Geography Reference
In-Depth Information
catch moisture at high elevations and may be more productive there. Thus, there are
96 species of butterflies in the coniferous forests of the Swiss Alps, but only 27 in the
shrub and meadow zone, while eight species range into the high tundra (Hesse et al.
1951). There are 61 species of grasshoppers at the base of the Front Range in Colorado
at 1,650 m (5,000 ft). At an altitude of 3,300 m (10,000 ft), there are 17 and, at 4,300
m (13,000 ft), only two (Alexander 1964: 79). In New Guinea, 320 species of birds live
in the lowlands, but only 128 at 2,000 m (6,600 ft) and eight above 4,000 m (13,200 ft)
(Kikkawa and Williams 1971). The entire fauna of the upper part of Kilimanjaro—birds,
mammals, reptiles, amphibia, and insects—has been estimated as shown in Table 8.1.
The decrease in number of species with altitude is also accompanied by decreases in
species diversity and may lessen interspecies competition. The primary adaptations are
those that allow the organism to survive the rigors of the physical environment. As with
vegetation, the lower number of species may be counterbalanced somewhat by an in-
crease in the numbers of individuals within any given species, but the total biomass and
productivity are, nevertheless, low. This is particularly true today, since the number of
large mammals able to cope year round with the extremes of the alpine tundra is relat-
ively low, largely due to postglacial extinctions of the once rich Pleistocene megafaunas
(Martin and Klein 1984; Leaky and Lewin 1996, Barnosky et al. 2004). For the same
reason, there is also a significant deficit in bird species, in all ecosystems, mountain eco-
systems included (Steadman and Martin 1984, Tyrberg 1998). Smaller creatures have
been less affected by extinctions, and are consequently better represented, including in
the alpine.
TABLE 8.1
Number of Species of Fauna in the Upper Part of Kilimanjaro
High mountain environments contain relatively undeveloped, young ecosystems, con-
tinually set back to earlier successional stages by climatic factors such as severe frosts,
avalanches and rock slides, glacial actions, altitudinal temperature inversions, flash
floods, or rapid soil erosion. Consequently, the majority of inhabitants are pioneers/col-
onizers, opportunists, a rough-and-ready lot taking advantage of new and unpopulated
land. Being pioneers, most species are able to cope with a broad range of environment-
al conditions, yet they are specialists, each highly skilled in some narrow spectrum of
circumstances. Versatility and flexibility are the qualities with highest survival value.
For this reason, the bulk of today's high-altitude faunas consist of mobile ungulates with
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