Application of Geo-Spatial Technology in Coastal Studies
Remote Sensing and GIS is very
useful tool for mapping historical changes in coastal system and to predict future conditions of coastal ecosystem. Benthic cover is one of the important
feature of coastal ecosystem, it plays significant role in maintaining coastal
activities and its environment.
Effective mapping of benthic cover provides
many important information for maintain and development of coastal ecosystem.
Mapping Changes in Benthic cover
Coral reefs need
our attention because of the high biodiversity and their key role in the
tropical marine biosphere. These fragile ecosystems are under growing pressure
from land-based sources of pollution as the result of increasing deforestation,
soil loss, and excess use of fertilizers and pesticides.
Coastal coral reefs,
like other marine coastal ecosystems are increasingly exposed to growing loads
of nutrients, sediments and pollutants discharged from the land.
The
deteriorating water quality from marine pollution and coastal development adds
pressure to coral reefs due to which coral reef communities change to
increasing proportion of macroalgae.
The efforts to
accurately monitor and assess the changes in coral reef community composition
by incorporating satellite and airborne imagery is now increasing in the
scientific community at a variety of spatial and temporal scales.
On the
contrary for the small islands, the use of an airborne platform may be the most
appropriate for mapping and monitoring the coral reefs. Aerial photographs and
digital image processing techniques have been successfully applied for mapping
the optically clear and shallow reef waters.
The reflectance properties of
coral reef, seagrass and algal communities could be applied to differentiate
and map the benthic cover.
Figure : Aerial
photograph of the Kuroshima Island
Interpreted Information from Mapped Benthic Cover
- The classified data (below figure) revealed considerable changes in the benthic cover adjoining the coastal area during 1977 to 2005.
- The benthic cover change analysis results indicated the increase in pavement area (6.97%) especially in the northern part of the Island.
- However, coral cover reduced by 10.49% during 1977 to 2005 due to increase in algae (4.75%) and seagrass (1.10%).
- The spatial distribution of benthic cover indicates that maximum increase in seagrass and algae was in northern, western and southeastern part of the Kuroshima Island.
- The overgrowth of algae and seagrass may result in a loss of fish and invertebrate biodiversity, as a loss of habitat heterogeneity occurs compared to that presented by the live coral.
Figure: Benthic
cover change analysis from 1977 to 2005
Analysis From Mapped Benthic Cover
The anthropogenic
sources on land have been identified as the major controlling factor for the
phase shifts in reef ecosystem. At local scale causal links between reef
degradation and the diffuse pollution with changing land use practices have
often been more difficult to demonstrate, because of a lack of historic data.
Therefore, this study is quite important to monitor such kind of changes and
impacts on surrounding reefs.
The landscape development intensity (LDI) index,
an indicator of human activity was also calculated from land use/cover data and
used to identify the watersheds which may have more impact on changing coral
condition. Hence to quantify the LDI, first watersheds were delineated for the
study area.
Although, there is no perennial river in Kuroshima Island, but
using digital elevation model of 1m spatial resolution, six different
watersheds (W1 to W6) were delineated in the study area.
These watersheds were
used to measure the human disturbance gradient at each watershed level and to
investigate the impact of land driven activities on adjacent reef areas.
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