Geoscience Reference
In-Depth Information
16
Middle-latitude wetland
case studies
16.1 Introduction
end of the Baltic Sea. While subject to a long
history and prehistory of human occupation
and land modii cation, this region still preserves
substantial wetlands, some of which are heavily
impacted while others remain relatively
pristine.
The middle latitudes span the world north and
south of the equator generally between 30° and
60°, ranging from subtropical deserts to regions
with permafrost. For most of the middle lati-
tudes, climate is distinctly seasonal with mark-
edly hot and cold, wet and dry intervals driven
principally by changes in solar radiation as the
Earth orbits the Sun. Climatic conditions are
modii ed regionally and locally by proximity to
large water bodies, prevailing winds, mountain
ranges, ocean currents, and other geographic
factors, which may inl uence precipitation, cloud
cover, evapotranspiration and, thus, available
water for wetlands. The inl uence of high alti-
tude on wetland environments is considered in
chapter 17.
In this chapter, wetland case studies are pre-
sented for the Great Plains region of North
America, including the Arkansas River valley in
Colorado and Kansas, the Nebraska Sand Hills,
and the Missouri Coteau region of southern
Saskatchewan. These regions are sparsely popu-
lated for the most part with agriculture and
resource production as the main economic
activities. The Atlantic coastal region is reviewed
for Maine and Massachusetts in the northeastern
United States, where denser human popula-
tion has a longer history of landscape modii ca-
tion and impacts on wetlands. The i nal case
study comes from central Europe, specii cally
Estonia and its neighbors bordering the eastern
16.2 Great Plains of North America
The North American Great Plains extend from
Texas and New Mexico northward into Sas-
katchewan and Alberta, with forested lowlands
to the east and the Rocky Mountains to the west.
The geological basis is l at-lying to slightly
inclined sedimentary strata ranging from Paleo-
zoic to Holocene in age. Rivers draining from
the Rocky Mountains toward the east and south
have sculpted the current landscape, glaciation
molded the northern plains, and wind has
played a conspicuous role in shaping many
parts of the Great Plains. Vegetation consists
mostly of grasslands, prairie and savanna with
sparse trees following stream valleys.
The plains exhibit strong north-south and
east-west gradients. From the Rocky Mountains,
the High Plains slope from
2000 m altitude
downward toward the east into lower plains and
hills, eventually descending below 300 m eleva-
tion. Precipitation also follows an east-west
pattern with more than 1 m per year at lower
elevations to the east, decreasing westward to
less than 30 cm in the rain shadow of the Rocky
>
