Patches can have both positive and negative impacts on landscape. While forest patches between agricultural areas may prove beneficial for the ecological health, a landfill next to a sensitive wetland may have an adverse effect (Dramstad et al., 1996). Below, patches are categorized according to size, number, and location (Table 1).
|
Patch Size |
Patch Number |
Patch Location |
|
Edge habitat and species Interior habitat and species |
Habitat loss |
|
|
Local extinction probability |
Metapopulation |
Extinction |
|
Extinction |
dynamics |
Recolonization |
|
Habitat diversity |
Number of large patches |
Patch selection for |
|
Barrier to disturbance |
Grouped patches as |
conservation |
|
Large patch benefits |
habitat |
|
|
Small patch benefits |
1.1 Edges and boundaries
An edge is the outer section of a patch displaying different characteristics than the interior conditions of a patch, in terms of vertical and horizontal structure, width, and species composition and abundance. These differences constitute the edge effect and the edge acting as a transition zone between habitats presents opportunities for landscape planners to facilitate the achievement of an ecological goal. While the shapes of patches can be natural, i. e. due to their boundaries, they can as well be artificial, i. e. administrative, and thus, differ to a varying extent from natural edges (Dramstad et al., 1996). (Table 2).
|
Edge |
Boundaries |
Shapes of patches |
|
• Edge structural diversity • |
Natural and human edges • |
Edge and interior species |
|
• Edge width • |
Straight and curvilinear • |
Interaction with |
|
• Administrative and natural |
boundaries |
surroundings |
|
ecological boundary • |
Hard and soft boundaries • |
Ecologically "optimum" |
|
• Edge as filter • |
Edge curvilinearity and |
patch shape |
|
• Edge abruptness • |
width • Coves and lobes |
Shape and orientation |
|
Table 2. Edge, boundaries, and shapes of patches |
