1. Forests and people: A long history in brief
2. Forest ecosystem services: Types and scales of delivery
3. Provisioning services: Harvest of forest products
4. Regulating services: Benefits from forests’ functioning
5. Cultural services: Benefits from forests’ subtle values
6. Reduction of world’s forests: Prospective supply
Forest ecosystem services by definition are dependent on the use and value assigned to them by people’s needs and perceptions. Humans have historically interacted with forested biomes around the globe and changed their ecological structure as well as their flow of services; consequently, forest biological states, human uses, and anthropocentrically assigned values have changed throughout human history. Although global demand for forest products and services has continuously increased, the impoverishment of the world’s forests continues, and their future capacity to support human needs is at risk.
anthropocentrism. A human-centered perception and explanation of any given system, e.g., assessing a tropical forest in terms of timber value is an environmental anthropocentric perspective.
biotic impoverishment. The generalized series of transitions that occur in the structure and function of ecosystems under chronic elevated disturbance.
critical habitat. The ecosystems on which any target species—e.g., endangered and threatened pollinators—depend.
environmental uncertainty. Unpredictable sources of density-independent changes in population level parameters.
forest ecosystem management. An approach to maintaining or restoring the composition, structure, and function of natural and modified forests, based on a collaborative vision that integrates ecological, socioeconomic, and institutional perspectives, applied within naturally defined ecological boundaries.
forest fragmentation. Disruption of extensive forest habitats into isolated, smaller patches.
resilience. The capacity of an ecosystem to tolerate disturbance without collapsing into a qualitatively different state that is controlled by a different set of processes. Resilience has three defining characteristics: the amount of change the system can undergo and still retain the same controls on function and structure; the degree to which the system is capable of self-organization; and the ability to build and increase the capacity for learning and adaptation.
scale. The magnitude of a region or process, involving both spatial size and temporal rates.
Even before the development of agriculture, human hunter-gatherers made their way onto all continents, except Antarctica, and selectively consumed and settled in forested regions. Historical evidence confirms the growth and later collapse of ancient civilizations as their forests were used, impoverished, and ultimately degraded. At the onset of Western civilization, massive and destructive forest-use patterns were repeated in Syria, Persia, Greece, and North Africa and later in Rome. The same seems to have occurred in Central America with the Mayan civilization. There are examples in contemporary nations as well, where overpopulation and deforestation have degraded landscapes to uninhabitable stages; this in turn contributed to social crises and made it difficult to create or maintain stable economic and political systems. Human use of forests over the last 8000 to 10,000 years has led to a world where today 25 countries are completely deforested and another 29 have lost more than 90% of their forest cover. At the beginning of the twenty-first century, the human population surpassed 6 billion, and dependency on forest products and services not only is still vital but continuously grows in magnitude and type, while forest use and deforestation have dramatically intensified since the second half of the last century. Today, virtually all major watersheds globally suffer some degree of disruption from forest clearing. Seeking economic growth and development, many countries are repeating forest-clearing patterns experienced by developed countries at much earlier times. Direct deforestation or climate-related forest droughts, fires, impoverishment, and degradation processes occur across extensive regions in China, India, Pakistan, Russia, Southeast Asia, the Philippines, Java, Central America, and South America—mainly in the Amazon.
Forests and their functioning depend on processes that take place over a range of spatial and temporal scales; consequently, their ecosystem services are generated at several ecological scales as well. Essential ecological, biogeochemical, hydrologic, and climate functions naturally performed by forest ecosystems have historically provided services to humanity at scales varying from short-term, site levels (e.g., food) and medium-term, regional levels (e.g., landscape-level hydrologic and climatic stability) to long-term, global levels (e.g., carbon sequestration).
In terms of human use, the types of services provided by forest can be categorized in three groups: provisioning, regulating, and cultural ecosystem services. Forest provisioning services include food, water, fuel, timber, fibers and other raw materials, biochemical and medicinal resources and genetic resources, and soil formation. Regulating services include carbon sequestration, regulation of climate, water quality and control of hydrology, erosion and sedimentation, source of critical habitat, regulation of wild plant and animal species reproduction, breakdown of pollution, source of pollinators, regulation of diseases, pests, and pathogens, biological fixation of nitrogen, other nutrient cycling, and primary productivity. Cultural services include spiritual and religious, aesthetic, and recreational services. The 2005 Millennium Ecosystem Assessment (MA) included a category of supporting ecosystem services that takes into account ecological processes underpinning the functioning of ecosystems. Here those services are incorporated into the other three categories because ecosystems services are described from a functional perspective.
Most forests in developing countries are being used by local people for subsistence. Forests are daily providers of the most essential goods such as food, wood for fuel and heating, timber, fibers, and plants for medicinal use; those services are so critical for survival that millions of humans depend exclusively on them. Forests supply important and diverse provisioning services to the global economy and developed nations as well.
Wood as timber and fiber has noncommercial and commercial market value from local to global levels. Local demands for food and fuel vary from region to region depending on population density, climate, soils, and differences in culture and governance structures. Wood has value as fuel for cooking and heating; as construction material for dwellings, furniture, and tools; and as raw material for many other ingenious and artistic uses.
The sale of wood, charcoal, and timber is a reliable source of income for people and governments around the world. Global supply of wood production reached a peak of 3.4 million cubic meters in 2004, with about 59% of that harvested in developing nations. Fuel wood and charcoal accounted for about 52% of the total harvest, and 48% was used for industrial purposes, mainly as lumber, panels for construction, and pulp for paper. Developing countries accounted for about 90% of the wood cut for fuel. It is estimated that about 8% of the global forests’ wood harvest for industrial uses is from illegally harvested operations across important supply regions in Brazil, Eastern Russia, Indonesia, and West Africa.
Between 2000 and 2005, global deforestation caused a total forest loss of 65 million hectares—offset by forest regrowth and the expansion of planted forests, the net loss was 36.6 million hectares. The larger losses occurred in Africa and South America, with 3.2% and 2.5% of total forest lost, respectively. Most of the losses in South America were in the Brazilian Amazon, which represents the world’s largest continuous region of tropical forests left, and which lost 3.2% of its total forested area. European countries had either no change in forested area or a slight increase in forested area.
Increases in wood consumption are mainly driven by increase in population and economic growth. Analyses of future demand on industrial wood—e.g., using econometric models that take into account population growth, economic growth, land-use patterns, technological change, and other factors—estimate that, by 2010, there will be a demand of 2.5 billion cubic meters of industrial wood per year compared to 3402 million cubic meters today. Future wood production will be driven by regional developments further affecting forests in China, other Asian and Pacific region countries, Latin America, South Africa, Russia, and Eastern Europe. Even outside commercial markets, fuel from forests is a critical resource in Africa and in densely populated regions of the world including the Himalayas, the Indus and Ganges plains, the lowlands and islands of Southeast Asia, and Latin America.
The potential of forest plantations—those that are seeded with fast-growing species that produce regular harvests for commercial use—has not yet been fully realized. At the end of the twentieth century, human-created forests were planted at annual rates of about 2.6 million hectares in tropical regions and 10 million hectares in temperate zones. In 2005, the Food and Agriculture Organization of the United Nations (FAO) estimated that planted forest accounts for about 3% of the world’s forests. Although industrial planted forests fulfill some of the functions and services of natural forests, planted forests are usually less diverse in habitat for other species and substantially less complex in structure, function, and their ecological capacity to absorb disturbance, and hence, their resilience is lower.
Substances obtained from forests’ biodiversity are essential supplies in industry, medicine, and agriculture. Modern advances in molecular biology and biochemistry have allowed greater and more innovative use of chemicals and genes from the world’s ecosystems, and increasing demand has turned bioprospecting attention to the abundant and as yet untapped supply of those resources provided by the biodiversity of forest ecosystems. Genetic engineering has opened new opportunities for forest genetic services; for instance, the discovery of the PCR enzyme and several other drug discoveries based on forest plants has led to a surge of confidence about the untapped economic value of forest biodiversity, with the use of biochemical and genetic forest resources increasing.
Genetic diversity has been a key raw ingredient in agricultural research, accounting for roughly half of the gains in U.S. agricultural productivity from 1930 to 1980. The human use of genes across plant species is now common industrial practice; for example, a gene responsible for a sulfur-rich protein found in the Brazil nut was isolated, cloned, and transferred into tomatoes and yeast. At the beginning of the twenty-first century, genetically modified species of food and fiber crops are commercially grown and harvested around the world.
Similarly, the study of medicines used by traditional communities and the pharmaceutical use of natural chemical compounds has intensified over the last decades. Industries not only commercialize the direct use of natural medicinal products but also use them for the design and chemical synthesis of new drugs; it is estimated that after screening, about one in 10,000 natural chemicals yields a valuable product. In the United States, 25% of prescriptions are filled with drugs whose active ingredients are extracted or derived from natural ecosystems, often forest ecosystems.
Nontimber products are important to local populations as well and include the provisioning of vines used as ropes; rattan; resins such as latex; cork; wild game for hunting and fishing; and other food and medicine sources such as mushrooms, tropical fruits, wild seeds, roots, flowers, fruits, stems, and leaves. This use of forest resources for medicine is particularly important because about 4 billion people have no or little access to Western medicine and in times of sickness depend on plant extracts for treatment. In the tropics, some nonwood products, including Brazil nuts, wild cacao, and açai, can produce economic yields between $80 and $100 per hectare per year.
Forests provide a vital service to humans in the form of healthy and intact soils. For most of the 10,000-year history of agriculture, the impact on forests was local, and only in the last century or so has the demand for forest soil services—such as soil contributions to food and timber production—become global. Although demand for agricultural land has decreased in temperate forested regions, today about one-fourth of the Earth’s terrestrial surface has been transformed into cultivated systems. FAO estimates that by 2030 there will be a need for 120 million hectares of new agricultural land in developing countries, and most of these hectares will most likely come from transforming currently standing forests.
Supporting ecosystem services provided by forest soils include physical support to plant and animal communities, retention and cycling of organic matter and wastes, regulation of nutrients and major element cycles, and buffering control of hydrologic cycles—further discussed in regulation services. The natural physical, chemical, and biological processes that produce soil’s structure and productivity can take up to hundreds of thousands of years to occur; whereas their cumulative properties and services can be destroyed in scales of decades or less. Soil productivity is a critical determinant of future economic development of nations—particularly for poorer ones—and the total value of the soils’ services is extremely high, as they do literally represent the physical base for survival of human societies and of millions of other species.
In general, large-scale, long-term phenomena set physical constraints on smaller-scale, shorter-time ones, but many large-scale processes are also driven by the combined impact of small-scale ones. For example, local changes in forest growth rates can add up and influence carbon sequestration and climate at the regional and global scales. Similarly, forest soil microbes operating at scales of micrometers and minutes can control the biological fixation of nitrogen, consequently enhancing soil fertility and primary productivity at ecological scales from individual plants to the whole forest ecosystem. At larger scales, such biological regulation affects the global nutrient cycling. Large-scale processes can also constrain smaller-scale processes; for instance, global change in ocean surface temperatures and currents such as the El Niño Southern Oscillation drives changes in precipitation, e.g., drought events, that in turn impact the productivity of ecosystems and life-history cycles of plant and animal species At the landscape level, forests and their biodiversity in large patches and corridors also serve to mediate smaller-scale population dynamics of pests and diseases, regulating their spread.
Water flows and water quality link forests to other global ecosystems and to essential human interests. Forests act as buffers regulating the volume, quality, and timing of water flows from soils, rivers, and groundwater, which in turn divide and over time define landscape physiography and drainage basins around the globe. Water from soils is released back to the atmosphere as vapor and by percolation to streams flows, cleansed of pollution and excess nutrients, flowing at regular seasonal rates across landscapes. Highly populated continental drainage basins—including the Ganges, Danube, Mississippi, Congo, Mekong, and several others—were all covered by forests, and today their hydrologic functions are disrupted as a result of massive deforestation.
The impact of tropical rainstorms has caused more soil erosion in deforested areas than anywhere else on Earth. Deforestation destabilizes soils, causing various levels of erosion depending on the amount and frequency of precipitation, geology, topography (mainly slope), and local soil structure. Deforested systems do not have the robust vegetation required to absorb, retain, and evapotranspire water into the atmosphere. The soil’s permeability and capacity to absorb and retain water are reduced after vegetation has been removed or degraded. In healthy forests, the multilayered structure of vegetation reduces the impact of drops from rain and storms when raindrops are stopped by foliage, with water then dripping down leaves, branches, and tree trunks to reach and percolate into the ground and flow into streams more gradually. Rain episodes in deforested landscapes increase surface runoff and soil erosion and diminish the recharge of the groundwater. River channels are blocked by silt from erosion, sometimes causing water to flood across landscapes, killing humans and livestock and destroying crops, living spaces, and other infrastructure of high economic value. Siltation as a consequence of deforestation is a major problem in many watersheds of the humid tropics including Indonesia, Africa, India, Asia, and America.
Forest ecosystems have a direct effect on climate by influencing the energy budget of the atmosphere and moderating local and regional temperature and rainfall regimes. Changes from forested to deforested landscapes involve alterations in albedo, heat, water pressure deficit, and leaf area index, directly impacting landscape-level evapotranspiration. It is estimated that about half of the warming that occurred in northern latitudes during the Holocene was caused by shifts in albedo from tundra to forest vegetation.
Current large-scale deforestation in the Amazon forests and elsewhere is impacting regional climates. Research has shown that Amazon trees draw water from soil layers 15–20 m deep. Once trees are removed, the landscape becomes more arid, and during the dry season, moist forests become susceptible to fire events that further impoverish the ecosystem. Over the past three decades, during El Niño-caused droughts, forest fires have been observed not only across large regions of the Amazon basin but also in southern Borneo and Mexico. Sweeping across forested landscapes, fires triggered massive tree mortality, biomass and biodiversity losses, and carbon emissions to the atmosphere, further exacerbating global climatic change. In the Amazon, forest changes at those scales have affected local and regional climate and reduced cloud formation and the intraregional precipitation cycle, further increasing the fire–drought–forest impoverishment cycle. With global warming, boreal forests are also becoming more flammable and vulnerable to natural and human-caused fires. In Canada, for instance, in the last two decades of the twentieth century, the burned area increased sixfold compared with the century trend. This trend is worrisome given that Boreal forests occupy 9.2 million square kilometers, and about half of the global forest carbon is stored in them.
Through respiration and photosynthesis, forests annually release carbon dioxide equivalent to 12–14% of the atmospheric content; if there is little deforestation, this contribution to the atmosphere is offset by forest carbon uptake. Either way, forests have a significant functional role in the global carbon balance. Forests hold in their trees and soils more carbon per unit area than any other ecosystem and account for 65% of the global net plant primary productivity on land. It is estimated that forests currently hold more than 1200 billion tonnes of carbon in their vegetation and soils, a significant magnitude compared with the estimated 750 billion tonnes in the atmosphere at present. About half of the forests’ carbon is stored in temperate forests, which have probably more carbon than the earth’s estimated fossil fuel reserves. By sinking carbon in several biomass and soil compartments, forests take out of the atmosphere at least 1015 g of carbon each year, an equivalent of 14% of the total emitted by human activities. Because of their capacity to serve as carbon sinks and to control the global energy balance, effectively managed forest ecosystems will be essential in regulating and mitigating current global climatic changes.
About 25% of the increase in atmospheric CO2 concentrations over the last 150 years came from changes in land use, mainly from clearing forests and the cultivation of their soils for food production. It has been calculated that global deforestation between 1990 and 2005 caused the carbon storage capacity of the world’s forests to decline by 5%. Given current climate change conditions, carbon sequestration is a globally important forest service, potentially as valuable as any other. In 2007, carbon markets were estimated at a US$64 billion value. There is expectation that in a future carbon market, forest carbon values alone could surpass their value in timber and other products by an order of magnitude.
Pollinators are regulators of plant dispersal and community structure and are significant agents of evolution. Important groups of pollinators include beetles, bees, wasps, flies, birds, and bats. The earliest seed-bearing plants were pollinated passively when large amounts of pollen blown by the wind reached their ovules. The evolution of many angiosperms is linked to their evolving ability to attract insects and other animals with their flowers and directing the behavior of pollinators so that cross-pollination occurs with higher frequency. The more attractive plants were to insects, the more frequently they were visited, and the more seed they could produce, gaining a selective advantage. Specialized groups of flower-visiting insects, such as bees and butterflies, evolved with plants for 50 million years and, in the early Tertiary—between 40 and 60 million years ago—became even more abundant and diverse. The increase and diversification of these groups of insects were directly related to the increase in diversity of an-giosperms. Consequently, there is a long and profound evolutionary influence and mutual dependence between angiosperms and their pollinators. In evolutionary time, pollinators continue to allow the adaptive radiation of angiosperms into current biomes, affect the composition of floras, and influence the spatial and temporal patterns in plant communities and therefore regional and global patterns of primary productivity.
Research has shown that reproduction in many plant populations stranded in highly fragmented and degraded habitats might be pollinator limited. Scientific results have led the International Union for the Conservation of Nature to warn of the diminishing trend of pollinator diversity available to both wild and domesticated plants. Community- and ecosystem-level impacts of declines in pollinators on natural vegetation are extremely difficult to predict. Nevertheless, it is clear that the evolutionary and ecological functions of pollinators regulate the functioning and resilience of ecosystems and, therefore, provide a critical support service.
There are more analyses on the economic value of pollinators as they interact with agricultural systems than for natural forest. More than 70% of at least 1300 crop species require pollen movement by some vector, and less than 2% depend exclusively on wind. Clearly, the importance of animal vectors for agricultural crops has essential present and future economic value.
In the last half of the twentieth century, the concurrence of three processes—the emergence of so-called third-generation human rights during the 1970s and 1980s (e.g., environmental rights, international heritage patrimonies, amongst others); a broader recognition of minority groups’ rights (notably, those of indigenous peoples); and the commitment and compliance made by nation-states to safeguard them both through policies and adequate structures of governance—have brought a general acknowledgment of the symbolic and cultural interactions between forests and populations. This concurrence has contributed to a new understanding of the existence of forest cultural services and their relevance for local peoples and for humanity in general.
Cultural services provided by forests are difficult to measure, and therefore, data on their use and value are still scarce. Moreover, in terms of cultural services, as stated by the MA, there is considerable uncertainty regarding the importance that people in different cultures place on them, how “importance” changes over time, and how values influence decisions that lead to tradeoffs with net benefits and costs. The challenges of defining, measuring, and valuing subtle cultural services critically limit the ability to effectively conserve forests and implement the best management approaches to maintain their provisioning and regulating services in the long term.
Cultural services depend on human interpretation of forest ecosystems and their specific characteristics; in essence, they are culturally conceived, and their value is derived from the socially constructed meanings conferred to a particular forest and the services it supplies to social groups. Consideration of forests’ cultural services demands assessment of the number of people benefiting from forests and the type of interaction they have with them. In general, the group of stakeholders that value forest cultural services has been growing in spatial extent; the spread of information and ease of travel have extended cultural services beyond local users to a global community. For instance, although for native communities forests have often been a constituent element of their cosmogonies and spiritual lives, such a cultural role is now broadly recognized and valued not only by each local forest’s inhabitants but by distant peoples not directly affected by or involved with the service. Change in cultural services influences human well-being, affecting the sense of security, social relations, and both physical and emotional states, particularly in cultures that have retained strong connections to their local environments. The MA established three main categories of cultural services.
Loss of particular ecosystem attributes (sacred species or sacred forests), combined with social and economic changes, can sometimes weaken the spiritual benefits people obtain from ecosystems. According to MA, the tendency has been a decline in the numbers of sacred and protected areas. On the other hand, under some circumstances (e.g., where ecosystem attributes are causing significant threats to people), the loss of some attributes has enhanced spiritual appreciation for what remains.
Following an increase in urbanization, the demand for aesthetically natural landscapes has increased. A reduction in the availability of and access to natural areas for urban residents may have important detrimental effects on public health and economies. Studies show that the quantity and quality of areas that provide this type of service have been declining, and as the remaining places continue to become scarce, the value placed on them will likely increase.
Demand for recreational use of forested landscapes is rising; therefore, more areas are managed to provide this use, reflecting a cultural change in values and perceptions. Effective management of forest for recreation and ecotourism is an ongoing learning process more advanced in temperate forests, but global standards are still being developed. The MA estimates that although more natural areas are accessible, many are undergoing degradation; to date, comprehensive data on impacts on forest caused by recreation and ecotourism are lacking. The increasing ease of travel is enabling this value to be shared spatially, and although recreation may degrade some systems, it also allows others to be preserved because the value of the forest can actually be marketed; therefore, there may be a net gain for conserving forests.
Broad and democratized knowledge about forests has certainly influenced the matrix of values and cultural services that people recognize in them. From this perspective, the appropriate management of forest cultural services is highly relevant, as it will pave the way for informing decisionmaking processes and improving the management of forest resources more generally. Increased understanding and incorporation of forests’ cultural services into their management plans may allow similar advances in managing the delivery of provisioning and cultural values and can ultimately affect the way societies manage forests.
Globalization has created ample recognition of the crucial services provided by forests for human well-being. Worldwide cultural changes valuing forests have been reflected in the setting of international agreements, governance structures, and mechanisms to enable the changes necessary to improve global forests management and secure their services. Some significant initiatives that focus on forests and their services include the World Commission on Forest and Sustainable Development; the Intergovernmental Panel on Forests; the UN Food and Agriculture Organization Forestry Department; the Center for International Forestry Research; The World Conservation Union Forests Program; and the UN Conference on Trade and Development and Earth Council Institute joint Carbon Market Program.
Finally, international finance agencies are also responding to cultural changes in forest valuation. For instance, the World Bank Prototype Carbon Fund, the Community Development Carbon Fund, and the Bio-Carbon Fund, all deal with global forests to catalyze private-sector investment to address climate change. In the field of ecotourism, the Inter-American Development Bank undertakes work to identify new avenues for investment in the rational use of forest and biodiversity conservation.
After the last Pleistocene glaciations, tropical, temperate, and conifer forest ecosystems occupied more than 44% of the Earth’s land area. Over the past 50 years, humans have changed global forest ecosystems more rapidly and extensively than in any other period in history. The world has lost more than 46% of its forests, and most of the losses occurred during the last three decades of the twentieth century. At current deforestation rates, by 2030 there will be less than 10% of intact forests remaining with another 10% in a degraded condition, causing irreversible loss of millions of species whose genetic, chemical, and functional value cannot yet be determined.
There is enough evidence indicating that human impacts are increasing the likelihood of nonlinear dynamics causing abrupt and irreversible changes of unpredictable consequences to forest ecosystems and their services. The combined human activities of burning fossil fuels and transforming forests have changed the composition of the atmosphere, leading to a warming of the Earth at global average rates of 0.2–0.3 degree per decade. Scientific evidence shows that the rate of temperature increase is both high and fast enough to—at least temporarily—substantially change forest function.
The links between deforestation and reduction in regional rainfall patterns are clear, but there are uncertainties concerning the threshold levels at which feedbacks between different forest ecosystems and climate will trigger nonlinear abrupt changes that can negatively impact Earth’s biomes and global climate. Data show geographic differences where some forests seem to be invigorated by carbon fertilization whereas others are showing ecological impoverishment and lower biomass accumulation. There are changes in species composition caused by alterations in their growth, survival, dispersion, and reproductive rates. Higher temperatures also accelerate the biogeochemical processes in forests’ soils, increasing emissions of radiative gases (carbon monoxide, methane, and nitrous oxide) that further exacerbate global warming.
All these responses have clear influence on forest services primarily through direct changes in access to material well-being, health, and global security. The challenge is for all levels of society to make well-informed, responsibly agreed decisions and actions to govern the use of the world’s forests. By securing forest services in the long term, humanity has better chances to continue flourishing spiritually, culturally, ecologically, and economically.
Lovejoy, T. E., and L. Hannah, eds. 2005. Climate Change and Biodiversity. Ann Arbor, MI: Sheridian. Provides the most authoritative overview and evidence of climate change effects on biodiversity and vice versa.
Millennium Ecosystem Assessment. 2005. Ecosystems and Human Well-being: Synthesis. Washington, DC: Island Press. State-of-the-art scientific appraisal of the condition and trends of the world’s ecosystems and their services.
Millennium Ecosystem Assessment. 2005. Living Beyond Our Means: Natural Assets and Human Well-being: Statement from The Board. Washington, DC: World Resources Institute. Interpretation of the key communications from the Assessment, identifying 10 key messages and conclusions.
Myers, N. 1997. The world’s forests and their ecosystem services. In G. C. Daily, ed. Nature’s Services: Societal Dependence on Natural Ecosystems. Washington, DC: Island Press, 215–235. This chapter in Daily’s classic book on ecosystem services draws on well-known studies presenting an integrated picture of forests’ structure and function and their overall environmental values.
United Nations Food and Agricultural Organization (FAO). 2005. Change in extent of forests and other wooded land 1990–2005. In FAO, Global Forest Resources Assessment. Rome: FAO. Source of the most up-to-date quantitative data on the state of the world’s forests.
Woodwell, G. M. 2001. Forests in a Full World. New Haven, CT: Yale University Press. Comprehensive and accessible, offers an original, sound—and still up-to-date—vision of the world’s forest’s role and the necessary new approaches to confront the challenges of governance and effective management.