Bombina bombina has also been very closely monitored. It decreased from 22 populations in 1970 to only 7 populations in 1987. However, since then 100 ponds have been restored, and the number of ponds with successfully breeding populations has increased from only 10 in 1988 to 17 in 1994. For Hyla arborea , all populations have been surveyed at least once, and taken care of. A total of c.900 ponds have been created or restored.
Monitoring indicates that the total Danish population is increasing.
Hyla arborea has been reintroduced to a region near its former northern limit in Jutland. In nine years, the introduced population has grown to c.250 males, in 27 ponds. After these initiatives to save the above three rarest species, efforts are now also being focused on Pelobates fuscus , Bufo calamita , and Bufo viridis . Where nothing is done, declines continue and accelerate. Special issue on Scandinavian herpetology.