Geography Reference
In-Depth Information
and biotic effects. However, the main cause has
been human action, either direct or indirect. The
reclamation of wetlands has been an expensive
engineering operation that, in the short term,
increased the economic value of the wetland area,
outweighing the costs of drainage and/or flood
alleviation. Equally, dam construction typically
causes the loss of wetland habitat due to
impoundment of the floodplain. Other human
actions directly responsible for the loss and
degradation of wetlands have included conversion
for aquaculture, mining of wetlands for peat, coal,
gravel, phosphate and other materials, and
groundwater abstraction. Recently, indirect
human action has also been recognised as a cause
of wetland loss and degradation: discharges of
pesticides, herbicides and nutrients; hydrological
alterations by canals, roads and other structures;
and subsidence due to extraction of groundwater,
oil, gas and other minerals have all damaged
wetland sites.
Historical geographers have described this
wetland loss. For example, in Europe, most of the loss
occurred before the modern era, largely due to
agricultural drainage enterprises, many master-
minded by Dutch engineers. This experience and
skill was exported not only to countries like England
but further afield, for example to the peatlands of
Indonesia. The pressure for wetland alteration and
reclamation is now increasing in the tropics and
developing nations. The rate of loss cannot be
quantified in most countries but is relatively well
documented in the USA (Figure 20.2).
The increased perception and recognition of
the importance of wetlands at global, regional and
local levels has led to a conservation backlash,
trying to halt wetland loss and degradation
worldwide. The problem facing applied
geographers is first to take stock of the remaining
wetland resource and monitor its extent and
quality. This should also involve establishing a
value for any given wetland in order to ensure that
decision making that might impact on it directly
or indirectly is soundly based. The various wetland
processes must be properly researched, leading to
tried and tested management in the form of
conservation, restoration and creation. Lastly, the
success of this management should be appraised,
thereby validating the management and providing
useful feedback by way of action research. These
various stages can be viewed from different levels:
•
International
e.g. the Ramsar convention
confers protection on wetland sites of global
importance, virtually worldwide (Box 20.3).
•
Regional/national
e.g. developing a policy for
water resource management in the Mekong
basin; the Med-Wet programme financed by
the European Union.
Figure 20.2
Percentage of
wetland area lost in the
USA between the 1780s
and 1980s.
Source:
Dahl 1991.
