DIRECTIONAL CONNECTIVITY IN HYDROLOGY AND ECOLOGY AND ITS RESPONSE TO CHANGING HYDROLOGIC MANAGEMENT IN THE EVERGLADES

Hydrologic and ecological connectivity is often upheld as a desirable feature of fluvial landscapes, yet there is little consensus about how it should be quantified. In the Everglades, connectivity of flowing sloughs in a direction parallel to flow has been adversely affected by hydrologic modifications. Because this characteristic is essential for fish dispersal, there remains a critical need for quantifying directional connectivity. Universally, connectivity in particular directions (e.g., streamwise, along- or across-gradient, between sources and sinks) is critical information for predicting contaminant transport, planning conservation corridor design, and understanding how landscapes or hydroscapes respond to directional forces like wind or water flow. We developed a directional connectivity index (DCI) that synthesizes progress in computing connectivity in hydrology and ecology and is consistent with more computationally expensive hydrologic metrics that are strongly related to functional characteristics (e.g., flows, fluxes). Case-study application of the DCI to the Everglades in south Florida revealed that loss of directional hydrologic connectivity occurs more rapidly and is a more sensitive indicator of declining ecosystem function than other ecological metrics (e.g., habitat area) used previously. Fortunately, loss of directional connectivity is not irreversible. Portions of the Everglades have exhibited increases in maximum slough directional connectivity, though other structural characteristics of those landscapes remain altered relative to less impacted areas. In the Everglades and elsewhere, directional connectivity can provide insight into landscape drivers and processes, act as an early-warning indicator of environmental degradation, and serve as a planning tool or performance measure for conservation and restoration efforts.