Bernhard Nievergelt

Environmental conditions and human drivers for changes to north Ethiopian mountain landscapes over 145 years

As quantitative or spatially distributed studies of environmental change over truly long-term periods of more than 100 years are extremely rare, we re-photographed 361 landscapes that appear on historical photographs (1868-1994) within a 40,000 km(2) study area in northern Ethiopia. Visible evidence of environmental changes apparent from the paired photographs was analyzed using an expert rating system. The conditions of the woody vegetation, soil and water conservation structures and land management were worse in the earlier periods compared to their present conditions. The cover by indigenous trees is a notable exception: it peaked in the 1930s, declined afterwards and then achieved a second peak in the early 21st century. Particularly in areas with greater population densities, there has been a significant increase in woody vegetation and soil and water conservation structures over the course of the study period. We conclude that except for an apparent upward movement of the upper tree limit, the direct human impacts on the environment are overriding the effects of climate change in the north Ethiopian highlands and that the northern Ethiopian highlands are currently greener than at any other time in the last 145 years.

Recovery of alpine ibex from near extinction: the result of effective protection, captive breeding, and reintroductions

Beginning in the 1500s, over-exploitation and poaching led to a steady decline of ibex (Capra ibex ibex) numbers in the European Alps. The use of ibex products in many folk remedies guaranteed high financial returns for the hunter and resulted in the relentless pursuit of this species. By the early 1800s, <100 animals survived in a single population in the Italian Gran Paradiso mountain massif. The recovery to more than 20 000 animals today is the result of a four-stage conservation effort which returned alpine ibex to almost their entire original range of distribution: (1) effective protection of the last remaining population, (2) captive breeding of animals caught in the recovered last population, (3) reintroduction of captive-bred animals into protected original habitat, (4) translocation of animals from successfully established “reservoir” populations to uninhabited sites. Alpine ibex management faces two challenges today: (1) habitat destruction in areas of high population densities, and (2) low genetic variability possibly a result of inbreeding during a succession of four potential population bottleneck situations.

The Walia Ibex

The Walia ibex was first described by Ruppell in 1835, after an expedition in 1832 which took him from Massaua, through Aksum and Adwa along the old trade route to Gonder, over Ataba valley, Silki Pass, Arkwazye, Bwahit, Inchetkab, Debark through the Simen mountains, the latter being the range of the Walia ibex (Fig. 1, p.7, see also Ruppell 1838; Mertens 1949; Stahli 1978).

The Simen, an Ecosystem in Danger

Various reports and papers have been written concerning the uncertain future of both the natural flora and fauna of the Simen mountains as well as of the human population, including their culture and economic situation. There is an apparent variety of problems, but in fact, they are all firmly linked, and some are direct consequences of others. In the first part of this chapter I shall briefly review those problems that have arisen and require consideration on a human time scale. They have already received some attention. In Ethiopia, in the last ten years the Simen mountains have been recognized as a national asset, and many efforts have been made by the Government and the Ethiopian Wildlife Conservation Organization in cooperation with international organizations such as WWF and IUCN to preserve this area. This is still far from being sufficient to achieve the goal, but one must remember that the country is vast and the Simen mountains remote. This remoteness, however, has not discouraged the scientific interest, as is documented by an already remarkable literature on this area (see Schaerer 1979) and by UNESCO in listing the Simen Mountains National Park as World Heritage Site (World Heritage Committee Meeting in Washington, D.C., September 1978). In the second part of the chapter an attempt at taking a long-term view is made in that some expectations are discussed on an ecological time scale. Bearing in mind the various short-as well as long-term problems, in the last section of the chapter, suggestions are made with the aim of helping maintain or increase the value of this unique ecosystem for the benefit of all wildlife and the indigenous people depending on it.

Summary to Chapters 15 and 16

This part of the study deals with the social and ecological behaviour of different sex-age classes of the Walia ibex. Other species living in Simen are only considered in Chapter 16.6 on food selection.

The Vegetation in the Simen Mountains and Human Utilization of the Area

The three main vegetation belts distinguished in the literature are founded largely on the general appearance of the vegetation, as given by the dominating species. These fit in the following manner into the topographical features of the area as in (Hedberg 1955; Cloudsley-Thompson 1969; Coe and Foster 1972; Lind and Morrison 1974): (1) The upland forest belt or montane forest covers in its natural state the topographically rich lowland with wide terraces, ridges and gorges below 3,000 to 3,100 m. Among the tree species we find Juniperus procera, Hagenia abyssinica,Olea chrysophylla, Syzygium guineense, Rapanea simensis. As can be seen in Table 11 (p. 71), where various differences of gradients of the slope, of the vegetation and human influence are shown, there is much human activity in this belt. Several villages are located on the terraces and, as a consequence, only small areas from the natural forest are left. (2) The ericaceous or moorland belt has its lower limit at about 2,900 to 3,200 m and its upper limit between 3,600 and 4,000 m, with 3,700 m as mean for the Simen highland (Hurni 1980a, in prep.). It thus dominates the main part of the escarpment and is therefore less influenced by human interactions. Main trees and shrubs are the tree heather Erica arborea, and St. John’s wort Hypericum revolutum (see Figs. 8, 9). In the lower section, among others Nuxia congesta and Rapanea simensis also join the heather belt. (3) The afroalpine belt consists of all the country above the timberline. This zone includes the higher terrain of the escarpment but extends mainly on the high plateau. It is characterised by grasses such as Festuca macrophylla, Festuca abyssinica, Danthonia subulata which are interspersed in some areas by Giant Lobelias Lobelia rhynchopetalum. At higher altitudes, the handsome but spiny shrub Helichrysum citrispinum is increasingly represented (see Figs. 2, 5, 6). In many parts of this belt, particularly in flat areas, domestic animals, mainly cows and sheep, are grazed quite extensively. However most eroded areas on the hilly plateau, such as the cultivated terrain around the village Gich are already located in the ericaceous belt (see Hurni 1978).

The Theoretical Distribution Pattern of the Walia Ibex and the Klipspringer Within the Study Area

The places directly recorded where animals of the two species were observed do not reveal the true pattern of distribution. Such a map with all the records collected in Simen is heavily biased because of two reasons: Firstly, I visited several zones regularly, (this concerns the three main observation points G3, G4, E2), some only occasionally, but certain zones remained that happened to be ignored. Secondly, as described earlier, within a geographical unit the visibility was unlike from hectare field to hectare field, for instance because of different vegetation cover, relief and/or observation distance. I therefore decided against using a map to show all the observations.

The Simen Mountains: Geography and Climate of the Study Area

The mountainous nature of most parts of the country gave rise to the saying, “Ethiopia is the roof of Africa”. In fact Ethiopia does not house Africa’s highest mountains, but it does contain the largest extensions of alpine zones on the African continent.

Separation in the Habitat of the Walia Ibex, the Klipspringer, the Gelada Baboon, the Bushbuck, the Colobus Monkey, the Simen Fox and the Golden Jackal

The main characteristics of the habitat of the Walia ibex and that of the two further large mammals of the area, the Klipspringer and the Gelada baboon, as possible competitors of the ibex, were described in Chapters 10 and 11. In this chapter considerable emphasis is also given to these three, mainly spotted species, but, in order to widen the field of comparison, four additional mammal species are also examined.

The Habitat Selection of the Walia Ibex, the Klipspringer and the Gelada Baboon with Regard to Particular Environmental Factors

The gradient of the slope is correlated with a number of other environmental factors (see Chap. 8.5, p. 71). To one of these, the greatest difference in altitude to a neighbouring field, an interaction became evident. In a cross-table, the frequencies of the Walias observed were compared with the frequencies resulting from the environmental situation in Simen. This comparison is shown in Table 18. Very obviously, steep slopes as well as fields with a high difference in altitude to a neighbouring field are much frequented. It shows further that fields with a low difference in altitude turn out to be positive, if the gradient is above 45°, and that fields of a lower gradient have a positive value, if the difference in altitude to a neighbouring field is at least 300 m.