|
|
|
|
|
|
2. How much forest is there in the world?
|
|
|
|
|
|
|
|
|
2.2. Are the FAO figures reliable?
The FAO figures are challenged, particularly by
international conservation organizations, for a number of reasons:
According to the World Rainforest Movement, FAO
uses different definitions of "forest" in "developed"
and "developing" countries. In "developing"
countries forests are divided into "natural forests" and
"plantation forests", the latter resulting from tree planting
in lands without forests as well as from the substitution of "natural"
forests by exotic species. The World Rainforest Movement does not
consider tree plantations to be forests because they differ in their
origin, number and types of species, dynamics, uses and relationships
to the other components of the environment:
http://www.wrm.org.uy/bulletin/25/FAO.html
There is disagreement about the interpretation and
analysis of the data, but FAO data tend to be the point of reference
for all organizations concerned about the status of global forests.
For a detailed critique of the data and analysis in FAO’s
‘Forest Resources Assessment 2000’ see ‘Understanding
the FRA 2000’ by Emily Mathews of the World Resources Institute
(World Resources Institute Forest Briefing No. 1. March 2001). The
full text of the report can be downloaded from:
http://www.wri.org/wri/forests/fra2000.html
|
|
|
|
|
|
|
2.3. Why are there different estimates of forested land?
In addition to the fact that there are many different
definitions of a forest (see preceding section), the following are
some of the main reasons for differences in estimates of the area
of forested land:
|
|
|
|
|
|
- Practical and logistical difficulties in measurement
"There are considerable practical and logistical
difficulties in measuring areas of forested land, especially in
remote and inaccessible places.
Developing countries, in particular, often do not
have the budgets and trained staff to conduct detailed forest inventories
or to update existing databases. More than half of the developing
country inventories used in the FAO report in 2000 were either more
than 10 years old or incomplete."
http://www.wri.org/wri/forests/fra2000.html pg. 3
|
|
|
|
|
|
- Technical changes in data collection methods
"Data on forest cover are drawn from surveys
of forested land. The most basic techniques involve crews of forest
surveyors traveling through the forest sampling the sizes and distributions
of trees of different species. Aerial photography and more recently,
satellite imagery have made it possible to undertake surveys of
much larger, more inaccessible areas of forest, but have sometimes
generated debate and disagreement about the interpretation of the
data collected.
One of the major criticisms against the FAO 2000
report is that there have been significant changes in the methodologies
used to calculate global forest cover in 1990 and in 2000. The 1990
report estimated forest cover in 1990 at 34.424 million
km², whereas the 2000 report gives a significantly higher
figure of 39.522 million
km². (See WRI ‘Understanding the FRA’, in section
2.2). A large component of this difference was the result of a switch
from the use of mathematical models to estimate missing data in
the 1990 report, to the use of satellite images to estimate missing
data in the 2000 report. Satellite technology, however, is making
it possible to develop increasingly accurate maps and statistics
on land use cover."
|
|
|
|
|
|
Land uses are constantly changing over time. Land
where forest has been cut once might be considered as ‘deforested’
at the time of cutting and not included in forest cover statistics,
but ten years later, if it has been allowed to grow back, it might
be considered forestland again.
Even where satellite imagery is used to collect data on forest cover,
changes in the condition of forests over time can have an effect
on forest cover statistics. See the following section on ‘Changes
in Forest Area’ for more detailed information about difficulties
in assessing the causes and extent of deforestation.
|
|
|
|
|
|