Convention on biological diversity

II.Ecosystem functioning and services

Box 2 The ecosystem approach The implementation of the ecosystem approach to forest biological diversity, based on the description and the operational guidance endorsed by the Conference of the Parties in decision V/6, and on the principles recommended for application under the same decision, should substantially help to maintain these non-market goods and services. The ecosystem approach could be considered as a strategy for the integrated management of forests that promotes their conservation and sustainable use in an equitable way. Humans, with their cultural diversity, are an integral component of forest ecosystems. The ecosystem approach requires adaptive management to deal with the complex and dynamic nature of forest ecosystems and the absence of complete knowledge or understanding of their functioning. According to the ecosystem approach, forest ecosystems should be managed for their intrinsic values and for the tangible benefits they provide to human beings, in a fair and equitable way. Forest ecosystem managers should consider the effects – actual or potential – of their activities on forest ecosystems, to avoid unknown or unpredictable effects on their functioning and, therefore, on their values. Forest ecosystems should also be understood and managed in an economic context. In particular, costs and benefits in forest ecosystems should be internalized to the extent feasible. In addition, market distortions that adversely affect forest biological diversity should be reduced and incentives that promote forest biodiversity and sustainable should be aligned. Finally, the ecosystem approach stresses that forest ecosystems should be managed within the limits of their functioning. Therefore, the conservation of their structure and functioning should be a priority target. This is a prerequisite for keeping their full values, including the goods and services forests deliver, generally for free, to human beings.

The dependence of indigenous peoples and local communities on forest ecosystems and biological diversity (and the resulting goods and services) is greater than in the general population. Alterations and loss of ecosystems and forests therefore have a direct negative impact on the survival of indigenous peoples and cultures. Another problem occurs in areas where there is a change in land use of previously forested areas, often triggered by the induced dependence upon non-traditional goods and adaptation to a monetary economy, instead of traditional subsistence methods. In most instances, these changes are accompanied by equal opportunities for sustainable development for indigenous peoples.

Each of the three main forest biomes (boreal, temperate, tropical) has characteristic ecological functions, and human impacts may thus have different consequences, both currently and in a historical sense.

The boreal forest biome is characterized by low species richness and by extreme contrasts in the functional attributes of important species for ecosystem processes. So the loss of a key species may have significant impacts on an ecosystem. Large-scale human activities, such as extensive logging and those that cause global climate change, may have a dramatic impact on overall ecosystem functioning and forest goods and services. Boreal forests represent 49 per cent of the total vegetation and soil carbon contained in the three biomes, and so play a key role in global climate regulation.

Biological diversity in temperate forests is determined primarily by human-induced changes in land use and forestry practices, as well as by the site quality. Greatest diversity is reached in undisturbed, natural forests and on sites with highest fertility. Human-induced land conversion, fragmentation and air pollution can cause loss of biological diversity and ecosystem function, and climate change is likely to interact with these factors to cause further unpredictable changes. Many temperate forests, especially in Europe, have been fragmented, exploited and managed for many centuries as part of cultural landscapes, and some form of continued management will be required to maintain characteristic biological diversity and a desirable range of ecosystem goods and services. Some forest types and habitats have been particularly heavily destroyed or degraded (e.g. riparian forests). Only a very small amount of primary temperate forests remains and old growth characteristics and structures, such as dead wood, are usually under-represented in the majority of secondary and plantation forests. Overall, the temperate biome is currently an important terrestrial net carbon sink.

The main characteristics of tropical forest ecosystems are their high biological richness and high endemism and, unlike boreal forest ecosystems, the number of species greatly exceeds the number of key ecological processes. This situation gives the ecosystem an apparent stability. Tropical forests are also characterized by the very slow pace of their development, which presents a difficulty in studying their ecological processes. The consequences of species loss through human activity may be delayed and even possibly offset by redundancies in functional relationships. Tropical forest soils are vulnerable to rapid degradation and erosion after logging/forest clearing, because almost all organic matter is maintained in the vegetation. Unsustainable use in tropical forests results in the loss of key animal species, which act as vectors for reproduction and dispersal of forest trees, and loss of key structural attributes such as lianas and epiphytes, which could have long-lasting effects on biological diversity and its related goods and services. But there is also some evidence that secondary tropical forests can be carefully managed to sustain traditional products as well as some of the biological diversity and other environmental services found in primary forest. Tropical forests hold 37 per cent of forest carbon but, because of deforestation and land use changes, the tropical forest biome is currently a net source of carbon dioxide to the atmosphere.

Restoration of forest biological diversity in degraded forests and deforested lands is an issue of growing importance in both the developed countries and the developing world. Most studies of forest biological diversity have focused on natural forests. However, in the future there is a need to focus more on the potential, on the regional and landscape scales, for synergy from combining management of different forests, including primary, secondary, agro-forests and forest plantations, to achieve a specified range of goods and services. Where plantation forests are created on former agricultural lands, rather than as a direct replacement for natural forest, it has the potential to restore at least some of lost forest biological diversity and other goods and services, especially where native species of local origin are used. Plantations can also help reduce the pressure on natural forests for exploitation for fuel wood and timber. The rate of restoration of forest biological diversity in different situations is poorly understood and research should be increased in this area. Although considerable diversity may develop in a few decades, full restoration to levels of forest biological diversity approaching those found in primary forests may take centuries.