Lorraine Williamson
Across Europe, the comeback of the once-vanished beaver is often hailed as a conservation success. Spain, too, has witnessed the quiet return of Castor fiber—but in Zaragoza, the story is far from straightforward.
What began as an illegal release along the River Ebro has evolved into a test of how a modern city can coexist with a species that is both protected and destructive.
A conservation win with a cost
Beavers are ecosystem engineers. Their dams create wetlands that boost biodiversity and help store water in times of drought—an asset in a warming, drier Aragón. Yet those same instincts are now undermining the city’s carefully planned green spaces. Trees along the Ebro, Huerva, and Gállego rivers are being felled not by chainsaws, but by sharp teeth.
Trees falling before their time
The most striking casualty stands in Parque de Tenerías, where a mature black poplar has been gnawed so severely that officials fear it could collapse onto a busy riverside path. More than seventy trees have suffered similar damage. Many of these are between the Azud dam and the Club Náutico and near the Balcón de San Lázaro. Municipal teams are racing to wrap vulnerable trunks in metal mesh before more give way.
From forest to tarmac
Greening the city while keeping it safe
Ironically, Zaragoza is in the middle of one of its most ambitious urban rewilding drives. This year alone, 1,700 new drought-resistant trees are being planted, while schools replace concrete playgrounds with shaded green oases. The aim is to cool the city and boost biodiversity—a mission seemingly at odds with the need to control a protected animal that threatens the very trees meant to fight climate change.
Finding a middle ground
Because the European beaver enjoys legal protection, relocation or culling is not an option. For now, the city relies on constant monitoring, physical barriers, and selective tree removal to prevent accidents. The challenge is to prove that humans and beavers can share a riverbank without sacrificing safety or Zaragoza’s ambitious green future—a delicate balance that will shape the city’s relationship with nature for years to come.
Sources: El Periodico, Zaragoza.es