Table Of ContentJames A. Goodman
Samuel J. Purkis
Stuart R. Phinn Editors
Coral Reef
Remote Sensing
A Guide for Mapping, Monitoring
and Management
Coral Reef Remote Sensing
James A. Goodman Samuel J. Purkis
•
Stuart R. Phinn
Editors
Coral Reef Remote Sensing
A Guide for Mapping, Monitoring
and Management
123
Editors
James A.Goodman Samuel J.Purkis
Electrical andComputer Engineering Oceanographic Center, National
Universityof PuertoRico atMayagüez CoralReef Institute
Mayagüez, PR NovaSoutheastern University
USA Dania Beach, FL
USA
and
Stuart R.Phinn
HySpeed Computing School ofGeography, Planning
Miami, FL and EnvironmentalManagement
USA Universityof Queensland
Brisbane, QLD
Australia
ISBN 978-90-481-9291-5 ISBN 978-90-481-9292-2 (eBook)
DOI 10.1007/978-90-481-9292-2
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Foreword and Onward
Whilesailingaroundtheworldin1834,CharlesDarwinwassoimpressedwiththe
pristinecoralreefsthatheobservedintheAtlantic,Pacific,andIndianoceansthat
he devoted his first book, ‘‘The Structure and Distribution of Coral Reefs’’, pub-
lished in 1842, to an analysis of how atolls, fringing and coast-hugging barrier
reefswereformed.InVoyageoftheBeagle,henotes,‘‘...travellerstellusofthe
vast dimensions of the Pyramids and other great ruins, but how utterly insignifi-
cant are the greatest of these, when compared to these mountains of stone accu-
mulated by the agency of various minute and tender animals!’’
If Darwin could magically retrace his voyage in the twenty-first century, he
would likely be shocked at how much has been lost of that lacey garland of reef
plantsandanimalsthatoncespannedtheshallowbluewatersoftheglobebetween
30(cid:3)Northand30(cid:3)South.Buthewouldlikelyalsobeheartenedbythetechnologies
thatnowexistthatforthefirsttimemakeitpossibletoaccuratelyassessthenature
of the changes and to take actions to reverse the alarming trends.
This remarkable book,Coral Reef Remote Sensing: A Guide for Mapping,
MonitoringandManagementforthefirsttimedocumentsthefullrangeofremote
sensing systems, methodologies and measurement capabilities essential to under-
standingmorefullythestatusandchangesovertimeofcoralreefsglobally.Such
information is essential and provides the foundation for policy development and
for implementing management strategies to protect these critically endangered
ecosystems.
In Darwin’s time, the ocean seemed so vast, so resilient, that it seemed there
was little humans could do to alter its nature. Even more than a century later,
Rachel Carson in her 1951 Classic, ‘‘The Sea Around Us’’, imagined the ocean
wassomehowtoobigtofail.‘‘Eventuallyman...foundhiswaybacktothesea’’,
she wrote. ‘‘And yet he has returned to his mother sea only on her terms. He
cannot control or change the ocean as, in his brief tenancy of earth, he has
subdued and plundered the continents’’.
Now we know: unprecedented human activity is driving global warming,
climate change, sea level rise, pollution, acidification of the ocean, and loss of
species and entire ecosystems, including the focus of this volume—coral reefs.
v
vi ForewordandOnward
Whileoccupyinglessthan1 %oftheareaoftheocean,shallowcoralreefsystems
host an extraordinary diversity offish (about 25 % of the known marine species)
and twice as many phyla of animals as the notably rich and diverse rainforests of
theworld.Ifcoralreefsareintrouble,theoceanisintrouble.Thatisbadnewsfor
the planet, and therefore for us.
ArecentJointStatementbytheheadsoftheIntergovernmentalOceanographic
Commission, the United Nations Environment Program, and the International
Union for the Conservation of Nature states:
Globally, best estimates suggest that about 10% of coral reefs are already degraded,
manybeyondrecovery,andanother20%arelikelytodeclinefurtherwithinthenext20
years.Atleasttwothirdsoftheworld’scoralreefsmaycollapseecologicallywithinthe
lifetime of our grandchildren, unless we implement effective management of these eco-
systemsasanurgentpriority.
Thisassessmentmaybeoptimistic.The2011WorldResourcesInstitutereport,
‘‘ReefsatRisk’’notesthatthree-quartersofalloftheworld’scoralreefsareatrisk
from overfishing, pollution, and the effects of climate change. In the Philippines,
70 %ofthecoralreefsaregoneandonly5 %areestimatedtobeingoodcondition.
In the Caribbean and Gulf of Mexico, the decline may be as much as 80 % in 30
years.Morethan100countrieshavecoralreefswithintheirjurisdiction,andsome
islandnations,withsmalllandmasshavelargeoceanassetscenteredoncoralreefs.
Effective management of these valuable ecosystems requires the ability to docu-
ment their present status and monitor changes over time.
Duringthepasttwodecades,therehavebeenremarkableadvancesintheability
toremotelymeasureandmonitorthehealthandstatusofcoralreefsystemsacross
theplanetaswellastheconditionsofthewaterandsurroundingenvironment.The
techniques documented in this volume complement on-site observations and
together,providecriticallyimportantinsightsnecessaryfor effectivemanagement.
Included here is an overview of technologies for reef mapping, technical
information useful for scientists and other research and policy development
experts,ideasforapplicationofremotesensingtoresolvequestions,andthoughts
about future remote sensing technologies and their applications.
Iwholeheartedlyrecommendthisbooktoscientists,students,managers,remote
sensingspecialists,andanyonewhowouldliketobeinspiredbytheingeniousnew
ways that have been developed and are being applied to solve one of the world’s
greatest challenges: how to take care of the ocean that takes care of us.
Ifithadbeenavailablein1834,CharlesDarwinwouldsurelyhavehadacopy
on his shelf.
Sylvia A. Earle
National Geographic Explorer in Residence
Founder, Mission Blue
Preface
Overview. Remote sensing stands as the defining technology in our ability to
monitorcoralreefs,aswellastheirbiophysicalpropertiesandassociatedprocesses,
atregionaltoglobalscales.WithoverwhelmingevidencethatmuchofEarth’sreefs
are in decline, our need for large scale, repeatable assessments of reefs has never
beensogreat.Fortunately,thelasttwodecadeshaveseenarapidexpansioninthe
abilityforremotesensingtomapandmonitorcoralreefecosystems,aswellasthe
overlyingwater column and surroundingenvironment.
Remote sensing is now a fundamental tool for the mapping, monitoring and
management of coral reef ecosystems. Remote sensing offers repeatable, quanti-
tative assessments of habitat and environmental characteristics over spatially
extensive areas. As the multi-disciplinary field of coral reef remote sensing con-
tinues tomature, resultsdemonstrate thatthe techniquesandcapabilitiescontinue
to improve. New developments allow reef assessments and mapping to be per-
formed with higher accuracy, across greater spatial areas, and with greater tem-
poral frequency. The increased level of information that remote sensing now
makes available also allows more complex scientific questions to be addressed.
As defined for this book, remote sensing includes the vast array of geospatial
datacollectedfromland,water,ship,airborne,andsatelliteplatforms.Thebookis
organized by technology, including: visible and infrared sensing using photo-
graphic, multispectral and hyperspectral instruments; active sensing using light
detection and ranging (LiDAR); acoustic sensing using ship, autonomous under-
water vehicle (AUV), and in-water platforms; and thermal and radar instruments.
EmphasisandAudience.Thisbookservesmultipleroles.Itoffersanoverviewof
the current state-of-the-art technologies for reef mapping, provides detailed
technical information for coral reef remote sensing specialists, imparts insight on
thescientificquestionsthatcanbetackledusingthistechnology,andalsoincludes
a foundation for those new to reef remote sensing. The individual sections of the
book include introductory overviews offour main types of remotely sensed data
used to study coral reefs, followed by specific examples demonstrating practical
applicationsofthedifferenttechnologiesbeingdiscussed.Guidelinesforselecting
vii
viii Preface
the most appropriate sensor for particular applications are provided, including an
overview of how to utilize remote data as an effective tool in science and
management. The text is richly illustrated with examples of each sensing tech-
nology applied to a range of scientific, monitoring and management questions in
reefs around the world. As such, the book is broadly accessible to a general
audience, as well as students, managers, remote sensing specialists, and anyone
else working with coral reef ecosystems.
Outline and Roadmap. The book is divided into five sections, with the first four
highlighting different suites of remote sensing technologies and the fifth section
discussing the best use of remote sensing in effective science and management.
Eachofthefourtechnologysectionsbeginswithanintroductorychapterfollowed
byaseriesofapplicationchaptersthatdiscusseachtechnologyinmoredetailand
define the applications for which they are best suited.
• Section I. Visible and Infrared Remote Sensing.
Chapters1–4introducepassiveopticalremotesensing(i.e.,sensingtechnologies
thatrelyonvisibleandinfraredspectraofreflectedsunlightasthebasisforimage
measurements). These technologies include aerial and astronaut photography,
andmultispectralandhyperspectralaerialandsatelliteimaging.Suchtechniques
are best suited for assessing habitat characteristics (e.g., habitat type, composi-
tion, and distribution) in clear, shallow (\20 m) water. The typical spatial
resolution,orpixelsize,employedinvisibleandinfraredremotesensingranges
fromfine(\0.5–5 m)tomoderate(10–30m)scale.Visibleandinfraredremote
sensing is also suitable for assessing associated surrounding environmental
conditions at varying degrees of detail (e.g., water properties, bathymetry, and
coastal/islandland characteristics).
• Section II. LiDAR Remote Sensing.
Chapters 5–7 introduce active optical remote sensing (i.e., technologies that
measurethereturnsignalofanactivelyemittedenergysource).Thistechnology
is centered on LiDAR, but also includes an evolving set of techniques that
merge LiDAR and hyperspectral imagery. LiDAR data are commonlyacquired
from aircraft platforms and are best suited for measurements of water depth,
seafloor topography, geomorphology, and recently general habitat categories
(e.g., broad cover types, such as reef versus seagrass versus sand) in clear,
moderatelydeep(\40 m)water.Spatialresolutionvariesasafunctionofdepth,
butistypicallyatrelativelyfine(1–5 m)scale.EmergingtechniquesinLiDAR
sensorsandanalysistechniquesarealsoextendingthelevelofdetailthatcanbe
achieved for reef characteristics and surrounding water properties.
• Section III. Acoustic Remote Sensing.
Chapters 8–10 present the field of acoustic remote sensing (i.e., sensors that
measure sound, either sound emitted directly from objects/organisms or return
signals from actively emitted pulses of sound). Acoustic remote sensing is pri-
marilyaship-basedtechnology,butisalsodeployedonAUVsorusingin-water
platforms.Thebreadthofplatformsavailableforacousticremotesensingallows
Preface ix
collectionofacousticdataacrossarangeofwaterdepths,fromshallow(5–20m)
to deep ([100 m). Spatial resolution for this technology typically ranges from
fine(1–10 m)tomoderate(20–50 m)scale.Acoustictechniquesarebestsuited
forassessingwaterdepth,seafloortopography,geomorphiczones(withvariable
roughness), general habitat categories (e.g., distinguishing biological cover
types, as well as hard- versus soft-bottom habitats), water velocity, and fish
presence/distribution. As with other technologies, advances in this field are
currently extending the level of detail and types of information that can be
retrieved from acousticremote sensing.
• Section IV. Thermal and Radar Remote Sensing.
Chapters11–13introducetwotechnologiesthatcommonlycenteronmeasuring
the environment surrounding coral reef ecosystems. Thermal remote sensing is
an example of passive optical remote sensing, which focuses on measuring
emitted heat, and hence temperature of the water surface. Thermal remote
sensing is predominantly a satellite-based technology that typically operates in
coarse ([1 km) scale spatial resolutions. Radio detection and ranging (Radar)
remote sensing is an active sensing technology, which uses radio waves to
measure the range, altitude, direction, and speed of sea surface characteristics
(i.e., waves and currents). Radar remote sensing includes both ground-based
systems and satellite platforms, ranging from moderate (25–50 m) to coarse
([1 km) scale spatial resolution. Both thermal and radar technologies provide
valuable information on processes affecting coral reefs.
• Section V. Effective Use of Remote Sensing in Science and Management.
Chapters 14–15 explain and demonstrate the concepts of validation and accu-
racyassessment ofimage-basedmapproducts,aswellashowtomeasurethese
parametersandeffectivelyutilizetheminscienceandmanagementapplications.
The need to understand the accuracy and reliability of remote sensing products
is highlighted as a fundamental component of effective decision-making using
this data. Discussion in these chapters focuses on recognizing the different
strengths and weaknesses of the various remote sensing techniques and illus-
trating which techniques are best suited for different specific goals. Additional
discussion in this section includes the importance of developing an under-
standing between the needs and expectations of those using remote sensing
image products and those producing products.
Thefollowingtablesrepresentthebookoutlineinacondensedformat,providing
aquick-lookroadmaptothetypicalcapabilitiesthatcharacterizeeachtechnology.
Note that this is a summary only, and thus represents a simplified view of the
different aspects of coral reef remotesensing.
x Preface
Datatype Assessmentlevel Appropriatetechnology
Habitat Detailedspeciesassessment FieldObservationandMeasurement
Habitattypeandcomposition Chapter3.Multispectral
Shallowwater(\20m) Chapter4.Hyperspectral
Chapter7.LiDAR/Hyperspectral
Generalhabitatcategories Chapter2.Photography
Shallowwater(\20m) Chapter6.LiDAR
Generalhabitatcategories Chapter6.LiDAR
Moderatedepth(20–50m) Chapter9.Acoustic
Generalhabitatcategories Chapter9.Acoustic
Deepwater([50m) Chapter10.DeepAcoustic
Geomorphology Reefandlandscapelevel Chapter2.Photography
Shallowwater(\20m) Chapter3.Multispectral
Chapter4.Hyperspectral
Chapter6.LiDAR
Chapter7.LiDAR/Hyperspectral
Reefandlandscapelevel Chapter6.LiDAR
Moderatedepth(20–50m) Chapter9.Acoustic
Reefandlandscapelevel Chapter9.Acoustic
Deepwater([50m) Chapter10.DeepAcoustic
Waterproperties Generalwatercomposition Chapter4.Hyperspectral
Shallowwater(\20m) Chapter7.LiDAR/Hyperspectral
Generalwatercomposition Chapter6.LiDAR
Moderatedepth(20–50m)
Bathymetry Highaccuracydepth Chapter6.LiDAR
Shallowwater(\20m) Chapter7.LiDAR/Hyperspectral
Moderateaccuracydepth Chapter3.Multispectral
Shallowwater(\20m) Chapter4.Hyperspectral
Highaccuracydepth Chapter6.LiDAR
Moderatedepth(20–50m) Chapter9.Acoustic
Highaccuracydepth Chapter9.Acoustic
Deepwater([50 m)
Watertemperature Watersurfacetemperature Chapter12.Thermal
Currents/waves Watersurfacecharacteristics Chapter13.Radar
