These ecological systems are always changing due to environmental factors. Geographic features such as the Western Flatwoods, Eastern Flatwoods, and the Atlantic Coastal Ridge affect drainage patterns. Geologic elements, climate, and the frequency of storms and fire are formative processes for the Everglades. They help to sustain and transform the ecosystems in the Shark River Valley, Big Cypress Swamp, coastal areas, and mangrove forests. Ecosystems have been described as both fragile and resilient. Minor fluctuations in water levels have far-reaching consequences for many plant and animal species, and the system cycles and pulses with each change.