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into eight categories: mangrove swamps and associated wetlands; deciduous
forests; evergreen forests; high humid tropical forests; coniferous forests;
low lying subtropical and tropical forests; savannahs; and coral reefs (Fig.
4-1). Active volcanic areas could also be considered a specific ecosystem
type, and many integrated ecotones exist depending on soil type,
precipitation, fire history, elevation and human activity. The length of the
rainy season has a major influence on the types and distributions of
ecosystems present throughout the isthmus. The complexity of CA ecosystems is
enormous and perhaps best exemplified by Costa Rican natural history (Janzen,
1983). The Tropical Science Center in San Jose, Costa Rica, for example,
recognized for its work carrying out national and international ecological
classification, lists 22 Roldridge life zones in Costa Rica (Fig. 4-1) from a
"reduced version" map which includes only forest types.
4.2.2 Biological Diversity
The biotic history and paleogeography of the CA dispersal
route for flora and fauna between North and South America has formed one of
the most diverse regions on Earth. Even an abbreviated description of each of
the major life zone of the isthmus would be outside the scope of requirements
of this Environmental Assessment. In general, however, and in spite of its
relatively small size, the natural environment of Central America can be
characterized as an admixture of steep mountains, tropical rain forests,
deserts, inland wetlands, highly variable coastal ecosystems on both the
Atlantic Ocean and Caribbean Sea, significant mangrove ecosystems, and the
second largest coral reef in the world. The region is also characterized by
frequently recurring natural disasters, including earthquakes, volcanism,
hurricanes and flooding, which result in a unique array of seral stages.
While this complicates the classification of regional biotypes, it also--with
the overlay of ancient and new agricultural activities--results in some of the
very richest and biologically diverse ecosystems for its area found anywhere
in the world.
Two ecosystems are of special Interest
projects
with respect
in Central
to development
America: (1) mangrove swamps and associated
(2) forests.
wetlands
About
and
8980 square kilometers of mangrove
wetlands
swamps
were present
and associated
in Central America in 1983 (Leonard
are
1986).
not necessarily
Mangroves
diverse in terms of vegetation, but they:
very
(1)
high
tend
primary
to have
and secondary productivity; (2) are
cycles
critical
of a range
to the
of
life
species, serving as spawning grounds
estuarine
for many
organisms;
marine and
(3) are important habitats for
robins,
migrating
gulls,
species
terns,
such
swallows,
as
warblers, flycatchers, and
as sea
such
turtles:
marine species
(4) are important ecosystems for nutrient
highly complex
cycling;
in
(5)
terms
are
of their structure and function;
buffers
and
against
(6) are
erosional
important
forces (e.g., hurricanes) along
Mangrove
some coasts
systems
in
are
CA.
currently under pressure in much of the
and
region--directly
indirectly--from agricultural use, fish farming,
development,
wood cutting,
and
"urban"
a range of Industrial operations. While
are
many
said
mangrove
to be substantially
sites
depleted, however, significant locations are
believed to remain virtually untouched.