Editing IPCC:AR6/WGIII/Chapter-7 (section)

=== 7.3.1 Anthropogenic Direct Drivers: Deforestation, Conversion of Other Ecosystems, and Land Degradation ===

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The global forest area in 2020 is estimated at 4.1 billion ha, representing 31% of the total land area ( [[#FAO--2020a|FAO 2020a]] ). Most forests are situated in the tropics (45%), followed by boreal (27%), temperate (16%) and subtropical (11%) domains. Considering regional distribution of global forest area, Europe and the Russian Federation accounts for 25%, followed by South America (21%), North and Central America (19%), Africa (16%), Asia (15%) and Oceania (5%). However, a significant share (54%) of the world’s forest area concerns five countries – The Russian Federation, Brazil, Canada, the USA and China ( [[#FAO--2020a|FAO 2020a]] ). Forest loss rates differ among regions though the global trend is towards a net forest loss ( [[#UNEP--2019|UNEP 2019]] ). The global forest area declined by about 178 Mha in the 30 years from 1990 to 2020 ( [[#FAO--2020a|FAO 2020a]] ). The rate of net forest loss has decreased since 1990, a result of reduced deforestation in some countries and forest gains in others. The annual net loss of forest area declined from 7.8 Mha in 1990–2000, to 5.2 Mha in 2000–2010, to 4.7 Mha in 2010–2020, while the total growing stock in global forests increased ( [[#FAO--2020a|FAO 2020a]] ). The rate of decline in net forest loss during the last decade was due mainly to an increase in the rate of forest gain (i.e., afforestation and the natural expansion of forests).

Globally, the area of the more open, other wooded land is also of significant importance, with almost 1 billion hectares ( [[#FAO--2020a|FAO 2020a]] ). The area of other wooded land decreased by 30.6 Mha between 1990 and 2020 with larger declines between 1990–2000 ( [[#FAO--2020a|FAO 2020a]] ). There are still significant challenges in monitoring the area of other wooded land, largely associated with difficulties in measuring tree-canopy cover in the range of 5–10%.The global area of mangroves, one of the most productive terrestrial ecosystems ( [[#Neogi--2020a|Neogi 2020a]] ), has also experienced a significant decline ( [[#Thomas--2017|Thomas et al. 2017]] ; [[#Neogi--2020b|Neogi 2020b]] ), with a decrease of 1.0 Mha between 1990 and 2020 ( [[#FAO--2020a|FAO 2020a]] ) due to agriculture and aquaculture ( [[#Bhattarai--2011|Bhattarai 2011]] ; [[#Ajonina--2014|Ajonina et al. 2014]] ; [[#Webb--2014|Webb et al. 2014]] ; [[#Giri--2015|Giri et al. 2015]] ; [[#Thomas--2017|Thomas et al. 2017]] ; Fauzi et al. 2019). Some relevant direct drivers affecting emissions and removal in forests and other ecosystems are discussed in proceeding sections.

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==== 7.3.1.1 Conversion of Natural Ecosystems to Agriculture ====

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Previous IPCC reports identify land-use change as an important driver of emissions and agriculture as a key driver of land-use change, causing both deforestation and wetland drainage (P. [[#Smith--2019|Smith et al. 2019]] a). The AR5 reported a trend of declining global agricultural land area since 2000 (Smith et al. 2014). The latest data ( [[#FAO--2021b|FAO 2021b]] ) indicate a 2% reduction in the global agricultural area between 2000 and 2019 (Figure 7.10). This area includes (though is not limited to) land under permanent and temporary crops or pasture, temporary fallow and natural meadows and pasture utilised for grazing or agricultural purposes ( [[#FAO--2021b|FAO 2021b]] ), although the extent of land used for grazing may not be fully captured ( [[#Fetzel--2017|Fetzel et al. 2017]] ). Data indicate changes in how agricultural land is used. Between 2000 and 2019, the area classified as permanent meadow and pasture decreased (–6%) while cropland area (under arable production and temporary crops) increased (+2%). A key driver of this change has been a general trend of intensification, including in livestock production (Barger et al. 2018; [[#OECD/FAO--2019|OECD/FAO 2019]] ; [[#UNEP--2019|UNEP 2019]] ), whereby less grazing land is supporting increasing livestock numbers in conjunction with greater use of crops as livestock feed (Barger et al. 2018). The share of feed crops, such as maize and soybean, of global crop production is projected to grow as the demand for animal feed increases with further intensification of livestock production ( [[#OECD/FAO--2019|OECD/FAO 2019]] ). Despite increased demand for food, feed, fuel and fibre from a growing human population ( [[#FAO--2019b|FAO 2019b]] ), global agricultural land area is projected to remain relatively stable during the next decade, with increases in production expected to result from agricultural intensification ( [[#OECD/FAO--2019|OECD/FAO 2019]] ).

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[[File:b0434d0760f149058329c3f76c6ebb5e IPCC_AR6_WGIII_Figure_7_10.png]]

'''Figure 7.10 | Trends in average global and regional land area under specific land uses ( [[#FAO--2021b|FAO 2021b]] ), inorganic nitrogen fertiliser use ( [[#FAO--2021e|FAO 2021e]] ) (top) and number of livestock ( [[#FAO--2021c|FAO 2021c]] ) (bottom) for three decades.''' For land use classification ‘cropland’ represents the FAOSTAT category ‘arable land’ which includes land under temporary crops, meadow, pasture and fallow. ‘Forest’ and ‘permanent meadow and pasture’ follow FAOSTAT categories.

Despite a decline in global agricultural area, the latest data document some regional expansion between 2000 and 2019, specifically in Africa (+3%) and Asia and the Pacific (+1%). Agricultural area declined in all other regions, notably in developed countries (–9%), due to multiple factors including among others, urbanisation (see [[#7.3.1.2|Section 7.3.1.2]] ).

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==== 7.3.1.2 Infrastructure Development and Urbanisation ====

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Although built-up areas (defined as cities, towns, villages and human infrastructure) occupy a relatively small fraction of land (around 1% of global land), since 1975 urban clusters (i.e., urban centres as well as surrounding suburbs) have expanded approximately 2.5 times ( [[#UNEP--2019|UNEP 2019]] ; Chapter 8, this report). Regional differences are striking. Between 1975 and 2015, built-up areas doubled in size in Europe while urban population remained relatively constant. In Africa built-up areas grew approximately fourfold, while urban population tripled ( [[#UNEP--2019|UNEP 2019]] ). Trends indicate that rural-to-urban migration will continue and accelerate in developing countries increasing environmental pressure in spite of measures to mitigate some of the impacts (e.g., by preserving or enhancing natural systems within cities, for example, lakes or natural and urban green infrastructures ( [[#UNEP--2019|UNEP 2019]] ). If current population densities within cities remain stable, the extent of built-up areas in developed countries is expected to increase by 30% and triple in developing countries between 2000 and 2050 (Barger et al. 2018).

Urban expansion leads to landscape fragmentation and urban sprawl with effects on forest resources and land use ( [[#Ünal--2019|Ünal et al. 2019]] ) while interacting with other drives. For example, in the Brazilian Amazon, the most rapid urban growth occurs within cities that are located near rural areas that produce commodities (minerals or crops) and are connected to export corridors ( [[#Richards--2015|Richards and VanWey 2015]] ). Urbanisation, coastal development and industrialisation also play crucial roles in the significant loss of mangrove forests (Hirales-Cota 2010; [[#Richards--2016|Richards and Friess 2016]] ; [[#Rivera-Monroy--2017|Rivera-Monroy et al. 2017]] ). Among infrastructural developments, roads are one of the most consistent and most considerable factors in deforestation, particularly in tropical frontiers ( [[#Pfaff--2007|Pfaff et al. 2007]] ; [[#Rudel--2009|Rudel et al. 2009]] ; [[#Ferretti-Gallon--2014|Ferretti-Gallon and Busch 2014]] ). The development of roads may also bring subsequent impacts on further development intensity due to increasing economic activities (see Chapter 8) mostly in the tropics and subtropics, where the expansion of road networks increases access to remote forests that act as refuges for biodiversity ( [[#Campbell--2017|Campbell et al. 2017]] ) (Box 7.1). Logging is one of the main drivers of road construction in tropical forests ( [[#Kleinschroth--2017|Kleinschroth and Healey 2017]] ) which leads to more severe long-term impacts that include increased fire incidence, soil erosion, landslides, and sediment accumulation in streams, biological invasions, wildlife poaching, illicit land colonisation, illegal logging and mining, land grabbing and land speculation ( [[#Laurance--2009|Laurance et al. 2009]] ; [[#Alamgir--2017|Alamgir et al. 2017]] ).

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