COS 203-1 - Forest community responses to canopy realignment on a Pacific atoll

Abstract: Islands and their simplified species networks are fundamental to understanding ecosystem functions and community connectivity. However, this reduced community composition makes them vulnerable to disruptions from introduced species. Managing these invasive species presents an opportunity to better understand both species linkages in these systems and how communities respond to management interventions. A major threat to tropical island communities is introduced rats which can disrupt a wide variety of taxa and particularly pressure nesting bird populations. Eradication of rats on islands has led to unexpected secondary challenges, however. Palmyra atoll, an uninhabited island within the Pacific Remote Island Marine National Monument, eradicated rats in 2011 but saw an exponential increase in Coconut Palms (Cocos) that began crowding out other forest vegetation. In 2019, forest realignment began removing Cocos, with over one million removed to date. This management intervention has created three distinct forest canopies; Mature native forests dominated by Pisonia grandis, mature exotic forest dominated by Cocos, and a recovering realigned canopy where Cocos has been removed. To investigate short term effects of forest realignment and long term effects of rat eradication, in the fall of 2022, we surveyed 21 transects throughout the atoll within these three forest types documenting the abundance of the major terrestrial animals (land crabs, spiders, and geckos) across trophic positions. We also took tissue to investigate through stable isotope analysis how their trophic position is shifting in response to these restoration management efforts. Preliminary analyses indicate three distinct communities related to forest type, as well as differential distribution of crab abundance and crab burrows within the respective forests.