Environmental Engineering Reference
In-Depth Information
We must emphasize that, even with the largest mangrove extent and the best developed
area being located in the Yucatan Peninsula (Campeche, Yucatan, Quintana Roo and
Chiapas states), which accounts for approximately 60% of the mangrove forests in Mexico
(Acosta et al., 2009), the shrimp farming in this area represents less than 1% of the total
extent and production of Mexico (CONAPESCA, 2010). For this reason, neither of the
abovementioned states were included in the analysis. The four states analyzed here
currently amount to 97% of the area dedicated to shrimp farming (CONAPESCA, 2010),
which is enough to document the impact of this activity on mangrove cover.
The present findings indicate that Mexico has approximately 82 500 ha dedicated to shrimp
production, though not all of this area is necessarily in operation. From these areas, between
1.5% and 1.7% could be constructed on mangrove cover, removing approximately 1300 ha,
which is equivalent to less than 1.0% of the 770 000 ha of mangrove reported by the Mexican
National Commission for the Knowledge and Use of Biodiversity (Acosta et al., 2009). These
results greatly contrast with other tropical and subtropical countries, where shrimp farming
has been responsible for of most of the mangrove deforestation (Bangladesh, Ecuador) or an
important part of it (Honduras, India, Thailand). However, although shrimp farming could
not be considered a risk to Mexican mangrove cover, it has been established on other
important coastal wetlands rarely mentioned in literature (estuaries, lagoon, saltmarsh).
The worldwide estimation of mangrove deforestation caused by shrimp farming is difficult
because not all producing countries have reliable data at the national level. The analysis of
the literature shows that in many instances, nationwide or global estimates are based on
local or regional case studies or are extrapolated from foreign conditions, such as those from
Thailand and Ecuador, or even Indonesia, where mangrove loss has been severe though
mostly independent of shrimp farming activity.
In agreement with FAO (2007), the global mangrove cover declined from approximately 19
million ha in 1980 to almost 16 million ha in 2000, while the shrimp pond area was 1.25
million ha in 1998 (Rönnbäck, 2002). Considering the extreme case of all the shrimp ponds
constructed on mangroves areas, this activity could be responsible for 41% of mangrove
loss. As observed here, in approximately 70% of the cases, the shrimp farming accounted for
less than 50% of deforestation, and within this 70%, the half has contributed with less than
30% of mangrove decline. Considering both scenarios, shrimp farming could be directly
responsible for 20.8 to 12.5% of the mangrove loss between 1980 and 2000.
The Mexican case could be a result of a postponed development of the industry, with a
delay of approximately 10 to 15 years in respect to other countries due to legal constraints.
After this late beginning, the industry grew rapidly even while acknowledging
environmental problems and is now among the ten top producers, second to Latin America,
which is after Ecuador. Consequently, shrimp farming has been responsible for mangrove
deforestation but not at the same level observed in the former shrimp producers.
Regrettably, the risk has been transferred to other coastal wetlands, as 46% of the ponds
have been built on saltmarshes. This land cover is more suitable for shrimp pond
construction farms because of soil characteristics and topography. In addition, these
wetlands are cheap in economic terms, as they are considered unproductive, and they are
barely protected by Mexican laws. Studies on saltmarsh loss show that 12% of this cover in
Nayarit and Sinaloa was lost because of 25 000 ha of ponds (Berlanga-Robles et al., 2011).
Even more, the impact of shrimp farming on the coastal landscapes goes beyond the direct
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