Geoscience Reference
In-Depth Information
High-latitude and
high-altitude wetland
case studies
17
17.1 Introduction
elevations below 300 m, and nearly 90% live
below 1000 m altitude (Cohen and Small 1998).
Thus, it is no surprise that most wetland
science has been undertaken at relatively low
altitudes. Similar circumstances have limited sci-
entii c work done at high latitudes. Nonetheless,
high-latitude and high-altitude wetlands play
important environmental roles for global bio-
geochemical cycles and habitats.
Case studies presented here include the
Andes Mountains of Venezuela, Rocky Moun-
tains and San Luis Valley of southern Colorado,
United States, the North Slope and Yukon Delta
of Alaska, United States, and the Lena River
delta of Russia. These sites span low, middle and
high latitudes with altitudes decreasing north-
ward from 5000 m in Venezuela to sea level on
the Yukon Delta and with climatic conditions
ranging from relatively mild in the tropics to
quite harsh in the Arctic.
High latitudes (
>
60°) and high altitudes
(
2500 m) include regions with mild to severe
climates characterized by cold temperatures.
Glaciers, permafrost and periglacial phenomena
are common features in these realms. The
ground and surface water bodies may remain
frozen much of the year, and the growing season
is quite short. Vegetation is restricted to those
hardy species that tolerate extreme cold, strong
winds, and prolonged snow cover. Included in
these zones are vast expanses of boreal forests
across northern Eurasia and North America as
well as tundra regions still farther north. At
lower latitudes, similar conditions may exist on
high mountain peaks and plateaus, even in gla-
ciated tropical locations such as the Andes
Mountains, East Africa, the Himalayas and Tibet
Plateau, and Irian Jaya.
Mountains display distinct climatic differ-
ences from surrounding terrain, which include
colder temperature, enhanced cloud cover (Fig.
17-1), and more precipitation than for adjacent
lowlands. Such mountains were also frequently
sites for alpine glaciation. Just as with ice-sheet
glaciation of lowlands (see chapter 16), alpine
glaciers created numerous landscape settings
for potential wetlands in cirques, valleys, and
moraines (Fig. 17-2). High-altitude environ-
ments have received relatively less scientii c
study than lower-lying regions of the Earth's
surface. More than half of all humans live at
>
17.2 Andes Mountains, Venezuela
The Andes Mountains are the second highest
mountain system in the world and extend from
Tierra del Fuego at the southern tip of South
America to Colombia in the north, thus span-
ning several climatic and environmental zones.
One branch of the Andes, the Cordillera de
Mérida, trends from southwest to northeast
across the western portion of Venezuela at lati-
tudes 7-9° N (Fig. 17-3). Between deep valleys
