7. What are the protective effects of forests?
- 7.1 How much of the forest area has been set aside for protective purposes?
- 7.2 How much forest is planted for protective purposes?
The source document for this Digest states:
Early assessments of forest resources were focused on the productive functions of forests, particularly wood supply, as this was the main issue identified by policy-makers. In response to increased awareness in many countries of the important role of forests in providing environmental services including protection вЂ“ and consistent with the overall concept of sustainable forest management вЂ“ FRA 2005 also evaluates trends in those forest resources with a protective function.
Each succeeding FRA has given more attention to environmental services. While demand for wood has remained static or increased only slightly and demand for nonwood forest products (NWFPs) has increased steadily but slowly, the demand for environmental services of forests вЂ“ largely unmonetized вЂ“ has burgeoned (Leslie, 2005). Many of these services have to do with the protective role of forests.
The worldвЂ™s forests have many protective functions, some local and some global.
Influence on climate. Forests affect climate globally by reflecting less heat back into the atmosphere than other types of land use that have more bare soil and less green cover. They also play a very significant role in the global carbon cycle that affects global climate change (see Chapter 2). Locally, in both cities and rural areas, trees provide shade and absorb heat energy, producing a cooling effect. During the cold season, they obstruct, filter and deflect wind, reducing wind chill. Windbreaks of trees can reduce evaporative losses from small water bodies. These functions of reducing wind velocity, moderating soil temperature and increasing relative humidity are also beneficial in agroforestry systems (Vergara and Briones, 1987).
Protection from wind erosion. Wind-rows and shelterbelts reduce the loss of nutrient-rich topsoil and protect young plants from wind within their zone of influence. They also help stabilize dunes.
Coastal protection. Coastal forests, particularly mangroves, reduce shoreline erosion and siltation and the impacts of storm surges and tsunamis. Mangroves also filter and remove some of the nutrients and heavy metals coming from upstream land uses and industry, immobilizing them in the mud вЂ“ as long as they prove non-toxic to the mangroves themselves (Wharton et al., 1976). Salt-spray barriers of salt-tolerant trees have been planted along windward coasts to protect crops.
Protection from avalanches. The Alpine countries in Europe have had much experience with protection from snow avalanches by forests and have many forests designated for this purpose. As more tourism and infrastructure enter the mountain areas of other countries, this function of forests should be increasingly recognized.
Air-pollution filters. Trees perform a valuable role in intercepting and trapping windborne particulate matter вЂ“ again, as long as the pollution does not damage or kill them. This is one of the benefits of urban forests and greenbelts. Dust, ash, pollen and smoke that adversely affect human health and visibility can be вЂrakedвЂ™ from the atmosphere, then washed to the ground by rainfall or snow.
Protecting water resources. Forests protect water by reducing surface erosion and sedimentation, filtering water pollutants, regulating water yield and flow, moderating floods, enhancing precipitation (e.g. вЂcloud forestsвЂ™) and mitigating salinity. Additional information on forests and water is presented in a separate thematic study (Box 6.1).
Many countries have identified forest areas that serve a protective function and have given them special status, e.g. avalanche protection, watershed reserve, natural catchment area or multiple-use management area. Maintenance of these environmental services, including protective functions, looms large among the management objectives of the IUCN Category System for Protected Areas (1994). This is the system of nomenclature most widely accepted and adopted throughout the world (Table 6.1), and efforts are underway to determine how it can be appropriately applied to the protective functions of the forest estate.
Forests in all categories, whether they be in national parks or marine/coastal reserves, perform some of the protective functions discussed above. For example, a watershed reserve might fall within Category I (Strict Protection) or Category VI (Managed Resource Protection Area). Yet not all protected areas have protection of soil and water as their main objective. Many are primarily established for the conservation of biological diversity or natural/cultural features. Conversely, some forests that have protection as their primary management objective may not form part of a protected area network, e.g. plantations established to combat desertification. The area of forest in protected areas is thus not necessarily a good measure of the protective functions of forests.
Data for two variables in FRA 2005 provide some indication of the role of protective forests and are reviewed in this chapter:
- area of forest designated for protective purposes (as the primary function or as one of several functions);
- area of protective forest plantations.
Limited quantitative information for these variables is available ( Figure 6.1 ), but an initial evaluation has been made of the importance of the protective functions of forests
7.1 How much of the forest area has been set aside for protective purposes?
The source document for this Digest states:
FOREST AREA DESIGNATED FOR PROTECTIVE PURPOSES
This variable indicates to what extent forest areas have been set aside for protective purposes, either by legal prescription or by decision of the landowner or manager. Forest designation is reported in two ways: вЂprimary functionвЂ™ and вЂtotal area with functionвЂ™. Forest areas with a specific, designated function considered to be significantly more important than other functions are reported as вЂprimary functionвЂ™.
All forest areas with a designated function (not necessarily primary) are reported under вЂtotal area with functionвЂ™. As mentioned previously, it is important to stress that the concept of вЂprotective functionвЂ™ goes beyond the protected area definition, because forests and other wooded land can have a protective function although outside protected areas.
Of 229 country reports, 172 contained information on designated primary functions of forests, together accounting for 95 percent of the worldвЂ™s forest area (Figure 6.2). Of these, only 134 reported that they had areas specifically designated for protective purposes, while several countries reported that they had insufficient information on this specific category or they included such areas as part of the category вЂmultiple purposeвЂ™
In 2005 a total of 85 countries, representing 46.6 percent of the worldвЂ™s forest area, reported data on total area of forests with a function of protection (not necessarily primary) (Figure 6.3). Some countries, for example Japan, stated that all forests are expected to perform multiple functions. Such countries may not have designated any land as having a primary function of protection: the entire forest area is expected to have protective, productive and possibly other functions.
Results show an improvement in the overall reporting of countries over the past 15 years. There is a clear prevalence of Asian countries among those reporting data for all three years, followed by European countries.
The total extent of forests with protection as their primary function ( Table 6.2 ) was estimated in 2005 at 348 million hectares, equivalent to 9 percent of total forest area. Asia has the highest proportion of forests with a primary function of protection (24 percent), followed by South America (11 percent) and Europe (9 percent). The figures for Western and Central Africa are quite low. This may be due to the fact that only a few countries in this subregion have reported on the protective function of forests.
The relatively small proportion of forests with protection as the primary function reported in North and Central America (0.5 percent) is due to lack of information on protection as a primary function from Canada and the United States, which have included those areas in the multiple purpose category, identifying that as the primary function. This affects the overall analysis, given the large forest area in these two countries. A similar explanation is provided for the very low figure for Oceania: Australia does not have a classification system that can directly report on the designated function classes used by FRA, and so has included areas with protective functions in the multiple purpose category.
It is also useful to cons >Table 6.3 ). North America has the highest proportion of forests with a protective function, followed by Oceania and Asia.
Twenty-three countries reported that all their forests had protection as one of the designated functions. These countries are Afghanistan, American Samoa, Austria, Bahrain, Belarus, Canada, the Democratic PeopleвЂ™s Republic of Korea, Egypt, Georgia, Guadeloupe, India, Japan, Kuwait, Kyrgyzstan, Libyan Arab Jamahiriya, New Zealand, Singapore, Tunisia, Ukraine, United Arab Emirates, United States of America, Viet Nam and Wallis and Futuna Islands.
The results of the trend analysis, based on those countries that provided information for all three reporting years (1990, 2000 and 2005), show an overall increase in the area of forests with protection as their primary function, from 8 percent in 1990 to 9 percent in 2005 (Table 6.4 and Figure 6.4). Similarly, there has been an increase in the proportion of the worldвЂ™s forests with protection as one of the designated functions (not necessarily the primary one) from 61 percent in 1990 to 65 percent in 2005 вЂ“ or an increase of 58 million hectares in the 80 reporting countries providing information for all years.
7.2 How much forest is planted for protective purposes?
The source document for this Digest states:
PROTECTIVE FOREST PLANTATIONS
Recognizing the important protective role of forests, many countries have planted substantial areas of forests and trees for this purpose. These range from large-scale forest plantations to stabilize sand dunes and combat desertification to windbreaks and individual trees planted to provide shade.
For FRA 2005, countries were asked to characterize their forests in five classes: primary, modified natural, semi-natural, protective plantation and productive plantation. While the previous section focused on the total area of forests with a protective function, including both naturally regenerated and planted forests, this section focuses on forest plantations having a primary objective of protection вЂ“ i.e. the fourth class.
Protective forest plantations are defined as those with introduced species and in some cases native species, established through planting or seeding, with few species, even spacing and/or even-aged stands, predominantly for the provision of services such as protection of soil and water, rehabilitation of degraded lands, combating desertification, etc.
Some countries had difficulty in differentiating whether the purpose of a forest plantation was predominantly productive or protective because of forest plantation management policies for multipurpose or multiple functionality. Protective forest plantations do not totally preclude some harvesting of wood, fibre and other products.
It should be noted that this category only captures a subset of all the forests and trees planted for protective purposes. It does not include, for instance, the planted component of semi-natural forests (sown or planted native species), windbreaks with a width of less than 20 m or an area of less than 0.5 ha or individual trees or groups of trees. A thematic study on planted forests, to be released during 2006, complements FRA 2005 with more detailed data and analysis (see Chapter 2, Box 2.1).
Of the 174 countries that provided information on the characteristics of their forests, 93 reported protective plantation data for 1990, 103 for 2000 and 101 for 2005. The remaining countries reported that they had no protective forest plantations or were unable to distinguish between productive and protective plantations.
As can be seen in Figure 6.5, data availability is generally good, with all subregions except Western and Central Africa and the Caribbean providing information for more than 85 percent of the total forest area in the respective subregions.
The global area of protective forest plantations reported in 2005 was 30.1 million hectares (Table 6.5). A few countries dominated their respective regions, including the Russian Federation, which accounted for 84 percent of all protective forest plantations in Europe; Japan, with 50 percent in Asia; Mexico, with 83 percent in North and Central America; and Algeria and the Sudan, accounting respectively for 31 and 29 percent in Africa. The ten countries with the largest area of protective forest plantations (Figure 6.6) accounted for 25.7 million hectares or 85 percent of the global protective forest plantation area.
Trends were reported for those countries that provided data sets for all three reporting years. On a global basis, the protective forest plantation area increased by 405В 000 ha per year during 1990вЂ“2000 and 330В 000 ha per year during 2000вЂ“2005. The proportion of protective forest plantations increased from 0.63 percent of total forest area in 1990, through 0.75 percent in 2000, to 0.82 percent in 2005. However, regions and subregions reported changes that differed significantly (Table 6.6).
The top ten countries reported markedly varied trends in protective forest plantation area for 1990вЂ“2000 and 2000вЂ“2005 (Table 6.7). Overall, the protective forest plantation area in these countries increased by 346В 000 ha per year 1 for 1990 and by 300В 000 ha per year during 2000вЂ“2005. However, it did not increase to the same extent for all countries.
1 Excluding Mexico, which did not report for 1990