Hurricanes may destroy organisms, but they may also promote their spread. Seeds borne on their ferocious winds may be sown far from their sources, thus facilitating the dispersal of plant species. In South Florida, tropical hardwood hammocks are patches of rich jungle scattered amid expanses of sawgrass glades and pine forests. Most of the shrubs and trees composing these shadowy, wild pockets -- West Indian mahoganies, gumbo-limbo, strangler fig and others -- are allied with the Caribbean and the Central and South American tropics. While many likely reached the toe of Florida via bird gullets or ocean currents, scientists speculate that hurricanes churning in from the Atlantic or Gulf of Mexico are also responsible.
Hurricanes deposit vast quantities of seafloor and estuarine sediment as they muscle ashore, accumulations that provide footholds for coastal vegetation communities. The storms may ravage existing mangrove swamps, for example, but also mound up banks of sand, mud or marl for seedlings or dislodged mature trees to establish new stands. In hypersaline lagoons, such as the Laguna Madre complex of southeastern Texas and adjoining Mexico, hurricanes can serve to periodically “flush” the salty waterways, providing notable contributions of more diluted seawater and freshwater rain and runoff.
A hurricane flattening a hardwood hammock or a deciduous forest may seem purely an agent of destruction, but such disturbances are a natural and necessary part of ecosystem function. The toppling or defoliation of mature canopy trees allows sunlight to reach the previously dark understory, permitting shade-intolerant species to proliferate. These may experience years of dominance until shade-tolerant trees again overtop them. Such cycling of vegetation communities is called succession, and it promotes biodiversity by giving more species the chance to occupy a given ecosystem and maintaining landscape mosaics of greater complexity.
The often-torrential rainfall associated with hurricanes can be a double-edged sword. Flooding is commonplace in the wake of a storm, threatening human life and property. But the deluges of passing hurricanes and their weakening but still wet remnants can also be a boon for areas experiencing the late-summer droughts that sometimes coincide with tropical-cyclone season. Storm precipitation may benefit parched crops in a severely dry stretch of the growing season, or help douse long-raging wildfires.