Editing IPCC:AR6/WGII/Cross-Chapter-Paper-7 (section)

== CCP7.2 The Current State of Tropical Forests ==

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In the most recent Global Ecological Zones map produced by the Food and Agriculture Organization (FAO) for the year 2010, tropical vegetation has been defined as encompassing regions which are frost-free during all months in the year ( [[#FAO--2012|FAO, 2012]] ). Further, the tropical vegetation has been sub-classified into tropical rainforest, tropical moist forest, tropical dry forest, tropical shrubland, tropical desert and tropical mountain systems based on climate in combination with vegetation physiognomy and orographic zone (Table SMCCP7.1). IPCC has used the basic FAO classification in its National Greenhouse Gas Inventories Guidelines ( [[#IPCC--2019a|IPCC, 2019a]] ).

Since the FAO ecological zones represent potential biome extents, the present area under forest is assessed using the European Space Agency Climate Change Initiative Land Cover data set ( [[#ESA--2017|ESA, 2017]] ). The ESA data set provides a direct mapping to IPCC land categories (e.g., ‘forest’), allowing for standardised and consistent reporting of existing forest and forest gain/loss in each ecological zone. The most extensive tropical ecological zone is the tropical rainforest (1459 Mha or about 25% of all tropical ecological zones), followed by tropical desert (which is not further considered here), tropical moist forest, tropical shrubland, tropical dry forest and tropical mountain system (Table CCP7.1; Figure CCP7.2). Mangroves are not explicitly considered in the FAO classification. Tropical rainforest occurs largely in South America, Africa, and South and Southeast Asia, and is the most intact tropical forest biome (Table CCP7.1). Significant portions of tropical moist forest, which abut tropical rainforest in many regions but experience a longer dry season, have been lost in most regions (Table CCP7.2). Tropical moist forest typically grades into the highly threatened tropical dry forest ecological zone, of which only about a third exists under forest cover at present. Only about 44% of tropical mountain systems, which occur approximately above 1000 m above mean sea level, are presently under forest cover. While the FAO classification provides the potential tropical ecological zones (roughly, ‘vegetation types’), there are large differences in the extents of global tropical forest biomes which are still remaining as reported by different sources (Sayre et al., 2020; Ocón et al., 2021). These differences result from differences in biome definition, data source, the definition of ‘forest’, and the method used for classifying remotely sensed data. For example, the reported global area of tropical dry forests ranges from 105 to 645 Mha (Pan et al., 2013; Bastin et al., 2017; Ocón et al., 2021).

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[[File:feeb5f909fe50f66483d0280d894bd10 IPCC_AR6_WGII_Figure_CCP7_002.png]]

'''Figure CCP7.2 |''' '''Colours represent tropical ecological zones as defined by the FAO ( [[#FAO--2012|FAO, 2012]] ).''' Areas classified as ‘forest’ in the 2020 ESA Land Cover CCI Product ( [[#ESA--2017|ESA, 2017]] ) are overlaid in grey.

'''Table CCP7.1 |''' Areas in tropical ecological zones as defined by the FAO ( [[#FAO--2012|FAO, 2012]] ). 1 Existing forest represents areas classified as ‘forest’ in the 2020 ESA Land Cover CCI Product ( [[#ESA--2017|ESA, 2017]] ). All units are in million hectares, except where indicated.

{| class="wikitable"
|-
! Ecological zone

! Africa

! South America

! North America

! Asia

! Australia

! Oceania

! '''Global'''

! '''Existing forest''' 1

! '''Existing forest (%)''' 1

|-
| Tropical rainforest

| 399

| 659

| 48

| 323

| 3

| 13

| '''1459'''

| '''1140'''

| '''78.2'''

|-
| Tropical moist forest

| 464

| 428

| 43

| 139

| 0

| 0

| '''1077'''

| '''509'''

| '''47.3'''

|-
| Tropical dry forest

| 366

| 167

| 39

| 143

| 67

| 0

| '''784'''

| '''236'''

| '''30.0'''

|-
| Tropical shrubland

| 595

| 11

| 0

| 116

| 85

| 0

| '''808'''

| '''60'''

| '''7.4'''

|-
| Tropical desert

| 871

| 13

| 0

| 269

| 141

| 0

| '''1296'''

| '''6'''

| '''0.4'''

|-
| Tropical mountain system

| 147

| 188

| 16

| 90

| 0

| 2

| '''443'''

| '''194'''

| '''43.9'''

|}

'''Table CCP7.2 |''' Trends in net tropical forest loss, reforestation and expansion rates (1000 ha yr −1 ) from 2010–2015 and 2015–2020 periods by regions.

{| class="wikitable"
|-
!
! colspan="3"| Net loss rate

! colspan="3"| Reforestation rate

! colspan="3"| Forest expansion rate

|-
! Region

! 2010–2015

! 2015–2020

! Observed

Trend

! 2010–2015

! 2015–2020

! Observed

Trend

! 2010–2015

! 2015–2020

! Observed

Trend

|-
| Africa

| 3911.37

| 3982.97

| 406.82

| 297.55

| 442.89

| 390.47

|-
| Asia and Oceania

| 1083.02

| 780.49

| 627.46

| 582.06

| 1227.15

| 1130.38

|-
| Central America and Caribbean

| 59.4

| 122.45

| 51.36

| 44.51

| 104.74

| 41.34

|-
| South

America

| 2663.96

| 2498.65

| 1081.9

| 846.24

| 447.88

| 297.19

|-
| Total

| 7717.76

| 7384.57

| 2167.49

| 1770.36

| 2222.66

| 1859.38

|-
| colspan="2"|
| colspan="4"| Trend direction

| colspan="4"| Magnitude of trend (%)

|-

| Increase

| Decrease

| 0–25

| 25–50

| &gt;50

|}

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=== CCP7.2.1 Distribution and Biodiversity of Tropical Forest Ecosystems ===

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Tropical forests are indisputably the areas with highest biological diversity on Earth, both in absolute and density (species per area) terms (Plotkin et al., 2000). Estimates account that tropical forests harbour half or even more of world’s biodiversity (Kier et al., 2009; Jenkins et al., 2013), even though this figure is highly uncertain owing to varying estimates of undescribed species (Mora et al., 2011). For example, it is estimated that there are at least 40,000, but possibly more than 53,000 tree species in tropical forests (Slik et al., 2015). A vast majority of this biodiversity and Indigenous knowledge and local knowledge associated with its use remains poorly explored, presenting a vast unlocked genetic reserve at risk of loss, although many of today’s important medicines, foods and ecosystem products originate from tropical forests ( [[#Kouznetsov--2008|Kouznetsov and Amado Torres, 2008]] ; Calderon et al., 2009, [[#Maia--2016|Maia and Mourão, 2016]] ).

Rates of global biodiversity loss in the past few decades have acelerated to levels that are, for some taxa, approaching the estimated rate of 75% of taxa extinction found in Earth’s ‘big five’ mass extinction events (Barnosky et al., 2011; Díaz et al., 2019; [[#Davison--2021|Davison et al., 2021]] ). Even though species–area relationships tend to overestimate extinction rates ( [[#He--2011|He and Hubbell, 2011]] ), there is evidence that species richness in tropical forests is alarmingly approaching or surpassing the taxa extinction value in this period (45% for dung beetles, 51% for lizards, 65% for ants, and 80% for mammals) should deforestation and habitat loss continue at the current pace ( [[#Alroy--2017|Alroy, 2017]] ; Ceballos et al., 2017). Moreover, there is reasonable understanding that these numbers are underestimated and, as such, tropical forest loss and degradation alone will precipitate a sixth mass extinction event ( [[#Giam--2017|Giam, 2017]] ). A total of 13 out of the 25 global biodiversity hotspots for conservation are located in tropical forests, such as Brazil’s Atlantic Forest and India’s Western Ghats/Sri Lanka (Myers et al., 2000). While forest loss and degradation have been the main cause of tropical biodiversity loss in the past, climate change now arises as a major threat not only for individual tropical forest species or taxa—as already observed for frogs (Pounds et al., 2006)—but for whole communities (Esquivel-Muelbert et al., 2019), and even entire tropical forest ecoregions (Lapola et al., 2018).

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=== CCP7.2.2 Rates of Deforestation, Tropical Reforestation and Connections to Climate Resilience of Tropical Forests ===

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More than 420 million ha of forest were lost globally in the 1990–2020 period because of deforestation, and more than 90% of that loss took place in tropical areas ( [[#FAO--2020|FAO, 2020]] ). For the 2015–2020 period, the tropical deforestation rate decreased compared with 2010–2015, being estimated at 10.2 Mha yr −1 ( [[#FAO--2020|FAO, 2020]] ). But reforestation and afforestation rates have also decreased, resulting in a tropical forests net loss rate of 7.3 Mha yr −1 in the 2015–2020 period. Overall, the net loss rate has slightly decreased (−4%) since 1990 ( ''high confidence'' ). However, a particularly high upward trend is observed in Central America and the Caribbean, while a small increase (2%) is observed in the tropical zone of Africa, during the periods from 2010–2015 to 2015–2020 (Table CPP7.2).

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=== CCP7.2.3 Drivers of Deforestation and Forest Degradation ===

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Deforestation and forest degradation both affect carbon stocks, biodiversity loss and the provision of ecosystem services, leading to a reduction in resilience to climate change and exacerbating forest landscape vulnerability even in the absence of direct anthropogenic action ( ''high confidence'' ) (Barlow et al., 2016; Aleixo et al., 2019; Feng et al., 2021; Saatchi et al., 2021). There is also clear evidence of deforestation influencing temperatures and the hydrological cycle at local to regional scales resulting in reduced precipitation and evaporation and increased runoff relative to unaffected areas ( ''high confidence'' ) [CCP7.3.6] (Jia et al., 2019; Douville et al., 2021). Negative trends in biodiversity and ecosystems are predicted to undermine 80% of the Sustainable Development Goals targets related to poverty, hunger, health, water, cities, climate, oceans and land (IPBES, 2019). Therefore, besides greenhouse gas (GHG) mitigation, reducing the driving forces leading to deforestation and forest degradation is of the utmost importance for forest resilience, biodiversity protection, avoiding regional climatic changes and the provision of critical ecosystem services, and communities whose livelihoods depend on forests ( ''high confidence'' ) (Curtis et al., 2018; IPBES, 2019; Jia et al., 2019; [[#Seymour--2019|Seymour and Harris, 2019]] ; Pörtner et al., 2021; Saatchi et al., 2021).

Drivers of deforestation and forest degradation can be distinguished between proximate (i.e., direct) and underlying (i.e., indirect). Direct drivers, such as agriculture (including crops, livestock and plantation forestry), infrastructure development (which often provides access to intact forests and catalyses deforestation) or timber extraction, are place-based and visible. They are influenced by underlying driving forces, such as demographic, economic, technological, political and institutional, or cultural factors, which typically form complex interactions and act at multiple scales, frequently without any direct connection to the areas of forest loss ( [[#Geist--2002|Geist and Lambin, 2002]] ).

Agriculture is by far the largest direct driver of tropical deforestation, with great differences between commercial and subsistence farming and large variation across regions (Figure CCP7.3). Over 80% of tropical deforestation between 2000 and 2010 was caused by agriculture, proportionally ranging from ca. 75% in Africa and Asia to ca. 95% in the Americas ( [[#FAO%20and%20UNEP--2020|FAO and UNEP, 2020]] ), but both the scale of deforestation and the relative contribution of different drivers have changed considerably over time ( ''high confidence'' ) (Hosonuma et al., 2012; Curtis et al., 2018; [[#Seymour--2019|Seymour and Harris, 2019]] ; [[#FAO%20and%20UNEP--2020|FAO and UNEP, 2020]] ).

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[[File:783954b95b38babcaeaab7da39812f04 IPCC_AR6_WGII_Figure_CCP7_003.png]]

'''Figure CCP7.3 |''' '''Primary drivers of tropical forest cover loss for the period 2001–2015.''' Darker colour intensity indicates greater total quantity of forest cover loss. While some tropical forest cover loss is temporary, a large portion is related to deforestation. Source: Curtis et al. (2018). Cropped figure reprinted with permission from AAAS.

Forest degradation is more difficult to track, but can have large negative effects on carbon storage, provision of ecosystem services, and biodiversity (Griscom et al., 2017; [[#Houghton--2017|Houghton and Nassikas, 2017]] ). A recent analysis suggests that forest degradation is increasing and is now surpassing deforestation rates in the Brazilian Amazon (Aparecido Trondoli Matricardi et al., 2020). As with deforestation, drivers of forest degradation differ by region, such that timber extraction was by far the most important degradation driver in Latin America and Asia, whereas in Africa wood fuel consumption contributed to about half of forest degradation between 2000 and 2010 (Hosonuma et al., 2012).

Though not as visible as direct drivers, indirect or underlying causes can greatly influence direct drivers, and must be addressed to reduce pressures on forests ( ''high confidence'' ) (e.g., [[#FAO--2016b|FAO, 2016b]] ; Fehlenberg et al., 2017; Pendrill et al., 2019b; Bos et al., 2020; Junquera et al., 2020; Ken et al., 2020; [[#Kissinger--2020|Kissinger, 2020]] ; Siqueira-Gay et al., 2020; [[#Hoang--2021|Hoang and Kanemoto, 2021]] ). Next to population growth, poverty and insecure land tenure (Ariti et al., 2015; [[#Arevalo--2016|Arevalo, 2016]] ; [[#FAO--2016a|FAO, 2016a]] ; Ken et al., 2020; Siqueira-Gay et al., 2020; Verma et al., 2021), many developing tropical countries identify weak forest sector governance and institutions, lack of cross-sectoral coordination, and illegal activity (related to weak enforcement) as critical underlying drivers ( [[#FAO--2016a|FAO, 2016a]] ; Ken et al., 2020; [[#Kissinger--2020|Kissinger, 2020]] ) [CCP7.6].

International and market forces, particularly commodity markets and, increasingly, large-scale land acquisitions are also key underlying drivers ( ''high confidence'' ) (Assunção et al., 2015; Henders et al., 2015; Conigliani et al., 2018; Ingalls et al., 2018; Garrett et al., 2019; Pendrill et al., 2019b; [[#Kissinger--2020|Kissinger, 2020]] ; [[#Neef--2020|Neef, 2020]] ; [[#Hoang--2021|Hoang and Kanemoto, 2021]] ) [WGII Chapter 5.13]. Deforestation related to commodity imports is increasing, illustrating the growing influence of global markets in deforestation dynamics (Henders et al., 2015). Although some of this production is consumed domestically, 29–39% of deforestation was driven by international trade, primarily from Europe, China, the Middle East and North America (Pendrill et al., 2019a). While many developed countries, as well as China and India, have achieved net domestic forest gains, their consumption patterns have increased deforestation embodied in their imports to varying degrees, frequently from biodiversity hotspots ( [[#Hoang--2021|Hoang and Kanemoto, 2021]] ). Fifty percent of the biodiversity loss associated with consumption in developed economies occurs outside their territorial boundaries (Wilting et al., 2017). The increasing prominence of medium- and large-scale clearings of forest between 2000 and 2012, particularly in Southeast Asia and South America, suggests the growing need for policy interventions targeting industrial-scale agricultural commodity producers (Austin et al., 2017). However, countries have been slow to address underlying drivers such as international demand for agricultural commodities. A review of 43 countries’ REDD+ readiness documents found that proposed policy interventions largely missed the agricultural drivers identified (Salvini et al., 2014). An assessment of policy responses to rubber and coffee production highlights the challenges governments face in identifying correlations between the direct drivers and related underlying drivers, with international drivers being the most challenging to address ( [[#Kissinger--2020|Kissinger, 2020]] ).

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