For many animals, birds and plants for
which man has made life impossible in the
countryside the marshes provide a refuge, especially for the more timid water birds
and waders. The swamps of Louisiana and Florida give shelter to alligators and
turtles; the papyrus marshes of the upper Nile are the home of the rare grey
shoebili, or 'whale-headed' heron—one of the oddest looking of birds, both
majestic and absurd. In tropical swamps lungfish recall the Devonian period, while
in 1948 it was discovered that a kind of flightless moorhen called takahe, believed
to be extinct, still lived on the shores of Lake Te Anau in New Zealand. Upland bogs
support less varied and more specialized flora and fauna. The modern
conservation value of wetlands lies in their intrinsic fauna and flora, and also in their
role as refuges for species that have been persecuted in more accessible
environments.
Wetlands around Lake Victoria in East
Africa are dominated by papyrus swamps
which may represent an important refuge for native fish threatened by the
introduced Nile perch (Lates niloticus). Lates is inhibited by low oxygen levels and
the structural complexity of the fringes of these wetlands. In contrast, many of the
threatened native fish species, having evolved on the fringes of Lake Victoria or in
isolated satellite lakes, are naturally predisposed to the oxygen concentrations and
can take advantage of the structural diversity of the wetland fringe. Losses of native
fish species in Lake Victoria are likely to be very high, but some of those believed
to be extinct may persist in adjacent wetlands, either as remnants of formerly more
widespread populations or species which have shifted their distribution away from
the open water in response to heavy predation pressure.
In Britain, coastal reedbeds, despite
great losses to intensive agriculture, make an
important contribution to the United Kingdom's biodiversity inventory.
