The park contains many different habitats. The largest habitat is the forests, followed by the salt marshes, the salt flats, the meadows, the mixed scrub, and the fresh water marsh. In total, about 67% of the park is estimated to be in its natural state, while 33% of the park is estimated to be developed. In the latter half of the 20th century, Pelham Bay Park's biodiversity decreased: in that time, the park was observed to have lost 25% of its 569 native species of plants as well as 12.5% of its 321 non-native species.