Editing IPCC:AR6/SRCCL/Chapter-1 (section)

== Box 1.1 Land in previous IPCC and other relevant reports ==

<div id="section-1-1-1-objectives-and-scope-of-the-assessment-block-1"></div>

Previous IPCC reports have made reference to land and its role in the climate system. Threats to agriculture, forestry and other ecosystems, but also the role of land and forest management in climate change, have been documented since the IPCC Second Assessment Report, especially so in the Special Report on land use, land-use change and forestry (Watson et al. 2000 <sup>[[#fn:r50|50]]</sup> ). The IPCC Special Report on extreme events (SREX) discussed sustainable land management, including land-use planning, and ecosystem management and restoration among the potential low-regret measures that provide benefits under current climate and a range of future, climate change scenarios. Low-regret measures are defined in the report as those with the potential to offer benefits now  and lay the foundation for tackling future, projected change. Compared to previous IPCC reports, the SRCCL offers a more integrated analysis of the land system as it embraces multiple direct and indirect drivers of natural resource management (related to food, water and energy securities), which have not previously been addressed to a similar depth (Field et al. 2014a <sup>[[#fn:r51|51]]</sup> ; Edenhofer et al. 2014 <sup>[[#fn:r52|52]]</sup> ).

The recent IPCC Special Report on Global Warming of 1.5°C (SR15) targeted specifically the Paris Agreement, without exploring the possibility of future global warming trajectories above 2°C (IPCC 2018 <sup>[[#fn:r53|53]]</sup> ). Limiting global warming to 1.5°C compared to 2°C is projected to lower the impacts on terrestrial, freshwater and coastal ecosystems and to retain more of their services for people. In many scenarios proposed in this report, large-scale land use features as a mitigation measure. In the reports of the Food and Agriculture Organization (FAO), land degradation is discussed in relation to ecosystem goods and services, principally from a food security perspective (FAO and ITPS 2015 <sup>[[#fn:r54|54]]</sup> ). The UNCCD report (2014) discusses land degradation through the prism of desertification. It devotes due attention to how land management can contribute to reversing the negative impacts of desertification and land degradation. The IPBES assessments (2018a <sup>[[#fn:r55|55]]</sup> , b <sup>[[#fn:r56|56]]</sup> , c <sup>[[#fn:r57|57]]</sup> , d <sup>[[#fn:r58|58]]</sup> , e <sup>[[#fn:r59|59]]</sup> ) focus on biodiversity drivers, including a focus on land degradation and desertification, with poverty as a limiting factor. The reports draw attention to a world in peril in which resource scarcity conspires with drivers of biophysical and social vulnerability to derail the attainment of sustainable development goals. As discussed in Chapter 4 of the SRCCL, different definitions of degradation have been applied in the IPBES degradation assessment (IPBES 2018b <sup>[[#fn:r929|929]]</sup> ), which potentially can lead to different conclusions for restoration and ecosystem management.

The SRCCL complements and adds to previous assessments, whilst keeping the IPCC-specific ‘climate perspective’. It includes a focussed assessment of risks arising from maladaptation and land-based mitigation (i.e. not only restricted to direct risks from climate change impacts) and the co-benefits and trade-offs with sustainable development objectives. As the SRCCL cuts across different policy sectors it provides the opportunity to address a number of challenges in an integrative way at the same time, and it progresses beyond other IPCC reports in having a much more comprehensive perspective on land.

<div id="section-1-1-1-objectives-and-scope-of-the-assessment-block-3"></div>

The SRCCL identifies and assesses land-related challenges and response options in an integrative way, aiming to be policy relevant across sectors. Chapter 1 provides a synopsis of the main issues addressed in this report, which are explored in more detail in Chapters 2–7. Chapter 1 also introduces important concepts and definitions and highlights discrepancies with previous reports that arise from different objectives (a full set of definitions is provided in the Glossary). Chapter 2 focuses on the natural system dynamics, assessing recent progress towards understanding the impacts of climate change on land, and the feedbacks arising from altered biogeochemical and biophysical exchange fluxes (Figure 1.2).

<div id="section-1-1-1-objectives-and-scope-of-the-assessment-block-4"></div>

<span id="figure-1.2"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 1.2'''

<span id="overview-over-the-srccl."></span>
<!-- IMG CAPTION -->
'''Overview over the SRCCL.'''
<!-- IMG FILE -->
[[File:596d2da11bc43a08b0e5dca7177db9c4 Figure-1.2-1024x301.jpg]]

Overview over the SRCCL.

<!-- END IMG -->
<span id="status-and-dynamics-of-the-global-land-system"></span>
=== 1.1.2 Status and dynamics of the (global) land system ===

<div id="section-1-1-2-1-land-ecosystems-and-climate-change"></div>

<span id="land-ecosystems-and-climate-change"></span>
==== 1.1.2.1 1.1.2.1 Land ecosystems and climate change ====

<div id="section-1-1-2-1-land-ecosystems-and-climate-change-block-1"></div>

Land ecosystems play a key role in the climate system, due to their large carbon pools and carbon exchange fluxes with the atmosphere (Ciais et al. 2013b <sup>[[#fn:r60|60]]</sup> ). Land use, the total of arrangements, activities and inputs applied to a parcel of land (such as agriculture, grazing, timber extraction, conservation or city dwelling; see Glossary), and land management (sum of land-use practices that take place within broader land-use categories; see Glossary) considerably alter terrestrial ecosystems and play a key role in the global climate system. An estimated one-quarter of total anthropogenic GHG emissions arise mainly from deforestation, ruminant livestock and fertiliser application (Smith et al. 2014 <sup>[[#fn:r61|61]]</sup> ; Tubiello et al. 2015 <sup>[[#fn:r62|62]]</sup> ; Le Quere et al. 2018 <sup>[[#fn:r63|63]]</sup> ; Ciais et al. 2013a <sup>[[#fn:r64|64]]</sup> ), and especially methane (CH <sub>4</sub> ) and nitrous oxide (N <sub>2</sub> O) emissions from agriculture have been rapidly increasing over the last decades (Hoesly et al. 2018 <sup>[[#fn:r65|65]]</sup> ; Tian et al. 2019 <sup>[[#fn:r66|66]]</sup> ) (Figure 1.1 and Sections 2.3.2–2.3.3).

Globally, land also serves as a large CO <sub>2</sub> sink, which was estimated for the period 2008–2017 to be nearly 30% of total anthropogenic emissions (Le Quere et al. 2015 <sup>[[#fn:r67|67]]</sup> ; Canadell and Schulze 2014 <sup>[[#fn:r68|68]]</sup> ; Ciais et al. 2013a <sup>[[#fn:r69|69]]</sup> ; Zhu et al. 2016 <sup>[[#fn:r70|70]]</sup> ) (Section 2.3.1). This sink has been attributed to increasing atmospheric CO <sub>2</sub> concentration, a prolonged growing season in cool environments, or forest regrowth (Le Quéré et al. 2013 <sup>[[#fn:r71|71]]</sup> ; Pugh et al. 2019 <sup>[[#fn:r72|72]]</sup> ; Le Quéré et al. 2018 <sup>[[#fn:r73|73]]</sup> ; Ciais et al. 2013a <sup>[[#fn:r74|74]]</sup> ; Zhu et al. 2016 <sup>[[#fn:r75|75]]</sup> ). Whether or not this sink will persist into the future is one of the largest uncertainties in carbon cycle and climate modelling (Ciais et al. 2013a <sup>[[#fn:r76|76]]</sup> ; Bloom et al. 2016 <sup>[[#fn:r77|77]]</sup> ; Friend et al. 2014 <sup>[[#fn:r78|78]]</sup> ; Le Quere et al. 2018 <sup>[[#fn:r79|79]]</sup> ). In addition, changes in vegetation cover caused by land use (such as conversion of forest to cropland or grassland, and vice versa) can result in regional cooling or warming through altered energy and momentum transfer between ecosystems and the atmosphere. Regional impacts can be substantial, but whether the effect leads to warming or cooling depends on the local context (Lee et al. 2011 <sup>[[#fn:r80|80]]</sup> ; Zhang et al. 2014 <sup>[[#fn:r81|81]]</sup> ; Alkama and Cescatti 2016 <sup>[[#fn:r82|82]]</sup> ) (Section 2.6). Due to the current magnitude of GHG emissions and CO <sub>2</sub> carbon dioxide removal in land ecosystems, there is ''high confidence'' that GHG reduction measures in agriculture, livestock management and forestry would have substantial climate change mitigation potential, with co-benefits for biodiversity and ecosystem services (Smith and Gregory 2013 <sup>[[#fn:r84|84]]</sup> ; Smith et al. 2014 <sup>[[#fn:r85|85]]</sup> ; Griscom et al. 2017 <sup>[[#fn:r86|86]]</sup> ) (Sections 2.6 and 6.3).

The mean temperature over land for the period 2006–2015 was 1.53°C higher than for the period 1850–1900, and 0.66°C larger than the equivalent global mean temperature change (Section 2.2). Climate change affects land ecosystems in various ways (Section 7.2). Growing seasons and natural biome boundaries shift in response to warming or changes in precipitation (Gonzalez et al. 2010 <sup>[[#fn:r87|87]]</sup> ; Wärlind et al. 2014 <sup>[[#fn:r88|88]]</sup> ; Davies-Barnard et al. 2015 <sup>[[#fn:r89|89]]</sup> ; Nakamura et al. 2017 <sup>[[#fn:r90|90]]</sup> ). Atmospheric CO <sub>2</sub> increases have been attributed to underlie, at least partially, observed woody plant cover increase in grasslands and savannahs (Donohue et al. 2013 <sup>[[#fn:r91|91]]</sup> ). Climate change-induced shifts in habitats, together with warmer temperatures, cause pressure on plants and animals (Pimm et al. 2014 <sup>[[#fn:r92|92]]</sup> ; Urban et al. 2016 <sup>[[#fn:r93|93]]</sup> ). National cereal crop losses of nearly 10% have been estimated for the period 1964–2007 as a consequence of heat and drought weather extremes (Deryng et al. 2014 <sup>[[#fn:r94|94]]</sup> ; Lesk et al. 2016 <sup>[[#fn:r95|95]]</sup> ). Climate change is expected to reduce yields in areas that are already under heat and water stress (Schlenker and Lobell 2010 <sup>[[#fn:r96|96]]</sup> ; Lobell et al. 2011 <sup>[[#fn:r97|97]]</sup> , 2012 <sup>[[#fn:r98|98]]</sup> ; Challinor et al. 2014 <sup>[[#fn:r99|99]]</sup> ) (Section 5.2.2). At the same time, warmer temperatures can increase productivity in cooler regions (Moore and Lobell 2015 <sup>[[#fn:r100|100]]</sup> ) and might open opportunities for crop area expansion, but any overall benefits might be counterbalanced by reduced suitability in warmer regions (Pugh et al. 2016 <sup>[[#fn:r101|101]]</sup> ; Di Paola et al. 2018 <sup>[[#fn:r102|102]]</sup> ). Increasing atmospheric CO <sub>2</sub> is expected to increase productivity and water use efficiency in crops and in forests (Muller et al. 2015 <sup>[[#fn:r103|103]]</sup> ; Nakamura et al. 2017 <sup>[[#fn:r104|104]]</sup> ; Kimball 2016 <sup>[[#fn:r105|105]]</sup> ). The increasing number of extreme weather events linked to climate change is also expected to result in forest losses; heat waves and droughts foster wildfires (Seidl et al. 2017 <sup>[[#fn:r106|106]]</sup> ; Fasullo et al. 2018 <sup>[[#fn:r107|107]]</sup> ) (Cross-Chapter Box 3 in Chapter 2). Episodes of observed enhanced tree mortality across many world regions have been attributed to heat and drought stress (Allen et al. 2010 <sup>[[#fn:r108|108]]</sup> ; Anderegg et al. 2012 <sup>[[#fn:r109|109]]</sup> ), whilst weather extremes also impact local infrastructure and hence transportation and trade in land-related goods (Schweikert et al. 2014 <sup>[[#fn:r110|110]]</sup> ; Chappin and van der Lei 2014 <sup>[[#fn:r111|111]]</sup> ). Thus, adaptation is a key challenge to reduce adverse impacts on land systems (Section 1.3.6).

<div id="section-1-1-2-2-current-patterns-of-land-use-and-land-cover"></div>

<span id="current-patterns-of-land-use-and-land-cover"></span>
==== 1.1.2.2 Current patterns of land use and land cover ====

<div id="section-1-1-2-2-current-patterns-of-land-use-and-land-cover-block-1"></div>

Around three-quarters of the global ice-free land, and most of the highly productive land area, are by now under some form of land use (Erb et al. 2016a <sup>[[#fn:r112|112]]</sup> ; Luyssaert et al. 2014 <sup>[[#fn:r113|113]]</sup> ; Venter et al. 2016 <sup>[[#fn:r114|114]]</sup> ) (Table 1.1). One-third of used land is associated with changed land cover. Grazing land is the single largest land-use category, followed by used forestland and cropland. The total land area used to raise livestock is notable: it includes all grazing land and an estimated additional one-fifth of cropland for feed production (Foley et al. 2011 <sup>[[#fn:r115|115]]</sup> ). Globally, 60–85% of the total forested area is used, at different levels of intensity, but information on management practices globally is scarce (Erb et al. 2016a). Large areas of unused (primary) forests remain only in the tropics and northern boreal zones (Luyssaert et al. 2014 <sup>[[#fn:r116|116]]</sup> ; Birdsey and Pan 2015 <sup>[[#fn:r117|117]]</sup> ; Morales-Hidalgo et al. 2015 <sup>[[#fn:r118|118]]</sup> ; Potapov et al. 2017 <sup>[[#fn:r119|119]]</sup> ; Erb et al. 2017 <sup>[[#fn:r120|120]]</sup> ), while 73–89% of other, non-forested natural ecosystems (natural grasslands, savannahs, etc.) are used. Large uncertainties relate to the extent of forest (32.0–42.5 million km <sup>2</sup> ) and grazing land (39–62 million km <sup>2</sup> ), due to discrepancies in definitions and observation methods (Luyssaert et al. 2014 <sup>[[#fn:r121|121]]</sup> ; Erb et al. 2017; Putz and Redford 2010 <sup>[[#fn:r122|122]]</sup> ; Schepaschenko et al. 2015 <sup>[[#fn:r123|123]]</sup> ; Birdsey and Pan 2015 <sup>[[#fn:r124|124]]</sup> ; FAO 2015a <sup>[[#fn:r125|125]]</sup> ; Chazdon et al. 2016a <sup>[[#fn:r126|126]]</sup> ; FAO 2018a <sup>[[#fn:r127|127]]</sup> ). Infrastructure areas (including settlements, transportation and mining), while being almost negligible in terms of extent, represent particularly pervasive land-use activities, with far-reaching ecological, social and economic implications (Cherlet et al. 2018 <sup>[[#fn:r128|128]]</sup> ; Laurance et al. 2014 <sup>[[#fn:r129|129]]</sup> ).

The large imprint of humans on the land surface has led to the definition of anthromes, i.e. large-scale ecological patterns created by the sustained interactions between social and ecological drivers. The dynamics of these ‘anthropogenic biomes’ are key for land-use impacts as well as for the design of integrated response options (Ellis and Ramankutty 2008 <sup>[[#fn:r130|130]]</sup> ; Ellis et al. 2010 <sup>[[#fn:r131|131]]</sup> ; Cherlet et al. 2018 <sup>[[#fn:r132|132]]</sup> ; Ellis et al. 2010 <sup>[[#fn:r133|133]]</sup> ) (Chapter 6).

The intensity of land use varies hugely within and among different land-use types and regions. Averaged globally, around 10% of the ice-free land surface was estimated to be intensively managed (such as tree plantations, high livestock density grazing, large agricultural inputs), two-thirds moderately and the remainder at low intensities (Erb et al. 2016a <sup>[[#fn:r134|134]]</sup> ). Practically all cropland is fertilised, with large regional variations. Irrigation is responsible for 70% of ground- or surface-water withdrawals by humans (Wisser et al. 2008 <sup>[[#fn:r135|135]]</sup> ; Chaturvedi et al. 2015 <sup>[[#fn:r136|136]]</sup> ; Siebert et al. 2015 <sup>[[#fn:r137|137]]</sup> ; FAOSTAT 2018 <sup>[[#fn:r138|138]]</sup> ). Humans appropriate one-quarter to one-third of the total potential net primary production (NPP), i.e. the NPP that would prevail in the absence of land use (estimated at about 60 GtC yr <sup>–1</sup> ; Bajželj et al. 2014 <sup>[[#fn:r139|139]]</sup> ; Haberl et al. 2014 <sup>[[#fn:r140|140]]</sup> ), about equally through biomass harvest and changes in NPP due to land management. The current total of agricultural (cropland and grazing) biomass harvest is estimated at about 6 GtC yr <sup>–1</sup> , around 50–60% of this is consumed by livestock. Forestry harvest for timber and wood fuel amounts to about 1 GtC yr <sup>–1</sup> (Alexander et al. 2017 <sup>[[#fn:r141|141]]</sup> ; Bodirsky and Müller 2014 <sup>[[#fn:r142|142]]</sup> ; Lassaletta et al. 2014 <sup>[[#fn:r143|143]]</sup> , 2016; Mottet et al. 2017 <sup>[[#fn:r144|144]]</sup> ; Haberl et al. 2014 <sup>[[#fn:r145|145]]</sup> ; Smith et al. 2014 <sup>[[#fn:r146|146]]</sup> ; Bais et al. 2015 <sup>[[#fn:r147|147]]</sup> ; Bajželj et al. 2014 <sup>[[#fn:r148|148]]</sup> ) (Cross-Chapter Box 7 in Chapter 6).

<div id="section-1-1-2-2-current-patterns-of-land-use-and-land-cover-block-2"></div>

<span id="table-1.1"></span>
<!-- START IMG -->
<!-- TABLE IMG -->
<!-- IMG TITLE -->
'''Table 1.1'''

<span id="extent-of-global-land-use-and-management-around-the-year-2015."></span>
<!-- IMG CAPTION -->
'''Extent of global land use and management around the year 2015.'''
<!-- IMG FILE -->
[[File:e3d41fd1998d4fdcd307deb1ab7a72f4 table-1.1a.png]] [[File:79f4c97e80bcbf7bab026e72f3ea760c table-1.1b.png]]

<!-- END IMG -->
<div id="section-1-1-2-3-past-and-ongoing-trends"></div>

<span id="past-and-ongoing-trends"></span>
==== 1.1.2.3 Past and ongoing trends ====

<div id="section-1-1-2-3-past-and-ongoing-trends-block-1"></div>

Globally, cropland area changed by +15% and the area of permanent pastures by +8% since the early 1960s (FAOSTAT 2018 <sup>[[#fn:r149|149]]</sup> ), with strong regional differences (Figure 1.3). In contrast, cropland production since 1961 increased by about 3.5 times, the production of animal products by 2.5 times, and forestry by 1.5 times; in parallel with strong yield (production per unit area) increases (FAOSTAT 2018 <sup>[[#fn:r150|150]]</sup> ) (Figure 1.3). Per capita calorie supply increased by 17% since 1970 (Kastner et al. 2012 <sup>[[#fn:r151|151]]</sup> ), and diet composition changed markedly, tightly associated with economic development and lifestyle: since the early 1960s, per capita dairy product consumption increased by a factor of 1.2, and meat and vegetable oil consumption more than doubled (FAO 2017 <sup>[[#fn:r152|152]]</sup> , 2018b <sup>[[#fn:r153|153]]</sup> ; Tilman and Clark 2014 <sup>[[#fn:r154|154]]</sup> ; Marques et al. 2019 <sup>[[#fn:r155|155]]</sup> ). Population and livestock production represent key drivers of the global expansion of cropland for food production, only partly compensated by yield increases at the global level (Alexander et al. 2015 <sup>[[#fn:r156|156]]</sup> ). A number of studies have reported reduced growth rates or stagnation in yields in some regions in the last decades ( ''medium evidence, high agreement'' ; Lin and Huybers 2012 <sup>[[#fn:r157|157]]</sup> ; Ray et al. 2012 <sup>[[#fn:r158|158]]</sup> ; Elbehri, Aziz, Joshua Elliott 2015 <sup>[[#fn:r159|159]]</sup> ) (Section 5.2.2).

The past increases in agricultural production have been associated with strong increases in agricultural inputs (Foley et al. 2011 <sup>[[#fn:r160|160]]</sup> ; Siebert et al. 2015 <sup>[[#fn:r161|161]]</sup> ; Lassaletta et al. 2016 <sup>[[#fn:r162|162]]</sup> ) (Figures 1.1 and 1.3). Irrigation area doubled, total nitrogen fertiliser use increased by 800% (FAOSTAT 2018 <sup>[[#fn:r163|163]]</sup> ; IFASTAT 2018 <sup>[[#fn:r164|164]]</sup> ) since the early 1960s. Biomass trade volumes grew by a factor of nine (in tonnes dry matter yr <sup>–1</sup> ) in this period, which is much stronger than production (FAOSTAT 2018 <sup>[[#fn:r165|165]]</sup> ), resulting in a growing spatial disconnect between regions of production and consumption (Friis et al. 2016 <sup>[[#fn:r166|166]]</sup> ; Friis and Nielsen 2017 <sup>[[#fn:r167|167]]</sup> ; Schröter et al. 2018 <sup>[[#fn:r168|168]]</sup> ; Liu et al. 2013 <sup>[[#fn:r169|169]]</sup> ; Krausmann and Langthaler 2019 <sup>[[#fn:r170|170]]</sup> ). Urban and other infrastructure areas expanded by a factor of two since 1960 (Krausmann et al. 2013 <sup>[[#fn:r171|171]]</sup> ), resulting in disproportionally large losses of highly fertile cropland (Seto and Reenberg 2014 <sup>[[#fn:r172|172]]</sup> ; Martellozzo et al. 2015 <sup>[[#fn:r173|173]]</sup> ; Bren d’Amour et al. 2016 <sup>[[#fn:r174|174]]</sup> ; Seto and Ramankutty 2016 <sup>[[#fn:r175|175]]</sup> ; van Vliet et al. 2017 <sup>[[#fn:r176|176]]</sup> ). World regions show distinct patterns of change (Figure 1.3).

<div id="section-1-1-2-3-past-and-ongoing-trends-block-2"></div>

<span id="figure-1.3"></span>
<!-- START IMG -->
<!-- IMG TITLE -->
'''Figure 1.3'''

<span id="status-and-trends-in-the-global-land-system-a.-trends-in-area-production-and-trade-and-drivers-of-change.-the-map-shows-the-global-pattern-of-land-systems-combination-of-maps-nachtergaele-2008-ellis-et-al.-2010-potapov-et-al.-2017-faos-animal-production-and-health-division-2018-livestock-lowhigh-relates-to-low-or-high"></span>
<!-- IMG CAPTION -->
'''Status and trends in the global land system: A. Trends in area, production and trade, and drivers of change. The map shows the global pattern of land systems (combination of maps Nachtergaele (2008); Ellis et al. (2010); Potapov et al. (2017); FAO’s Animal Production and Health Division (2018); livestock low/high relates to low or high […]'''
<!-- IMG FILE -->
[[File:500059f02cc4372eb106850ef773be66 Figure-1.3-724x1024.png]]

Status and trends in the global land system: '''A''' . Trends in area, production and trade, and drivers of change. The map shows the global pattern of land systems (combination of maps Nachtergaele (2008) <sup>[[#fn:r177|177]]</sup> ; Ellis et al. (2010) <sup>[[#fn:r178|178]]</sup> ; Potapov et al. (2017) <sup>[[#fn:r179|179]]</sup> ; FAO’s Animal Production and Health Division (2018); livestock low/high relates to low or high livestock density, respectively). The inlay figures show, for the globe and seven world regions, from left to right: (a) Cropland, permanent pastures and forest (used and unused) areas, standardised to total land area, (b) production in dry matter per year per total land area, (c) trade in dry matter in percent of total domestic production, all for 1961 to 2014 (data from FAOSTAT (2018) <sup>[[#fn:r180|180]]</sup> and FAO (1963) <sup>[[#fn:r181|181]]</sup> for forest area 1961). (d) drivers of cropland for food production between 1994 and 2011 (Alexander et al. 2015 <sup>[[#fn:r182|182]]</sup> ). See panel “global” for legend. “Plant Produc., Animal P.”: changes in consumption of plant-based products and animal-products, respectively. '''B''' .Selected land-use pressures and impacts. The map shows the ratio between impacts on biomass stocks of land-cover conversions and of land management (changes that occur with land-cover types; only changes larger than 30 gC m <sup>–2</sup> displayed; Erb et al. 2017 <sup>[[#fn:r183|183]]</sup> ), compared to the biomass stocks of the potential vegetation (vegetation that would prevail in the absence of land use, but with current climate). The inlay figures show, from left to right (e) the global Human Appropriation of Net Primary production (HANPP) in the year 2005, in gC m <sup>–2</sup> yr <sup>–1</sup> (Krausmann et al. 2013 <sup>[[#fn:r184|184]]</sup> ). The sum of the three components represents the NPP of the potential vegetation and consist of: (i) NPP <sub>eco</sub> , i.e. the amount of NPP remaining in ecosystem after harvest, (ii) HANPP <sub>harv</sub> , i.e. NPP harvested or killed during harvest, and (iii) HANPP <sub>luc</sub> , i.e. NPP foregone due to land-use change. The sum of NPP <sub>eco</sub> and HANPP <sub>harv</sub> is the NPP of the actual vegetation (Haberl et al. 2014 <sup>[[#fn:r185|185]]</sup> ; Krausmann et al. 2013 <sup>[[#fn:r186|186]]</sup> ). The two central inlay figures show changes in land-use intensity, standardised to 2014, related to (f) cropland (yields, fertilisation, irrigated area) and (g) forestry harvest per forest area, and grazers and monogastric livestock density per agricultural area (FAOSTAT 2018). (h) Cumulative CO <sub>2</sub> fluxes between land and the atmosphere between 2000 and 2014. LUC: annual CO <sub>2</sub> land use flux due to changes in land cover and forest management; Sink <sub>land</sub> : the annual CO <sub>2</sub> land sink caused mainly by the indirect anthropogenic effects of environmental change (e.g, climate change and the fertilising effects of rising CO <sub>2</sub> and N concentrations), excluding impacts of land-use change (Le Quéré et al. 2018 <sup>[[#fn:r187|187]]</sup> ) (Section 2.3)

<!-- END IMG -->
<div id="section-1-1-2-3-past-and-ongoing-trends-block-3"></div>

While most pastureland expansion replaced natural grasslands, cropland expansion replaced mainly forests (Ramankutty et al. 2018 <sup>[[#fn:r188|188]]</sup> ; Ordway et al. 2017 <sup>[[#fn:r189|189]]</sup> ; Richards and Friess 2016 <sup>[[#fn:r190|190]]</sup> ). Noteworthy large conversions occurred in tropical dry woodlands and savannahs, for example, in the Brazilian Cerrado (Lehmann and Parr 2016 <sup>[[#fn:r191|191]]</sup> ; Strassburg et al. 2017 <sup>[[#fn:r192|192]]</sup> ), the South American Caatinga and Chaco regions (Parr et al. 2014 <sup>[[#fn:r193|193]]</sup> ; Lehmann and Parr 2016 <sup>[[#fn:r194|194]]</sup> ) or African savannahs (Ryan et al. 2016 <sup>[[#fn:r195|195]]</sup> ). More than half of the original 4.3–12.6 million km <sup>2</sup> global wetlands (Erb et al. 2016a <sup>[[#fn:r196|196]]</sup> ; Davidson 2014 <sup>[[#fn:r197|197]]</sup> ; Dixon et al. 2016 <sup>[[#fn:r198|198]]</sup> ) have been drained; since 1970 the wetland extent index, developed by aggregating data field-site time series that report changes in local inland wetland area, indicates a decline of more than 30% (Darrah et al. 2019 <sup>[[#fn:r199|199]]</sup> ) (Figure 1.1 and Section 4.2.1). Likewise, one-third of the estimated global area that in a non-used state would be covered in forests (Erb et al. 2017 <sup>[[#fn:r200|200]]</sup> ) has been converted to agriculture.

Global forest area declined by 3% since 1990 (about –5% since 1960) and continues to do so (FAO 2015a <sup>[[#fn:r201|201]]</sup> ; Keenan et al. 2015 <sup>[[#fn:r202|202]]</sup> ; MacDicken et al. 2015 <sup>[[#fn:r203|203]]</sup> ; FAO 1963; Figure 1.1 <sup>[[#fn:r204|204]]</sup> ), but uncertainties are large. ''Low agreement'' relates to the concomitant trend of global tree cover. Some remote-sensing based assessments show global net-losses of forest or tree cover (Li et al. 2016 <sup>[[#fn:r205|205]]</sup> ; Nowosad et al. 2018 <sup>[[#fn:r206|206]]</sup> ; Hansen et al. 2013 <sup>[[#fn:r207|207]]</sup> ); others indicate a net gain (Song et al. 2018 <sup>[[#fn:r208|208]]</sup> ). Tree-cover gains would be in line with observed and modelled increases in photosynthetic active tissues (‘greening’; Chen et al. 2019 <sup>[[#fn:r209|209]]</sup> ; Zhu et al. 2016 <sup>[[#fn:r210|210]]</sup> ; Zhao et al. 2018 <sup>[[#fn:r211|211]]</sup> ; de Jong et al. 2013 <sup>[[#fn:r212|212]]</sup> ; Pugh et al. 2019 <sup>[[#fn:r213|213]]</sup> ; De Kauwe et al. 2016 <sup>[[#fn:r214|214]]</sup> ; Kolby Smith et al. 2015 <sup>[[#fn:r215|215]]</sup> ) (Box 2.3 in Chapter 2), but ''confidence'' remains ''low'' whether gross forest or tree-cover gains are as large, or larger, than losses. This uncertainty, together with poor information on forest management, affects estimates and attribution of the land carbon sink (Sections 2.3, 4.3 and 4.6). Discrepancies are caused by different classification schemes and applied thresholds (e.g., minimum tree height and tree-cover thresholds used to define a forest), the divergence of forest and tree cover, and differences in methods and spatiotemporal resolution (Keenan et al. 2015 <sup>[[#fn:r216|216]]</sup> ; Schepaschenko et al. 2015 <sup>[[#fn:r217|217]]</sup> ; Bastin et al. 2017 <sup>[[#fn:r218|218]]</sup> ; Sloan and Sayer 2015 <sup>[[#fn:r219|219]]</sup> ; Chazdon et al. 2016a <sup>[[#fn:r220|220]]</sup> ; Achard et al. 2014 <sup>[[#fn:r221|221]]</sup> ). However, there is ''robust evidence''  and ''high agreement'' that a net loss of forest and tree cover prevails in the tropics and a net gain, mainly of secondary, semi-natural and planted forests, in the temperate and boreal zones.

The observed regional and global historical land-use trends result in regionally distinct patterns of C fluxes between land and the atmosphere (Figure 1.3B). They are also associated with declines in biodiversity, far above background rates (Ceballos et al. 2015 <sup>[[#fn:r222|222]]</sup> ; De Vos et al. 2015 <sup>[[#fn:r223|223]]</sup> ; Pimm et al. 2014 <sup>[[#fn:r224|224]]</sup> ; Newbold et al. 2015 <sup>[[#fn:r225|225]]</sup> ; Maxwell et al. 2016 <sup>[[#fn:r226|226]]</sup> ; Marques et al. 2019 <sup>[[#fn:r227|227]]</sup> ). Biodiversity losses from past global land-use change have been estimated to be about 8–14%, depending on the biodiversity indicator applied (Newbold et al. 2015 <sup>[[#fn:r228|228]]</sup> ; Wilting et al. 2017 <sup>[[#fn:r229|229]]</sup> ; Gossner et al. 2016 <sup>[[#fn:r230|230]]</sup> ; Newbold et al. 2018 <sup>[[#fn:r231|231]]</sup> ; Paillet et al. 2010 <sup>[[#fn:r232|232]]</sup> ). In future, climate warming has been projected to accelerate losses of species diversity rapidly (Settele et al. 2014 <sup>[[#fn:r|]]</sup> 233; Urban et al. 2016 <sup>[[#fn:r234|234]]</sup> ; Scholes et al. 2018 <sup>[[#fn:r235|235]]</sup> ; Fischer et al. 2018 <sup>[[#fn:r236|236]]</sup> ; Hoegh-Guldberg et al. 2018 <sup>[[#fn:r237|237]]</sup> ). The concomitance of land-use and climate change pressures render ecosystem restoration a key challenge (Anderson-Teixeira 2018 <sup>[[#fn:r238|238]]</sup> ; Yang et al. 2019 <sup>[[#fn:r240|240]]</sup> ) (Sections 4.8 and 4.9).

<span id="key-challenges-related-to-land-use-change"></span>