Connectivity: Landscape

“Although riverine systems differ from terrestrial systems by virtue of the strong physical force of hydrology and the inherent connectivity provided by water flow, all of these themes (longitudinal, lateral, vertical and temporal connectivity) apply equally to aquatic and terrestrial ecosystems, and to the linkages between the two” (Wiens).  

Landscape connectivity is 'the degree to which the landscape facilitates or impedes movement among resource patches' (Taylor et al, 1993). Biological components - both plant and animal – must have access to all the habitats necessary for all stages of their life cycle. This includes both physical and temporal access to habitats. For example, the need for seasonal timing is acute for many wildlife species to accommodate breeding, reproduction, and migration. For plant species it is equally important for dispersal, growth and competition.

Landscape connectivity has two components:

  • Structural connectivity – the spatial structure of a landscape that can be described from map elements
  • Functional connectivity – the response of individuals to landscape features (Brooks).

Habitat does not need to be structurally connected in order to be functionally connected. Some organisms have the ability to bridge the gaps between habitat patches and can link resources by crossing over uninhabitable or partially inhabitable locations (Taylor, 2006). For example, a neotropical migrant bird will perceive a landscape as connected across a greater range than would a salamander restricted to moist forest floors (With). “These movements… of individuals, materials, nutrients, energy or disturbances… are affected by how (habitat) patches are arrayed in the mosaic…. Although landscape connectivity is often thought of in terms of corridors - roughly linear strips of habitat connecting otherwise isolated habitat patches – connectivity is in fact a complex product of:

  • patch quality (e.g. resistance to movement or patch-residence time)
  • boundary properties ...
  • the movement characteristics of the features of interest” (Weins).

Fragmentation

As people use the land, the natural landscape is divided into ever-smaller pieces by elements like railways, utility lines, roads, houses, and parking lots. The remaining natural areas, or fragments, are reduced in size and degraded in quality, resulting in a decline in plant and animal populations, and the disappearance of some sensitive animal species and plant communities.

How does fragmentation impact the environment?

  • Fragmentation results in a dramatic increase in 'edge' habitat, which provides increased access to the more protected interior habitats by predators, including domestic animals.
  • Fragmentation creates barriers to wildlife movement, and is especially harmful to reptiles and amphibians that depend on the ability to move between their aquatic habitats and upland areas.
  • Fragmentation creates opportunities for harmful exotic plant species to invade. Many exotic species can out-compete native plant communities and often provide little or no habitat value.
  • Because it's associated with human activity, fragmentation often brings pesticides, noise, lights, and other pollutants and disturbances that can profoundly impact a species' ability to function (MN DNR Natural Resource Guide, "Changes to the Land").