3.1. What is the FAO estimate of losses and gains in forest cover
FAO calculates a global net rate of forest loss
for 1990 - 2000 of 94,000
km² per year. This figure comes from a net loss of tropical
forest of 123,000
km² per year and a net gain in temperate forests of 29,000
km² per year.
These figures refer to changes in the extent of
forest area, not to changes in forest condition, or in forest composition
This represents a net change in forest cover of
minus 0.24 % per annum, globally. These figures are not universally
accepted (see above for some of the criticisms of the FAO estimates).
3.1.1. Is forest clearance a new phenomenon?
Forest clearance has been under way over a very
long period. Historically, forests have been cleared extensively
to make way for agriculture and for urban settlements. Rates and
patterns of forest clearance have also varied considerably over
Attempts to reconstruct global vegetation at the
end of the last Ice Age (app. 8,000 - 10,000 years ago) are based
on remaining vegetation, on analysis of pollen in soils and at the
bottom of bodies of water such as lakes, and sometimes, for later
periods, on documentary records. Estimates of the global loss of
forest cover over this period vary from 20% to 50%.
For one attempt (by WRI) at mapping potential historic
forest cover, see:
The majority of this conversion of forests has taken
place in the northern hemisphere, particularly in Europe during
the Bronze Age, and then during the Industrial Revolution, and in
North America during the 19th Century. Tropical deforestation appears
to have been insignificant until the 19th Century, then increasing
to reach a peak in the late 20th Century to the present.
3.1.2. Do rates of loss of forest cover vary geographically?
In addition to the significant difference between
temperate and tropical forests, there are big differences between
the rates of loss of tropical forest in Central America, South America,
Africa, Southeast Asia, and the Pacific Islands. It seems that tropical
forests are now being cleared most rapidly in the equatorial regions
of Africa (FAO, 2000, Forest
The geography of the change is important because
all sources do agree that while the area of forest lost each year
seems to have stabilized in temperate forests, there continues to
be a loss of forest area in the tropics. The global impact of loss
of temperate forests (especially northern temperate forests in Europe,
Russia, and North America) is very different from the loss of tropical
forest, since the two are ecologically very different, especially
in terms of biodiversity (see sections below on bioregions and on
Temperate forests usually have less biodiversity
than tropical forests, and have a much longer history of clearance.
Present increases in the area of temperate forest represent only
a very small fraction of the total area of temperate forest that
has probably been cleared in the last 5,000 to 8,000 years.
2000) believes that the rate of loss in tropical forests has
slowed (but that there continues to be a loss) and now stands at
an annual rate of 123,000 km² (12.3 million ha.)—an area
close to the combined total area of the Czech Republic and Slovakia.
Others note that while the rate of loss in Latin America seems to
be slowing, it is continuing at about the same rate in Southeast
Asia, and increasing in central Africa and in Oceania / Pacific
Worldwide, both in temperate (and boreal) areas
and in tropical areas, the most intense concern is focused on remaining
natural forests. The World Resources Institute (WRI) and its partners
in the Forest Trends program call these ‘frontier forests’
(see also section 1.3.2 above on frontier forests) and have highlighted
the fact that they are currently the areas where clearance and conversion
to other uses are taking place at a faster rate than in other forests.
WRI defines ‘frontier forest’ as: "…
the world's remaining large intact natural forest ecosystems. These
forests are relatively undisturbed and big enough to maintain all
of their biodiversity, including viable populations of the wide-ranging
species associated with each forest type"
3.2. Some differing views about the geography of change
FAO calculates a net loss of tropical forest of
km² per year.
There are disagreements about the rate of change
- FAO figures may underestimate the rate at which forest cover is
being lost. Criticisms of the FAO estimates are particularly sharp
for tropical forests.Changes in the definition of forest in successive
reports make it particularly difficult to make informed comparisons
of changes in the rate of deforestation.
The figure given by the WRI is higher. "WRI
calculations [for tropical forests] indicate that natural forest
losses in all tropical countries amounted to nearly 160,000
km² per year, for a total loss of 1,580,000
km² between 1990 and 2000. In other words, the rate of
natural forest loss in the tropical region appears to be about 17
percent higher than the rate reported by FAO." http://www.wri.org/wri/forests/fra2000.html
"According to the [FAO FRA] 2000 report, about
km² of natural forest were lost during the 1990s, of which
km² (about 94 percent) were in the tropical world. The
2000 report puts total global forest cover at about 39,000,000
km², 95 percent of which is "natural forest,"
meaning that there are about 37,000,000
km² of natural forest. Of this, 47 percent, or 17,400,000
km², is in the tropics. Thus if 1,520,000
km² of natural tropical forests were lost during the 1990s,
from a total natural tropical forest area of 17,400,000
km², then tropical forests shrank by 8.7 percent over the
decade -- an annual average rate of 0.87 percent." (Emily
Mathews, World Resources Institute, in Grist magazine)
3.2.1. Can plantations substitute for natural forest?
"Observers disagree on the role of plantations
in assessing global forest cover and about how the ‘net’
loss or gain is calculated. One source of concern is whether plantations
are a substitute for natural forest.
Europe was almost entirely covered by forest after
the last Ice Age. The continent as a whole (not including Russia)
now has forest cover of 35 %(www.fao.org/forestry/
p186), after having reached a low of 25% during the 19th Century.
These aggregate figures for temperate regions suggest
that there is a balance between harvested forest and regrowth—and
that there may be an overall increase in the area of forest in temperate
areas. Since much of this increase comes from newly established
or reforested areas, there are questions, though, about whether
these planted forests have the same ecological functions as natural
forests and whether the area of planted forest should therefore
be included in calculations of overall changes in forest cover.
Forest plantations usually have fewer species, are subjected to
more intensive management regimes (fertilization, pruning, thinning)
and so are often not considered to be an ecological substitute for
‘natural’ forest. A statement of the problems associated
with comparing plantations with natural forests is provided by Forest
Trends, a forum of leaders from forest industry, donors and environmental
"Plantations are intensive tree crops maintained
for the singular purpose of providing fiber and timber. Often, the
area is planted with a single species, treated with herbicides and
pesticides as well as fertilizers and silvicultural measures are
used relatively frequently. The understory and other plants common
in natural and semi-natural forests are actively suppressed in order
to maximize the yield. There is a gradient of pure plantations of
a single species, such as eucalyptus, (or even a single 'tree' where
clones are used) through the moderately heavy silviculture of much
of the forest conversion of many temperate areas, to more natural
stands that sprout up after the harvest of a forested area. Often,
where old-growth forests are logged, 'forests' akin to plantations
are planted or encouraged."
It should be noted, that while this statement is
true for most plantation forests, some of the increase in temperate
forests has come from forest that has become re-established naturally
when land has been taken out of agriculture—a practice which
has been encouraged recently by the EU in particular.
3.2.2. What is the range of different estimates
for changes in forest cover?
"Estimates of forest loss have varied considerably
over the last fifty years or more. During the 1970s and 1980s, estimates
of forest losses varied from 2.3% to a high estimate of 4.8% annually
(a figure cited by President Carter’s commission).
In the 1970s, deforestation was highlighted as one of the most urgent
environmental issues. With little reliable information available
at the time, some predictions of the extent of deforestation were
dramatic. In 1979, the biologist Norman Myers predicted that "it
is not unrealistic to suppose that a large portion of Amazonia’s
forests could disappear as early as the end of this century."
. Later, in 1991, he further predicted that "in just another
few decades, we could witness the virtual elimination of tropical
forests" (Myers, 1991, pg. 47) .
Alternative figures proposed for rates of deforestation
km² of rainforest each year, an area larger than Poland"
(The land area of Poland is 305,000km²). Grist
Magazine (online magazine of the Earth Day Network).
Grist Magazine gives the Natural Resources Defense
Council (NRDC) as the source of its estimate - but NRDC gives a
figure of 121,000
km² per year for all forests: "Half the world's forests
are now gone, and well over 121,000
km² more are lost each year". Natural Resources Defense
Council (NRDC). (There is no reference to a source for these data).
- The World Resources Institute (WRI) estimates
km² of tropical forest are lost each year. This estimate
is based on WRI review of FAO data, which does not include plantations
and replanted forests as substitutes for cleared natural forest.
http://www.igc.org/wri/forests/pdf/fra2000.pdf [broken link]
- "Globally, the overall area covered by forest
has not changed much since 1950…" (Bjørn Lomborg.
The Skeptical Environmentalist. pg 111). Lomborg mostly uses FAO
data, but does not differentiate between forest type (temperate
vs. tropical) and his analysis of the data appears to accept that
plantation forests are a substitute for natural forest. It can
be argued that Lomborg’s analyses are misleading because
they aggregate the very different situations and ecological roles
of temperate and tropical forests and of planted forests with
natural (but not always ‘untouched’) forests.
With a few exceptions, most estimates of deforestation
now converge around a figure for a net annual global loss of forest
of an order of magnitude of between 0.5% and 0.9% or 120,000 km²
and 160,000 km² each year (equivalent to approximately one
half of the land area of Poland - see http://www.ed-u.com/area-of-countries-a.htm)
In summary, some of the estimates of loss of forests
which attracted international attention during the 1970s and 1980s
may have been over-pessimistic.
In temperate areas, the area of forestland seems to be stable or
even increasing with an expansion of plantations and reforestation,
although there continues to be a loss of natural forest. In the
tropics, there continues to be significant loss of forest which
is not compensated for by reforestation or natural regrowth.