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Facts on Forests and Forestry

  NEW: Read GreenFacts' new Digest on Forests:

1 Introduction – Measuring progress towards sustainable forest management
2 How much forest is there on the planet and at what rate is it disappearing?
3 How can forests affect climate change?
4 What is the biological diversity of the world’s forests?
5 How healthy are the world’s forests?
6 What products are extracted from forests?
7 What are the protective effects of forests?
8 What are the economic and social benefits of forests?
9 Are forests managed in a sustainable way?
10 Conclusions

  A faithful summary of the "Global Forest Resources Assessment"
  produced in 2005 by the FAO (Food and Agriculture Organization). More...



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2. How much forest is there in the world?

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2.1. What are the different estimates?

"The land surface of the globe covers 148.9 million km² (29% of the surface area of the earth)."
External linkhttp://www.ed-u.com/area-of-countries-a.htm

The Food and Agriculture Organization (FAO) of the United Nations estimates that in 2000, 38.7 million km² (26%) of this land was ‘forested land’.
External linkFAO. Global Forest Resources Assessment, 2000. Part 1. Forest Cover.

The FAO reports every two years on the status of forests, on recent policy and institutional developments and key issues concerning the forest sector.
External linkReports are available for 1995, 1997, 1999 and 2001.

The Global Forest Watch initiative of the World Resources Institute in the USA proposes a lower estimate, for the year 1997, of 33.36 million km².
External linkhttp://www.globalforestwatch.org/english/about/faqs.htm#faq1

The World Conservation Monitoring Centre (together with UNEP and CIFOR) gives a higher estimate of global forest cover of 39.88 million km² for the year 1996.
External linkhttp://www.unep-wcmc.org/forest/data/cdrom2/gchts.htm#Chart1

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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:
External link 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:
External link http://www.wri.org/wri/forests/fra2000.html

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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:

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  • 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."
External link http://www.wri.org/wri/forests/fra2000.html pg. 3

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  • 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."

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  • Changes in land use

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.

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