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GIS-BASED ENVIRONMENTAL ANALYSIS, REMOTE SENSING AND
NICHE MODELING OF SEAWEED COMMUNITIES


KLAAS PAULY AND OLIVIER DE CLERCK
Phycology Research Group
Biology Department
Ghent University, 9000 Ghent, Belgium



1 GIS and Remote Sensing in a Nori Wrap
1.1 INTRODUCTION

In the face of global change, spatially explicit studies or meta-analyses of published
species data are much needed to understand the impact of the changing environment on
living organisms, for instance by modeling and mapping species’ distributional shifts. A
Nature Editorial (2008) recently discussed the need for spatially explicit biological data,
stating that the absence or inaccuracy of geographical coordinates associated to every
single sample prohibits, or at least jeopardizes, such studies in any research field. In this
chapter, we show how geographic techniques such as remote sensing and applications
based on geographic information systems (GIS) are the key to document changes in
marine benthic macroalgal communities.
Our aim is to introduce the evolution and basic principles of GIS and remote sensing
to the phycological community and demonstrate their application in studies of marine
macroalgae. Next, we review current geographical methods and techniques showing
specific advantages and difficulties in spatial seaweed analyses. We conclude by
demonstrating a remarkable lack of spatial data in seaweed studies to date and hence
suggesting research priorities and new applications to gain more insight in global
change-related seaweed issues.

1.2 THE (R)EVOLUTION OF SPATIAL INFORMATION

The need to share spatial information in a visual framework resulted in the creation of
maps as early as many thousands of years ago. For instance, an approximately 6200
year old fresco map covering the city and a nearby erupting volcano was found in Çatal
Höyük, Anatolia (Turkey). Dating back even further, the animals, dots and lines on the
Lascaux cave walls (France) are thought to represent animal migration routes and star
groups, some 15000 years ago. Throughout written history, there has been a steady
increase in both demand for and quality (i.e., the extent and amount of detail) of maps,
concurrent with the ability to travel and observe one’s position on earth. Like many
aspects in written and graphic history, however, a revolutionary expansion took place

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with the introduction of (personal) computers. This new technology allowed to store
maps (or any graphics) and additional information on certain map features in a digital
format using an associated relational database (attribute information). It is important to
note that the creation of GIS is not a goal in itself; instead, GIS are tools that facilitate
spatial data management and analysis. For instance, a Nori farmer may wonder how to
quantify the influence of water quality and boat traffic on the yields (the defined goals),
and use GIS as tools to create and store maps and (remotely-sensed) images, and
perform spatial analyses to achieve these goals (figure 1).
At least 300001 publications dating back to 1972 involve GIS (Amsterdam et al.,
1972), according to ISI Web of Knowledge2. However, twelve years went by before the
first use of GIS in the coastal or marine realm was published (Ader, 1982), and since
then only a meager 2257 have followed.
Parallel to the evolution of mapping and GIS, the need to observe objects without
being in physical contact with the target, remote sensing, has played an important role
in spatial information throughout history. In its earliest forms, it might have involved
looking from a cliff to gain an overview of migration routes or cities. However, three
revolutions have shaped the modern concept of remote sensing. Halfway the 19th
century, the development of (balloon) flight and photography allowed to make
permanent images at a higher altitude (with the scale depending on the altitude and
zoom lens) and at many more times or places than were previously feasible, making
remote sensing a valuable data acquisition technique in mapping. Halfway the 20th
century, satellites were developed for Earth observation, allowing to expand ground
coverage. At the end of the 20th century, the ability to digitally record images through
the use of (multiple) CCD and CMOS sensors quickly enhanced the abilities to import
and edit remote sensing data in GIS. Two kinds of remote sensing have been developed.
Active remote sensing involves the emission of signals with known properties, in order
to analyze the reflection and backscatter, with RADAR (RAdio Detecting And
Ranging) as the most wide-spread and best known application. Passive remote sensing
means recording radiation emitted or reflected by distant objects, and most often the
reflection of sunlight by objects is investigated. This chapter will only cover passive
remote sensing and laser-induced active remote sensing, as sound-based active sensing
(RADAR, SONAR) is limited to (3D) geomorphological and topographical studies,
rather than distinguishing benthic communities and their relevant oceanographic
variables.
The first remote sensing applications are almost a decade older than the first GIS
publications (Bailey, 1963), and the first coastal or marine use of remote sensing
appeared only few years later, starting with oceanographical applications (Polcyn and
Sattinger, 1969; Stang, 1969) and followed by mapping efforts (Egan and Hair, 1971).
Out of roughly 98500 remote sensing records in ISI Web of Knowledge, however, little
less than 8500 cover coastal or marine topics.


1 This number is based on the search term ‘”geographic* information system*”’. The search term ‘GIS’
yielded 32706 records, but an unknown number of these, including the records prior to 1972, concern other
meanings of the same acronym.
2 All online database counts and records mentioned throughout this chapter, including ISI Web of Knowledge,
OBIS and Algaebase records, refer to the status on July 1st, 2008.