3. Results

The collection and analysis of the available information, not only allowed the compilation of country briefs, whose importance and structure have been already discussed, but also allowed to analyze data at regional and global level (Table 2).

Region	Forest Area	Volume		Biomass
	000ha	m3/ha	Mm3	t/ha	Mt
Africa	649,886	100	65,269	163	106,194
Asia	547,793	106	58,065	170	92,997
Oceania	197,623	66	13,120	84	16,595
Europe	1,039,251	112	116,449	59	61,055
North and Central America	549,304	121	66,414	104	56,988
South America	885,618	151	133,741	228	202,285
World	3,869,475	117	453,058	139	536,115

Table 2: Forest volume and aboveground biomass by region.

3.1. Wood volume 2000

The reviewed global volume of the growing stock was estimated at 453 billion cubic meters for 2000. The regions with the largest volume were South America with 29% (134 billion cubic meters) followed by Europe with 26% (116 billion cubic meters). The highest volumes per hectare were found in South America (with an average volume of 151m3/ha) and North and Central America (121m3/ha). The region with the lowest total volume and average volume per hectare is Oceania with 13 billion cubic meters and 66 m3/ha respectively.

Figure 2: Distribution of total volume among regions.

3.2. Woody biomass 2000

At the year 2000, the global estimates for the above-ground woody biomass were 536 billion tons: the regions with the largest quantity of biomass were South America with 38% of the world total (202 billion tons) and Africa with 20% of the world total (106 billion tons). The highest mean biomass per hectare was found in South America with an average of 228 t/ha and Asia with 170 t/ha. Europe showed the lowest mean biomass per hectare.

Figure 3: Distribution of woody biomass among regions.

3.3. Changes 1990-2000 and discussions

Volume and biomass changes due to forest area changes occurred in the period 1990-2000, were estimated for each country separately by country by multiplying the net forest area change 1990-2000 with the average standing volume and average above ground biomass per hectare. These changes provide a simplified picture of the real situation since gained forest area will only over a longer period result into well-stocked forests while on the other hand, the conversion of forests to other land uses may result in a degraded wooded land with lower levels of biomass and volume but not necessarily in a treeless landscape.

As showed in Table3 the total changes of volume between the period 1990-2000 was estimated equal to-11 billion cubic meters. The losses of woody biomass was estimated at -18 billion tons.

Losses mainly occurred in the tropics, whereas in Europe there is an increase of 983 million cubic meters of growing stock and 516 million tons of woody biomass. It is interesting to notice that volume increase in the European countries is larger than the corresponding in woody biomass increase, while for the rest of the tropical countries biomass changes are larger than volume changes. This is due to the fact that the tropical forests contain considerably more biomass in relation to stem volume than the temperate and boreal forests. A change in forest area affects much more biomass than volume in tropical countries and much more volume than biomass in temperate and boreal zones.

Forest volume and biomass stocks also changes within the forests as a balance of increment, natural losses and felling. Unfortunately data on increment, losses and felling were available only for industrialized countries, while no information is available for the developing countries.

Table 3: Changes in volume and aboveground woody biomass in the period 1990-2000.

3.4. Carbon sequestration

Forest statistics provide a useful tool to estimate the carbon stores of the forest ecosystems. In order to obtain the carbon store starting from the woody biomass, it was assumed that 50% of it is carbon and consequently the biomass data was multiplied by 0.5. This conversion could be considered valid, because the carbon concentration of biomass varies only slightly between different trees and tree parts.

Carbon balance is the rate of changing of a carbon store. Increasing biomass implies a net flux of carbon from the atmosphere to the forest and thereby a sink of atmospheric carbon, while a biomass decrease implies a net flux from the forest to the atmosphere and thus a source of carbon.

Carbon balance (amount of carbon released or sequestrated) could be calculated multiplying the changes in woody biomass by 0.5.

Regional results of carbon store and carbon balance are shown in Table 4.

Region	Forest area	Biomass		Carbon store	Biomass change	Carbon balance
		by area	total
	000 ha	t/ha	Mt	Mt	Mt	Mt
Africa	649,886	163	106,194	53,097	-8,601	-4,301
Asia	547,793	170	92,997	46,498	-620	-310
Oceania	197,623	84	16,595	8,297	-306	-153
Europe	1,039,251	59	61,055	30,528	516	258
North and Central America	549,304	104	56,988	28,494	-591	-296
South America	885,618	228	202,285	101,143	-8,477	-4,239
Total	3,869,475	139	536,115	268,057	-18,080	-9,040

Table 4: Forest area, biomass, biomass change, carbon store and carbon balance by region.

The total amount of carbon store is 268 billion tons. It is worth to specify that this amount refers to the woody biomass as earlier defined, calculated from inventoried wood volume. This means that the provided amount of carbon store comes from a portion of the total vegetation, since it is not including stumps and roots, trees with diameter smaller than 10 cm, other wooded land and other non woody vegetation types. The total amount of carbon stored in the world vegetation was calculated by the IPCC 2001 as showed in Table 5.

Table 5: Global carbon stock in vegetation (source IPCC, 2000)