Perceptions of Threats to Mangroves
Respondents were asked about their perceptions of the impact
of threats on mangroves from human activities and natural
events (Table 4). Fishing was acknowledged in all three villages
to be the major threat from human activity (rated low to
medium, 2.2–2.5). For example, when fishers collect sesarmid
crab, mud crab, and any kinds of fish species in mangrove
forest, they might step on seedlings of mangroves or damage
the branches of mature trees and saplings. Informal interviews
indicated that fishing activities were conducted daily in the
mangrove area and possibly increase the chance of unintentional
damage to the mangrove. Additionally, Hoq (2007)
reported that destruction of mangrove can occur during fishing
in mangrove areas because boats that enter themangrove need
to use anchor posts, and fishers often cut the mangrove trees for
this purpose.
The mean perception scores for the impacts of threat to
mangrove from natural events were low to medium for strong
wind and wave (2.7) and storm (2.3), and very low for natural
predators (0.9). The respondents in the three sites were aware
of the impacts of strong wind and storm causing erosion to the
mangrove areas. The impact of erosion of mangrove areas from
strong wind and storm was rated higher by the respondents in
PNY (2.7–3.4) with the youngest forest than in KK (2.0–2.3)
andTPH(1.8–2.3) with oldermangrove forests. This perception
of threat tomangrove by respondents in PNY is consistent with
Sherman, Fahey, and Martinez (2001), who found few saplings
survived after strong wind and storm.
Although sesarmid crab is considered a propagule predator
and has a potential negative effect on mangrove regeneration
(Dahdouh-Guebas et al., 1998), the respondents rated this
effect to be very low (0.9). The respondents might consider the
benefits of sesarmid crabs as a fishery resource provided by the
mangrove ecosystem rather than the negative effects on
mangrove areas. In the study area, sesarmid crabs collected
by fishers were used as bait for mud crab fishing or were salted
(Islam and Ikejima, 2010) and sold to the market or consumed
in the household.
The most important variables related to the perception of
threats on mangroves identified by the ordinal regression were
residence location (VIL) and membership of local group (GRO)
(Table 4). Perceptions differed by residence locations for most of
the threats to mangroves from human activities and natural
events, except for the use of mangrove areas for fishing and for
collection of plants for food and herbs. As an example, when
considering differences in perceptions about the impact on
mangroves due to dam operation, respondents in KK, which is
closest to the dam, perceived the highest impact and respondents
in TPH, which is farthest from the dam, perceived the
lowest impact. The impact of damoperation on mangrove forest
was discussed earlier in the mangrove state section. The
respondents who were a member of a local group perceived
greater impacts from the use of mangroves for house
construction and collecting of plants for food and herbs and
perceived lower impacts of storm to the mangrove compared
with those not in a local group.