One fifth of world's plants at risk of extinction

Over one fifth of all the world's plants are at risk of dying out, according to a recent report. Loss of habitats through converting natural areas to agricultural use is the largest threat to plants, affecting 33 per cent of plants assessed by this study.

Plants are an integral part of most ecosystems found throughout the world. Ecosystems and plants under stress or in decline are less able to provide vital goods and services, such as food, timber, fibre, medicine, the regulation of water, soil erosion control and climate change mitigation. In addition, plants contribute to human well-being through the provision of recreational, spiritual and aesthetically pleasing environments.
Over 380,000 plants around the world have been identified by scientists to date and there are potentially many more in existence. Yet, compared with mammals, birds and amphibians, only a small proportion (about 3 per cent) of the world´s plants have been evaluated for risk of extinction using the IUCN Red List categories and criteria.

The researchers therefore based their assessment of the state of the world's plants on samples of 1500 species taken from each of five major plant groups: gymnosperms (conifers and cycads and related species, only ~1000 species in total), monocotyledons (includes orchids, bulbs, palm trees and grasses), pteridophytes (ferns and allied species), legumes (peas and beans) and bryophytes (mosses and liverworts).

Overall, the study showed that over one fifth (22 per cent) of all the world's plants are at risk of extinction. Another 10 per cent of plant species are categorised as 'Near Threatened' and may become threatened unless conservation actions are taken. Plants face the same level of threat as mammals and are more threatened than birds. The percentage of threatened species in the different plant groups was assessed for the first time: gymnosperms were the plant group most at risk (36 per cent threatened); monocotyledons (22 per cent), pteridophytes (14 per cent), legumes (12 percent) and bryophytes (preliminary results - 15 per cent).

In addition, the study identified hotspots of risk to plants. Regions where plants are under the greatest threat include:

• South East Asia, where plants are particularly threatened by the conversion of natural forests to oil plantations
• Brazil - Mata Atlântica, where over 90 per cent of the Atlantic rainforest has been cleared for agricultural or urban use
• Australasia, where an alien fungus, Phytophthora cinnamomi, from Asia, is threatening entire ecosystems.
• Madagascar, where forests are being cleared at the rate of 1500km² a year, threatening the rich biodiversity found there.

In Europe, plants species are under pressure from intensification of land-use and the expansion of large-scale agricultural practices.

Climate change, growing populations and economic development will put further pressures on plants. Human impacts, such as agricultural expansion, harvesting of species, development, logging, and pollution account for about 81 per cent of the threats. Loss of habitats through converting natural areas to agricultural use is the greatest threat affecting 33 per cent of plants in this study. It is estimated that 20 per cent of global carbon emissions come from clearing and burning tropical forests for agricultural use and development.

Assessing the status of plants around the world is an ongoing project. Results to date show that urgent action is needed otherwise plants will continue to slip towards extinction.

Source: Plants under pressure: a global assessment. The first report of the IUCN Sampled Red List Index for Plants. (2010) Royal Botanic Gardens, Kew, UK. This report can be downloaded from: www.kew.org/ucm/groups/public/documents/document/kppcont_027709.pdf

Contact: n.brummitt@nhm.ac.uk and s.bachman@kew.org