Between the coastal zone and the Western Desert proper are numerous groves of Acacia tortilis raddiana. These groves stretch from the Nile Valley to the border of Libya and can vary in size from a few to several hundred trees of assorted sizes. Acacia trees can live in areas that get 10mm rain or less annually and are apparently able to survive for long periods on the mere memory of moisture. Many ephemeral herbs grow in association with the trees and form an important food source for highly mobile herbivores such as Dorcas Gazelle, Gazella dorcas.
There are seven major depressions in the Western Desert, of which the most northerly and by far the largest is the Qattara Depression, which covers an area of 19,500km² and encompasses sabkhas (salt flats), lakes and salt marshes of 5,800km². At its lowest point this depression is 134m below sea level. This vast depression is very sparsely inhabited and due to the inaccessibility of much of its area, is refuge for otherwise rare species such as the Cheetah, Acinonyx jubatus, and the Dorcas Gazelle, Gazella dorcas.
Siwa Oasis, which lies
to the west of the Qattara Depression, has a long and
checkered history. Although there is no evidence that
it was known during the Old, Middle or New Kingdoms,
it is possible that it was colonized during the Twenty-sixth
Dynasty (664-525 B.C.). By 331 B.C., when Alexander
the Great went there to consult the Oracle, Siwa was
known throughout the Mediterranean region.
The earliest name for Siwa was Sekhet-imit (the Place of the Palm Trees). It could well be called that today, for this 82km-long, rather narrow depression abounds with palm groves and its dates are famous throughout Egypt. Palm trees, which do well on brackish water, olives and a few vegetables are the only crops grown in Siwa because, although there are many lakes and more than a thousand springs, the water is very saline.
Other major depressions
have potable water and have been settled and cultivated
for thousands of years. The Fayoum Depression is closest
to Cairo and has a history that goes back to the Old
Kingdom (2613-2181 B.C.) of Ancient Egypt. This depression
receives its potable water from the Nile by means of
three canals: the Ibrahamiya and Bahr Wahbi canals and
the Bahr Yusuf, which is very ancient and may be a natural
branch of the Nile. The Fayoum has been known since
earliest times for its agriculture. It is also famous
for its extraordinary assemblage of fossil animals,
among which is a Hyrax, Megalohyrax, as big
as a pony. Another elephantid called Arsinotherium
was 2m high at the shoulder and had immense horns on
its nose.
Among the characteristic birds of these habitats are the Rufous Bush Robin, Cercotrichas galactotes, and the Turtle Dove, Streptopelia turtur. Many small migratory species take advantage of these habitats and feed on the mosquitoes for which some of the depressions are notorious.
In the dry sabkhas of the depressions and surrounding
desert, a few reptile species are found, including the
Fringe-toed Lizard, Acanthodactylus scutellatus,
and the Desert Monitor, Varanus griseus. Twelve
species of mammals have been recorded in the depressions
but none is specific to this eco-zone. Henley's Dipodil,
Dipodillus henleyi, is found here together
with the Nile Rat, Arvicanthus niloticus, and
the Swamp Cat, Felis chaus. While the Nile
Rat may have been introduced, it is possible that the
Swamp Cat in Farafra and Dakhla Oases is a relict species.
Of the smaller depressions, Wadi el-Natrun is 50km long
and a maximum of 8km wide. In early pharaonic times
natron, a naturally occurring chemical mixture of carbonates,
chlorides and sulphates, was mined here for use in the
mummification process. Since the fourth century of our
era the wadi has been noted for its association with
the Christian Church.
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