Abstract
Although there is a significant body of literature that describes the relationship between human activities and mangrove health, relatively few studies assess the in situ effects that global climate change may have on mangrove forests. The goal of this study was to establish baseline data as the initiation of a long-term monitoring project to assess the effects of global climate change on mangrove forest structure, and to fill in knowledge gaps that existed about the structural characteristics of forests in Broad Key, Florida and Isabela Island, Galápagos. I used the Point Centered Quarter Method (PCQM) to analyze forest structure and complexity, and I used leaf data to determine the stress experienced by the mangroves. The forest at Broad Key is very uniform throughout, with Rhizophora mangle contributing almost entirely to forest structure. In contrast, the forest at Isabela Island exhibited two separate zonation patterns, and Laguncularia racemosa was the dominant species. Along three of the five transects at Isabela Island, white mangroves were dominant along the shoreline, with red and black mangroves scattered throughout white mangroves further inland. Along the other two transects, red mangroves occupied the zone closest to shore, white mangroves occupied the zone furthest inland, and the zone between the two was occupied by a ban of mangrove associates. Leaves at Broad Key were smaller than those at Isabela Island, indicating higher stress levels due to the proximity of Broad Key to the northernmost range of mangrove distribution. Between the two sites, climate, substrate and topography are likely responsible for the differences between the two forests. Global climate change is one of the greatest contemporary threats to ecosystems worldwide, and it is important to understand how mangrove forests will respond to the associated environmental changes. Continued annual monitoring of these sites will help us detect the long-term effects of global climate change on mangrove ecosystems.