For such a small island, Puerto Rico  has a wide diversity of biological environments.
For instance, Bosque Estatal de Guánica  in the southwestern corner of the island is classified as a subtropical dry forest, where cacti, grasses, and evergreen trees hosting Spanish moss and mistletoe compete for water and nutrients from sun-bleached rocky soil. On the opposite end of the island is the Caribbean National Forest , which contains subtropical moist forest, also called rain forest. Palm trees, a multitude of ferns, tabonuco trees, orchids, and bromeliads grow here. And along the coast are mangrove forests, where the mighty land-building trees flourish in the salty water and provide vital habitat to marine life.
The first extensive study of Puerto Rico ’s diverse flora was undertaken in the early 1900s, thanks to American botanists Nathaniel and Elizabeth Britton, founders of the New York Botanical Gardens. Their annual trips to the Caribbean, beginning in 1906, led to the publication in 1933 of The Scientific Survey of Puerto Rico and the Virgin Islands, the first systematic natural history survey in the Caribbean region.