Puerto Rican dry forests are subtropical dry forests located in southwestern and eastern Puerto Rico and on the offshore islands. These forests grow in areas receiving less than 1000 mm of rain annually. Many of the trees are deciduous, losing their leaves during the dry season which normally lasts from December to July.
The vast majority of studies have focused on the south coast - almost nothing has been published about the northeastern dry forest. Studies of the offshore islands have been limited to species lists and qualitiative descriptions of the vegetation.
Although most of the forest was destroyed for agriculture prior to the 1940s, some patches of forest which pre-date that period still exist. Areas that were used for charcoal production or for fence-posts have recovered rapidly - after 50 years forests that had been used for charcoal production recovered to the point where they were indistinguishable from much older forests.
In addition, large areas of secondary forest have grown back on abandoned agricultural land. Unlike areas which were only lightly used, these forests on abandoned farmland have far fewer species than do natural forests. Their path to recovery remains uncertain.
Puerto Rican dry forests are dominated by plants in the Rubiaceae, the Euphorbiaceae and the Myrtaceae. In this regard they are similar to Jamaican dry forests, but differ sharply from dry forests on the mainland of South and Central America which are dominated by the Fabaceae and the Bignoniaceae.
The best example of dry forests in Puerto Rico (and probably, in the Caribbean as a whole) are in the Guánica State Forest (Bosque Estatal de Guánica) outside the town of Guánica. This site has also been the focus of the vast majority of studies of dry forests.