After going extinct 30 years ago in the U.K, a rare plant called the stinking hawk's-beard (Crepis foetida) has returned its former homelands. The successful reintroduction could offer lessons for the reintroduction of other extant species.

The stinking hawk's-beard, known for its bitter-almond smell, was never exactly common in the U.K. Human development further shrank its habitats, and the plant disappeared from its last site in Dungeness, Kent, in 1980.

Since then, the organizations Natural England, the Royal Society for the Protection of Birds (RSPB), and Royal Holloway College have initiated several projects to try to reintroduce the plant, using seeds collected before it died off. Those first reintroduction projects failed or had limited success, but they offered enough information to help with the latest, successful, effort. Now at least 1,000 plants are thriving at the Rye Harbour Nature Reserve, where just 10 plants existed four years ago.

Keeping rabbits away from the plants turned out to be one of the most important factors in the successful reintroduction. Historically, rabbits populations may have been suppressed in certain areas by predators or factors that no longer exist in modern times, says Jane Sears, biodiversity projects officer for the RSPB.

The failed reintroduction attempts also allowed the project team to find the optimal factors that the stinking hawk's-beard needs to survive. "We now have a much better understanding of the ecological requirements of this plant," says Spears. These include ideal soiland weather conditions, and researchers are learning how other factors, including changing climates, make the plant vulnerable to predatory snails and slugs.

Stinking hawk's-beard still exists in several other parts of Europe, but populations appear to be shrinking in all of its habitats. "It appears to be showing the same retreat elsewhere in north western continental Europe that we have seen in Britain where it became restricted to isolated populations before dying out," says Spears. In particular, the plant's range has dramatically shrunk in the Netherlands and Belgium, and possibly also in France.

According to Spears and her project partners—conservation consultant Brain Banks and Royal Holloway College botany lecturer Brian Ferry—the understanding gained through reintroducing the stinking hawk's-beard may be applicable to other scarce species facing habitat loss in the U.K. "One interesting lesson that has been learned is that life is complex and that changes that might appear to be beneficial do not always have the anticipated outcome," says Spears. "For a southern European plant you might expect a trend towards milder conditions to have been advantageous, yet this does not always seem to have been the case."

The work for this project has been funded with money from Natural England and the RSPB, and Rye Harbour Nature Reserve paid for the rabbit-proof fencing at the site. The entire project boasts a very small budget—between £1,000 and £2,000 ($1,600 to $3,200) per year—which funds ecological research, rearing the young plants and monitoring their survival. "Much of the work has been carried out at non-commercial rates and through the good will of the key partners," says Spears. "The key components are dedication and patience."

Image: Stinking hawk's-beard, © Franklyn Perring, BSBI, via the UK Biodiversity Action Plan