Rich inshore food resources were vital to the coastal Calusa, who were primarily a fishing people. The mangrove forests, seagrass meadows, and mud flats near the coast provided the energy base for a complex food web as well as nutrition and safe havens for small fishes.
Some scholars have argued that the Calusa became socially complex and politically powerful without recourse to plant and animal husbandry due mainly to their exceptionally bountiful coastal environment. However, more recent research shows that resources were spatially and temporally variable. Based on our accumulated information, we think that changes in settlement, subsistence, technology, and cultural practices were associated significantly with environmental fluctuations. The responses to them reveal a process of learning about and adjusting to an environment that was bountiful during long stretches of time, paltry and unforgiving during others, and possessed of a capacity to devastate with little warning. Calusa adaptations included a belief system that valued the knowledge of the elders and even the deceased; engineering skills that improved living conditions and enhanced cultural connections, and buffering mechanisms that allowed the resilient Calusa to survive, and even to prosper, during periodic episodes of resource deprivation.
Both environmental conditions and specific historical processes can lead to higher or lower levels of social complexity. In typical chiefdoms, centralizing and decentralizing tendencies exist in opposition. Moreover, chiefdoms do not exist in isolation but are related to broader-scale ideological, exchange, and political systems that are themselves dynamic and influenced by environmental and historical processes. When populations expand, either from internal population increases or by means of conquest or encapsulation, food production must increase.
One of the ways in which the Calusa may have been able to intensify their food production was by means of large-scale fish weirs, wing dams, traps, and holding pens. Linear keys still visible today in the greater Charlotte Harbor estuarine system that was the heartland of the Calusa cannot be explained by modern dredging, and may be the remnants of elaborate large-scale fishing facilities. South Florida natives had several different kinds of watercraft, including seagoing vessels, small cargo canoes, and barges made of platforms connecting two parallel canoes.
The Calusa and other south Florida Indians are known to have engineered substantial canals (e.g., Josslyn Island, Big Mound Key, Mound Key, Pineland, Naples, and the Lake Okeechobee area), both within their island settlements and between their towns and interior waterways. The paths of these canals are clearly visible on aerial photographs of the area taken prior to modern development, and are described in detail by explorers of the late nineteenth and early twentieth centuries. In 1895 and 1896, when Frank Cushing visited the Pineland Site Complex, parts of the Pine Island Canal were still 30 feet wide and 6 feet deep.
The Calusa were characterized by most or all of the conditions known to foster the emergence of ranked societies, and probably functioned intermittently as a weak tribute-based state during the post-contact period. However, the extreme complexity and instability reported by the Spaniards was probably conditioned by internal conflicts and stimulated by their reactions to European commerce and militarism.