Greening the Desert - Feral: Rewilding the Land, the Sea, and Human Life - page 86

impacts - and failed. 42 Despite intense hunting and culling, willow
trees disappeared from the meadows and aspens were in danger of
vanishing from large areas of the park. 43 Even when hunting by
humans is intense, its effects are likely to differ sharply from those of
hunting by wolves. Wolves hunt at all times of the day and night,
throughout the year. They pursue their prey, rather than killing it from
a distance. 44 Wolves and humans hunt in different places and select
different animals from the herd. Fencing might keep out the deer, but
unlike wolves it does so entirely, while also excluding other animals
and reducing the connectedness of the ecosystem.
Where salmon run, the reintroduction of wolves in North America
could trigger even wider effects. The wolves create habitats for both
salmon and beavers, and the beavers create further habitats for sal-
mon, potentially boosting their numbers. The salmon are caught by
bears, otters, eagles and ospreys. Their carcasses are often dragged or
carried onto land. The nutrients they contain are distributed in the
animals' dung. One study suggests that between 15 and 18 per cent of
the nitrogen in the leaves of spruce trees within 500 metres of a salmon
stream comes from the sea: it was brought upriver in the bodies of the
salmon. 45 Top predators and keystone species unwittingly re-engineer
the environment, even down to the composition of the soil.
A starker example is provided by the Arctic foxes introduced by fur
trappers to some of the Aleutian islands - the sickle-shaped chain
across the northern Pacific between Alaska and Siberia - where they
are not native. Those islands with Arctic foxes are covered in shrubby
tundra, those without foxes are covered in grass. 46 By hunting sea-
birds, the foxes have ensured that sixty times less guano is brought to
the islands. This means that there is three times less phosphate in the
soil than where they are absent. As a result, they have changed the
entire natural system.
Human hunters might have imposed a similar change in the great
steppes of Beringia, the landmass incorporating eastern Siberia,
Alaska and the area in between (now covered by the Bering Straits,
but exposed during the last Ice Age). Perhaps 15,000 years ago, hunt-
ers using small stone blades moved into the region that had hitherto
been occupied by people hunting with sharpened bones or antlers. 47
Gradually, they wiped out the mammoths, musk oxen, bison and