Our comparison indicates that patterns of wild edible plant usage appear to depend mainly on socio-cultural factors rather than biological ones such as climate or richness of the wild edible flora. Availability of running water, free time to tend allotments, better communications and information exchange, direct contact with nature in everyday life, cultural values, fads and taste preferences are some of the factors that explain why wild plants are either consumed or rejected.
There is a clear preference for wild edible fruits that are consumed raw or used to make jams and liqueurs. By contrast, people in most of the study areas reject many available wild vegetables.
Some wild species are still gathered, including plants historically consumed in all areas with a high number of URs. They are the most important species in each use-category (fruits, vegetables, infusions or liqueurs), grow in all the survey sites and if not easily available from the wild, they are often cultivated. These "key plants" represent the core wild food flora.
Many wild edible plants are regarded as famine food and are no longer gathered. In rural Spain and Portugal they are often considered to be old fashioned, unprofitable, or too time-consuming, cultivated plants or bought food being consumed in preference.
Radical changes in the way of life of rural people in Spain and Portugal have severely eroded knowledge and customs relating to the exploitation and management of most wild resources. This rich element of biocultural diversity needs, therefore, to be studied before it is too late [58].
New trends relating to these resources can be traced in other Mediterranean countries, and the social significance and meaning of some are being reinterpreted. Although in general terms wild edible plants often have a stigma attached to them, being regarded as poor people's food, some are increasingly popular as delicacies, local specialities, gourmet food and local food that reflects regional identity. For example, both demand and supply are increasing in the cases of Asparagus acutifolius in many European regions, Muscari comosum in Italy and Sideritis hyssopifolia in Cantabria [20,37,59,60]
Movements such as Slow Food [61] and chefs' interest in offering new flavours and dishes can play a crucial role in boosting the social importance of such resources. Moreover, the way local people perceive and use their resources plays an important role in their conservation. Changes can lead to unpredictable consequences to their sustainable development.
Competing interests
The author(s) declare that they have no competing interests.
Authors' contributions
MP, EB, ES, AC and JL designed and carried out the field work; MP and JT wrote the paper, which was revised and improved by the comments of all the authors. RM coordinated, helped in the design of most of the surveys and supervised the paper. All authors read and approved the final manuscript.
Acknowledgements
We are grateful to everyone who kindly shared their knowledge and time. We hope to have contributed to saving and spreading their valuable knowledge. We also thank the Spanish Ministry of Science and Education for the grants made to Elia San Miguel and Manuel Pardo-de-Santayana, Los Picos de Europa National Park, the Leader Project of the European Commission for funding the field work done in Picos de Europa and Sanabria. Thanks also to the Portuguese Ministry of Science and Education and the Portuguese Foundation for Science and Technology for the grant to Ana Maria Carvalho and for funding the field work, to Laura Aceituno, Susana González and Lesley Ashcroft for their input, and to Gonzalo Gómez Casares for providing many information about plant uses in Picos de Europa.
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