Impact of Forest Loss and Degradation on Biodiversity

Nigel Dudley

Key Points to Retain

Assessment of current forest condition is a necessary precursor to restoration.

Ecological assessments should consider issues related to biodiversity, level of naturalness, and more generally ecological integrity.

A number of assessment tools exist, for national, landscape, and site-level assessments. They include: at national scale, frontier forests; at landscape scale, forest quality assessment; and a number of site-level tools including High Conservation Value Forest assessments.

1. Background and

Explanation of the Issue

1.1. The Need for Assessment and Likely Impacts of Forest Loss

Assessment of forest condition is an important precursor to the planning and implementation of restoration programmes. Restoration is a process that in the case of forests generally aims at rebuilding the ecosystem to some earlier or more desirable stage. There is widespread recognition of the need for restoration; for example, in its Programme of Work on Protected Areas the Convention on Biological

Diversity advises governments to "rehabilitate and restore habitats and degraded ecosystems, as appropriate, as a contribution to building ecological networks, ecological corridors and/or buffer zones." Given limited time and resources, restoration must be strategic, focussing on forests that have the highest importance to biodiversity or to society, and considering the four goals of conservation biology: representation, maintenance of evolutionary/ecological processes, maintenance of species, and conservation of large habitat blocks. Reasonably fine-scale analyses are needed to choose specific sites where restoration might bring the highest benefits. From a conservation perspective, this means evaluating the impacts of forest loss, including analysis of biodiversity, authenticity, and ecological integrity.

Impacts on biodiversity: Complete forest loss has the clearest impact on biodiversity, with most forest-dwelling species unable to live in habitats that replace forests. However, it is harder to measure the impacts of changes such as fragmentation and loss of microhabitats. Management often simplifies forests, reducing biodiversity and age range; as older and dead trees disappear, so do many associated species. Conversely, pioneer or weed species may increase. Biodiversity monitoring is costly, and our knowledge of many forest ecosystems is still incomplete. One concept that has gained increasing recognition in the last few years is that of critical thresholds for particular species, that is, the population level below which further decline and eventual extirpation or extinction is likely, and where these thresholds are known they can play a key role in monitoring impacts and planning restoration strategies.

Impacts on authenticity or naturalness: On an ecosystem scale, measuring impacts on overall naturalness of forests is easier than surveying biodiversity and acts as a partial surrogate; generally the greater the naturalness of a forest, the more of its original constituent species are likely to survive. Worldwide forest authenticity is declining fast. In most West European countries less than 1 percent of forests are classified by the United Nations as "undisturbed."21 A growing proportion of forests in Africa, the Pacific, and the Amazon have been logged at least once.

Ecological integrity: This concept covers many of the above issues. It is defined by Parks Canada as "a condition that is determined to be characteristic of its natural region and likely to persist, including abiotic components and the composition and abundance of native species and biological communities, rates of change, and supporting processes."22

Evaluation of options for restoration should also consider the reasons why forest loss or degradation have occurred. Many restoration programmes fail because the pressures that caused deforestation are not addressed, and restored forests suffer the same fate as the original forests. If population or economic pressures mean that there is insufficient fuelwood, then planted trees will be burned long before they have a chance to mature and reach a useful size. On the other hand, understanding the nature of the pressures and working with local communities to plan restoration in ways that are mutually beneficial increases the chances of restoration succeeding. Assessment needs to address several different aspects:

• Impacts of forest loss and degradation on biodiversity, naturalness, and ecological integrity;

• Some of the key factors causing change;

• Changes in biodiversity, naturalness, and ecological integrity following restoration interventions.

21 UNECE and FAO, 2000.

22 Parks Canada, undated.

Whilst the first two can be assessed through single surveys, assessment of trends implies the need for a monitoring system.

2. Examples

2.1. New Caledonia

In New Caledonia the overall loss of forests creates a critical threat to biodiversity and ecological integrity. Today only 2 percent of the dry forest remains in the island, in scattered fragments of 300 hectares or less, leading to extreme threats to the remaining biodiversity. Over half of the 117 dry forest plant species assessed by the IUCN Species Survival Commission are threatened, and it is likely that several have already gone extinct. For example, the tree Pittosporum tanianum was discovered in 1988 on Leprédour Island in an area that has been devastated by introduced rabbits and deer, declared extinct in 1994, and rediscovered in 2002. This level of damage suggests an urgent need for both restoration of forest cover and a carefully designed series of interventions to protect and allow the spread of species that may already be at critically low levels.23

2.2. Western Europe

Changes in management and human disturbance have reduced near-natural forests to less than 1 percent of their original area in most western European countries, despite an expanding forest estate. In Europe as a whole, almost nine million hectares are defined as "undisturbed by man," but most of this exists in the Russian Federation and Scandinavia; Sweden records 16 percent of its forest as natural, Finland 5 percent, and Norway 2 percent. In most of Europe the proportion is usually from zero to less than 1 percent; for instance, Switzerland records 0.6 percent.24 Even in forest-rich countries like Finland and Sweden, many forestd-welling species are threatened because the forests contain only a proportion of the

23 Vallauri and Géraux, 2004.

24 UNECE and FAO, 2000.

expected habitats and ecosystem functions. Here the challenge is less to recover forest area (although this may sometimes be important) than to restore natural ecosystem processes and microhabitats. Specific monitoring criteria are needed and these have started to be developed, for instance by the Ministerial Conference on the Protection of Forests in Europe.25

2.3. Brazilian Atlantic Forests

In the Atlantic forest of Brazil, forest loss and fragmentation are combining to threaten endemic species. Although international attention tends to focus on threats to the Amazon, the Atlantic forests of Brazil have undergone far more dramatic losses. The forests have already been reduced to just 7 percent of their original size, and the associated threats to biodiversity are increased because the remaining areas are fragmented and the populations are genetically isolated. The area is home to many endemic species, including some of the 19 resident primates and 92 percent of amphibian species found there. Attention has focussed particularly on the golden lion tamarins (Leontop-ithecus rosalia), which now inhabit less than 2 percent of their original range. Their population is currently around 1000, up from little more than 200 twenty years ago following a major conservation effort. However, population is still believed to be below long-term viability, and subpopulations are isolated in remaining forest fragments. Restoration efforts, therefore, focus particularly in reconnecting the remaining forest fragments of high biological importance.

2.4. Uganda

In Uganda loss of connectivity is separating populations of mountain gorillas even in areas with relatively high forest cover. The world's remaining mountain gorillas (Gorilla beringei beringei) live in isolated rain forests in the mountains on the borders of Uganda, Rwanda, and the Democratic Republic of Congo, with half of the world's known population, 350 indi

25 Ministerial Conference on the Protection of Forests in Europe, 2002.

viduals, in Bwindi Impenetrable Forest Reserve in Uganda. Another major population is in the Virunga volcanoes area, some of which is in Mgahinga National Park. Neither of these populations is considered large enough to be genetically secure over time, but both reserves are also thought to be reaching their natural carrying capacity. Linking the two populations is important for their long-term survival, but the intervening land has all been converted to agriculture, and any restoration efforts will need a long period of planning and negotiation (information from park staff in Bwindi).

Understanding of what has been lost, and what is at risk of being lost, should be the basis for any forest restoration that has biodiversity conservation amongst its aims. This needs to be augmented with an understanding of what type or quality of forest is needed to maintain biodiversity. If the key issue is connectivity for large mammals and birds, for example, managed secondary forests or even plantations or shade-grown coffee may be suitable. If the threats are more generally to forest biodiversity, restoration efforts should probably be aimed at creating a forest as near to natural as possible.

3. Outline of Tools

Detailed biodiversity surveys are expensive and rely on a high level of expertise. Methodologies for achieving these have become increasingly sophisticated, and a number of short cuts have been developed where time and money are limited.

3.1. National Level Surveys

National level surveys can help identify the scale of the problems and the locations of valuable remaining forest habitat, which should usually serve as the starting point for restoration efforts. The U.N. Economic Commission for Europe and the Food and Agriculture Organisation asked countries to report on the proportion of their forest that was "undisturbed by man," taken here to mean left without management interventions for at least 200 years. This has created a fairly crude but effective international database for many of the temperate countries, but as yet no similar exercise has been attempted in the tropics. It also does not create a very useful way of measuring progress in restoration. Some individual countries (e.g., Austria, France, and the U.K.) have also carried out detailed surveys of ancient forest.

3.2. High Conservation Value Forests (HCVF)

This is a WWF/ProForest methodology for identifying the forests of the highest conservation and social value in a landscape, drawing on six different types of HCVF: (1) forest areas containing globally, regionally, or nationally significant concentrations of biodiversity values (e.g., endemism, endangered species, refugia); (2) forest areas containing globally, regionally, or nationally significant large landscape level forests, where viable populations of most if not all naturally occurring species exist in natural patterns of distribution and abundance; (3) forest areas that are in or contain rare, threatened, or endangered ecosystems; (4) forest areas that provide basic services of nature in critical situations; (5) forest areas fundamental to meeting basic needs of local communities; and (6) forest areas critical to local communities' traditional cultural identity.26 Although designed initially for site-level assessments, a landscape-scale methodology is being developed.

3.3. Forest Quality Assessment

WWF and IUCN have developed an approach to landscape assessment of forest quality using indicators to map social and ecological values, including identifying different elements of naturalness or authenticity, drawing on the following: composition, pattern, ecological functioning, process, resilience, and area (also see "Restoring Quality in Existing Native Forest Landscapes"). Assessment is based on a seven-stage process: identification of aims, selection of the landscape, selection of a toolkit (relevant indicators), collection of information about each indicator, assessment, presentation

26 Jennings et al,2003.

of results, and incorporation into management. Information is collected through primary research, literature review, and interviews. The extent to which assessment is a participatory process can change depending on the situation and aims.27

3.4. Frontier Forest Analysis

Frontier forest analysis is a World Resources Institute/Global Forest Watch approach28 that defines frontier forests as free from substantial anthropogenic fragmentation (settlements, roads, clearcuts, pipelines, power lines, mines, etc.); free from detectable human influence for periods that are long enough to ensure that it is formed by naturally occurring ecological processes (including fires, wind, and pest species); large enough to be resilient to edge effects and to survive most natural disturbance events; containing only naturally seeded indigenous plant species; and supporting viable populations of most native species associated with the ecosystem.29 It is mainly used at a national scale.

3.5. Site-Scale Survey Methods

A wide range of survey methods exist including some that have specifically been developed to facilitate rapid surveys for conservation practitioners, amongst these are the Rapid Ecological Assessment methodology developed by The Nature Conservancy.30 Increasingly surveys by outside experts are being augmented by interviews and collaboration with local communities, which often have great understanding of population levels of key plants and animals; these sources are usually referred to as traditional ecological knowledge.

4. Future Needs

Despite expertise in survey methods, there is still much to be learned about accurate ways

27 Dudley et al, in press.

28 Bryant et al, 1997.

29 Smith et al, 2000.

30 Sayre et al, 2002.

of monitoring of both biodiversity and, more critically, ecological integrity that would allow proper assessment of restoration outcomes over time and thus help set realistic goals for restoration. In general, quick and cost-effective methods of monitoring the impacts of restoration on biodiversity and ecology are still required in many ecosystems.


Bryant,D., Nielsen, D.,and Tangley,L. 1997.The Last Frontier Forests: Ecosystems and Economies on the Edge. World Resources Institute, Washington, DC.

Dudley, N., Schlaepfer, R., Jackson, W., and Jeanrenaud, J. P. In press. A Manual on Forest Quality.

ECE and FAO. 2000. Forest Resources of Europe, CIS, North America, Australia, Japan and New Zealand. U.N. Regional Economic Commissions for Europe and the Food and Agriculture Organisation, Geneva and Rome.

Jennings, S., Nussbaum, R., Judd, N., et al. 2003. The High Conservation Value Toolkit. Proforest, Oxford (three-part document).

Ministerial Conference on the Protection of Forests in Europe. 2002. Improved Pan-European Indicators for Sustainable Forest Management: as adopted by the MCPFE expert level meeting, October 7-8, 2002, Vienna, Austria.

Parks Canada. Undated. np-pn/eco_integ/index_e.asp.

Sayre, R., et al. 2002. Nature in Focus: Rapid Ecological Assessment. The Nature Conservancy and the Island Press, Covelo and Washington, DC.

Smith, W., et al. 2000. Canada's Forests at a Crossroads: An Assessment in the Year 2000. Global Forest Watch, World Resources Institute, Washington, DC. See also the Global Forest Watch Web site:

Vallauri, D., and Géraux, H. 2004. Recréer des forêts tropicales sèches en Nouvelle Calédonie. WWF France, Paris.

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