Walia Special Edition on the Bale Mountains (2011) - Zoologische ...

on the continent (Miehe and Miehe 1994). They have a distinctive endemic fauna and flora resulting
from their combination of area, isolation and climatic history (Kingdon 1990). The sediments
of some of the lakes in the area record provide an appropriate archive to assess how the aquatic
biota has responded to ecological changes over the past ~400 years. As such, paleo-ecological
data from the Bale Mountains can contribute to our understanding of the ecosystem’s integrity and
resilience to global change effects, and guide effective conservation practices. Previous research
on the Bale Mountain lakes is very scarce. Löffler (1978) visited some 15 lakes and pools to obtain
paleolimnological information and to learn about the zoogeographical relationships with the East
African high mountain lakes (i.e. Mount Kenya, Mount Elgon and the Rwenzoris). Unfortunately,
presented data are incomplete and taxonomic resolution is low (mostly up to genus level only).
Moreover, geographic coordinates are lacking complicating monitoring work in a region dotted
with numerous waterbodies. Subsequent studies (Umer et al. 2007; Tiercelin et al. 2008) focused on
the Late Pleistocene and Holocene climate and vegetation history, using a 16700-year record from
Garba Guracha (3917 m a.s.l.). In these studies, however, time resolution over the last centuries
is low preventing assessment of recent trends of environmental change and associated ecosystem
response.
In sum, given increased pressure on the Bale Mountain lakes, there is an urgent need to (1)
document the physical and chemical properties of these (still relatively) undamaged lakes to assess
their vulnerability to global change, (2) document the poorly known biodiversity of aquatic algae,
insects and micro-crustacea in the unique setting of the Bale Mountain lakes and pools to have
a baseline against which to compare future changes; and (3) document the response of the Bale
Mountain’s aquatic biota to global change effects over the past ~400 years. A better understanding
of aquatic ecosystem resilience to (future) environmental change is of wider benefit as changes
in mountain lake ecosystems can forewarn impending change in areas far beyond the mountains
themselves. Here, we will outline our project strategy, and present some preliminary field data.
More data will become available shortly (particularly on the paleorecord and biological surveys),
and will be presented as a series of peer-reviewed papers.
Study Area
The Bale Mountain massif, situated between 6°30’-7°20’ N and 39° -40°30’ E, consists of Miocene
basalt and trachyte lavas overlying Mesozoic marine sediments (Mohr 1971; Gobena et al. 1996,
1998). Boulder spreads and till ridges indicate the former presence of a 30 km² ice cap around the
4400 m peak of Tullu Dimtu, and valley glaciers on the north. Tullu Dimtu and Mt Batu (4340
m), the highest peaks in southern Ethiopia, rise above a high plateau, situated at altitudes of 4000
to 4200 m and with an area of approximately 500 km². Until recently, the plateau was sparsely
populated by humans, but vegetation disturbance by cutting, burning and domestic stock grazing
has increased in the last 30 years (Miehe and Miehe 1994). Air temperatures in the study area have
a wide diurnal range but relatively slight seasonal variation (Löffler 1978). Frost is a common
<strong>Walia</strong>-<strong>Special</strong> <strong>Edition</strong> on the Bale Mountains 172