Big Bend is famous for its natural resources and spectacular geology. The park's varied array of habitats support more than 1,200 species of plants (including some 60 cacti species), 11 species of amphibians, 56 species of reptiles, 40 species of fish, 75 species of mammals, over 400 species of birds, and about 3,600 species of insects. The park boasts more types of birds, bats, butterflies, ants, scorpions, and cacti than any other national park in the United States.

From 500-million year old rocks at Persimmon Gap to modern-day windblown sand dunes at Boquillas Canyon, Big Bend preserves tremendous geological diversity. Marine sedimentary rocks, continental sedimentary rocks, volcanic rocks, and evidence of the three great North American mountain-building episodes are found within the park boundaries.