Plants under pressure

Humans are causing unprecedented change to the natural world, in a time referred to by many as the Anthropocene. 

We are measuring how many plant species are threatened with extinction, where these plants grow and why they are threatened.

Together with the Royal Botanic Gardens, Kew, we produced a first IUCN Sampled Red List Index (SRLI) for Plants, using a sample of thousands of species from around the world drawn at random from major plant lineages. 

Each plant species we assess is given a IUCN Red List category.

Improving our understanding of plants

There is still much to understand about plants and many species have not undergone botanical study for decades.

We are helping to mobilise information about the plant world and highlight gaps in our knowledge. 

As part of the Plants Under Pressure programme, we are:

• assessing the conservation status and characteristics of individual species from many different lineages of plants
• studying the areas where these species are found and predicting where they might be found in the future
• establishing threats to plant survival and potential consequences of plant loss
• evaluating the impact of different biodiversity measures on our knowledge of the plant world and meeting international targets for conservation.

This work fed into the recent report by the Inter-governmental Science Policy Platform on Biodiversity and Ecosystem Services (IPBES) that estimated a total of one million plant and animal species worldwide are being threatened with extinction due to human activities.

Improving species assessment reliability

The IUCN Red List status of species changes over time, and the status of each species needs to be periodically re-assessed.

To record changes to the Red List Index correctly, it is important that at each iteration of the IUCN Red List, only genuine changes in the status of individual species contribute to the new value of the Index, and not merely improvements in our knowledge of the species.

We assess species under multiple criteria (where possible), to improve assessment reliability and to detect a genuine change in the Red List status of a species. 

Our assessments involve inference of the appropriate IUCN Red List Category at an earlier point in time using information only known at a later point in time, a technique known as back-casting.

We also apply the results of other assessment programmes, for example assigning Evolutionarily Distinct and Globally Endangered (EDGE) scores to the most endangered gymnosperm species in the world.