By helping prevent fire, wild horses play a key role in preserving the northwestern region of Galicia's delicate ecosystems, scientists say. But Europe's largest herd of wild horses has dwindled to less than half the 22,000 that roamed its mountains, forests and heathlands in the 1970s.

"Studies show that where wild horses graze, the heath's biodiversity increases," said Laura Lagos, a researcher at the University of A Coruna. "They are a fundamental part of the ecosystem. They benefit both the flora and the fauna associated with these open spaces."