Abstract:
Hydrologic connectivity refers to water-mediated transfer of matter, energy,
and/or organisms within or between elements of the hydrologic cycle
(sensu Pringle 2001). While this property is essential to maintaining
the biological integrity of ecosystems, it also serves to perpetuate the
flow of exotic species, human-derived nutrients, and toxic wastes in the
landscape. All too often, we have acknowledged the importance of hydrologic
connectivity in hindsight as a result of environmental crises.
Examples range from: the transport of exotic species that disrupt the
food webs of rivers and lakes (e.g., Stokstad 2003); to the occurrence of
extremely high levels of persistent organic pollutants (e.g., polychlorinated
biphenyls PCBs) that bioaccumulate in global ‘‘hotspots’’ such as the
Arctic (e.g., Aguilar et al. 2002); to effects of dams which impede riverine
transport of essential elements such as silicon to coastal regions which
has been implicated in coastal eutrophication and the creation of coastal
dead zones (e.g., Humborg et al. 2000).
Management and policy decisions regarding land-use activities are
often made in the absence of adequate information on hydrologic connectivity
in the landscape. An important area of research is to understand
how human alterations of this property (e.g., dams, stream flow regulation,
water diversion, inter-basin water transfers, water extraction)
influence ecological patterns on local, regional, and global scales. Half
of the accessible global freshwater runoff has already been appropriated.
