Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Reintroduction analysis

The ultimate goal of conservation efforts is to preserve species in their natural settings. Because many species survive regionally through a balance of colonisations and extinctions we need not only to preserve local habitat conditions but also the possibilities to re-colonise suitable habitat from which the species has gone extinct. However, because of continued habitat destruction the remaining habitat for many species have today become so fragmented that they are not able to re-colonise suitable habitat. Central issues are therefore to determine the extent to which the current distribution of species is limited by the dispersal capacity and if re-introduction of plant species through seed sowing experiments constitutes a realistic management option.

A series of seed sowing experiments was carried out for the four target species, Succisa pratensis, Tragopogon pratense, Ranunculus bulbosus and Carlina vulgaris. The experiments included disturbance treatments and were performed both at occupied and un-occupied sites. Positive results, i.e. recruitment after seed sowing, at un-occupied sites indicate dispersal limitation, and provide support for the expected success of re-introduction of species. For all four species results suggested dispersal limitation, and, as a corollary, that re-introductions are expected to be a useful tool in restoration of species richness in semi-natural grasslands fragments in the present-day landscape. However, there were also differences among species in the degree of dispersal limitation.

In addition to the results of dispersal limitation, our studies indicated that the success of the seed sowing depends on the floristic composition at the sites. This implies that local habitat conditions are also important for recruitment success. Furthermore, suitable targets for re-introductions could be identified by species surveys.

Re-introductions are thus useful to counteract present species loss and decline of biodiversity. Furthermore, the results provide insights to knowledge about species regional dynamics, indicating dispersal limitation, and that this in turn may influence ongoing change in vegetation cover, due to altered land use. However, re-introductions are not uncontroversial, since they may be considered as negative for authenticity values. Further studies on the appreciation of artificial biodiversity should therefore be performed.

Results from re-introductions may also add to risk assessments for endangered species. If re-introductions generally fails, this indicates that other factors than availability of apparently suitable sites, are responsible for species decline, i.e. the real suitability of sites has been misinterpreted. On the other hand, if the re-introductions are often successful, this implies that species are dispersal limited and that landscape configuration is essential, and must be taken into account in conservation planning. The fact that the degree of dispersal limitation varies among species indicates that the benefits of re-introductions will also vary among species.

For agriculture the results imply that preservation of traditional management in semi-natural grasslands is essential. To promote dispersal and provide habitats for species, and thereby development of new populations, the surrounding landscape should also be used for extensive grazing. Conservation programmes should increase focus on whole landscapes. Economically sustainable systems for maintaining grazing, and for cooperation among farmers in order to increase the extent of grazed areas, should be developed. Such landscapes will also promote recreational values of landscapes.

The results will also be valuable for research on regional plant population dynamics, since they add to a growing body of evidence that plant species in fragmented landscapes are dispersal limited.

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