Corcovado National Park, on the Osa Peninsula, protects the largest expanse of tropical rainforest on the Pacific coast of Central America. National Geographic called it the most biologically intense place on earth, and the claim holds up: roughly three per cent of the planet's biodiversity lives in some fifty thousand hectares.
What you see here and nowhere else
Corcovado holds viable populations of Baird's tapir, the largest land mammal in Central America, and is the last significant stronghold of the scarlet macaw in the country — noisy flocks crossing the beach at dusk. All four Costa Rican monkey species are present, along with white-lipped peccaries in herds of dozens, and jaguars, though seeing one takes extraordinary luck.
Guides and booking
For some years now you cannot enter without a certified guide, and both permits and bunks at Sirena station must be booked well ahead because capacity is small. This is not bureaucracy: the forest is dense, trails cross tide-dependent rivers, and without someone who can read the terrain you see a tenth of what is there.
Access
There are three main ways in. From Drake Bay, by boat along the coast to Sirena, which is the usual choice for a day or overnight visit. From Carate to the south, walking about three hours along the beach to La Leona. And from Los Patos inland, the hardest and least used route.
Sleeping at Sirena, in bunks or on tent platforms, is what changes the experience: dawn and dusk activity bears no comparison to the middle hours, when day groups come and go.
Real conditions
It is hot and enormously humid, you walk through mud, you ford rivers and insects are constant. Bring strong repellent, rehydration salts, quick-drying clothing and boots or trekking sandals you are happy to soak. There is no mobile signal and no reliable electricity.
Gentler alternatives
If Corcovado sounds like too much, the peninsula offers excellent options without the same demands: the Golfito National Wildlife Refuge, Caño Island for diving and humpback whale watching — they arrive in two separate seasons, from the northern and southern hemispheres — and numerous private lodges with their own trails on the park boundary.
Why it survived
Osa was slated for logging and gold mining well into the twentieth century, and the park was declared in 1975 partly to stop both. Illegal gold panning continued for years afterwards and remains a pressure on the park boundary, along with hunting. Visiting with licensed local guides puts money directly into the alternative economy, which is the argument the conservation organisations here make most often.