Where The Wild Things Were: Re-wilding and the Sixth Extinction - Biodiversity Conservation and Environmental Change - page 36

(a) (b)

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0 30 60 90 20 40 204060 10 20

% Upland pollen sum

30 5 10 15 3 692468 0.2 0.4 60120180

900

SCD # of particles

Figure 3.2 Palaeoecological evidence for dramatic ecosystem change associated with the decline of
megaherbivores, as indicated by Sporormiella abundance (shaded grey). (a) At Appleman Lake Indiana,
USA the pollen record shows combinations of broad-leaved trees and boreal conifers during megaherbi-
vore decline, that have no modern analogue. Percentage pollen data are shown for selected tree taxa,
non-arboreal pollen (NAP), Sporormiella , minimum squared chord dissimilarity (MSCD), and charcoal
counts (Gill et al. 2009). (b) At Lynch's Crater, northeast Australia, pollen, charcoal and Sporormiella
time series indicate a dramatic shift from rainforest to fire-prone sclerophyllous shrubland and grass-
land (Rule et al. 2012).

The loss of megafauna from NE Australia is thought to have caused a switch from rainforest
to fire prone grass/sclerophyllous shrub, as a result of direct effects on vegetation and
increased fire, due to accumulating biomass (Figure 3.2b) (Rule et al. 2012). Isotopic evidence
from the Murray-Darling Basin, in southeastern Australia, suggests a dramatic increase in
trees and shrubs that would previously have been browsed, following human arrival and
megafunal extinction, causing biomass build up and intense fires (dos Santos et al. 2013,
Flannery 1990). In Siberia, the loss of megafauna played a role in the conversion of product-
ive, diverse grassy steppe vegetation to inhospitable, waterlogged, and nutrient-poor moss
tundra (Zimov et al. 2012). In Amazonia, the loss of megafauna decreased nutrient cycling,
possibly contributing to phosphorus limitation (Doughty et al. 2013). In Europe, controversy
over the impacts of loss of megafauna on forest structure poses a conundrum for the re-
wilding of forests (Vera 2000, Birks 2005, Mitchell 2005). The complex ecological conse-
quences of de-faunation highlight the need to understand the ecological implications of
extinction and reintroduction.