Coastal Habitat Mapping of the Philippines

• Understand our process of mapping coastal habitats in the Philippines.
• Be familiar with the mapping tool that has been created.
•  Access and view the mapping tool .

Coral reefs, mangroves, seagrasses, and other habitats are critical to healthy, productive coasts and fisheries. To better understand mangrove and habitat cover and change in the Philippines, a state-of-the-art robust and repeatable analysis using satellite imagery is being conducted as part of the USAID Fish Right Program. This work is needed to add information about the coast and inform managers and the public about habitats changes due to human (e.g., mangrove clearing, runoff from development) or natural (e.g., typhoon) events. This brief guide provides an overview of the analysis approach with a link to a viewer for one of the study areas. This mapping provides important, immediate insights, but any actions will require on-the-ground verification, local knowledge and input. 

A major advantage of the technique being used versus other approaches is the potential for immediate and rapid processing of free and wide-scale imagery to help assess the coast. The viewing tool for the maps is made publicly available to encourage broad use. Furthermore, while other global analyses have been conducted or are underway, some of these are problematic because they are typically for one time period using data of varying quality or time. Also, globally applied techniques are typically not sufficiently accurate for detailed, local-scale investigation and management. 

This work is part of the USAID Fish Right Program. The primary goals of Fish Right and its Philippine partners are to (1) reduce threats to critical coastal, biodiverse habitats and (2) help enhance marine ecosystem productivity to sustain the nation and its economy.

Motivation for this effort was in part provided by the Tagbanwa indigenous people in the Calamianes Island Group. In their community of Calauit, they are striving for sustainability and to teach others about environmental value and stewardship. They host visitors to educate them about Dugong. In their teaching area, they have a large map (see below) of the the coastal system that serves as a tool to help explain the importance of these habitats for the community and visualize the interconnectedness of coastal habitats. Our aim was to attempt to recreate a similar mapping tool for communities around the Philippines for use for planning and management. Also, we strive to be able to reproduce this map over time to look at changes and related concerns.

For the purposes of this module, we will be showing examples of the mapping efforts underway in the Calamianes Island Group, the northwestern-most circle in the map below. The project has also mapped areas in two other study areas, the Visayan Sea and Southern Negros, also circled below. The final tool accessible at the end of this module includes all three of these regions.

The mapping process involves two primary components: 1) mapping habitats using satellite images and 2) making on-the-ground observations. Images from satellites are used to map or "classify" areas by computer into several habitats including seagrass, coral reef, mangrove and others over a specific study areas. This process is done by "training" a computer to associate areas of known habitat types with specific image properties (e.g., measurements of color) and then identifying other areas of similarity. For example, sandy areas of ocean floor have a specific appearance from above compared to areas covered by seagrasses. The accuracy of this mapping can then be validated with other locations where habitats have been identified by underwater images, acoustic mapping or drone imagery (see diagram on right).

In brief, the satellite mapping involves imagery collected from Copernicus Sentinel-2 mission deployed by the European Space Agency. A "composite" image of all cloud-free imagery was created for a specific time period. Areas of known habitat area used to train the computer to determine habitats in unknown areas based on the satellite measurements.

Field observations and measurements are critical to "training" the computer mapping and determining the mapping accuracy. A limited amount of data have been collected in the study areas during brief visits, using a variety of methods (see image above). Below, you can see some of our drone imagery collected around to the community of Calauit in the Calamianes Island Group. These very-high-resolution images are overlain on satellite imagery below.

We also collected underwater and above-water photos with GPS locations as well as acoustic data from small boat explorations in the Calamianes Island group.

Also, underwater videos were collected using a camera attached to a canoe or by someone towed behind it to view how the seafloor habitats varied. An example is shown below.

For ease of access, we've combined the maps of the seascape and landscape categorization in a mapping display hosted by Google Earth Engine. Below is a screen-shot of those two category layers- slide the arrows back and forth to compare the satellite imagery to the coverage classifications on the same section of coast in the Calamianes as the previous drone imagery.

One of the main reasons maps like this are important is so we can visualize change over time- if we know how and where the coast has already changed, we can be better prepared for future coastal changes, whether due to storms, sea-level rise, or changes in human use. You can learn more about how habitat mapping has been used to rapidly map mangrove damage from Super Typhoon Odette by clicking  this link .

To access the current land and sea habitat classifications at various sites in the Philippines, simply click the button below.