
NPS photo
The variety of vegetation that flourishes at Dry Tortugas National Park is influenced by the area's unique combination of subtropical climate, extreme weather events, harsh maritime environment (sun, sand, and salt), and history. Both native and nonnative plant species compete for the same basic resources: space, sunlight, water, and nutrients. Tides, currents, and migrating wildlife are sources of seeds from distant lands, and humans have cultivated an assortment of plants throughout history. Of the 125 plant species reported in Dry Tortugas National Park, 81 species (65% of the total) are of exotic origin; the result of accidental and deliberate introduction by man during the past century. The smaller islands consist mainly of native species, while the larger islands (Garden and Loggerhead keys), with their long history of human habitation and disturbance, have a substantially larger abundance of exotic species.