Primate richness and abundance is driven by both forest structure and conservation scenario in Costa Rica

Abstract

Variation in tropical forest management directly affects biodiversity and provisioning of ecosystem services on a global scale, thus it is necessary to compare forests under different conservation approaches such as protected areas, payments for ecosystem services programs (PES), and ecotourism, as well as forests lacking any formal conservation plan. To examine the effectiveness of specific conservation approaches, we examined differences in forest structure and tree recruitment, including canopy cover; canopy height; seedling, sapling, and adult tree density; and average and total diameter at breast height (DBH) across 78 plots in 18 forests across Costa Rica representing protected areas, private forests utilizing PES and/or ecotourism, and private forests not utilizing these economic incentives. The effectiveness of conservation approaches in providing suitable primate habitat was assessed by conducting broad primate census surveys across a subset of eight forests to determine species richness and group encounter rate of three primate species: mantled howler monkey (Alouatta palliata), Central American spider monkey (Ateles geoffroyi), and the white-faced capuchin monkey (Cebus imitator). Only canopy height was significantly different across the three approaches, with protected areas conserving the tallest and likely oldest forests. Canopy height was also significantly associated with the group encounter rate for both mantled howler and spider monkeys, but not for capuchins. Total group encounter rate for all three monkey species combined was higher in incentivized forests than in protected areas, with capuchin and howler monkey group encounter rates driving the trend. Group encounter rate for spider monkeys was higher in protected areas than in incentivized forests. Incentivized conservation (PES and ecotourism) and protected areas are paragons of land management practices that can lead to variation in forest structure across a landscape, which not only protect primate communities, but support the dietary ecologies of sympatric primate species.

Fig 1. Conservation scenarios across study sites.

Three conservation approaches: protected areas (purple), incentivized ownership (orange), and non-incentivized ownership (green) were examined across two areas, Las Cruces (Area 1) and La Selva (Area 2), in Costa Rica, with a total of 18 sites and 78 plots. Reprinted from ArcGIS Pro 3.0 under a CC BY license, with permission from ESRI, original copyright 2023.

Fig 2. Canopy height and conservation scenarios.

Differences in canopy height across forests in protected areas, privately-owned forests utilizing conservation incentives, and privately-owned forests not utilizing incentives. Protected areas had a significantly taller canopy height (m) than both incentivized and non-incentivized privately-owned forests.

Fig 3. Conservation scenarios compared to primate group encounter rate for the primate community and each monkey species.

Primate group encounter rate (group/hour) for the primate community (total encounter rate) was higher for incentivized conservation scenarios than protected areas, and both capuchin and mantled howler monkeys had higher group encounter rates in forests with incentivized conservation scenarios, and their group encounter rate was higher than that of spider monkeys. The group encounter rate for spider monkeys was higher for protected areas than for forests with incentivized conservation scenarios.