Once in April every year, traffic in Dresden comes to a halt when 500 Suffolk sheep cross the city to reach the bank of the Elbe river. The sheep play an important role in protecting nature because they keep the grass short which is vital to many species in the meadows, like birds that can breed here only then. Dresden is not only a historic city, but also a green one. Its floodplains, gardens and parks are home to many other animals such as the Italian wall lizard, the kestrel and the tawny owl. Environment protection has also had its effect on the river itself: The beaver and salmon both returned to the Elbe in the 1990s after decades of absence.