Geoscience Reference
In-Depth Information
Figure 16-47.
Records of Holocene climate from Estonia, southern Sweden, and Latvia. A warm, dry period took
place across the central Baltic region in the middle Holocene between
8000 and 4000 calendar years ago. Adapted
from Heikkilä, M. and Seppä, H. 2010. Holocene climate dynamics in Latvia, eastern Baltic region: A pollen-based
summer temperature reconstruction and regional comparison.
Boreas
39, p. 705-719, Fig. 6.
∼
because of its good access, long observation
record, and nearly pristine conditions (Fig. 16-
50; see also Fig. 2-21).
are ephemeral and saline in the rain shadow of
the Rocky Mountains. Western wetlands are
subject to frequent droughts, and l ooding may
take place throughout the Great Plains. Millions
of waterfowl and shorebirds utilize the Great
Plains l yway in their twice yearly migrations.
They exploit wetland habitats in sand hills, river
valleys, glacial potholes, and playas for breed-
ing, nourishment, protection, and rest during
their annual life cycles. The Great Plains are an
essential part of the North American Waterfowl
Management Plan, which involves Canada,
Mexico, and the United States.
Coastal salt-water marshes, brackish and
fresh-water marshes are highly productive eco-
systems dominated by grasses in low-lying,
tidally inundated zones near estuaries, sheltered
bays and inlets. Across northern New England,
these marshes exhibit species zonation based on
16.5 Summary
The middle latitudes span the world north and
south of the equator generally between 30° and
60°. Temperate climate is distinctly seasonal
with marked hot and cold, wet and dry intervals.
Consequently wetland habitats vary greatly
within these conditions, ranging from subtropi-
cal deserts to regions with permafrost. The
Great Plains of North America display strong
gradients in precipitation and temperature from
Texas to the Canadian Prairie region. Toward
the east, wetlands and water bodies are peren-
nial and fresh; whereas, to the west water bodies
