Felipe Saad PhD Dissertation Defense | The Purple Giants within Tropical Forests: A Complex Legacy of Deforestation and Fires

The Purple Giants within Tropical Forests: A Complex Legacy of Deforestation and Fires, by Felipe Saad

The Department of Geography and Environmental Systems at UMBC invites you to attend the PhD Dissertation Defense of Felipe Saad

Abstract: Emergent trees play a disproportionate role in tropical forest function, yet their low density, long lifespans, and uneven distributions have limited understanding of their responses to disturbance. This dissertation develops an open-access, multi-sensor remote-sensing framework to detect individual crowns of Dipteryx panamensis and estimate persistence and mortality risk across northern Costa Rica and southern Nicaragua. First, I compared four optical and radar sensor configurations and found that models combining phenological and SAR structural information most accurately mapped D. panamensis across forest and non-forest environments (F1 = 0.94). Second, Bayesian hierarchical state-space models applied to 77,270 trees over nine years showed high baseline persistence (98.2%) but higher mortality risk under pasture isolation, fire exposure, and cumulative forest clearing, with weaker and more localized edge effects. Finally, a propensity-score-matched evaluation of protected areas showed that demographic protection did not always align with legal protection: annual mortality risk was lower in Costa Rica than Nicaragua overall, but increased inside protected areas in both countries, especially for disturbed trees in Nicaragua. Together, these results show that open-access remote sensing can move beyond forest-cover mapping to monitor individual tropical trees and evaluate conservation outcomes using demographic indicators.