Where The Wild Things Were: Re-wilding and the Sixth Extinction - Biodiversity Conservation and Environmental Change - page 42

that Europe's woodlands were more likely to have been a mosaic of woodland and herbivore-
friendly glades or wood-pastures. According to the wood-pasture hypothesis, canopy struc-
ture would have been patchy, with an important role for large herbivores in opening up
park-like woodland glades, in which grasses and light-demanding taxa can flourish (Olff et al.
1999, Vera 2000, Rackham 2003).
In his book Grazing Ecology and Forest History , Frans Vera suggests that the wood-pasture
hypothesis is an important motivator for the re-wilding of European woodlands, on the
grounds that large herbivores are essential in creating and maintaining the heterogeneous
structure that supports a wide range of biodiversity (Vera 2000). Vera's model suggests a
dynamic patch mosaic, where open park-like vegetation is initially colonized by unpalatable
shrubs that shelter the establishment of trees by protecting them from herbivory. These trees
eventually shade out their nurse plants, forming a forest grove, which will eventually break up
as individual trees die due to senescence or windthrow (Figure 3.5). In addition, fire may also
have played a role forest patch dynamics, preventing tree establishment in open areas that
were then maintained by herbivores (Bradshaw et al. 2003).

2

Break-up Park

1 3

Scrub

Grove

4

6

5

Figure 3.5 The wood-pasture hypothesis, illustrating how large herbivores help to create and maintain
a dynamics patch mosaic in temperate woodlands. (1) Trees in a closed canopy grove degenerate and die
leading to opening of the canopy. (2) The increase in light allows grasses to establish, attracting grazing
animals, which prevent the establishment of shrubs and trees, though some trees may remain within
this open landscape (wood-pasture/park). (3) Dung and soil disturbance provide opportunities for non-
palatable plants to establish. (4) Scrub species like blackthorn can establish within the non-palatable
patches within them. (5) The patches of scrub protect palatable tree seedlings from grazers. (6) Trees
shade out the scrub creating a grove with a scrub understory. Adapted from Olff et al. (1999), Vera (2000),
and Hodder et al. (2005).