Where The Wild Things Were: Re-wilding and the Sixth Extinction - Biodiversity Conservation and Environmental Change - page 46

National Park in the 1920s and their loss cascaded throughout the ecosystem. Because all of
these changes took place over the past century, the use of long-term records of vegetation
change and animal abundance is invaluable in setting restoration targets and monitoring the
successful reinstatement of vital ecological processes (Smith et al. 2003).
One of the main effects of wolflessness was an increase in elk populations, which over-
browsed riverine vegetation in many areas, leading to a dramatic decline in aspen, cotton-
wood and willow (Ripple and Beschta 2004). Data from Aspen cores and stem diameters
showed that recruitment in the northern range of Yellowstone National Park varied dramatic-
ally over the past 200 years (Ripple and Larsen 2000). Aspen overstory recruited successfully
from the 1700s, but stopped in the 1920s, when wolves became locally extinct and elk brows-
ing increased (Beschta 2003). Especially in the northern range, trees failed to recruit along
river channels, which became denuded, causing beavers to abandon large valleys, further
degrading riparian habitat and impoverishing local biodiversity (Ripple and Beschta 2004).
River channels became incised, isolating streams from floodplains and causing the loss of
complex, heterogeneous wetland systems. Tree recruitment did not improve when National
Park Services tried to control ungulate numbers; the removal of 75,000 elk from the Greater
Yellowstone Ecosystem in the period 1926-1968 had little effect, so the practice was discon-
tinued in 1968.
Following reintroduction of wolves in 1995, however, elk populations have declined and
pressure has on the riverine vegetation has reduced. As well as increasing predation, the
presence of wolves caused elks to disperse to higher elevations and steeper slopes during the
summer, facilitating tree recruitment at lower elevations (Mao et al. 2005). As a result, tree
density and height along rivers has increased, stabilizing riverine channels, and restoring
connectivity of streams, wetlands, and flood plains, which are now once again important
habitat for aspen, willow, and associated birds, small mammals, beavers, and moose (Ripple
and Beschta 2003, 2004) (Figure 3.6). Thus, even though beaver are a prey item of wolves, they
have re-established along rivers in the northern territory since the wolves' return (Smith et al.
2003). In addition, populations of meso-predators like coyote have declined, due to competi-
tion with and aggression by wolves, increased vigilance of prey species and direct killing (Rip-
ple and Beschta 2004). Such interactions have probably benefitted other carnivores like
grizzly bear, which can drive wolves away from their kills, as well as scavengers like ravens,
eagles and magpies and red foxes, that compete more closely with coyotes than any of the
other carnivores. The survival of pronghorn antelope fawns has increased due to reduced
predation by coyote (Smith et al. 2003).
Wolf reintroductions are now underway in several more US states, including Montana,
Idaho, Arizona and New Mexico (Ripple and Beschta 2004). Wolf populations are also
rebounding naturally in Europe and are expanding their ranges in France, Germany, Pol-
and, Scandinavia, and Italy, possibly associated with increased habitat availability due to
rural land abandonment (Navarro and Pereira 2012) (see Chapter 6). Despite all of the eco-
logical, ethical, and aesthetic benefits of wolf introductions, the return of large carnivores
remains an emotive subject because of fears over the safety of humans and livestock (Wil-
liams et al. 2002).