Convention on biological diversity

Restoration of functioning of forest biological diversity in degraded forests or deforested lands

Watershed rehabilitation

Restoration and expansion of woodlands for biodiversity and other goods and services

Both in Europe and in North America (and in the southern hemisphere) the forest area in many countries has increased considerably during the last 150 years through planting and by natural colonisation of abandoned farmland and industrial/mining areas. The current ecological value of these new woodlands from this period depends on their history (afforestation of agricultural land, heathland and eroded areas), management and actual forest functions. Where development to more natural woodlands is accepted or promoted (and especially in countries with low forest cover) they can contribute to a valuable increase in biodiversity.

Afforestation of agriculture lands with new ‘natural’ woodlands is becoming more popular, for example in the UK and the Netherlands. There is a programme of ‘new native woodlands’ where the aim is to develop woodland ecosystems that approach the original natural ones in their composition and functions and characteristic biodiversity, within the constraints imposed by losses of key species in former centuries and the irreversible naturalisation of some alien species. It is still unclear how long it will take for these woodlands to approach the biodiversity of surviving remnant natural forest. In the United Kingdom, it may take 200 years or more in some lowland arable landscapes, but 100 years or less in some upland pastoral landscapes, to allow slow colonists to cross hostile habitats. However many common species arrive much more quickly, perhaps within 50 years (Peterken and Game, 1984; Rodwell and Patterson, 1994). Much depends on the degree of linkage to existing old woodlands.

Planted forests established on agricultural lands, even those composed of exotic species, can eventually acquire significant biodiversity value, in combination with timber and other objectives (Cannell, 1999). Their potential contribution as part of landscape and regional scale strategies for conserving FBD should be given more attention in the future, as it is likely to be necessary for planted forests to continue to expand to relieve the pressure on natural forests for timber and fuelwood. They may help to buffer core natural forests against fragmentation effects and also help sustain larger populations of many of the more adaptable species .

Plantations and areas of natural regrowth have increased recently in some tropical areas, as well as in temperate regions. In Cuba, for example, forest area has increased from 14% to 21.1%, between 1959 and 2000, due to forest plantations and also to recovering natural forests [Modesto Fernandez Diaz-Silveira, pers. comm.].

6. Assessing Status and Trends of forest ecosystem functioning

For natural forest regions being opened up for the first time a simple and practical means of assessing forest ecosystem functioning could be found through the monitoring of macro-indicators, such as density of forest roads and socio-economic surveys. This information could be easily collected and analysed. The density of the forest road network could give a good indication of the fragmentation of the forest ecosystem, its “penetrability” and how intensively the forest is managed and which natural resources are used. Socio-economic surveys, on a local or regional basis, can give accurate information on the goods and services provided by the forest resources and their associated effect on the economy and on the benefits to the society. The correlation between these two indicators could provide a general idea on status and trends of the quality of the ecosystem functioning and its capacity to provide goods and services to the society.

7. Conclusions concerning ecosystem functioning and human impacts

The boreal forest biome is characterised by relative low species richness, and by extreme contrasts in the functional attributes of important species for the ecosystem processes (Pastor et al., 1996). Therefore, the loss of a few species can have significant impact on the ecosystem. Human activities such as logging and those that cause climate change may have a dramatic impact on the overall ecosystem functioning, which can, in turn, affect the delivery of good and services. Boreal forests represent 49% of the total vegetation and soil carbon contained in the three biomes and, for this reason, they play a key role in global climate regulation.

The effects of biodiversity on temperate forest ecosystem functions are indirect and interact through the chemical composition of foliage (C/N ratio), which affects decomposition (Schulze et al., 1996). Biodiversity in temperate forest is determined to a major extent by the base saturation of the soil with the highest diversity being reached at high base saturation and high nitrogen availability. However, human-induced changes, such as land conversion, fragmentation and air pollution, are major factors in decreasing the diversity in deciduous forests and affecting their associated ecosystem functions (Schulze et al., 1996). Climate change is likely to interact with these to cause further changes. Temperate forest in some regions has been exploited and managed for many centuries as part of cultural landscapes, and some form of continued management will be required for most areas to maintain a desirable range of ecosystem goods and services including characteristic biodiversity. Reducing fragmentation is vital in this biome, to buffer forests against impacts and insufficient or insensitive management

As explained in paragraph , overall the temperate biome is an important terrestrial net carbon sink. It is however unclear how long this situation will last as a saturation effect is expected (UNEP, 2000).

The main characteristic of tropical forest ecosystems is their biological richness and, unlike in boreal forest ecosystems, the number of species greatly exceeds the number of key ecological processes. This situation gives these ecosystems an apparent stability and probable resistance to invasive species. Tropical forests are also characterised by the very slow pace of their evolution, which is one of the reasons why it is difficulty to study and understand the ecological processes occurring within them. Thus, the consequences of the removal of a species by human activities may not be immediately observed. In addition to containing an important proportion of the world biodiversity, tropical forests also hold more than 37 % of the world’s terrestrial carbon. However, because of deforestation and land use change, tropical forests represent a net source of carbon dioxide in the atmosphere.

Critical levels of biodiversity loss/change which can affect forest ecosystem functioning and, in turn, the goods and services provided by forests, are still hard to discern, and this needs to be a focus for future work. Keystone species or structures and functional groups need to be identified and validated in order to develop reliable indicators. While it is likely that some degree of biodiversity loss in some situations will have little or no long term effect on other goods and services, as long as the forest remains relatively intact, the linkages between biodiversity and ecosystem functions and the critical thresholds of impacts on biodiversity loss must be understood. This reinforces the value of following the precautionary principle when there is a reasonable doubt about the impacts of human activities on a forest ecosystem.

*Non-timber forest products (includes wild animals, fish, birds, honey, nuts, gums, fruits, flowers, spices, plants for local medicine use, fodder for animal, berries, mushrooms, etc.).

3. 
   The Value of Forest Ecosystems