Las Cabezas de San Juan
Perched on the coast of Fajardo,Las Cabezas de San Juan is a vast tract of land spanning several hundred acres and encompassing no less than 11 ecosystems. A visit here can be organized through the Conservation Trust, which conducts several Nature Tours on the island (note: you have to book in advance).
Las Cabezas is truly a unique and special part of Puerto Rico. The tram tour will take you through a mangrove forest (a critically important contributor to the island's natural environment), a coastal beach landscaped by rock and coral formations, a bioluminescent lagoon (that you won't be able to fully appreciate because it's not night), and El Faro de Fajardo, or the Fajardo Lighthouse, a neoclassical structure built in 1880.
The reserve is home to more than 800 species, including two thirds of Puerto Rico's indigenous reptiles and amphibians and three species of sea turtles.
Isla de Caja de Muerto
Firmly on the list of roads less traveled, Isla Caja de Muertos (Coffin Island) is located 4.8 nautical miles south of Ponce. The rather morbid name comes from an 18th Century French writer by the name of Jean Baptist Labat, who called the island Coffre A’mor (Caja de Muertos in Spanish) due to the fact that, when viewed from a certain perspective, the island has the appearance of a dead body lying on a plateau. It's not the best name for marketing purposes, but perhaps it has kept the tourist hordes away.
It didn't keep pirates away; or the masons, for that matter ( there's a monument to the masons on the way to the lighthouse). And it remains to this day something of a secret treasure, a pristine natural reserve in which you'll find mangrove forests, hiking trails, sandy beaches, rocky coast, a dry forest, a lighthouse and even a cave with Taíno petroglyphs carved into its walls.
Reserva Natural de Humacao
Located on the eastern coast of Puerto Rico, the Humacao Natural Reserve spans 3,000 acres and encompasses diverse ecosystems including mangrove forests, estuaries and lagoons. It's a wonderful place to kayak through the dense canopy of mangroves and hike or bike along the rugged coast to World War II-era military bunkers left by the U.S. Navy.
The reserve is open Wednesday to Sunday, and you can rent bikes and kayaks from Water Sports and Eco Tours.
La PargueraThe Parguera Natural Reserve, located in the southwest, has mangrove swamps spanning more than 12,000 acres, estuaries and coral reefs; but it's best known for its biobay, one of just a handful in Puerto Rico. You can enjoy snorkeling, mountain biking, horseback riding, sailing, kayaking, and fishing here. As for fauna, you can spot manatees here, as well as more than 60 species of birds.
Probably the least known among tourists who visit Puerto Rico is Caño Tiburones, which happens to be the largest wetland in Puerto Rico. Located in the north near Arecibo, it covers about 7,000 acres. What makes this place a vital habitat is the mix of fresh water from the karst region and saltwater from the ocean. It's home to 200 animal species and more than 100 species of flora.