Where The Wild Things Were: Re-wilding and the Sixth Extinction - Biodiversity Conservation and Environmental Change - page 37

Pleistocene parks
Re-wilding takes on many guises, the most ambitious of which are Pleistocene parks, which
aim to recreate the pre-Agrarian landscapes of the late Pleistocene, when megafauna were
still abundant. As so many Pleistocene species are now extinct (see above), this requires a
creative approach that involves the replacement of lost creatures with their nearest func-
tional equivalents.
In the wilds of Siberia, an ambitious Pleistocene park aims to recreate the mammoth
steppe, a productive and diverse grassy habitat that once covered vast swathes of Eurasia and
supported mammoths, woolly rhino, musk ox, elk, reindeer, bison, giant deer, wild horses,
ibex, saiga, and woolly rhino as well as wolves, foxes, lynx, lion, wolverine, and bear (Markova
et al. 2009, Zimov et al. 2012). Led by Sergey Zimov, Russian scientists have established an
experimental area, where grazing trials with bison, musk ox, moose, horses, and reindeer are
carried out. Their aim is to restore the steppe vegetation, potentially helping to avert a cli-
matic disaster (Zimov 2005).
Zimov argues that northern grasslands would have persisted in the Holocene if it were not
for the loss of the herbivores that stimulated plant growth, increased evapotranspiration and
enhanced nutrient cycling. He asserts that humans were a major driver of megafaunal extinc-
tions (Zimov 2005, Zimov et al. 2006, Zimov et al. 2012). Though climatic changes may have
contributed, his argument is supported by the palaeoecological data, which show that mam-
moth steppe persisted in northeast Siberia in the Last Interglacial; dry steppe vegetation com-
posed of grasses, sedges, and other herbaceous plants coexisted in a mosaic landscape, with
patches of shrub tundra, wetland plants, and pioneer species (Chapin et al. 2004, Kienast et al.
2008, Johnson 2009, Schirrmeister et al. 2011). A drier climate with less snow cover facilitates
winter grazing, and thus both climate and megafauna likely contributed to the survival of
steppe vegetation in previous interglacials. Many of the plants were grazing tolerant, and the
presence of abundant fungal spores is consistent with abundant herbivores (Kienast et al.
2008). Furthermore, many Pleistocene animals had a very wide climatic tolerance, as indi-
cated by their widespread distribution. Mammoths survived on Wrangel island, off the coast
of Siberia, and St Paul island, of Alaska until the arrival of people 3,000 years ago (Prescott
et al. 2012). Further decimation of Siberian fauna has taken place in recent centuries, with the
loss of sable, reindeer, and snow geese due to overhunting and persecution (Zimov et al. 2012).
The loss of herbivores from the mammoth steppe had a dramatic effect on ecosystem func-
tion, and the once productive and diverse grassy steppe vegetation became an inhospitable,
waterlogged and nutrient poor moss tundra (Figure 3.3). As a result of megafaunal extinction,
vegetation trampling and cropping was disrupted, leading to reduced productivity, less
evapotranspiration and waterlogging. Thus, the mammoth steppe and mossy tundra can be
seen as two alternate stable states, which are not primarily determined by climate alone, but
by the interacting actions of herbivores and environment (Chapin et al. 2004, Johnson 2009,
Zimov et al. 2012). Experiments with grazing enclosures and exclosures suggest that the tun-
dra state can be reversed by grazing; where herbivores are present, ground becomes drier
and grass cover quickly establishes.