These areas are dry because they lie in the orographic rain shadow of the Blue Mountains.

The Hellshire Hills have been described as one of the last substantial areas of primary, undisturbed dry forest in the Caribbean.

[3] Much of the remaining Jamaican dry forest lies within the Portland Bight Protected Area[4] which includes the Portland Ridge and the Hellshire Hills, which are the best-studied areas of Jamaican dry forest.

[6][7] McLaren and coauthors (2005) found forests in the Hellshire Hills to be dominated by Drypetes lateriflora, Metopium brownei, Bauhinia divaricata and Krugiodendron ferreum.

[8] The endangered Jamaican iguana (Cyclura collei) is restricted to dry forests in the Hellshire Hills.