Corcovado National Park

Stand still for a moment and listen. The air is thick and warm, and it carries layers of sound. There is the dry clatter of palm fronds and the hiss of surf on dark sand. Somewhere above, a deep, rolling roar seems to come from a large animal. It is actually a howler monkey, a creature smaller than a medium-sized dog. Welcome to Corcovado, on the far southwestern edge of Costa Rica.

This park covers a large part of the Osa Peninsula, in Puntarenas Province. The peninsula reaches out from the mainland into the Pacific Ocean. On its eastern side lies the calm water of the Golfo Dulce, the Sweet Gulf. On its western side, the open ocean breaks against long, empty beaches. Between them sits one of the largest areas of lowland tropical rainforest left on the Pacific coast of Central America.

Costa Rica declared Corcovado a national park in 1975. That was early, even by the standards of a country now known around the world for conservation. At the time, loggers and settlers were moving onto the peninsula. The forest could easily have become cattle pasture or timber. Instead, scientists and Costa Rican officials pushed to protect it. Their decision is the reason you can stand among these giant trees today.

The forest was not always left in peace. In the decades after the park was created, gold miners worked the rivers inside its borders. Gold in the Osa region was real, and for many families it meant a living. But the digging muddied the streams and damaged the riverbanks. In the 1980s, the government removed the miners from the park. Some former miners later became guides and rangers. Today they share the forest they once dug through.

So what makes this place so special? The answer is concentration. The Osa Peninsula is a small piece of land, yet it holds an enormous share of the world's living species. Biologists often say it holds about two and a half percent of global biodiversity. Many different habitats sit side by side here. There are mangroves, swamps, cloud-covered ridges, rivers, beaches, and tall primary forest. Each one supports its own community of plants and animals.

Here is something many visitors miss. Look closely at the trunks around you. Some of the largest trees stand on huge, flat roots that spread out like walls. These are called buttress roots. Rainforest soil is thin, so the roots stay near the surface. The buttresses help hold the tree upright. On some old giants, they rise taller than a person. Small frogs, insects, and lizards shelter in the shaded gaps between them.

Now raise your eyes to the canopy. If you hear harsh, loud screeches, look for flashes of red, yellow, and blue. Those are scarlet macaws. They usually fly in pairs, and they often stay with one partner for life. Corcovado holds one of the strongest populations of these parrots in Costa Rica. They feed on wild almond trees near the coast. You may find their broken seed shells on the ground below.

Costa Rica has four species of monkey, and all four live in this forest. The howler monkey makes the deep roar you may have heard. The white-faced capuchin is curious, quick, and clever with its hands. The long-limbed spider monkey swings from branch to branch with the help of its tail. The tiny squirrel monkey travels in noisy groups. Its range in Costa Rica is very limited, and the Pacific south is one of its few homes.

One of the most remarkable animals here is Baird's tapir. It is the largest land mammal in Central America. A tapir has a heavy body, a short trunk-like snout, and a surprisingly calm manner. It is related to horses and rhinoceroses. Tapirs often rest in muddy pools during the heat of the day. Around the Sirena Ranger Station, sightings are fairly common. That is a rare privilege. In much of its range, this animal has become very hard to find.

The big cats are another matter. Jaguars and pumas both live in Corcovado, along with ocelots and other smaller wild cats. Most visitors never see a jaguar. You are more likely to find its tracks pressed into wet sand at the edge of a river. Even so, their presence matters. A large predator needs a large, healthy forest full of prey. If the jaguar survives here, much of the rest of the system survives too.

The rivers and the coast carry their own surprises. Where the Sirena River meets the sea, the water is shared by crocodiles and bull sharks. Bull sharks are one of the few shark species that can swim into fresh water. For this reason, guides plan river crossings with great care, usually around low tide. Out on the beaches, sea turtles come ashore to nest during certain seasons. Their wide tracks look like the marks of a small tractor.

Visiting Corcovado takes effort, and that is part of its character. There are no roads through the park. People arrive on foot, by small boat, or by light aircraft to the airstrip at Sirena. Main entry points include La Leona near Carate, San Pedrillo near Drake Bay, and Los Patos inland. Since 2014, visitors must enter with a certified local guide. The rule protects the wildlife and keeps hikers safe in difficult terrain. It also brings income to communities on the peninsula.

The trails here can be long, hot, and muddy. On the beach routes, you walk on soft sand under strong sun. Inland, the ground is often slick with clay and fallen leaves. The humidity soaks through clothing within minutes. Yet walking slowly has its rewards. A good guide will stop and point to things you would never notice yourself. It might be a sleeping sloth, a line of leafcutter ants, or a tiny bright poison dart frog.

Before you move on, take one more quiet moment. Feel the damp air on your skin. Notice the smell of wet earth and rotting leaves, which is the smell of a forest feeding itself. Look up at the layers of green above you, from the ferns at your feet to the crowns of the tallest trees. All of this was almost lost. As you walk on, listen again for the howlers. They will still be calling long after you leave.