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Landscape forest cover, not edge contrast, modulates edge effects on palm diversity

Trujillo-Miranda, Alma Lucrecia1; Tame-Ibáñez, Abraham2; Cantos, David3; Karubian, Jordan4; Browne, Luke1; González, Nelson3; Zahawi, Rakan5; Comita, Liza1

Research facility: Fundacion para la Conservacion de los Andes Tropicales
Published May 12, 2026 on Dryad. https://doi.org/10.5061/dryad.cz8w9gjkh

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Abstract

Edge effects are among the most important consequences of habitat fragmentation, altering abiotic conditions and biological communities in remnant forests. However, the magnitude of edge effects is highly variable, and the factors that modulate them, particularly the interplay between local edge type and the landscape context, remain poorly understood. Given ongoing increases in the proportion of the world's remaining forest found near edges, understanding these effects is critical for conservation.

We investigated how edge effects are mediated by type of edge (cacao plantation vs. cattle pasture) and landscape forest cover (%), shaping palm density and diversity across forest fragments in the Ecuadorian Chocó. We established plots (100 m2) at four distances to the edge (0-10 m, 30-40 m, 60-70 m, and 90-100 m) in 30 sites, 15 for each type of edge across a gradient of landscape forest cover. In each plot, we recorded all adult palms, juveniles and seedlings.

The response of palms to distance to the edge and level of landscape forest cover varied across life stages: seedling communities were primarily associated with distance from the edge, showing an increase in density and richness, but a decrease in evenness, towards the forest interior. For juveniles, landscape forest cover was as important an additive predictor as distance to the edge, both increased density and richness, whereas evenness declined with higher surrounding forest cover. Adult density also increased with distance to edge and higher levels of landscape forest cover. Negative edge effects on adult richness and evenness were buffered with an increase in landscape forest cover. Unexpectedly, the type of edge contrast had no significant effect on palm density or diversity at any life stage.

Synthesis and applications: Our findings demonstrate that landscape forest cover plays a critical role in modulating edge effects in plant communities in our study system, but not all woody crops systems provide buffering benefits, as cacao plantations in our study failed to soften edge effects. Consequently, conservation strategies should prioritize maintaining high landscape forest cover to ensure the integrity of remaining forest fragments.