Environmental Engineering Reference
In-Depth Information
Fig. 4. Magdalena Bay mangrove (CONABIO, 2009).
birds. The mangroves of the lagoon system are the largest in the Baja California peninsule
(Enriquez-Andrade et al ., 1998; Malagrino, 2007).
Recent studies on the coverage, distribution and structure of the mangroves of Magdalena Bay,
indicates that the mangrove area is estimated above 17000 ha (Acosta-Velazquez & Ruiz-Luna,
2007). Mangrove class were subclassified into shrub, mixed and monospecific forest, based on
field data (Acosta-Velazquez & Ruiz-Luna, 2007). The forest subclasses include Rhizophora
mangle and Laguncularia racemosa species, being dominant the last species, with densities from
2339 to 5922 individuals/ha and basal area ranging from 20.6 to 58.5 m /ha. Shrub mangroves
includes also Avicennia germinans , whit densities up to 30000 individuals/ha. The mangrove
area diminished more than 1500 ha between 1990 and 2005, with the shrub subclass as the most
disturbed, while the monospecific forest displayed a significant increase (48%). The estimated
annual mean deforestation rate was 0.55, but it was lower (0.15/year) if only the mangrove
forests were included (Acosta-Velazquez & Ruiz-Luna, 2007).
Aquaculture and environmental impact on mangroves
The coastal zone bears most of the ecological consequences of aquaculture development.
These include habitat loss/modification, excessive harvesting of wild seed/spawners and
damage to bycatch, introductions of exotic species, escapes of cultured animals, spread of
diseases, interactions with wild populations, misuse of chemicals and antibiotics, release of
wastes, and dependence on wild fisheries.
Globally, more than a third of mangrove forests have disappeared in the last two decades,
and shrimp culture is the major human activity accounting for 35% of such decline. This
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