In June 2015, the Organization for Tropical Studies (OTS) offered a field-based graduate course in Costa Rica titled “Tropical Biology: An Ecological Approach.” To supplement the field-based instruction and incorporate a GIS/remote sensing component, Dr. Eben Broadbent, assistant professor of geography at the University of Alabama and co-director of the Spatial Ecology and Conservation Lab, requested a high-resolution satellite image of Cabo Blanco National Park on Costa Rica’s Guanacaste Peninsula.
The DigitalGlobe Foundation was able to fulfill Dr. Broadbent’s request, providing a cloud-free WorldView-2 image to use in the course.
The WorldView-2 image proved to be critical to the course, as it was used for both a faculty-led intensive research project and a half-day conservation workshop. “The image enabled the course to have a broad perspective of the park and its surrounding region, but at a resolution enabling the identification of small hiking trails, individual trees and open areas within the park’s forest,” said Dr. Broadbent.
The research project included a team of international graduate students from the U.S., Colombia, Ecuador, Puerto Rico, Brazil and Cuba. During the four days of the project, the students and faculty hiked nearly 15 miles a day carrying heavy backpacks of field equipment to link remote sensing-based metrics, using the WorldView-2 image, with a number of field-based biological inventory methods.
Within the first hour of working with the satellite image, the team identified and located the biggest tree in the park, resulting in an interesting finding—that the tree had a crown diameter exceeding 44 meters.
Once the emergent largest trees were identified, the team used GPS units to locate them in the field and set up a complex suite of ARBIMON audio recorders, camera, footprint, Sherman and pitfall trap equipment to measure all forms and types of biodiversity. This was combined with wildlife-sighting data. A large number of species were identified, including many troops of howler and white-faced monkeys, coyotes, coatimundi and more. The team conducted detailed analysis of the buffer zones around each tree crown to assess the diversity and types of land cover surrounding each tree.
The research project, the team believes, was the first known study to identify clear linkages between landscape diversity and audio diversity, but not between landscape and trap-based diversity. Additionally, the results highlight the different advantages in these techniques for monitoring biodiversity at short time scales, and the power of high-resolution remote sensing technology to enable research questions not previously feasible. The group is now writing the study for submission to a peer-reviewed journal (preliminary citation at end).
Following the research project, the class held a half-day conservation workshop, starting at the scale of Costa Rica and all its national parks, working down to specific issues at Cabo Blanco. Dr. Broadbent, who was leading the workshop, used the WorldView-2 image to dynamically zoom into locations being discussed by park rangers as they described their experiences in the region. This provided an exemplary educational experience that fully leveraged satellite remote sensing with the park rangers’ decades of field-based experience.
In one discussion, a park ranger described removing more than 1,500 meters of illegal gill nets being used to trap baby sharks. The class zoomed into the bay the ranger was describing at Cabo Blanco and did some quick measurements, quickly realizing 1,500 meters of net was enough to fully enclose the entire bay.
With the insight gained from the image and park ranger’s story, the workshop was able to highlight a major conservation issue in the Cabo Blanco area and great vulnerability of the marine ecosystems—not just the terrestrial ecosystems that high-resolution remote sensing is typically used to monitor and study.
Preliminary citation: Andres Hernandez, Carly Aulicky, Diana Parker, Peter Delgado, Stephanie Diaz, Thais Lopes, Eben Broadbent (in prep). Landscape diversity determines biological diversity under emergent trees in a dry tropical forest at Cabo Blanco Absolute Preserve, Costa Rica.