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The
Natural Value of Large Intact Forest Landscapes
Criteria & Definitions
The Natural Value of Large Intact Forest
Landscapes
Researchers recognize the special value
of large natural areas for preserving all strata of
biological diversity (McCloskey, Spalding, 1989, Bryant
et al., 1997, Noss, 1990 etc.). Forest biodiversity
largely depends on intact forest landscapes. Large animal
populations (such as forest elephants, great apes, bears,
wolfs, tigers, jaguars, eagles, deer etc.) especially
require these intact forest landscapes for preservation.
The fragmentation and loss of natural habitats is a
main factor threatening plant and animal species with
extinction. Also regionally or globally important ecological
processes and services (such as water and air purification,
nutrient cycling, carbon sequestration, erosion and
flood control, etc.) are supported by intact forest
landscapes and other intact ecosystems. All of this
makes the conservation value of intact forest landscapes
relatively high overall while it may differ from area
to area.
For many factors, reserve size is vital
to the success of conservation efforts. Such factors
include stable populations of large animals that are
especially sensitive to human impact or habitat changes,
lakes and wetlands as objects of reference, and the
natural dynamics of forest ecosystems associated with
large-scale disturbances such as fire or wind damage.
Also, the central parts of large reserves are better
protected from "edge effects," which include invasion
of alien species, increased human access with subsequent
increase of poaching and fires, drying-out of the forest,
etc. Relatively small forest fragments can exhibit increased
vulnerability to threats beyond their borders.
It's impossible to pinpoint the minimum
area required for indefinite preservation of all natural
components of a forest landscape. Habitats of different
sizes are needed to support a diversity of bio-components.
These areas also depend on a vast variety of local conditions
with best estimates utilized to approximate the needed
space for intact habitat viability.
Certainly, the greater the area, the greater
the number of organisms and natural properties that
can be preserved and ultimately the greater the overall
viability of the intact forest landscape. Also of note
is the knowledge gap regarding spatial relationships
among the components of forest ecosystems. The same
is true for the mechanisms that govern the survival
of particularly sensitive plant and animal species.
Protecting large intact forest landscapes is therefore
a matter of reasonable precaution, as it promotes the
conservation of all species, both those well-studied
and those yet unknown.
In this study, large intact areas were
defined as landscapes greater than or equal to 500 km2,
internally undivided by infrastructure, and with a minimum
linear dimension no smaller than 10 kilometers. Such
spaces are capable of maintaining most natural values
and functions of a self-sustaining boreal landscape,
including the following:
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Small-scale (the falling
down or death of individual trees) and large-scale
(fire, insect infestations, extreme weather conditions)
random disturbances |
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Self-maintaining
populations of plant and animal species especially
sensitive to human disturbance |
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Intact catchment
basins around rivers, bogs and streams |
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Spatial patterns
of ecosystems and habitats |
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Rare or extremely sensitive
ecosystems, that disappear in fragmented landscapes
as a result of permanent human influence |
These dimensions sufficiently buffer most
edge effects, including the collapse of the forest edge
of logging sites, outbreaks of pest insects in logging
debris, changes in water regime due to clearing of neighboring
areas, and the effects of intensive hunting and fishing.
Criteria & Definitions
Intact Forest Landscape
An intact forest landscape is a territory
within the forest zone which contains forest and non-forest
ecosystems minimally disturbed by human economic activity,
with an area of at least 500 km2 and with
a minimal width (diameter of the inscribed circle) of
10 km.
The following objects are excluded from
the intact forest landscapes:
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Settlements (with 1 km
buffer zone) |
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1 km buffer zones around
infrastructure used for communication between settlements
and industrial sites; or for industrial exploitation
of natural resources (including motor roads, railways,
navigable waterways, pipelines, trunk power transmission
lines and other linear objects) |
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Agricultural lands,
except small scale which are used by local communities
for their needs and are not connected with the rest
of the world by infrastructure |
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Territories disturbed
by economic activities during the last 30-70 years (logging,
mining operation sites, abandoned agricultural lands,
etc.) |
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Artificially restored
forests, tree plantations |
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Burnt lands and young
tree sites adjacent to infrastructure objects (buffer
zones of 1 km) |
The ratio of forest and non-forest ecosystems
within intact forest landscapes has no restriction;
the key criteria are absence of disturbed territories
and infrastructure objects. Thus, intact forest landscapes
can consist primarily of non-forest nature ecosystems
that are minimally disturbed by human economic activity
(for example, treeless swamps or mountains fully surrounded
by forest).
It should be noted that some human impact
is invisible from space (for example, small forest roads
and paths or, specifically in Central African forests,
the decline of populations of large mammals as a result
of over-hunting). Also, smaller-scale impacts (including
some selective logging) that occurred more than 30-70
years ago - depending on the region - often become invisible
on satellite imagery, undistinguishable from the natural
dynamics of the forest.
The map was based primarily on 2000-2002
Landsat images. The most recent human impacts are also
not shown on it as the satellite imagery used is on
average 4-5 years old. All this leads to some - albeit
globally insignificant - overestimations of intact forest
landscape areas despite the 1 km buffer exclusion zones.
Only on local ground verifications can provide a more
accurate picture in these situations.
Forest Zone
Borders of the forest zone were defined
according to the "Global Percent Tree Cover at a Spatial
Resolution of 500 meters" map (Hansen et al., 2003).
The forest zone includes all parts of the forests with
a tree cover density of 20 percent or more, if the distance
between them is less than two kilometers, and all non-forest
plots which are fully surrounded by forests. All forest
plots generated in this way were considered to be part
of the forest zone if their area was 500 km2
and more.
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Intact Forest Landscapes. Russia
© Greenpeace/Kantor
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Intact Forest Landscapes in
Amazon. Brazil
© Greenpeace/Cannalonga
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