Remote Sensing

Remote Sensing Working Group

Coral reefs are complex systems affected by multiple natural and human processes. Remote sensing provides that only practical way to measure meaningful large scale variations to coral reefs.

Until now, the remote sensing of coral reefs has been conducted on an ad-hoc basis with little consistency or general insight into its limitations. For example we know that some aspects of reef health can be resolved on shallow reefs in French Polynesia but we cannot predict whether this would be realistic in, say, Jamaica, where reefs have a different flora and fauna, are located in deeper water, and where light penetration is slightly reduced.

Without a generic understanding of reef remote sensing, the technology may continue to be oversold or used to meet unrealistic management objectives, resulting in an inappropriate use of financial resources.

Background

The CRTR Remote Sensing Working Group is investigating the potential and limitations of remote sensing of coral reefs so that the technology can be used for realistic and practical management objectives.

Remote sensing is a technology-driven practice, and prior to this targeted research effort, the remote sensing of coral reefs has been conducted on an ad hoc basis with little consistency or general insight into its limitations.

Without a generic understanding of the limitations of coral reef remote sensing, the technology may continue to be oversold or deployed for unrealistic management objectives, resulting in an inappropriate use of financial resources.

Our Research

Research Activities

The Remote Sensing Working Group (RSWG) will be developing and testing a wide range of remote sensing tools, including satellite, airborne, acoustic and in-field methods. The RSWG will quantify the limitations of coral reef remote sensing by combining modeling and field experiments.

The Group will be focusing on four key areas:Creation of decision-support and analysis software for monitoring the health of coral reefs using remote sensingDevelopment of methods to detect changes in coastal environmentApplication of remote sensing to the inventory, monitoring and management of biodiversityCreation of an Ocean Atlas and tools to manage coral bleaching.

Creation of decision-support and analysis software for monitoring the health of coral reefs using remote sensing
In this program the RSWG will quantify the limitations of coral reef remote sensing by combining modelling and field experiments. Models predict the ability of a given remote sensing instrument to detect the subtleties of bottom reflectance that distinguish reef habitats or the cover of corals and macroalgae within habitats. While the passage of light through the water column is relatively well understood, the interaction of light between reef organisms, many of which have complex structures, presents a research challenge.

This problem is being addressed using radiosity methods which were originally developed in the computer graphic industry. Coral structures are divided into thousands of individual patches, each of which behaves as a reflecting surface. On reaching the reef, sunlight is reflected and scattered in predictable directions from which we can calculate the net light recorded by the sensor once it has passed back through the water and atmosphere.

Computer models will be refined and tested in the laboratory and then tested under field conditions in a unique, large-scale remote sensing experiment.

Development of methods to detect changes in the coastal environment
Remote sensing is needed to identify the habitat type and possibly predict the cover of corals and algae on a reef. This requires high resolution imagery and direct field survey at the time of image acquisition and therefore there is limited application for archived or low resolution imagery. A wealth of satellite and photographic data is often available for reefs, sometimes archived as far back as World War II.

In this program the RSWG will improve the way in which changes in reef condition can be predicted indirectly using remote sensing. These methods will highlight which areas of the coast have undergone the greatest change and help managers quantify the rate of change in reef habitat.

Application of remote sensing to the inventory, monitoring and management of biodiversity
Recent remote sensing research has improved the detail of reef habitat maps but there is not necessarily a good understanding by management of the interpretation and uses of these products. Specifically, what do habitat maps mean in terms of biodiversity and reef function and how should they be used for conservation planning?

Within the Centers of Excellence, there is an excellent opportunity to quantify the ecological basis of habitat maps. Through the work of the RSWG the species composition of habitats are being surveyed in Belize and Mexico and compared and assessed at a Caribbean-wide scale using comparable data from the Bahamas. Comparable surveys will take place in Palau and the Philippines but with less reliance on species-level identification.

A second biodiversity activity is quantifying the relationship between the topographic complexity of reef habitats (called rugosity) and the relative density of reef fish.

Creation of an Ocean Atlas and tools to manage coral bleaching
A wide variety of oceanographic and atmospheric remote sensing products are available for reef relevant management but many are not user-friendly and in disparate locations. Some US government agencies are establishing a national Ocean Atlas to collate data sets relevant for coastal management within a single website.

The RSWG will extend this initiative to an international Ocean Atlas for coral reef environments. The website will display a number of standard environmental products (e.g. wind speeds, wave heights, solar radiation) and will also develop and test new products which are especially relevant to coral bleaching.

An important aspect of this program is that the Ocean Atlas will be used by managers, scientists and students interested in many other ecosystems and part of the world.

Research Update

The Remote Sensing Working Group (RSWG) has data for more than 25 collaborative publications to be completed by June 2009 [dowload summary, July 2008].

The RSWG has also developed a new algorithm approach to incorporating spatial patterns of acute and chronic thermal stress into marine reserve networks. In collaboration with the Connectivity Working Group (CWG) the RWG presented a case study at the ICRS.

By the end of August 2008 the RSWG aims to have produced a distributable Beta-test level version of the plane-parallel software, plus preliminary documentation. This will make industry-standard methods for modeling light interactions in natural waters available to students and developing-world scientists who cannot afford current commercial solutions. In particular, the Dr Hedley has validated his plane-parallel software against commercial models across a range of water quality parameters, which far exceed those of natural waters. The results are in exact agreement to machine accuracy, i.e. given inevitable rounding errors. These results indicate that the algorithm implementation is error-free and this work will be essential in building future user-confidence in the software. The plane-parallel software is already finding use within the RSWG, with the far greater ease of arranging highly efficient batch processing and other specialist uses than in the commercial model. For Hedley’s remote sensing sensitivity-analysis paper mentioned above, the software was used to model in excess of 15 million individual remote sensing reflectances.

Professor Mumby has collaborated with Dr Steneck (CWG) to brief the Fisheries Administrator in Belize and reef managers in Bonaire concerning the predicted impacts of climate change on coral reefs. He will return in December to give further presentations to the public, fishers, and policy makers In a program organised in collaboration with the Fisheries Department and Wildlife Conservation Society. Mumby and Steneck are currently helping the marine park director draft legislation to ban the use of fish traps and parrotfish exploitation.

Who we are

Working Group Members

Working Group members bring international experience to this targeted research.

Project Partners

Working Group partners bring capacity to this research endeavour.

Contact

Remote Sensing Working Group:

Chair: Professor Peter J Mumby
University of Exeter, United Kingdom

Co-chair: Dr Laura T David
University of the Phillipines

Project Executing Agency:

Global Coral Reef Targeted Research and Capacity Building for Management Program
The University of Queensland
Brisbane QLD 4072
Australia
Tel: 61 7 3346 9942
Fax: 61 7 3365 4755
Email:

Information Resources

Poster: CRTR Program Remote Sensing Working Group [download]
Brochure: CRTR Program Summary [download]
Research Update, July 2008 [download]
NOAA's Coral Reef Watch: Free online data resources for reef managers