This section presents the results at the global level on the current status of forest cover and its rate of change, growing stock, forest management and conservation. Environmental implications of forest cover change, in relation to land degradation, global climate change and biodiversity loss, are dealt with briefly.
The definition of forest used in the present assessment is rather broad and includes lands with a minimum crown cover of 20% in the developed countries and 10% in the developing ones.
The assessment shows that forests (see Table 3) constitute 3 442 million-ha or 27% of the land area. Forest area on a per caput basis amounts to 0.6 ha. The distribution of forest area and population by region is given in Figure 3.
The forest area, as percent of land area, in the developed and developing countries is 27% and 26%, respectively. In terms of per caput, however, the distribution is very uneven: 1.1 ha, in the developed and 0.5 in developing countries.
Forest and other wooded land, (the latter includes other formations of woody vegetation such as open woodland, scrub and brushland, forests under shifting cultivation, etc.), covers 5 120 million ha or one and a half times as much as the total area of forests alone.
In the developed countries, (excluding former USSR), there is an annual increase, mainly in Europe, by 0.19 million ha of forest and other wooded land and a decrease, mainly in North America, by 0.32 million ha. For the Developed Regions as whole there is an annual decrease by 0.08 million ha of forest and other wooded land.
In the developing countries (see Annex 1: Table 4) there is an annual increase through forest plantations by 4.1 million ha, and a decrease of forest area by 16.3 million ha through deforestation, of which 15.4 million ha in the tropics. This gives a net decrease of forest area of 12.2 million ha. However, 2.0 million ha of deforested area goes to other wooded lands specially shifting cultivation, thus the net change in the forest and other wooded land class is only 10.2 million ha. Thus, the net decreases, of forest and other wooded lands including developed and developing countries, is estimated annually by 10.3 million ha.
The above shows that a detailed account of area changes is necessary in order to understand fully the environmental implication of forest changes.
The Forest Resources Assessment 1990 Project conducted a special study of the long-term forest area changes in the tropics during 1960 - 1990 using all available reliable data relating to forest cover at sub-national level (145 multi-date and 499 single date surveys). The loss of forest cover during the period 1960-1990 was estimated approximately at 450 million ha. This equals the total forest area of the North America region estimated in 1990. Future trend, as in the past, is expected to be determined mostly by changes in the developing countries. Demographic changes will, probably, be the most important determining factor in accounting for change, followed by other factors such as economic growth, and government policy.
During 1960-1990 the population in the developing countries roughly doubled in number, from 2 to 4 billion (see Table 4). It is projected by the UN that in 2020 the population will reach a level of 7 billions, viz. an increase of 3 billions in a 30 year period.
To the people and governments of these countries, food and shelter will be their first concerns followed by fuel and fodder. The adverse effects on forests of this unprecedented population growth are not difficult to conceive.
A FAO study on future need of agricultural land (1982) provides the important statistics (see Table 5) relating to agricultural land use in the developed and developing countries.
In the developed countries, it is most likely that no new land will be needed for agriculture during 1990-2020. The additional population, in any case, will be rather small. Owing to improved inputs and technology, the per caput need for agricultural land may in fact decline further as the past trend suggests.
The scenario is quite different for the developing countries. The pressure on agricultural land is expected to increase significantly by the year 2020 as compared to 1990. The scarcity of capital for intensive agriculture, as well as the availability of new cultivable land will be the main limiting factors.
The extension of cultivated area in the developing countries, to be sustainable, will require fresh capital. Generally, the more marginal the land, the higher the level of inputs required. Due to the scarcity of capital, the level of inputs in agriculture tends generally to be low. Adequate soil conservation measures are not usually applied. It is estimated that the developing countries are losing annually about 1% of their prime agricultural land (personal communication by FAO, Agriculture Department). The lack of capital leads to a lack of proper soil conservation measures which, in turn, leads to land degradation. This consequently increases the per caput need for agriculture: a vicious circle.
In conclusion, the risk of deforestation in the developing countries is very high. Unless serious efforts are made to meet the basic needs of the population with minimum damage to environment, the consequence will be a spiraling rise in deforestation and forest degradation.
The growing stock of global forests is estimated at 384 billion m3 overbark corresponding to an average of 114 m3/ha which is almost the same in the developing as in the developed countries (see Table 6). The distribution of total volume is also in the same proportion as the forest area, about 58:42. In terms of biomass, the ratio between developing and developed countries is 75:25. This is mainly attributed to the higher density of wood and higher percentage of branch wood in the tropical forests. The distribution of volume per caput, as expected, is very uneven (see Figure 4), ranging from 244 m3/inh in Latin America and the Caribbean to 19 m3/inh in the Asia and Pacific Region.
The growing stock/ha in the last 30 years has steadily increased in almost all of the developed countries. In North America, Europe, Japan, Australia and New Zealand the net annual increment has been higher than fellings even though such countries reported an increasing trend in annual fellings as well.
In the developing countries, two groups of processes namely deforestation and forest degradation, are re-enforcing and contributing towards a decrease in the total growing stock. In addition to the net loss of forest area and associated stock, there has also been a reduction in the volume per hectare of the remaining forest, where removals exceed growth: a vicious circle again.
The possibility of global climate change, due to increases in the level of carbon dioxide and other greenhouse gases in the Earth's atmosphere which are largely the result of human activities, is one of today's key environmental concerns. The rate of exchange of carbon between the earth's surface, the oceans and the atmosphere, known as the carbon cycle, is the primary driving force with regard to possible climate change. Through the process of photosynthesis, green plants absorb carbon dioxide from the atmosphere. Trees and forests store the absorbed carbon in woody biomass. Approximately 50% of dry woody biomass is carbon. Therefore, changes in land cover, which result in changes in the woody biomass, will have direct effects on the rate of carbon released into the Earth's atmosphere.
Dixon et al (1994) have made use of the FAO tropical deforestation data base and related information to produce new estimates of the amount of carbon stored in forests and the net influence of forests in the present day global carbon cycle. Their conclusion is that the world's forests are presently a net source of atmospheric Carbon Forests in the high and mid latitudes presently store 0.74 ± 0.1 petagrams (Pg = 1015g) of carbon per year. The forests of the low latitudes (largely tropical forests), on the other hand, presently contribute approximately 1.65 ± 0.4 Pg carbon to the earth's atmosphere. This results in a net annual contribution of 0.9 ± 0.4 Pg carbon from forests, largely due to deforestation associated with land use change in the tropics. This is equivalent to about 16% of the carbon emissions from burning fossil fuels by e.g., industry and transport sectors, currently estimated to be about 5.5 Pg/year.
Forest sector contributions to atmospheric carbon dioxide can be reduced through a number of measures including slowing the rate of deforestation, increasing forest productivity through intensified management and protection, and establishment of forest plantations. For maximum effectiveness, these actions must be part of an integrated programme designed to reduce emissions of greenhouse gases from all sectors.
It is important to note that estimates of carbon used by scientists concerned with climate change include not only that of the above ground biomass of stems and branches but also carbon stored in roots, non-tree vegetation, soil organic matter, coarse woody debris and fine litter.
Reliable estimates of global biomass plays an important role in providing a better understanding of the impact of deforestation and land use change on the environment. For this purpose, an indication of data reliability is a must in order to distinguish the real changes from spurious changes arising from errors in reported data.
The term “forest management” is used here in a wider sense, to include both the production and conservation functions of forests.
Since the World Forest Inventory in 1963, there has been an all-round improvement in forest management in developed countries. This is evident from the rise in growing stock per ha and the increase of net annual increment despite the higher level of removals per ha mentioned earlier. On the other hand, the total area under active management has declined in developing regions. FAO then reported a managed forest area of 89 million ha. According to the present assessment, the area of tropical forests managed in some form or another is estimated to be 60 million ha. Though working plans exist for these forests, prescriptions are not generally being implemented due to lack of funds and forests are undergoing a slow process of degradation, owing to the lack of silvicultural treatment, heavy grazing and over-exploitation for timber or for fuelwood by the local population (FAO 1993).
The above development is understandable because in many countries land use practices have not yet stabilized. Due to economic problems, which constitute the most important reason, adequate funds to support forest management, which is a long-term undertaking, are not forthcoming. Joint forest management, involving the local community in forest planning, is gaining momentum in several countries of the tropics. It should result in an increase of the forest area under sustainable management in developing countries.
The total roundwood consumption on a global basis increased from 1900 million m3 in 1961 to 3 429 million m3 in 1991, as shown in Table 7. Fuelwood and charcoal was the dominant form of wood use in the developing countries (about 80%), whereas it constituted only 16% of the total roundwood consumption in the developed countries. The pattern of wood consumption did not change significantly in either the developing or developed countries during the last 30 years.
The FAO projections indicate a rising trend on a global basis, in the consumption of industrial Roundwood from 1 599 million m3 in 1990 to 2 674 million m3 in 2010, and in the consumption of fuelwood/charcoal from 1 830 million m3 to 2 395 million m3 in the same period.
The areas currently protected, based on assessments by the World Conservation Monitoring Centre (WCMC 1993), are given in Table 8. According to WCMC, it is often difficult to know from the available data whether or not a conservation area network is operating effectively, particularly in terms of biodiversity, and its extent of forest cover. Conservation areas have frequently been established with little or no regard for the ecological criteria in their selection. Continuing and growing pressure on land throughout the tropics, particularly in densely populated Asian nations, has forced the selection of conservation areas to be made on pragmatic rather than scientific grounds.
The biological diversity needs to be evaluated and conserved at the ecosystem, species and gene levels. The “forest principles”, formulated refer to “management, conservation and sustainable development of all types of forests” of the world. To implement these principles, and, in particular to conserve the main ecosystems of the world effectively, it is essential that a worldwide zoning of forest types and mapping out of the remaining vegetation is accomplished to constitute an informed basis for further action on conservation. The classification and mapping need to have worldwide coverage, to accurately identify unique types of vegetation cover on a sub-regional/regional basis, and to locate natural forests of which only limited areas remain intact, the rest having been drastically altered or modified by man. It would also be desirable to extend the coverage to other wooded lands (and not only forests). Furthermore, distinction will be necessary between natural and man-made or drastically altered natural vegetation types as these two types of vegetation have different genetic histories.
The species richness (i.e. the total number of species in a geographic area), based on data compiled by WCMC (1992), is given by region and sub-region in Table 9. These statistics show a significant level of species richness in the developed as well as in developing countries.
The conservation of biodiversity is a need shared equally by both developed and developing countries. Demographic pressure and the growing demand for farmland and settlements, for timber and fuel, mining, and transportation networks had similar effects on forests in former times on what today constitute developed regions , precisely the case at present in the developing world. Major changes in vegetation took place in the Mediterranean basin more than 2 000 years ago, in Europe in the Early and Middle Ages, and in North America in the 17-19th centuries. Owing to these large-scale land-use transformations, conservation of the remaining natural vegetation and its rehabilitation within a global framework presents a challenging task.
A model study on the risk of biodiversity loss associated with deforestation in tropical forests was conducted as part of the Forest Resources Assessment 1990 Project. Use was made of geo-referenced information, including eco-floristic zone and natural vegetation maps and demographic data over time at the sub-national level (see Figure 5).
Species richness was computed by ecological zone. The risk of species richness loss associated with deforestation was then estimated. As could be expected, the tropical Asian region was identified as the most threatened (FAO 1993). This can be expected because the region has a limited remaining area of natural forests, which are prone to further deforestation under relatively high population pressure. Clearly, there is an urgent need to extend such studies on a global basis in order to provide the basis for undertaking timely and effective conservation measures. The selection of conservation areas must be carried out on the basis of current settlement patterns and future demographic evolution, and how these factors relate to the size of the forest area to be conserved and managed under the multiple-use concept.