Editing IPCC:AR6/WGIII/Chapter-3 (section)

=== 3.4.6 Culture, Forestry and Other Land Use (AFOLU) ===

<div id="h2-19-siblings" class="h2-siblings"></div>

Mitigation pathways show substantial reductions in CO 2 emissions, but more modest reductions in AFOLU CH 4 and N 2 O emissions ( ''high confidence'' ) ( [[#Popp--2017|Popp et al. 2017]] ; [[#Roe--2019|Roe et al. 2019]] ; [[#Reisinger--2021|Reisinger et al. 2021]] ) (Figure 3.27). Pathways limiting warming to ''likely'' 2°C or lower are projected to reach net zero CO 2 emissions in the AFOLU sector around 2033 (2024–2060); however, AFOLU CH 4 and N 2 O emissions remain positive in all pathways (Figure 3.27). While IAMs include many land-based mitigation options, these models exclude several options with large mitigation potential, such as biochar, agroforestry, restoration/avoided conversion of coastal wetlands, and restoration/avoided conversion of peatland ( [[#IPCC--2019a|IPCC 2019a]] ; [[#Smith--2019|Smith et al. 2019]] ) ( [[IPCC:Wg3:Chapter:Chapter-7|Chapter 7]] and [[#3.4|Section 3.4]] ). Sectoral studies show higher mitigation potential than IAM pathways, as these studies include more mitigation options than IAMs ( ''medium confidence'' ) (Chapter 7).

<div id="_idContainer075" class="_idGenObjectStyleOverride-1"></div>

[[File:6ca1179605e4974fbfc970c271ee5845 IPCC_AR6_WGIII_Figure_3_27.png]]

'''Figure 3.27 | Reduction in AFOLU GHG emissions from 2019.''' The AFOLU CO 2 estimates in this figure are not necessarily comparable with country GHG inventories (see Chapter 7).

<div id="_idContainer018" class="Basic-Text-Frame"></div>

[[File:b965bdd198cd34c14de6a4b756f2a66a IPCC_AR6_WGIII_Figure_3_28.png]]

'''Figure 3.28 | Change in''' '''land''' '''cover from 2019 in million hectares.''' Positive values indicate an increase in area.

Limiting warming to ''likely'' 2°C (&gt;67%) or lower can result in large-scale transformation of the land surface ( ''high confidence'' ) ( [[#Popp--2017|Popp et al. 2017]] ; [[#Rogelj--2018|Rogelj et al. 2018]] a,b; [[#Brown--2019|Brown et al. 2019]] ; [[#Roe--2019|Roe et al. 2019]] ). The scale of land transformation depends, ''inter alia'' , on the temperature goal and the mitigation options included ( [[#Popp--2017|Popp et al. 2017]] ; [[#Rogelj--2018|Rogelj et al. 2018]] a; [[#IPCC--2019a|IPCC 2019a]] ). Pathways with more demand-side mitigation options show less land transformation than those with more limited options ( [[#Grubler--2018|Grubler et al. 2018]] ; [[#van%20Vuuren--2018|van Vuuren et al. 2018]] ; [[#IPCC--2019a|IPCC 2019a]] ). Most of these pathways show increases in forest cover, with an increase of 322 million ha (–67 to 890 million ha) in 2050 in pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot, whereas bottom-up models portray an economic potential of 300–500 million ha of additional forest (Chapter 7). Many IAM pathways also include large amounts of energy cropland area, to supply biomass for bioenergy and BECCS, with 199 (56–482) million ha in 2050 in pathways that limit warming to 1.5°C (&gt;50%) with no or limited overshoot. Large land transformations, such as afforestation/reforestation and widespread planting of energy crops, can have implications for biodiversity and sustainable development (Sections 3.7, 7.7.4 and 12.5).

Delayed mitigation has implications for land-use transitions ( [[#Hasegawa--2021a|Hasegawa et al. 2021a]] ). Delaying mitigation action can result in a temporary overshoot of temperature and large-scale deployment of CDR in the second half of the century to reduce temperatures from their peak to a given level ( [[#Smith--2019|Smith et al. 2019]] ; [[#Hasegawa--2021a|Hasegawa et al. 2021a]] ). IAM pathways rely on afforestation and BECCS as CDR measures, so delayed mitigation action results in substantial land-use change in the second half of the century with implications for sustainable development ( [[#Hasegawa--2021a|Hasegawa et al. 2021a]] ) ( [[#3.7|Section 3.7]] ). Shifting to earlier mitigation action reduces the amount of land required for this, though at the cost of larger land-use transitions earlier in the century ( [[#Hasegawa--2021a|Hasegawa et al. 2021a]] ). Earlier action could also reduce climate impacts on agriculture and land-based mitigation options ( [[#Smith--2019|Smith et al. 2019]] ).

Some AFOLU mitigation options can enhance vegetation and soil carbon stocks such as reforestation, restoration of degraded ecosystems, protection of ecosystems with high carbon stocks and changes to agricultural land management to increase soil carbon ( ''high confidence'' ) ( [[#Griscom--2017|Griscom et al. 2017]] ; [[#de%20Coninck--2018|de Coninck et al. 2018]] ; [[#Fuss--2018|Fuss et al. 2018]] ; [[#Smith--2019|Smith et al. 2019]] ) (AR6 WGIII Chapter 7). The time scales associated with these options indicate that carbon sinks in terrestrial vegetation and soil systems can be maintained or enhanced so as to contribute towards long-term mitigation ( ''high confidence'' ); however, many AFOLU mitigation options do not continue to sequester carbon indefinitely ( [[#Fuss--2018|Fuss et al. 2018]] ; [[#de%20Coninck--2018|de Coninck et al. 2018]] ; [[#IPCC--2019a|IPCC 2019a]] ) (AR6 WGIII Chapter 7). In the very long term (the latter part of the century and beyond), it will become more challenging to continue to enhance vegetation and soil carbon stocks, so that the associated carbon sinks could diminish or even become sources ( ''high confidence'' ) ( [[#de%20Coninck--2018|de Coninck et al. 2018]] ; [[#IPCC--2019a|IPCC 2019a]] ) (AR6 WGI Chapter 5). Sustainable forest management, including harvest and forest regeneration, can help to remediate and slow any decline in the forest carbon sink, for example by restoring degraded forest areas, and so go some way towards addressing the issue of sink saturation (IPCC 2019) (AR6 WGI Chapter 5; and [[IPCC:Wg3:Chapter:Chapter-7|Chapter 7]] in this report). The accumulated carbon resulting from mitigation options that enhance carbon sequestration (e.g., reforestation, soil carbon sequestration) is also at risk of future loss due to disturbances (e.g., fire, pests) ( [[#Boysen--2017|Boysen et al. 2017]] ; [[#de%20Coninck--2018|de Coninck et al. 2018]] ; [[#Fuss--2018|Fuss et al. 2018]] ; [[#Smith--2019|Smith et al. 2019]] ; [[#IPCC--2019a|IPCC 2019a]] ; [[#Anderegg--2020|Anderegg et al. 2020]] ) (AR6 WGI Chapter 5). Maintaining the resultant high vegetation and soil carbon stocks could limit future land-use options, as maintaining these carbon stocks would require retaining the land use and land-cover configuration implemented to achieve the increased stocks.

Anthropogenic land CO 2 emissions and removals in IAM pathways cannot be directly compared with those reported in national GHG inventories ( ''high confidence'' ) ( [[#Grassi--2018|Grassi et al. 2018]] , 2021) ( [[IPCC:Wg3:Chapter:Chapter-7#7.2|Section 7.2]] ). Due to differences in definitions for the area of managed forests and which emissions and removals are considered anthropogenic, the reported anthropogenic land CO 2 emissions and removals differ by about 5.5 GtCO 2 yr –1 between IAMs, which rely on bookkeeping approaches (e.g., [[#Houghton--2017|Houghton and Nassikas 2017]] ), and national GHG inventories ( [[#Grassi--2021|Grassi et al. 2021]] ). Such differences in definitions can alter the reported time at which anthropogenic net zero CO 2 emissions are reached for a given emission scenario. Using national inventories would lead to an earlier reported time of net zero ( [[#van%20Soest--2021b|van Soest et al. 2021b]] ) or to lower calculated cumulative emissions until the time of net zero ( [[#Grassi--2021|Grassi et al. 2021]] ) as compared to IAM pathways. The numerical differences are purely due to differences in the conventions applied for reporting the anthropogenic emissions and do not have any implications for the underlying land-use changes or mitigation measures in the pathways. Grassi et al. ( [[#Grassi--2021|Grassi et al. 2021]] ) offer a methodology for adjusting to reconcile these differences and enable a more accurate assessment of the collective progress achieved under the Paris Agreement ( [[IPCC:Wg3:Chapter:Chapter-7|Chapter 7]] and Cross-Chapter Box 6 in Chapter 7).

<div id="3.4.7" class="h2-container"></div>

<span id="other-carbon-dioxide-removal-options"></span>