by Tony Start, CALM WA
Rainforests
There are numerous rainforest patches in the region but they are
more common and more extensive in high rainfall, near-coastal areas
of the north and west Kimberley. They are usually islands in a sea
of savanna woodland and seldom larger than a few hectares. Although
they do not conform to the popular image of vast, lush, tropical
forests, they have closed canopies (at least when all the trees
have leaves for many are deciduous) and the plants in them are
rainforest species which cannot survive the fire regimes of the
surrounding savanna woodlands. Rainbow pittas and orange-footed
scrubfowl feed on the forest floor, while figbirds and pied
imperial pigeons which feed on the soft fruits are important
transporters of seed between patches. Unlike the highly visible
birds and plants, some of the most interesting inhabitants are hard
to find, particularly in the dry because they retreat underground.
These are earthworms and land snails. Many are unable to move
between patches because many of them have their own endemic
species.
Wetlands
In the wet, numerous depressions fill with water, rivers flow
and floodplains flood. Each has its own characteristic suite of
aquatic biota. Flying animals (e.g. waterbirds, dragonflies) and
plants with wind-borne seed (e.g. cumbungi) are widespread, but
some less mobile species with particular habitat requirements have
very restricted distributions. As the dry advances, rivers retreat
to series of pools and wetlands dry out, although a few billabongs
will hold water all year. Waterbirds concentrate on the remaining
wetlands and perennial, riparian plants tough it out but many
species depend on drought-hardy stages such as seeds, bulbs,
rhizomes or drought-resistant eggs. Examples of all these features
can be found at Parry Lagoons.
Ord River
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A watercourse in the more arid southern
Kimberley
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The Ord River has been dammed at two places to create Lake
Argyle and a diversion dam at Kununurra. Lake Argyle is the largest
freshwater body in the Kimberley but fluctuating water levels limit
the development of extensive riparian areas. Nevertheless, fish,
and their predators (e.g. fresh-water crocodiles and cormorants)
are common. Large numbers of waterbirds use inundated vegetation in
shallow water at the southern end but most shores are too steep for
them.
In contrast, the stable level in the diversion dam has
encouraged development of rich riparian vegetation. Many water
birds, including comb-crested jacanas, white-browed crakes and
darters use the dam while emerald doves, shining flycatchers and
azure kingfishers occur in riparian areas. Because water is now
released continuously from the diversion dam the once-seasonal
lower Ord flows year round and riparian vegetation is considerably
more extensive in the channel than it used to be but stock, weeds
and less flooding have degraded riparian vegetation of the levees.
The significance of the dams as wetlands is recognised by their
declaration as wetlands of international importance under the
Ramsar convention.
