Forest fragmentation occurs when large
continuous forests are divided into smaller blocks. Harvesting, road-building,
construction of hydro corridors and other human disturbances can result
in the creation of small isolated patches of forested land. These fragmented
forests are subject to a number of risks related to patch size and patch
Wildlife indicators of fragmentation
Aerial shot of fragmented
forest near Geraldton
“The fragmentation of a forest may disrupt
some ecological processes and wildlife habitat, and affect its capacity
to maintain species and processes usually found in those habitats. Forest
fragments may be too small to maintain viable breeding populations of species
and excessive fragmentation can contribute to the loss of plant and animal
species that are unable to adapt to fragmented forest conditions.”
Ontario State of the Forest
Report 2001 Section 1.1.4
Fragmentation changes habitat
area and type. Reducing the amount of forest interior and increasing the
amount of forest edge, favours species that prefer edge.
Species may become trapped in
fragments of forest. Many organisms e.g. salamanders, frogs, and turtles,
find it difficult or impossible to disperse across inhospitable terrain.
Even some bird species find it difficult to disperse across large clearcuts,
and many plants, insects and other animals become increasingly confined
to small ‘islands’. These islands support fewer species over time.
Populations isolated in small
patches are prone to decline due to inbreeding, and are prone to removal
from the patch due to disturbances such as blow-down or changes in microclimate.
From an ecological perspective,
forest fragmentation compounds the effects of habitat loss from clearcutting:
interpreting surveys of forest wildlife data as indicators of the effects
of fragmentation is challenging as it is difficult to distinguish between
the effects of habitat loss and fragmentation.
There is a lack of empirical
data and good fragmentation studies - the effects of forest fragmentation
and connectedness of ecosystem components are difficult to assess.
A variety of forest species – salamanders,
lynx, pine martin, caribou, and various plant species - are excellent indicator
species. Forest birds are excellent indicators of forestry effects
at both the stand and landscape level. Many interior birds, including endangered
or vulnerable species such as the Acadian Flycatcher and Louisiana Waterthrush,
now occur in very low numbers due to lack of forest interior habitat. Other
interior or area sensitive species of birds include Brown Creeper, Broad
Winged Hawk, Barred Owl, Pine Warbler, Cerulean Warbler, Black and White
Warbler, Winter Wren, Pileated Woodpecker, and the Ovenbird. Species that
prefer open or forest edge areas include Blue Jay, Chickadee, Northern
Flicker, Cowbirds, Ruffed Grouse, Grey Catbird, and Downy Woodpecker.
|The Forest Management
Planning Manual lists six indices of landscape fragmentation and connectedness:
forest composition and diversity,
forest isolation, and
forest spatial pattern.
|Ontario Forest Management Planning
See Table FMP 4 “Landscape
Pattern or Forest Diversity Indices” for details and check Annual Reports
and Reports of Past Forest Operations (RPFO) for indicators of fragmentation
& Ecology Links Viewpoints
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