Pacific mangroves barely exist. The cold Humboldt Current chills most of South America's western coast, making the water too cool for the trees that thrive in the warm Caribbean. But north of Tumbes, where the Humboldt finally falters and tropical water from the Panama Current takes over, mangroves return. They cluster on the border with Ecuador in a network of brackish channels called the manglares, where black mangroves and red mangroves stand on their stilt roots above brown water, their roots strung with oysters. Fishermen pole shallow wooden boats through them. Egrets stalk the edges. It looks like the Everglades and it happens nowhere else on the Peruvian coast.

Inland, the land turns dry. Cerros de Amotape National Park protects a Pacific dry forest that shares ecological relatives with the deciduous woodlands of Mexico and the Andean slopes of Colombia. The endangered Tumbes crocodile - Crocodylus acutus, American crocodile - still survives here in reduced numbers, and a small zoo in the region is trying to breed them back toward viability. Jaguarundis move through the undergrowth. Squirrel monkeys troop overhead. The park is dry enough to feel almost like scrub, then cracks open into gallery forests along the Tumbes River where the biodiversity suddenly concentrates. It is one of South America's least-visited national parks, and that is partly why the rare species are still there.

Tumbes lives from the Panamerican Highway and from the border at Aguas Verdes, 30 kilometers east. Buses from Lima, Piura, and Chiclayo roll through around the clock, and the streets swarm with trimotos - three-wheeled motorcycle taxis - that will take passengers anywhere in town for a few soles. International buses bound for Guayaquil in Ecuador wait at the joint frontier post where Peruvian and Ecuadorean officials now sit literally side by side, processing exits and entries at adjacent desks. The city's scam economy is notorious: fake taxi drivers who offer cheap rides to the border and then demand a hundred dollars at a secluded stop; currency exchangers slipping counterfeit soles into handfuls of change. Combis are safer than private cars. The police know all of this and do surprisingly little about it.

The city does have its moments. The Plaza de Armas is ringed with ceramic murals, and a six-meter, three-dimensional mosaic of Jesus ascending into heaven stands at one end of the plaza - an eccentric piece of public religious art at a scale most cities would not attempt. The malecon along the Tumbes River offers an evening walk past fishing boats and old colonial facades. Seafood is plentiful and cheap - ceviche, naturally, with the unusually sweet black shells called conchas negras that filter out of the mangroves. The chifas along Feijoo Street serve Peruvian-Chinese food shaped by a century of Cantonese immigration. For a city whose dominant literature is warnings, Tumbes keeps managing to surprise the travelers who stop long enough to look.

South of Tumbes the coast turns tropical for the last hundred kilometers of Peru. Mancora, just down the Panamerican, is the surf resort that draws backpackers and weekend crowds from Lima. But closer to Tumbes itself, Punta Sal, Zorritos, and Puerto Pizarro offer quieter beaches, a near-constant onshore wind, and the warmest ocean water in Peru. At Puerto Pizarro, wooden boats take visitors out to small mangrove islands where lunch is prepared on wood fires and the only access is by water. A crocodile zoo there is part conservation project, part roadside attraction. The boats come back as the sun drops behind the mangroves, and Tumbes, for a few hours, looks like a tropical town instead of a transit point.