By Fernando Valladares, Xiomara Quarry, Adrian Escudero* y Mar Gulis (CSIC)
In the 90s of the last century, the reintroduction of a small number of wolves in Yellowstone National Park (United States) caused a radical transformation of the ecosystems and the landscape. In a few years, the forest recovered ground and the trees grew again on the banks of the rivers.
Why the wolf turn, he wore more than a hundred years extinct in this natural spaceHe, did it have such a spectacular effect? The explanation lies in the so-called ‘ecology of fear’.
Lobo en Yellowstone. / NPS-Jim Peaco
As expected, the wolves helped regulate the population size of the species they hunted: mainly, two types of deer. However, what was decisive, and also surprising, was that the wolf modified the feeding habits of these animals with his mere presence, more than with their attacks and captures.
Pressured by the fear of the predator, the herbivores stopped moving freely through the territory and eating where there were more plants or they were more appetizing, and they began to stop visiting the most exposed and open places. The risk of being hunted there was too high. As a consequence of this behavior change, Opportunities were opened for more forestry plant and tree species to develop better without the pressure of these two species of ungulates.
Release of a wolf pup in Yellowstone in 1997. / NPS-Jim Peaco
Especially striking was the case of some trees attached to riverbedsLike the sauces, which prospered in ways unthinkable until then. The seeds of these trees are capable of moving long distances carried by the wind, since they are very light and are covered in hairs that facilitate their travel. However, with the extinct wolf, a good part of the banks of the national park appeared completely bare and deforested due to the excessive pressure of herbivores.
Thanks to the presence of the predator, the trees found an opportunity to increase their populations. In a very short time, the pattern of habitats and landscapes was completely changed. Now, forested areas, old or naturally reforested, coexist with areas dominated by grasses and other grass species where herbivores prefer to graze because they consider them safe. It has even been found that the structure and dynamics of the soil have changed in many places, giving rise to more fertile soils that better store carbon, something essential in the face of climate change.
NPS-Jim Peaco
The landscapes of the new Yellowstone have little to do with those of only 40 years ago and this shows that changes are possible. Also, the importance of the ecology of fear: fear of the predator, who with his mere presence changes behaviors and triggers cascading ecological processes.
* Fernando Valladares is a researcher of National Museum of Natural Sciences (MNCN, CSIC), Xiomara Quarry is the press officer of the MNCN and Adrian Escudero He is a researcher at the Rey Juan Carlos University. All three are authors of planetary health, belonging to the collection What do we know about? (CSIC-Waterfall).