Home > Level 3 > Question 3

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...



Previous Question Level 1 Questions Next Question
Move to top of screen

3. Is the area of forest changing?

Most sources agree that globally, there is a continuing loss of forest cover. They also agree that there is a significant difference in the rate of loss of forest cover in temperate areas and in tropical areas.

Back to Details Level 3 Questions  
  Next Sub-Question Top
Move to top of screen

3.1. What is the FAO estimate of losses and gains in forest cover per annum?

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.
External linkhttp://www.fao.org/forestry/fo/fra/main/index.jsp pg 9

These figures refer to changes in the extent of forest area, not to changes in forest condition, or in forest composition and structure.

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).

Back to Details Level 3 Questions  
  Next Sub-Question Top
Move to top of screen

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 time.

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:
External linkhttp://www.wri.org/wr2000/page_maps/for03.pdf

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.

Back to Details Level 3 Questions  
  Next Sub-Question Top
Move to top of screen

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, External linkForest Resources Assessment).

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 biodiversity).

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.

FAO (External linkFRA 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 Islands.

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"
External linkhttp://www.igc.org/wri/ffi/lff-eng/lff-defs.htm


Back to Details Level 3 Questions  
  Next Sub-Question Top
Move to top of screen

3.2. Some differing views about the geography of change

FAO calculates a net loss of tropical forest of 123,000 km² per year.
External linkhttp://www.fao.org/forestry/fo/fra/main/index.jsp (pg 9).

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." External linkhttp://www.wri.org/wri/forests/fra2000.html (pg 5).

"According to the [FAO FRA] 2000 report, about 1,610,000 km² of natural forest were lost during the 1990s, of which 1,520,000 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." (External linkEmily Mathews, World Resources Institute, in Grist magazine)

Back to Details Level 3 Questions  
  Next Sub-Question Top
Move to top of screen

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 %(External linkwww.fao.org/forestry/ p186), after having reached a low of 25% during the 19th Century.
External linkhttp://www.paperonline.org/cycle/forestry/europe_forest.html

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 groups:

"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."
External linkhttp://www.forest-trends.org/keytrends/trends_forestestates.htm#4

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.

Back to Details Level 3 : Questions  
Move to top of screen

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 are:

  • "316,000 km² of rainforest each year, an area larger than Poland" (The land area of Poland is 305,000km²). External linkGrist 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). External linkhttp://www.nrdc.org/land/forests/default.asp

  • The World Resources Institute (WRI) estimates that 158,000 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 External linkhttp://www.ed-u.com/area-of-countries-a.htm) each year.

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.

Back to Details Level 3 : Questions  
Previous Question Level 1 Questions Next Question
Send this page  Subscribe to GreenFacts newsletter Download this Digest

  Read GreenFacts' recent Digests:

Provided by GreenFacts  


Contact | Copyright Top