Environmental Engineering Reference
In-Depth Information
State
Subsidiary cover
Nayarit
Sinaloa
Sonora
Tamaulipas
TOTAL
Aquatic surfaces
103 (2)
1918 (5)
268 (1)
24 (1)
2313 (3)
Mangrove
392 (8)
689 (2)
85 (<1)
0
1166 (1)
Saltmarsh
1726 (35)
23225 (56)
10779 (33)
48 (6)
35778 (45)
Terrestrial covers
2507 (50)
12215 (30)
21133 (64)
929 (93)
36784 (46)
Shrimp farming*
238 (2)
3090 (2)
642 (2)
0
3970 (5)
Total shrimp farm
extent (ha)
4966
41137
32907
1001
80011
Table 1. Land use changes produced by shrimp farming in four states of Mexico. Area in
hectares and corresponding proportion (%) in parenthesis. *Some farms were built before
1986, the initial time for this study (t1), consequently, figures in this row represent no
change after this date.
projects. It is important to highlight that shrimp aquaculture started prior to 1986, the date
of the first Landsat image included in this analysis, which explains why 5% of the shrimp
aquaculture use was unchaged in land use . It means that approximately 4000 ha of shrimp
ponds had been constructed by 1986 on undetermined covers.
As most of the changes happened in the Gulf of California region, it is important to have
look at Tamaulipas, the only representative of shrimp aquaculture in the Gulf of Mexico. No
mangrove deforestation was associated with shrimp ponds, and the main subsidiary cover
was terrestrial cover, amounting to 93% of the total area used for shrimp pond installation.
Based on the 1973 estimates for mangrove distribution proposed by Ruiz-Luna et al. (2010)
for the Gulf of California region, the change detection analysis output some differences with
the previous analysis, showing a slight reduction of the assessed mangrove loss for Nayarit
and Sonora (Table 2). The mangrove change at Nayarit was 77 ha less, as evaluated with the
1973 map with respect to the 1986 map. The changes in Sonora were similar in both studies;
even so, the reduction is 14 ha more with the 1986 map than that estimated with the 1973
map. The differences in both cases are approximately 15-20%. By contrast, the mangrove
loss estimated for Sinaloa increased by approximately 40% when the 1973 map was
analyzed, agreeing with a technical report published by Ruiz-Luna et al. (2005). Even so, the
technical differences in both Landsat devices (MSS and TM) make an underestimation of the
1973 mangrove area possible due the low resolution of the Landsat MSS imagery (60 m)
used to produce these maps, as noted by Ruiz-Luna et al. (2010). Thus, the differences
among Nayarit and Sonora could be reduced, but in the case of Sinaloa, it could increase.
Land covers (1973)
State
Mangrove
Others covers
Total
Nayarit
315 (6)
4651 (94)
4966
Shrimp farms
(2010)
Sinaloa
956 (2)
40181 (98)
41376
Sonora
71 (<1)
32836 (>99)
32907
Table 2. Change detection matrix for land cover change from mangrove (1973) to shrimp
farms (2010). Area in hectares and relative proportion (%) in parenthesis.
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