Costa Rica: Preventing Ecosystem Collapse in the Osa Peninsula and beyond

Conservation Value:

The Osa Peninsula contains the largest mesic rainforest remaining on the Pacific slope of Central America, largely within Corcovado National Park. It has the largest expanse of mangrove wetlands on the Pacific slope of Central America and a unique coastal marine ecosystem—the Golfo Dulce tropical fjord.  The Osa is estimated to house 2.5% of the world’s biodiversity while covering less than 0.001% of its total surface area, and was described by National Geographic in 2016 as “the most biological intense place on earth”.

Threats:

The main threat in the Osa Peninsula is illegal hunting, which is still prevalent in the region.  The concern is greatest with respect to the lowland paca (Cuniculus paca), white-lipped peccary (Tayassu pecari) and collared peccary (Pecari tajacu). Other species are hunted to a lesser degree, including game birds such as: tinamou (Tinamus major and Tinamus major castaneiceps) and great curassow (Crax rubra).  Research has identified key areas of hunting pressure, however no concerted effort had been been made to reduce illegal hunting on the peninsula. A presentation at the 21st Mesoamerican Congress in San Jose in 2017 revealed that bushmeat offtake could be around 28.5 kg per year for each family hunting in the peninsula.

Actions & Results:

Osa Conservation (OC) is leading a conservation effort that mobilizes citizen scientists, community members, ecotourism operators, park administrators and multiple NGOs to preserve the globally significant biodiversity of the Osa Peninsula in the face of climate change.

In recent years this expanded into a Ridge to Reef initiative in order to restore ecological connectivity and climate resilience across an altitudinal gradient from the southern Pacific tropical lowlands of the Osa Peninsula to the high-elevation Parque Internacional La Amistad in the Talamanca Mountains.

In 2024, OC planted 240,231 native, rare, and/or threatened trees across 157 ha in their working landscape of the AmistOsa Biological Corridor. Trees were planted and sites maintained on 117 ha of farmland. And in the Térraba-Sierpe National Wetland, 72 community members were employed to restore 40 ha of mangrove.

OC’s Restoration Network had by mid-2025 grown to 372 members, led by small- and mid-sized landowners committed to regenerative practices and biodiversity-friendly production.

To address barriers to wildlife movement, OC has created canopy connectivity with (at last count) 29 arboreal bridges of various designs. The data from the first phase of the project was presented to the local government with a plan for additional arboreal bridges in the AmistOsa region.

OC is instilling civic responsibility for conservation, including biodiversity monitoring and mitigating human wildlife conflicts, in the Osa Peninsula and Piedras Blancas National Park. Workshops and events such as the first International Jaguar Day and an Environmental Festival emphasized the importance of predators and their habitats.

A cornerstone of these efforts is the AmistOsa Biodiversity Survey, which builds local capacity for biodiversity monitoring using citizen science tools like iNaturalist. In 2024, 29 workshops in 14 communities engaged 496 participants. Observations increased, with 26,674 new entries, involving 797 new species and 458 new observers. Baseline data from 2022 tripled in 2024.

OC’s Youth Nature Club continued to provide youth with an immersive nature-based learning experience, fostering the next generation of conservation stewards. Since its formation in 2021, the club has established twelve chapters across six communities and six educational centers reaching over 500 students annually. OC has built partnerships with elementary, middle, and high schools to enhance natural history education for underprivileged rural youth. A big thank you to the Paul W. O’Leary Foundation for making this possible.

Zero in on one community involved in this project in this short video from the Our Planet series.

See more videos below.