Environmental Engineering Reference
In-Depth Information
valuable managed landscapes do not necessarily have to exclude biodiver-
sity conservation goals. Indeed, there is a signii cant literature that sug-
gests that many managed systems may actually augment biodiversity and
that land abandonment or a decline in management activities can actually
threaten biodiversity. We now turn to some examples of how land manag-
ers from around the world manage systems that conserve biodiversity. We
also consider what can happen to biodiversity when land and management
activities are abandoned.
Landscape management and biodiversity
In many managed landscapes good conservation practice succeeds because
it is perceived to coincide with the interests of land managers whose
support is vital for conservation initiatives. Such conservation practices
may also have been developed to avoid over-utilization of the resource on
which the human population depends. Consequently most biodiversity
exists in human-dominated ecosystems (Pimmental et al., 1992).
First, some examples of where good conservation practice is coinciden-
tal with the interests of land managers are provided, and second, we look
at abandonment. In areas where human populations have long been an
integral part of the landscape and had much to do with its recent evolution,
species may have adapted to 'managed' landscapes. For example, human
impacts on biodiversity in the Mediterranean basin may play a positive
role where current levels of biodiversity are in part maintained by contin-
ued human inl uence. Pignatti (1978) reports that domestic livestock, and
an opening up of evergreen oak forests in the Mediterranean, provided
new opportunities for speciation of herbaceous annual l ora. For example,
the
dehesas
of south-west Spain have evolved around a distinct and long
history of anthropogenic inl uence. These open wood pasture systems are
derived from ancient Mediterranean forests and are managed to support
livestock production with some accompanying arable cultivation and
silviculture but are widely recognized as being of high conservation value
(Baldock et al.,
1993; Telleria and Santos, 1995; Díaz et al., 1996).
Floristic diversity is high and
dehesa
grasslands are remarkable for
maintaining some of the most species-rich grasslands outside the tropics,
with as many as 60 plant species per square metre having been recorded
(Marañon, 1986). A number of explanations have been advanced for the
high l oristic diversity associated with
dehesas
. The Mediterranean basin
acts as a transitional biogeographical location. It has been suggested that
its l ora, which comprises several dif erent genetic elements, has been
enriched by historical climatic l uctuations during the Quaternary, by
complexity of mountain relief and by altitudinal heterogeneity and histori-
cal human disturbance (Zohary, 1973; Whittaker, 1977; Marañon, 1986).
