Geoscience Reference
In-Depth Information
americana
) are commonly observed (Alho
2005).
Human inl uence within the Pantanal dates
back to early indigenous groups that settled the
region several millennia ago. In comparison to
other coastal parts of South America, population
numbers have generally been low across the
wetlands. A few larger cities encircle the wet-
lands including Cuiabá in the north, Corumbá
in the south, and towns like Bonito, Miranda
and Campo Grande which funnel tourists into
the wetlands. Current settlement patterns date
back to the colonial period and the introduction
of cattle ranching across the region during
the mid-nineteenth century. Approximately 95
percent of the Brazilian Pantanal is privately
owned by ranchers, with large cattle ranches
(
fazendas
) commonly observed across the land-
scape (Mittermeier et al. 2005).
Cattle ranching has coexisted with the native
l ora and fauna for more than a century. However,
changes in agrarian practices brought on by
Brazil's global position in agricultural produc-
tion and the biofuels revolution have meant
increased investment in cash crops like soybean,
corn and rice within and outside the Pantanal
( Junk and de Cunha 2004). The ramii cations of
deforestation and grassland conversions will
undoubtedly affect the ecological integrity of
the region. Already ranching activities have
been shown to inl uence i re regimes with dev-
astating short-term consequences for wetland
l ora and fauna (Alho, Lacher and Gonçalves
1988). The expansion of commercial agriculture
and large-scale ranching has introduced exotic
species that outcompete native grasses (Harris
et al. 2005), while the cultivation of monocul-
tures like soybean may impact long-term soil
productivity. The increased use of fertilizers,
pesticides and herbicides causes pollution
runoff entering streams and rivers, with poten-
tially important implications for i sh populations
and ecosystem balance. Road development and
urban expansion especially across the Brazilian
Pantanal require more careful planning and
management.
In the 1990s the governments of the La Plata
basin comprising Argentina, Bolivia, Brazil, Par-
aguay, and Uruguay proposed the idea of
undertaking the Hidrovia or Parana-Paraguay
Waterway project which included the dredging,
channelization and straightening of the river to
promote upstream transportation and develop-
ment. The consequences of Hidrovia on sections
of the Pantanal ecosystem, its
piracemas
and its
l ood-pulse system would be nothing short of
catastrophic. After consistent opposition from a
wide diversity of groups, Hidrovia's future
remains uncertain for the time being.
15.5 Gulf of Mexico, United States
The Gulf of Mexico is a semi-enclosed sea that
is bounded by the United States, Mexico, and
Cuba (Fig. 15-10). It connects eastward via the
Straits of Florida to the Atlantic Ocean and
southeastward between Cuba and the Yucatán
Peninsula to the Caribbean Sea. The United
States section stretches from the Florida Keys
to the southern tip of Texas in the subtropical
range
25° to 30° N latitude. This region is the
tectonically quiet trailing edge of the continent
characterized by low-lying, poorly drained land-
scapes in which geomorphic processes are
dominated by stream and coastal erosion and
sedimentation. For most of the U.S. Gulf region,
clastic sediment
-
sand, silt and clay derived
from inland
-
makes up coastal deposits and
landforms. In South Florida, however, carbon-
ate sediment produced by marine invertebrates
and chemical precipitation is predominant in
limestone plateaus, sandy shoals, and coral
reefs.
Plant hardiness zones are 9 for most of the
U.S. Gulf coast and 10 for southern Florida, the
Mississippi River delta, and the southern tip of
Texas (Arbor Day 2006). Freezing temperatures
occur rarely in zone 9 and never in zone 10 (see
Table 6-4). Average annual precipitation ranges
from approximately 2 m along the north-central
Gulf coast to about 0.7 m at South Padre Island,
Texas (Anderson and Rodriguez 2008). Gulf
surface water average temperature varies from
lows of about 10 °C in the winter along the
north-central Gulf shore to around 30 °C in
coastal southern Florida during the summer
(National Oceanographic Data Center 2008).
∼
