- ➔ Forests are resources of global significance. They cover nearly one-third of the Earth’s land surface and contain the majority of terrestrial biodiversity. The forest area continues to shrink, however, despite efforts to halt deforestation and restore degraded lands.
- ➔ Forests are crucial for mitigating climate change. They contain 662 billion tonnes of carbon, which is more than half the global carbon stock in soils and vegetation.
- ➔ Societies benefit from and are highly dependent on forests. More than half of world gross domestic product is estimated to depend significantly on ecosystem services. The forest sector contributes more than USD 1.52 trillion to world gross domestic product and employs 33 million people.
- ➔ Many forest-proximate people obtain insufficient benefits from forests. Seventy-five percent of all rural people live within 1 km of forest, but many have few rights to forests, with states owning nearly three-quarters (73 percent) of all forests. Eighty percent of the extreme poor live in rural areas.
- ➔ The COVID-19 pandemic had a significant impact on forest value chains and trade in early 2020. Most sectors rebounded quickly, but the risk of future pandemics remains. Forestry is well placed to play an important role in green recovery.
The world is at risk of large-scale and potentially irreversible environmental changes, with major threats related to climate, biodiversity, natural resources and human well-being. As the window for action narrows, and as population growth and aspirations place new demands on physical resources, it seems clear that natural ecosystems are vital assets that must be restored, maintained and sustainably managed. This chapter presents the most recent data on the status of, trends in, and value of global forest and tree resources as a baseline for designing cost-effective options and wide-impact pathways towards a healthy planet and sustainable and resilient societies.
2.1 Deforestation and forest degradation persist
Forests cover nearly one-third of the Earth’s land surface but the area is shrinking despite efforts to halt deforestation and restore degraded lands
Forests occur in the four major climatic domains (boreal, temperate, subtropical and tropical) (Figure 1). In total, they cover 4.06 billion ha (31 percent of the world’s land surface), but this area is decreasing, particularly in the tropics. The FAO Global Forest Resources Assessment (FRA) 2020 estimated that 420 million ha of forest was deforested (converted to other land uses) between 1990 and 2020; although the rate declined over the period, deforestation was still estimated at 10 million ha per year in 2015–2020 (approximately 0.25 percent per year) (Box 1 discusses the definition of deforestation; Chapter 3.1 examines its drivers).1 This deforestation was not fully matched by afforestation and natural forest expansion, estimated at about 5 million ha per year over the same period.
Figure 1The global distribution of forests, by climatic domain, 2020
Box 1Defining and measuring deforestation
According to the definition used in FAO’s Global Forest Resources Assessment (FRA), deforestation is “the conversion of forest to other land use independently of whether human-induced or not”.2 That is, deforestation is essentially referring to a change in land use, not in tree cover. Defining deforestation thus implies a definition of forest, which, in the FRA, combines physical criteria (minimum thresholds of 10 percent canopy cover, 0.5 ha in area and 5 m in height) and a notion of the predominant land use, excluding tree-covered areas where the predominant use is agriculture or urban; hence, the definition excludes plantations of agricultural tree crops (such as oil-palm plantations and orchards) as well as urban parks but includes various types of planted forests (including rubber plantations).3 Nevertheless, many technical and scientific studies do not use FAO’s definition but rather equate deforestation with tree-cover loss without taking land-use criteria into account. This approximation is used in remote-sensing-based methodologies for two reasons – it considers all tree cover (including tree-covered areas not meeting FAO’s forest definition); and it counts instances of non-permanent tree-cover loss (e.g. the clearfelling of a natural or planted forest that will later regrow, and the temporary consequences of a forest fire) as deforestation. When interpreting deforestation figures in different studies, therefore, users should be aware of the impacts of the definitions and tools used.
There are significant regional differences in the patterns of forest-area change: the highest net losses in 2010–2020 were in South America and Africa, while Europe and parts of Asia experienced net gains. The rate of net forest loss decreased in South America in 2010–2020 compared with the previous decade.1
Primary forests. Approximately one-third (34 percent) of the world’s forests are primary (that is, consisting of native tree species and having no clearly visible indications of human activities and no significant disturbances in ecological processes). Primary forests have decreased by an estimated 47 million ha globally since 2000, with the rate of loss more than halving in 2010–2020 compared with the previous decade. Combined, three countries – Brazil, Canada and the Russian Federation – host more than half (61 percent) of the world’s primary forests. Canada and the Russian Federation reported very low or no deforestation between 1990 and 2020; despite an overall reduction in deforestation, however, Brazil has experienced substantial forest loss since 1990, including of primary forests. Naturally regenerating forests (i.e. forests predominantly composed of trees established through natural regeneration, including primary forests) account for 93 percent of the world’s forest area.1
Planted forests. Seven percent (294 million ha) of the forest area worldwide was composed of planted forests in 2020. Globally, the rate of increase in planted-forest area declined from 1.4 percent per year in 2010–2015 to just less than 1 percent per year in 2015–2020. South America had the highest rate of increase in 2010–2015; although the rate declined in 2015–2020, the region still had the highest rate of increase in relative terms in that period, followed by North and Central America.1
Plantation forests (an intensively managed subcategory of planted forests) covered about 131 million ha in 2020, which was 3 percent of the global forest area and 45 percent of the total area of planted forests. Asia accounted for more than half this plantation-forest area. Plantation forests in North and Central America are composed mostly of native species, and those in South America consist almost entirely of introduced species.1
Other wooded land. Worldwide, the area of other wooded land was estimated at 977 million ha in 2020, which was 7 percent of the total land area (and about one-quarter the area of the global forest area). Africa had the largest area of this category (446 million ha), followed by Asia (191 million ha), South America (147 million ha), Europe (100 million ha), North and Central America (90.5 million ha) and Oceania (2.47 million ha; note, however, that Australia did not report on its area of other wooded land for FRA 2020).
The area of other wooded land decreased by nearly 1 percent (about 9 million ha) between 2000 and 2020. Many countries face challenges in monitoring change in this land-use category, largely associated with difficulties in measuring tree-canopy cover in the range of 5–10 percent; thus, they lack reliable data on it.4 Recent estimates based on FAO’s latest remote sensing survey suggest that the global area of other wooded land may be significantly higher than reported to FRA 2020.5
Other land with tree cover. Other land with tree cover has four subcategories: 1) trees in urban settings; 2) tree orchards; 3) palms; and 4) agroforestry (Figure 2). The area of palms more than doubled between 1990 and 2020, from 4.2 million ha to 9.3 million ha, based on the 83 countries that reported. Seventy-one countries and territories worldwide reported a total area of 45.4 million ha of agroforestry in 2020, mostly in Asia (31.2 million ha) and Africa (12.8 million ha) (there was also an estimated 1.28 million ha of agroforestry in North and Central America). In the 54 countries and territories that reported trend data on agroforestry, the area of land subject to this use increased by 4.21 million ha between 1990 and 2020, to 43.3 million ha. Most of the increase was in Asia and Africa.6 Note, however, that estimates based on FAO’s latest remote sensing survey suggest that the global area of other land with tree cover may be significantly higher than reported to FRA 2020.
Figure 2Global area of other land with tree cover, 1990–2020
In many countries with low forest cover, trees outside forests constitute the main source of wood products and also non-wood forest products (NWFPs), even though the trees may be scattered.
Biodiversity. Forests harbour most of Earth’s terrestrial biodiversity and its three components – ecosystem, species and genetic diversity. Trees are the foundations of forest ecosystems, and many of the world’s 60 000 tree species7 are also important components of woodlands and agricultural landscapes. Forests provide habitats for about 80 percent of amphibian species, 75 percent of bird species and 68 percent of mammal species.8 About 60 percent of all vascular plants occur in tropical forests.9 The genetic diversity of trees is being threatened and eroded by the loss of tree populations, unsustainable harvesting, overgrazing, climate change, fire and invasive species.10 Projected declines in the diversity and abundance of many major pollinators pose a threat to food security, human health and the cultural fabric and livelihoods of millions of people, especially rural and indigenous communities.11
Forest degradation is difficult to quantify but is likely increasing
Human activities, severe climatic events, fire, pests, diseases and other environmental disturbances may degrade forests and thereby reduce the provision of forest goods and services, biodiversity values, productivity and health. Forest degradation may also negatively affect other land uses (e.g. by causing a loss of downstream water quality and affecting groundwater recharge) and cause the emission of greenhouse gases (GHGs). Despite its importance, a widely applied definition of forest degradation is unavailable, and data are scarce. For FRA 2020, 58 countries representing 38 percent of the global forest area reported that they monitored the area of degraded forest, but they used varying definitions of degraded forest and few applied quantitative criteria.1
Human-induced land degradation and desertification, water scarcity and climate change are increasing the levels of risk for agricultural production and ecosystem services. Converging evidence indicates that, as agriculture intensifies, so too does the extent and severity of land degradation in terms of soil erosion, nutrient depletion and salinization.12 Human-induced degradation affects 34 percent of agricultural land: one-fifth of human-induced degraded land is in sub-Saharan Africa, followed by Southern America at 17 percent; Northern America and South Asia contribute 11 percent to global degradation; and, in relative terms, South Asia is the most-affected region, with 41 percent of its area suffering from human-induced degradation.13
Climate change and human influence affect the dynamics of forest ecosystems and their resilience to invasive species and diseases – with potentially very large ecological and economic impacts. For example, estimates show that southern pine beetle-induced timber mortality in the southern United States of America caused losses to timber producers of about USD 1.2 billion between 1982 and 2010 (i.e. USD 43 million per year, on average).14 The average annual damage caused by bark beetles in forests in parts of Europe (i.e. Belgium, Denmark, France, Germany, Luxemburg and the Netherlands) is projected to be almost six times higher in 2021–2030 than it was between 1971 and 2010.15
About one-third of global forest loss is fire-related
Forest fires (90 percent of which are caused by humans) can have wide-ranging negative impacts on ecosystems and serious implications for the achievement of many of the SDGs, including those related to biodiversity, water, health, life on land and climate. Fire affected approximately 98 million ha of forest globally in 2015 and damaged about 4 percent of the tropical forest area.16 Recent research shows that 29–37 percent of global forest loss (measured as permanent and non-permanent tree-cover loss) in 2003–2018 was fire-related.17 There are indications that the incidence and severity of fire are increasing. Australia, for example, suffered its worst fire season in history in 2019–2020, with an estimated 10.2 million ha burnt, including 8.19 million ha of native forest (the remainder comprising agricultural croplands and grasslands, forest plantations and other non-native forest, peri-urban lands, and native grasslands, heath and shrublands).18
Forests accumulated more carbon than they emitted in the last decade
Forests play an important role in the global carbon cycle, functioning both as a source of GHG emissions (through deforestation and degradation) and a sink (through carbon capture via photosynthesis and storage in biomass and soils). Forest carbon stock is the carbon contained in forests in four pools – living biomass, dead wood, litter and soil organic matter. Forests sequester carbon from the atmosphere during photosynthesis but can also release stored carbon, such as in the case of deforestation, fire and tree decay. Forest carbon stock, and changes in this, are important indicators of the role of forests in the global carbon cycle and of the quality of forest management.
The total carbon stock in forests was estimated at 662 Gt in 2020, at an average of 163 t per ha.19 About 45 percent of the forest carbon stock in 2020 was in living biomass, 45 percent was in soil organic matter and 10 percent was in dead wood and litter.20 The global forest carbon stock decreased between 1990 and 2020 but forest carbon stock per ha increased, likely partly due to improved forest management.21
Net emissions from land use, land-use change and forestry were 4.1 GtCO2 per year, or about 10 percent of total anthropogenic CO2 emissions, between 2011 and 2020.22 The terrestrial sink (mostly forests) has been significantly larger than emissions from land-use change,23 however, sequestering 11.4 GtCO2 per year, which was as much as 29 percent of annual anthropogenic CO2 emissions in 2011–2020.24 Tropical and subtropical regions represent 78 percent of gross emissions and 54 percent of gross removals.25
Other impacts of forests on climate. Changes in forest cover and characteristics also influence climate in other ways. For example, they affect albedo (the extent to which solar radiation and therefore heat is reflected back to the atmosphere), the emission of water vapour into the atmosphere (through evapotranspiration), the height above the Earth’s surface to which heat and water vapour are forced upward (by the “roughness” of tree canopies), and the extent to which dust and smoke particles, pollen and microbes enter the atmosphere as aerosols (with their own effects on temperature). Trees also emit other chemicals that affect climate, such as biogenic volatile organic compounds.
The negative local and regional effects of forest and tree loss on temperature and rainfall can be substantial, especially in the tropics. Declines in rainfall linked to deforestation in the southern Brazilian Amazon could cause agricultural losses (e.g. declines in soybean and livestock yields) valued at more than USD 1 billion per year between now and 2050;26 recent modelling also indicates that deforestation of remaining humid rainforests in Africa would likely dramatically affect rainfed agriculture across the continent, particularly maize-based cropping systems north of the equator.27 The local to regional impacts of forests on climate can be important for reducing urban heat (primarily through transpiration, shading and albedo); for example, trees in urban settings have been shown to reduce land surface temperatures in Central Europe in summer and during heat extremes by as much as 12 °C.28
Land-use change has caused the emergence of more than 30 percent of new diseases since 1960
Forest loss has negative direct and indirect impacts on human health, although data are limited (comparative datasets do not exist at the global level) and the risks of emerging infectious diseases (EIDs) associated with forest ecosystems are poorly studied. Most research tends to focus on a few specific diseases (and known reservoirs or hosts) rather than attempting to fully understand all relevant host–pathogen–environment dynamics in an ecosystem. Nevertheless, the majority (60 percent) of EIDs are caused by pathogens that have a non-human animal source (i.e. are zoonotic), and nearly three-quarters (71.8 percent) of such zoonotic EIDs originate in wildlife.29 Landscape change and biodiversity loss involve major shifts in the ecology of pathogens and the wildlife habitats or species they use as hosts and reservoirs, thus altering disease patterns. Moreover, such changes tend to put people physically in closer contact with pathogens, and the wildlife trade can bring pathogens into the human population. Land-use change (comprising deforestation, human settlement in primarily wildlife habitat, the spread of crop and livestock production, and urbanization) is a globally significant driver of pandemics; it is estimated to have caused the emergence of more than 30 percent of new diseases reported since 1960.30
Deforestation and forest fragmentation also bring people and livestock into closer contact with wildlife, increasing human–wildlife conflicts and the risk of disease transmission between them. Deforestation is an important factor in the spread of vector-borne diseases (i.e. diseases, such as malaria, that are transmitted by vector species between susceptible species).31 A recent study found that 15 percent of about 250 analysed EIDs were linked to forests,32 several of which (e.g. Ebola and human immunodeficiency virus infection/acquired immunodeficiency syndrome) are particularly harmful to human health and economies. Deforestation, particularly in tropical regions, has been associated with an increase in infectious diseases such as dengue fever, malaria and yellow fever.33
Ebola virus disease, which was first identified in humans in sub-Saharan Africa in 1976 and reportedly killed over 11 000 people across West Africa in an outbreak in 2014–2016, has been associated with rapid forest clearance: based on land-cover change and recent data on outbreaks, researchers found that an Ebola epidemic is more likely to occur in areas where forest cover has been fragmented by deforestation, typically within a time frame of two years after deforestation has occurred.34,35