Global Forest Area Research Articles

Air pollution and forest health: toward new monitoring concepts

It is estimated that 49% of forests (17 million km 2) will be exposed to damaging concentrations of tropospheric O 3 by 2100. Global forest area at risk from S deposition may reach 5.9 million km 2 by 2050, despite SO 2 emission reductions of 48% in North America and 25% in Europe. Although SO 2 levels have decreased, emissions of NO x are little changed, or have increased slightly. In some regions, the molar SO 4/NO 3 ratio in precipitation has switched from 2/1 to near 1/1 during the past two decades. Coincidentally, pattern shifts in precipitation and temperature are evident. A number of reports suggest that forests are being affected by air pollution. Yet, the extent to which such effects occur is uncertain, despite the efforts dedicated to monitoring forests. Routine monitoring programmes provide a huge amount of data. Yet in many cases, these data do not fit the conceptual and statistical requirements for detecting status and trends of forest health, nor for cause–effect research. There is a clear need for a re-thinking of monitoring strategies.

Evaluation of bioenergy potential with a multi-regional global-land-use-and-energy model

The purpose of this study is to evaluate the global bioenergy potential in the future using a multi-regional global-land-use-and-energy model (GLUE-11). The model covers a wide range of biomass flow including food chains from feed to meat, paper recycling, and discharge of biomass residues. Through a set of simulations, the following results are obtained. (1) Supply potential of energy crops produced from surplus arable land will be available in North America, Western Europe, Oceania, Latin America, former USSR and Eastern Europe. However, the potential of energy crops will be strongly affected by the variation of parameters of food supply and demand such as animal food demand. (2) Bioenergy supply potential of biomass residues will be stable against a change of a food demand parameter. The ultimate bioenergy supply potential of biomass residues will be 265 EJ/year in the world in 2100. The practical potential of biomass residues in the world will be 114 EJ/year , which is equivalent to one-third of the commercial energy consumption in the world in 1990. (3) Concerning land uses, the global mature forest area will decrease by 24% between 1990 and 2100, because of growth of both population and wood biomass demand per capita in the developing regions. The mature forest, especially, will disappear by 2100 in some developing regions, such as Centrally Planned Asia, Middle East and North Africa, and South Asia.

The relationships of population and forest trends

The relationship between national trends in forest area and population is reviewed at the global scale. Evidence of an inverse relationship is confirmed. The relationship, however, may have weakened in recent decades, and it has clearly undergone a reversal in some countries during the nineteenth to twentieth centuries. The theme of a changing relationship through time is thus developed, as is that of an asymmetrical relationship in the sense that the forest area is likely to stabilize before population. On the basis of modelling from the current demographic relationship, the global forest area should stabilize before the middle of the twenty‐first century.

Global tropical forest area measurements derived from coarse resolution satellite imagery: a comparison with other approaches

Definition of appropriate tropical forest policies must be supported by better information about forest distribution. New information technologies make possible the development of advanced systems which can accurately report on tropical forest area issues. The European Commission TREES (Tropical Ecosystem Environment observation by Satellite) project has produced a consistent map of the humid tropical forest cover based on 1 km resolution satellite data. This base-line reference information can be further calibrated using a sample of high-resolution data, in order to produce accurate forest area estimates. There is good general agreement with other pantropical inventories (Food & Agriculture Organization of the United Nations Forest Resources Assessment 90, World Conservation Union Conservation Atlas of Tropical Forests, National Aeronautics & Space Administration [USA] Landsat Pathfinder) using different approaches (compilation of existing data, statistical sampling, exhaustive survey with satellite data). However, for some countries, large differences appear among the assessments. Discrepancies arising from this comparison are here analysed in terms of limitations associated with each approach and they are generally associated with differences in forest definition, data source and processing methodology. According to the different inventories, the total area of closed tropical forest is estimated at 1090–1220 million hectares with the following continental distribution: 185–215 million hectares in Africa, 235–275 million hectares in Asia, and 670–730 million hectares in Latin America. A proposal for improving the current state of forest statistics by combining the contribution of the various methods under review is made.