Understanding Secondary Tropical Dry Forests with Lidar Technology

Lidar technology, in addition to other methods of remote sensing, can be integral to performing accessible research in a given area. This month on the GEOTalks Podcast, we spoke to Dr. Arturo Sanchez-Azofeifa about his team’s research in the Guanacaste Conservation Area at Santa Rosa National Park, Costa Rica. His team is in the process of creating accurate methods for studying secondary tropical dry forests using lidar technology. Listen to the episode to hear Dr. Sanchez-Azofeifa explore the history that established a need for this work and share his team’s ongoing research in this field.
In episode one of the GEOTalks Podcast, we discussed how the accessibility of lidar technology enabled Dr. Andrea Celeste Curcio’s team to analyze a robust, yet fragile, salt marsh ecosystem without causing damage to the study area. In our latest episode, we spoke with Dr. Arturo Sanchez-Azofeifa about the benefits of using remote sensing and lidar to understand tropical secondary forests in Costa Rica. This is a great episode for anyone interested in using the lidar tools in Global Mapper® to study forest ecosystems.

Tropical Secondary Forests

Dr. Arturo Sanchez-Azofeifa uses lidar to study secondary tropical dry forests in Costa Rica… but what are secondary tropical dry forests? One of the primary characteristics of these tropical forests is their “dry season.” According to an article by Joyita Ghose in the Yale Environment Review, “Tropical dry forests experience a dry season that lasts from five to eight months,” and the amount of rainfall they experience each year can vary. While these unique circumstances make it harder to develop accurate methods to study the forests, it’s also the reason they are home to a large percentage of Costa Rica’s biodiversity.

The term “secondary” refers to secondary succession: a process of ecological restoration that occurs when a forest’s life cycle is disrupted, but has the resources to start growing again. According to Menglei et al., “Tropical dry forest succession is a natural and complex ecological process affected by climatic and land-use history processes.” This is especially relevant because Costa Rica’s forests have been in the midst of recovering from significant deforestation since the 1980s. The deforestation that occured in the eighties was driven by a need for agricultural land, so the land-use factor played a significant role in the restoration of these forests.

Biodiversity in Costa Rica’s Tropical Dry Forests

The movement to understand these environments has been in part related to the biological variability of Costa Rica’s tropical dry forests. The abovementioned dry season that defines this ecosystem is the reason why so many species call these forests home. Menglei et al. indicated “Tropical dry forests contain a wealth of biodiversity and essential habitats for wildlife and — in combination with other tropical ecosystems — play a significant role in climate regulation and the carbon cycle.” Biodiversity was an important part of our conversation; Dr. Sanchez-Azofeifa shared how deforestation patterns can be linked to biodiversity loss.

GIS Technology and Tropical Dry Forests

Dr. Sanchez-Azofeifa’s team leverages the utility of lidar and remote sensing technology in their research. This technology is valuable for studying, analyzing, and visualizing their work in the forest. In our conversation, he mentioned, “[Global Mapper] allows us to not only observe changes and to look at the data, but it helps with the publication part of what we are doing with fast visualizations.” It’s exciting to see how people use Global Mapper to establish research workflows and make strides in their field.

Part of our discussion surrounded the challenges the team faced in their research. Among other factors, weather, time constraints, and budgeting all affected Dr. Sanchez-Azofeifa’s work. One challenge they faced was accurately identifying the lianas, or vines, that grow in the forest. The team chose to work with high-resolution lidar data because the visualization of the canopy with lidar enabled his team to identify changes in the microtopography in the trees. Diving deeper, in the late aughts, they discovered that lianas (vines) reflect and can be seen in the green spectrum of light. This became an asset to their research because — combined with the high-resolution lidar — it enabled them to find the lianas more efficiently.

The Future of this Research

We encourage anyone interested to connect with Arturo Sanchez-Azofeifa about his research. You can learn more about this work on Tropi-Dry’s website: https://www.tropi-dry.org/. You can also read his work on Google Scholar by searching “Arturo Sanchez-Azofeifa,” and for papers that aren’t open-access, you can reach out to Tropi-Dry directly.

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References

Ghose, Joyita. “The Case for Conserving Tropical Dry Forests.” Yale Environment Review, 24 Dec. 2020, https://environment-review.yale.edu/case-conserving-tropical-dry-forests

Liu, Chenzherui, et al. “Studying tropical dry forests secondary succession (2005–2021) using two different Lidar Systems.” Remote Sensing, vol. 15, no. 19, 24 Sept. 2023, p. 4677, https://doi.org/10.3390/rs15194677

Duan, Menglei, et al. “Characterizing transitions between successional stages in a tropical dry forest using Lidar Techniques.” Remote Sensing, vol. 15, no. 2, 13 Jan. 2023, p. 479, https://doi.org/10.3390/rs15020479