What is Forest health?
Healthy forests are essential for sustainable forest management, yet forests, like other ecosystems, are subject to a number of threats that can cause tree mortality or reduce their ability to provide a full range of goods and services. The causes of the negative impacts on forest health and vitality vary from place to place, and the magnitude and duration of the impacts are not easy to assess. Causes include, but are not limited to biotic and abiotic disturbances. The complexity and interrelationship of these factors and their impact on the health and vitality of forests are difficult to unravel. Indirect impacts may be far reaching and include social, economic and environmental dimensions.
Despite a number of indicators of forest health and vitality have been developed, e.g. under the auspices of regional and international processes on criteria and indicators for sustainable forest management, there is no clear way to measure the health of a forest. This pretty much depends on the goal of the forest itself (production, conservation, multipurpose, etc.)
Defoliation is one indicator monitored in many boreal and temperate regions. It is carried out mainly in Europe, Canada and the United States, and to some extent in East Asia. An indicator of forest health that is often suitable in tropical regions is the amount of post-logging woody debris after timber extraction, because excessive amounts of woody debris leave forests in a highly fire-prone state and provide insect breeding sites.
Biotic and abiotic disturbances
Biotic disturbances are caused by biotic agents such as insects, diseases, and other pathogens such as bacteria, fungi, phytoplasma or virus. They also include all kind of disturbances by wildlife browsing, grazing, physical damage by animals, etc.
On the contrary, abiotic disturbances are disturbances caused by non-living factors, that are natural components of the ecosystems (as air pollution, snow, storm, drought, fire, etc.). When they exceed their normal range of variation, however, the impacts on forests can be extreme affecting entire landscapes, causing large-scale tree mortality and complete destruction of undergrowth and soils. Global climate change is exacerbating many of these impacts by making forests more prone to damage by altering the frequency, intensity and timing of some events such as cyclones, landslides, insect and disease outbreaks, and heat waves and droughts which increase the risk of large-scale fires.
Disturbance: Damage caused by any factor (biotic or abiotic) that adversely affects the vigour and productivity of the forest and which is not a direct result of human activities (FRA 2010, Terms & definitions).
Forest invasive species vs native
Invasive species (or alien species) are species that are non-native to a particular ecosystem and introduction and spread cause, or are likely to cause, socio-cultural, economic or environmental harm or harm to human health. Native plant species (or indigenous species) are tree species which have evolved in the same area, region or biotype where the forest stand is growing and are adapted to the specific ecological conditions predominant at the time of the establishment of the stand. They sometime can become invasive when a natural ecosystem is affected by biotic or abiotic factors and natural successions can be altered, or when the species components within a certain environment are not managed adequately. To know more about the terminology, please also check the Glossary on Phytosanitary terms.
Activities to promote/restore forest health
Activities in the FAO forest protection and health programme aim to assist, advise and support countries and national institutes to safeguard the health and vitality of forests, forest ecosystems and trees outside forests, with special reference to insect pests, diseases and other harmful biotic and abiotic agents. FAO provides advice on preventive measures and Integrated Pest Management (IPM), and on recommended action to minimize risks of transboundary transfer. FAO offers assistance to countries not only in response to pest outbreaks and emergencies but also in establishing long-term prevention and forest protection strategies.
Direct technical assistance to countries is provided predominantly through FAO's Technical Cooperation Programme (TCP), in response to requests from governments related to specific pest problems affecting forests and food security. All projects offer more than emergency assistance, helping countries also to develop pest management strategies to prevent further outbreaks in the medium and long term. The implementation of ISPMs in forestry is also part of the pest management strategies.
Knowledge products: FAO develops several knowledge products (guidelines, elearning courses, etc.) to assist countries, governments and technical people to deal with increasing threats posed by pest movement in expanded international trade, that coupled with local climatic change which may increase the potential for establishment of pests in new areas. These knowledge products can be browsed under the section Resources.
Moreover, FAO has helped establish Regional Networks dedicated to the issue of forest pests, primarily forest invasive species, and the forest sector. These networks aim to facilitate the exchange of information and the mobilization of resources, raise regional awareness, and act as a link between and among experts, institutions, networks and other stakeholders concerned with forest invasive species.
The Guide to implementation of phytosanitary standards in forestry, prepared by a mutlistakeholder process, provides clear and concise guidance on forest health practices that will help to minimize pest presence and spread.
The Guide to the Classical Biological Control of insect pests in planted and natural forests, written by a team of experts, distils that information in a clear, concise guide aimed at helping forest-health practitioners and forest managers – especially in developing countries – to implement successful classical biological control programmes.