Mapping functional wetland connectivity across reserves and anthropogenic habitats

How good are protected areas at providing functional connectivity, and how do they stack up compared to man-made habitats?  In their recent publication in Ecological Applications, Uden et al. examined functional connectivity of wetlands in an agricultural ecosystem for supporting anuran community resilience.  They also looked at how good reserves, non-reserves, and other anthropogenic water bodies were at maintaining connectivity.  They focused on natural wetlands (both inside and outside of reserves) along with man-made irrigation reuse pits that populate the Rainwater Basin watershed of south-central Nebraska.

Using a graph-theoretic approach to assess functional connectivity at four potential anuran dispersal distances, they found (perhaps unsurprisingly) that current wetlands are less clustered and connected than they were historically.  Although man-made irrigation reuse pits did tend to hold water longer, other characteristics such as steep sides, less vegetation, and greater water fluctuations made them poorer habitat compared to wetlands.  Overall, they could not entirely compensate for the loss of natural wetlands throughout the region.  Their use as stepping stones to natural wetlands was limited for native short-distance dispersers ( ex. northern cricket frogs), but may encourage the spread of long-distance invasives (ex. American bullfrogs).  While reserves play a critical role in maintaining biodiversity, in the Rainwater Basin they are uncommon enough to contribute less to network connectivity than non-reserve wetlands or pits.  The system does have the potential to remain stable given the high connectivity with sub-optimal anthropogenic water bodies.  However, a key management question remains: should man-made habitats such as pits be removed to discourage invasives and encourage the use of natural wetlands, or should they remain as an important (if less than ideal) link providing connectivity in the region?  This, along with management decisions surrounding non-reserve habitats and wetland restoration, leave the future of ephemeral wetlands in the region in question.