Defining How Much of the World is Covered by Forests

Is
that
a
forest?

Like
mountains,
there
isn’t
an
exact
definition
of
what
forests
are.
Different
organizations
and
countries
use
varying
criteria
to
define
a
forest
–
often
based
on
the
percentage
of
land
covered
by
trees
(canopy
cover),
the
total
area
of
those
trees,
and
the
height
of
those
trees. 
Those
differences
in
defining
a
forest
can
result
in
large
differences
in
mapping
out
forest
cover.

What
is
a
forest?

Canopy
cover –
the
percentage
of
ground
shaded
by
tree
crowns
–
is
the
major
criteria
that
varies
among
countries
and
agencies
when
calculating
whether
or
not
an
area
is
a
forest.
The
United
Nations’
Food
and
Agriculture
Organization
(FAO)
uses
this definition:
any
land
area
over
0.5
hectares
(about
1.2
acres)
with
trees
taller
than
5
meters
and
a canopy
cover
above
10% qualifies
as
“forest,”
as
long
as
it’s
not
chiefly
under
agricultural
or
urban
use​.

Other
agencies
are
more
restrictive,
only
defining
forests
when
the
canopy
cover
is
30%
or
more.

This
means
that
plant
biomes
such
as
savannah
and
oak
woodlands
that
would
be
classified
as
a
forest
under
the
UN
FAO’s
definition,
drop
out
of
maps
that
use
the
higher
density
as
a
qualifier.

Examples
of
forest
definitions

The
European Forest Institute
(EFI)
has
a


table
of
forest
definitions
for
each
European
country.

United
Nations
Framework
Convention
on
Climate
Change
(UNFCCC)

Definition
(excerpt
from
the
Kyoto
Protocol
reporting
guidelines):
“Forest
is
a
minimum
area
of
land
of
0.05–1.0
hectares
with
tree
crown
cover
(or
equivalent
stocking
level)
of
more
than
10–30
percent,
with
trees
having
the
potential
to
reach
a
minimum
height
of
2–5
meters
at
maturity.”

United
States
Fish
and
Wildlife
Service
(USFWS)

Definition:
Forest
land
use
is
defined
as a
land
area
at
least
1
acre
in
size,
with
at
least
10
percent

tree
canopy
cover,
or
can
grow
such
canopy
cover,
and
is
not
managed
for
other
uses.
Approximately
35
percent
of
land
in
the
United
States
is
forest
land.

Using
satellite
imagery
to
map
the
extent
of
forests
based
on
percentage
canopy
cover

Researchers
found
that
global
forest
cover
estimates
can
vary
by
as
much
as
6%
to
13%
of
Earth’s
land
area
–
roughly
the
size
of China –
simply
due
to
different
forest
definitions​.
In
a
study
published
in

Nature
Climate
Change,
scientists
calculated
global
forest
at
10%
and
30%
canopy
coverage
by
analyzing

Landsat
satellite
imagery.
Under
a
10%
canopy
cover
rule,
vast
savanna
regions
with
scattered
trees
are
included
as
forests,
whereas
a
30%
threshold
would
classify
those
same
regions
as
non-forest
or
“other
land”​.

Mapping
forest
areas
in
the
Uinta
Mountain
Range

An
illustrative
example
of
this
was
done
by

NASA
researchers
who
mapped
the
extent
of
forests
in
the
Uinta
Mountain
Range
in
Utah
at
10%
and
30%
canopy
cover.
About
half
of
the
Uinta
Mountain
Range
area
is
covered
by
temperate
coniferous
forests.
Alpine
tundra
and
meadows
are
found
at
the
higher
evaluations
above
the
tree
line.

A
lack
of
a
universal
definition
for
a
forest
makes
comparing
forest
data
challenging

Such
inconsistencies
make
it
challenging
to
compare

forest
data
across
regions.
As
the
World
Resources
Institute
states, “there’s
no
international
exchange
rate” to
convert
forest
figures
from
one
definition
to
another​.
For
example,
in
Indonesia,
the
official
definition
(for
UNFCCC
reporting)
historically
required
a
minimum
area
of
6.25
hectares,
whereas
Côte
d’Ivoire’s
definition
used
just
0.1
hectare​.

References

Sexton,
J.
O.,
Noojipady,
P.,
Song,
X.
P.,
Feng,
M.,
Song,
D.
X.,
Kim,
D.
H.,
…
&
Townshend,
J.
R.
(2016).
Conservation
policy
and
the
measurement
of
forests. Nature
Climate
Change, 6(2),
192-196.

Go to Source
Author: Caitlin Dempsey