Scope of analysis
This study analyzes datasets at the global, national, and subnational levels, and draws on published and unpublished scientific studies. It develops selected indicators that describe the condition of the world’s forests, where condition is defined as the current and future capacity of forests to provide the full range of goods and services that humans need and consume.
Forest extent, change, and human modification
In this study, WRI defines forests as terrestrial ecosystems dominated by trees, where the tree canopy covers at least 10 percent of the ground area. The researchers chose this broad definition to allow use of a variety of datasets and to avoid somewhat arbitrary distinctions among different land cover types. The study examines the spatial extent of forests and modifications by humans that have altered the extent and structure of forest ecosystems over time. Forest extent is a basic measure of condition: if global forest cover shrinks, provision of goods and services from forest ecosystems – in the absence of compensating human action – will be reduced. Measures of the biological condition of the world’s forests are extremely difficult to develop, given data limitations and controversy over such concepts as ecosystem health. Therefore, we examine three forms of human modification of forests that are known to be leading indicators of environmental change: the spread of “transition zones” (agriculture practiced at the margins of intact forest), road construction, and the use of fire.
Forest goods and services
As further measures of condition, we compile data on the current “yield” of forest goods and services, whether measured as stocks (the amount of carbon stored), or annual production (the quantity of timber harvested). We present available data on trends over the past 30 to 40 years and assess forest capacity to continue to provide goods and services in future, based on indicators of changing forest extent and biological condition. We also look at human modifications to forests that have been undertaken deliberately to maximize production of a particular good or service or that have occurred as an unintended by-product (externality) of human action. What are some of the trade-offs that humans have made as they extended cropland or increased timber production?
We focus on a limited number of forest goods and services. The choice was determined partly in consultation with forestry experts in many countries and partly by data availability. Our preference was to use global datasets; where global data were not available, we used regional and national level information. Sometimes, local-level case studies were used to illustrate trends that appear to be important but for which national or global data do not exist. The data and indicators presented in this pilot analysis are concerned with the following:
- Global forest cover
- Human modification (transition zones, road construction, fire);
- Industrial roundwood production;
- Woodfuel production;
- Biodiversity;
- Carbon storage and sequestration; and
- Watershed protection.
Clearly, important issues are missing from this list. Nonwood forest products, including food (nuts, berries, fruits, mushrooms, honey, game), cash crops (coffee, palm oil, rubber) and industrial raw materials, have not been assessed. Data for most nonmarketed goods are patchy and noncomparable among countries, while information on industrial raw materials is usually commercially sensitive. In the case of cash crops, many of these products can be, and increasingly are, supplied from nonforest environments, such as agroecosystems and plantations. The condition of forests is not necessarily relevant to their future supply. In the longer term, this may be true also of industrial roundwood and woodfuels but forests will remain the dominant source of supply of these commodities for the foreseeable future.
The spiritual and aesthetic qualities of forests constitute perhaps the most important omissions from this study. People commonly respond to forests with a sense of awe, exhilaration, and reverence. Human values conferred on nature, however, cannot readily be captured by the kind of quantitative analysis presented here. Scattered data exist on tourism revenues and visitor numbers to forest reserves, which some analysts have used as proxy measures of human appreciation. A number of economists have attempted to monetize forest “existence” or “intrinsic” values. Such exercises have not been considered here. The very concept of analyzing forest goods and services is essentially utilitarian, while appreciation of forests as objects of expressive power is essentially aesthetic. The two perspectives cannot logically be combined. Further, any attempt to develop quantitative indicators of qualitative values risks removing the latter from their proper arena of political, moral, and cultural debate.
Conclusions
This study relied heavily on access to global and regional information collected and analyzed by many organizations, including FAO, UN-ECE, the European Commission, and NASA among others. We are indebted to their efforts, often in the face of tight budgetary constraints. A great deal of information and expertise also exists at the national level. PAGE researchers experienced few, if any, obstacles in accessing these information sources but noncomparability among datasets proved a major problem. Despite the abundance of information available, its quality is often poor. The uncertainty surrounding much of what we think we know about forests is sobering.
Virtually no hard (measured) forestry datasets exist at the global level, with the exception of industrial roundwood production. Even production data are estimated for some countries. All the other data cited in this report rely largely on modeled estimates and expert opinion. The weakest data of all relate to woodfuel production and biodiversity.
Remote sensing data that have become available over the past 10 years have improved our knowledge of forest extent and deforestation rates. Satellites have reduced data uncertainties but they are far from being eliminated. Most official data on forest extent and production still depend on conventional maps and forest inventories. The plethora of definitions – over 100 definitions of “forest” are currently in use globally – and outdated inventory data are major obstacles to interpreting these sources.
The single biggest change over time has been the clearance of forests to make way for agricultural land. In this century, the location of change has shifted from the temperate to the tropical zone, and the pace of conversion has quickened.
Of all the goods and services humans derive from forests, we currently manage most actively for wood products. Technology and markets have enabled us to compensate for reduced forest area by raising productivity. Forest plantations, in principle, could provide all our fiber needs, sparing natural forests altogether. Experience to date suggests that such a degree of substitution is unlikely over the medium-term in the absence of additional policy incentives.
We have not applied our management skills with equal energy to protect or enhance production of other goods and services from forests. Woodfuel supply, carbon storage, watershed protection, and biodiversity are obtained, exploited, or enjoyed rather opportunistically at the global level – until recently they have been assumed, more or less, to take care of themselves. (Numerous exceptions to this generalization exist at the local level but this report is concerned with the big picture.) However, substitution of such environmental services as carbon storage and watershed protection is infeasible for many countries under current economic and institutional conditions. Forest biodiversity, in all its complexity and beauty, appears irreplaceable.
There are some signs of change in both industrialized and developing countries. Forest management practices and legal protection reflect increasing recognition of the need to manage forests for multiple benefits and actors, and to make conscious decisions about trade-offs when they become inevitable. However, the full range of goods and services that forests provide is rarely factored into development decisions and our current information base does not allow us to consider and weight different goods and services in an integrated way.
Recommendations for the Millenium Ecosystem Assessment
This pilot analysis concludes that the generally poor quality of land cover and land use information means that the degree and speed of change in forest extent are difficult to determine. Changes in the condition of forest ecosystems are even harder to monitor because good baseline data are largely lacking and indicators of forest condition, applicable to different forest types that may be managed for different purposes, are still controversial.
Specific recommendations to document goods and services provided by forest ecosystems include the following:
- Use of higher resolution satellite data to provide a clear baseline of forest area and monitor change year on year.
- Ground-truthing to verify satellite-derived land cover classification.
- Remote sensing techniques and methodologies that can help with interpretation of below-canopy forest parameters, such as biomass density.
- Further work to harmonize national and agency definitions of forests and deforestation to improve comparability of national and international reporting.
- Improved spatial information on legal and illegal logging operations.
- Improved forest inventory information, including data on growth rates, harvest rates, mortality, disease, age and size classes, felling rates, in countries where these are not currently available.
- Compilation of reliable woodfuel energy statistics for developing countries.
- Further research on carbon sequestration and storage rates in specific tree species and climate and soil conditions.
- Greatly expanded systematic data collection on biodiversity, using nationally comparable parameters.
- Development of indicators that can be based on data obtainable from remote sensing and GIS, because comprehensive ground surveys are not economically feasible.
