those occurring in early 1998 and 2002, timely Ikonos data should be sensitive enough
to detect a benthic change (Andréfouët et al., 2003).
6.1.2 Existing Coral Reef Monitoring Applications with Remote Sensing
In a survey of 64 organizations involved in coral reef management and research
conducted in 2001, 62% of respondents reported using remote sensing in some capacity
for research, mapping, monitoring, or management activities (Joyce et al., 2002). The
number of years of use of these data were relatively equally distributed between new
users (less than 2 years) and longer term users. Remote sensing is used for a variety of
purposes in coral reef environments, though the most common applications are benthic
habitat mapping, coastal zone management, and change detection. The least common
use is rehabilitation monitoring. Given the inherent difficulties in mapping submerged
ecosystems, for example water column attenuation, spectral similarity between features,
and high levels of heterogeneity, it is not surprising that the more complex tasks of
rehabilitation monitoring are yet to be employed in reef environments.
Of note were the responses received from representatives of research and
development organizations, including educational institutions, which commonly stated
that remote sensing cannot as yet be used for effective monitoring of reef systems due
to the current state of knowledge and lack of understanding of light interactions in these
environments. The difficulties are seen as primarily related to the lack of algorithms
that can be used to measure reef properties related to health, especially due to the
spectral similarities of corals and algae in the limited portion of the spectrum able to
penetrate the water column. Furthermore, questions were raised as to the definition of
“reef health”. It was noted that there is a need for a greater understanding of reef
processes and a quantification of reef condition other than presence and absence of
algae, and detection of coral bleaching. Once an effective indicator of reef health is
established, then the process outlined in section 3 can be used to identify the most
appropriate form of remotely sensed data to address monitoring and management of the
ecosystem.
Remote sensing has been used most effectively in indirect coral reef monitoring,
such as the sea surface temperature data used for developing the degree-heating week
hot spot maps or coral bleaching index maps (see Chapter 2, this book). These data
are readily available to the public via the National Oceanic and Atmospheric
Administration’s (NOAA) website. These types of information and data are used
extensively by reef management agencies, e.g. the Great Barrier Reef Marine Park
Authority (GBRMPA). At present GBRMPA conducts extensive annual field surveys
along set transects covering the entire reef. However, the samples are limited to divebased video along set transects and do not provide spatially extensive coverage.
GBRMPA is currently mapping simple substrate types from Landsat ETM+ mosaic
over the entire Great Barrier Reef and is investigating the use of multi-temporal data for
mapping disturbance impacts.
6.1.3 Developing Remote Sensing for Increased Use in Coral Reef Monitoring
Effective monitoring of any environment requires reliability, repetition, and costeffectiveness. In tropical environments prone to cloud cover, repeatable remote sensing
image acquisition becomes a challenge. In addition, many reef locations are
inaccessible for extensive and repeated field validation, so the validity and consistency
of image-derived maps is a particularly pertinent question. The remoteness of some
reefs also means that airborne data are either prohibitively expensive or logistically
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to detect a benthic change (Andréfouët et al., 2003).
6.1.2 Existing Coral Reef Monitoring Applications with Remote Sensing
In a survey of 64 organizations involved in coral reef management and research
conducted in 2001, 62% of respondents reported using remote sensing in some capacity
for research, mapping, monitoring, or management activities (Joyce et al., 2002). The
number of years of use of these data were relatively equally distributed between new
users (less than 2 years) and longer term users. Remote sensing is used for a variety of
purposes in coral reef environments, though the most common applications are benthic
habitat mapping, coastal zone management, and change detection. The least common
use is rehabilitation monitoring. Given the inherent difficulties in mapping submerged
ecosystems, for example water column attenuation, spectral similarity between features,
and high levels of heterogeneity, it is not surprising that the more complex tasks of
rehabilitation monitoring are yet to be employed in reef environments.
Of note were the responses received from representatives of research and
development organizations, including educational institutions, which commonly stated
that remote sensing cannot as yet be used for effective monitoring of reef systems due
to the current state of knowledge and lack of understanding of light interactions in these
environments. The difficulties are seen as primarily related to the lack of algorithms
that can be used to measure reef properties related to health, especially due to the
spectral similarities of corals and algae in the limited portion of the spectrum able to
penetrate the water column. Furthermore, questions were raised as to the definition of
“reef health”. It was noted that there is a need for a greater understanding of reef
processes and a quantification of reef condition other than presence and absence of
algae, and detection of coral bleaching. Once an effective indicator of reef health is
established, then the process outlined in section 3 can be used to identify the most
appropriate form of remotely sensed data to address monitoring and management of the
ecosystem.
Remote sensing has been used most effectively in indirect coral reef monitoring,
such as the sea surface temperature data used for developing the degree-heating week
hot spot maps or coral bleaching index maps (see Chapter 2, this book). These data
are readily available to the public via the National Oceanic and Atmospheric
Administration’s (NOAA) website. These types of information and data are used
extensively by reef management agencies, e.g. the Great Barrier Reef Marine Park
Authority (GBRMPA). At present GBRMPA conducts extensive annual field surveys
along set transects covering the entire reef. However, the samples are limited to divebased video along set transects and do not provide spatially extensive coverage.
GBRMPA is currently mapping simple substrate types from Landsat ETM+ mosaic
over the entire Great Barrier Reef and is investigating the use of multi-temporal data for
mapping disturbance impacts.
6.1.3 Developing Remote Sensing for Increased Use in Coral Reef Monitoring
Effective monitoring of any environment requires reliability, repetition, and costeffectiveness. In tropical environments prone to cloud cover, repeatable remote sensing
image acquisition becomes a challenge. In addition, many reef locations are
inaccessible for extensive and repeated field validation, so the validity and consistency
of image-derived maps is a particularly pertinent question. The remoteness of some
reefs also means that airborne data are either prohibitively expensive or logistically
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