Abstract:
The mangrove cover in Sri Lanka is rapidly decreasing due to continuous
anthropogenic interferences. Among the highly threatened mangrove
ecosystems, Rekawa lagoon (060
03´N–800
50´E), situated in the intermediate
climatic zone of Sri Lanka, with high species diversity was selected for the
present study. The main objectives of the research were to investigate the land use changes in Rekawa lagoon region during the past two decades and to
determine the possible consequences of human impacts on the mangrove
ecosystem. The data on land-use changes were determined by field
observations coupled with questionnaire survey. The study on the spatial
changes over the past two decades were based on the GIS-based map produced
by Dahdouh-Guebas et al. (2005) depicting the situation in 1994 together with
2015 Google Earth imagery with the current mangrove cover in Rekawa
lagoon.
The total area of the land use that has been changed was 0.9933 km2
(19% of
the total land cover) and the total mangrove area that has been disturbed was
0.002 km2
during the past two decades. Moreover, human interference i.e. land
claimed for hotel constructions, acquiring to use as a private property, waste
disposal and clear-felling of mangrove species for housing, fencing etc. and the
invasion by exotic species were identified as the major factors that led changes
at the study site. Besides, cryptic ecological degradation as a result of intrusion
by invasive plants including Acacia auriculiformis, Chromalaena odarata and
Lantana camara which are co-occurring with true mangrove species and
mangrove associates at the buffer zone threaten the natural vegetation at
Rekawa lagoon. Higher anthropogenic impacts on Rekawa lagoon region over
the past two decades have reduced the mangrove cover in the area, thus we
strongly recommend active intervention in a scientific way to minimize threats
on this fragile ecosystem.
