Plants are a fundamental part of ecosystems, forming their physical structure, and are of essential importance to the functioning of the planet's atmosphere. The majority of plants conduct photosynthesis, a process that by using sunlight energy, converts carbon dioxide and water into organic compounds (such as sugar), water and most importantly into oxygen. Plant species provide habitat, enable the life of animal species and are primary producers for the food web. Plant cover significantly influences the climate, water resources and soil stability and composition. Humankind has relied on plants for thousands of years for food, shelter, fuel, fibre, clothing, for medicinal purposes and for their ornamental and cultural value.

Europe's flora comprises 20-25,000 species and the areas with the highest plant richness are in the Mediterranean region. This Red List includes 1,826 selected species of vascular plants native to Europe or naturalised before AD 1500. The species selected belong to one or more of three groups: policy species, crop wild relatives and aquatic plants:

Policy species

This group comprises 891 plant species and subspecies that are listed under European or international policy instruments (therefore referred to as "policy plants") of which there are four major instruments that concern plant species:

• Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora (Habitats Directive)
• Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention)
• Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) which includes the whole orchid family and all snowdrops
• Council Regulation (EC) No 338/97 of 9 December 1996 on the protection of species of wild fauna and flora by regulating trade therein

Crop wild relatives (CWR) of priority crops

CWR are the wild species closely related to crops that are defined by their potential ability to contribute beneficial traits for crop improvement. CWR have been used increasingly in plant breeding since the early 20th century and have provided vital genetic diversity to enhance food crops – for example, to confer resistance to pests and diseases, improve tolerance to environmental conditions such as extreme temperatures, drought and flooding and to improve nutrition, flavour, colour, texture and handling qualities.

Europe has significant endemic genetic diversity of global value in crops of major socio-economic importance and their wild relatives, such as oats (Avena sativa L.), sugarbeet (Beta vulgaris L.), carrot (Daucus carota L.), apple (Malus domestica Borkh.), annual meadow grass (Festuca pratensis Huds.), perennial rye grass (Lolium perenne L.) and white clover (Trifolium repens L.). Gene pools of many minor crop species and their wild relatives are also present in the region, such as asparagus (Asparagus officinalis L.) and lettuce (Lactuca sativa L.) as well as herbs such as chives (Allium spp.). In total, 591 wild relatives of a list of priority crops were selected based primarily on their food and economic security importance in Europe. The information presented here is only a very short summary – please consult the full report for detailed information on this process and the CWR selected.

Aquatic plant species

Aquatic plants provide a wide range of functions in freshwater ecosystems. They supply water with oxygen, fix atmospheric carbon, recycle nutrients, regulate water temperature and light, protect against erosion in flowing water and where the banks or margins are threatened by backwash from boat traffic. They also provide vital habitat and food for fish and aquatic invertebrates, which themselves support other animals and humans.

The aim of this assessment is to review the conservation condition of all vascular plants which occur in Europe and are dependent upon standing or flowing fresh or at most slightly salty water for their survival. The main difficulty with this process was the adoption of a definition of what constitutes an "aquatic plant" and one of the most important issues is that of obligation or tolerance. The growth forms of aquatic vascular plants include taxa which are:

• Always completely submerged (obligate submerged aquatics) such as the naiads (Najadaceae).
• Submerged with sexually reproductive parts emergent (held above the water), such as water-fan (Aldrovanda vesiculosa) and the bladderworts (Utricularia).
• Emergent, where the roots and base of the plant are submerged, but some photosynthetic parts and sexually reproductive parts are emergent, such as most of the Cyperaceae, including sedges (Carex), spike-rushes (Eleocharis) and club-rushes (Schoenoplectus).
• Floating, without roots or with roots hanging in the water column, such as rigid hornwort (Ceratophyllum demersum), floating fern (Salvinia natans) and duckweeds (Lemnaceae).
• Amphibious, growing from the land over the water or adopting a variety of the above forms, such as amphibious bistort (Persicaria amphibia).