Environmental Engineering Reference
In-Depth Information
4.
Biodiversity conservation in managed
landscapes
Tom M. van Rensburg and Greig A. Mill
Introduction
Biodiversity conservation has emerged as one of the most important and
controversial global environmental issues in recent years (UNEP, 1995).
First, it has been suggested that we are on the verge of mass extinctions,
the like of which have not been observed in the fossil record (Wilson,
1985). Second, it is argued that biodiversity loss matters because it is of
fundamental importance to human society. It provides food, shelter, fuel,
supports recreation and tourism and is thought to play an important part
in global life support and in the functioning of ecosystems (Lindberg,
1991; Raven et al., 1992; Brown et al., 1994).
A decline in habitat is thought to be one of the most signii cant causes
of the loss in terrestrial biodiversity (Wilson, 1985). A large proportion
of the earth's fertile land has been converted into managed agricultural,
forest and urban landscape. Recent estimates by the FAO (2004) indicate
that some 38 per cent of land globally is now utilized for agriculture. One
solution proposed by ecologists is to expand reserves and protected areas.
However, there are a number of problems with this approach: protected
areas cover a limited area - approximately 11 per cent of the earth's
surface (WRI, 2005); protected areas generally exclude economic activities
and they can impose costs on land managers and prevent future economic
opportunities from taking place. Consequently, it is unlikely that the pro-
portion of land allocated to protected areas will be sui cient to maintain
all biodiversity.
In recent years a number of studies indicate that biodiversity conserva-
tion must focus on managed human-dominated ecosystems (Miller, 1996;
Reid, 1996; Daily et al., 2001; Rosenzweig, 2003; Polasky et al., 2005).
Economically valuable managed landscapes do not necessarily have to
exclude biodiversity conservation goals. A wide range of species occur in
the presence of human activities and much of the world's biodiversity is
found in human-dominated ecosystems (Pimmental et al., 1992). Instead
of threatening biodiversity, many managed systems may actually enhance
biodiversity because of, rather than in spite of, the day-to-day manage-
ment activities carried out by land managers. Indeed, the phenomenon
75
