Restoration of dry grasslands and heathlands - Restoration Ecology - page 95

8

Restoration of dry grasslands
and heathlands

Jan P. Bakker and Rudy van Diggelen

8.1 Introduction: the historical context

lands, floodplains and nutrient-poor soils, whereas
uplands were probably covered by dense forest. It
is not clear in this context whether the megafauna
in North America might have been able to maintain
extensive prairies. When they were extirpated within
1000 years about 11,000 BP , climatic conditions were
different from the current ones. It is assumed that human
impact strongly increased the area of dry grasslands
and heathlands as a result of agricultural exploitation,
in what is nowadays referred to as low-intensity
farming (Bignal & McCracken 1996). Hence, they can
be classified as semi-natural landscapes (Westhoff
1983). They can only be maintained by this type of
farming; changes in land use both by intensification
and abandonment will change the communities. The
question for restoration is whether such changes are
reversible or irreversible.
In Europe, this agricultural farming system was intro-
duced from the Middle East, and it spread quickly after
about 7000 BP . In wetlands, people of the Swifterbant
Culture started keeping livestock at about 5800 BP
and crop cultivation at about 5300 BP . In uplands they
started agriculture at about 5000 BP in the northern
part of the Netherlands (Bakker 2003). Apart from arable
fields, common grazing lands were exploited and
resulted in the extension of heathland in the Atlantic
part of Europe, whereas dry grasslands developed
elsewhere. Dry grasslands can be subdivided in acid
grasslands and calcareous grasslands depending on the
occurrence of a limestone subsoil. Dry grasslands
and heathlands developed under a common grazing

Dry grasslands and heathlands can be characterized
from a hydrological point of view as infiltration
areas, fed by rainwater. Hence, for these types of hab-
itat restoration does not have to deal with complicated
groundwater-management practices as is the case for
mires (see Chapter 9 in this volume). After the last
glacial period natural communities of dry grasslands
and heathlands are supposed to have occurred on rocky
inland outcrops, for example on chalk grasslands, along
coasts, in river floodplains and at the edge of bogs.
Their area was restricted to marginal habitats with
extreme abiotic conditions such as shallow soil with
subsequent low nutrient availability. This traditional
view has recently received much attention. Several
authors suggest that large herbivores maintained a
mosaic of forest and grassland/heathland in a wooded
meadow system in the pre-agricultural landscape
(Gerken & Meyer 1996, Vera 2000). However, wooded
meadows may have been restricted to small stretches
along rivers, being the places with relatively open
forest on nutrient-poor soil where herbivores are able
to maintain patches of short plant communities (Olff
et al . 1999). Archaeologists doubt whether the density
of large herbivores was high enough to maintain
wooded meadows. Svenning (2002) reviewed the
literature and he concluded from findings of pollen,
macro-fossils (seeds, leaves) and dung beetles that large
herbivores may have played a role (together with fire)
in pre-agricultural locally open landscapes in chalk-

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