there is no reasonable doubt that the last individual has died.
  • Data Deficient (DD): when there is not enough information to reliably assess the status of the taxon.

Funded by

The second phase of this work is supported through a generous donation from 


Uncover some of the preliminary results and key findings from the Plants Under Pressure Project.

Biodiversity research

We are creating molecular and digital tools to explore undiscovered biodiversity

Plant research

Studying a wide variety of plants, including bryophytes, ferns and flowering plants

Botany collections

Explore our collection of an estimated six million specimens from around the world