Editing IPCC:AR6/WGIII/Chapter-12 (section)

=== Box 12.3 | Land Degradation Neutrality as a Framework to Manage Trade-offs in Land-based Mitigation ===

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The United Nations Convention to Combat Desertification (UNCCD) introduced the concept of Land Degradation Neutrality (LDN), defined as ‘a state whereby the amount and quality of land resources necessary to support ecosystem functions and services and enhance food security remain stable or increase within specified temporal and spatial scales and ecosystems’ (UNCCD 2015), and it has been adopted as a target of SDG 15 (life on land). At December 2020, 124 (mostly developing) countries had committed to pursue voluntary LDN targets.

The goal of LDN is to maintain or enhance land-based natural capital, and its associated ecosystem services, such as provision of food and regulation of water and climate, while enhancing the resilience of the communities that depend on the land. LDN encourages a dual-pronged approach promoting sustainable land management (SLM) to avoid or reduce land degradation, combined with strategic effort in land restoration and rehabilitation to reverse degradation on degraded lands and thereby deliver the target of ‘no net loss’ of productive land ( [[#Orr--2017|Orr et al. 2017]] ).

In the context of LDN, land restoration refers to actions undertaken with the aim of reinstating ecosystem functionality, whereas land rehabilitation refers to actions undertaken with a goal of provision of goods and services ( [[#Cowie--2018|Cowie et al. 2018]] ). Restoration interventions can include destocking to encourage regeneration of native vegetation; shelter belts of local species established from seed or seedlings, strategically located to provide wildlife corridors and link habitat; and rewetting drained peatland. ‘Farmer-managed natural regeneration’ is a low-cost restoration approach in which regeneration of tree stumps and roots is encouraged, stabilising soil and

enhancing soil nutrients and organic matter levels ( [[#Chomba--2020|Chomba et al. 2020]] ; [[#Lohbeck--2020|Lohbeck et al. 2020]] ). Rehabilitation actions include establishment of energy crops, or afforestation with fast-growing exotic trees to sequester carbon or produce timber. Application of biochar can facilitate rehabilitation by enhancing nutrient retention and water-holding capacity, and stimulating microbial activity ( [[#Cowie--2020a|Cowie 2020a]] ).

SLM, rehabilitation and restoration activities undertaken towards national LDN targets have potential to deliver substantial CDR through carbon sequestration in vegetation and soil. In addition, biomass production, for bioenergy or biochar, could be an economically viable land use option for reversing degradation, through rehabilitation. Alternatively, a focus on ecological restoration ( [[#Gann--2019|Gann et al. 2019]] ) as the strategy for reversing degradation will deliver greater biodiversity benefits.

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[[File:551abe74d7291c613c1b4db2b230cb81 IPCC_AR6_WGIII_Box_12_3_Figure_1.png]]

'''Box 12.3, Figure 1 | Schematic illustrating the elements of the Land Degradation Neutrality conceptual framework.''' Source: [[#Cowie--2018|Cowie et al. (2018)]] . Used with permission.

Achieving neutrality requires estimating the likely impacts of land-use and land-management decisions, to determine the area of land, of each land type, that is likely to be degraded ( [[#Orr--2017|Orr et al. 2017]] ). This information is used to plan interventions to reverse degradation on an equal area of the same land type. Therefore, pursuit of LDN requires concerted and coordinated efforts to integrate LDN objectives into land-use planning and land management, underpinned by sound understanding of the human–environment system and effective governance mechanisms.

Countries are advised to apply a landscape-scale approach for planning LDN interventions, in which land uses are matched to land potential, and resilience of current and proposed land uses is considered, to ensure that improvement in land condition is likely to be maintained ( [[#Cowie--2020a|Cowie 2020a]] ). A participatory approach that enables effective representation of all stakeholders is encouraged, to facilitate equitable outcomes from planning decisions, recognising that decisions on LDN interventions are likely to involve trade-offs between various environmental and socio-economic objectives ( [[#Schulze--2021|Schulze et al. 2021]] ).

Planning and implementation of LDN programmes provides a framework in which locally-adapted land-based mitigation options can be integrated with use of land for production, conservation and settlements, in multifunctional landscapes where trade-offs are recognised and managed, and synergistic opportunities are sought. LDN is thus a vehicle to focus collaboration in pursuit of the multiple land-based objectives of the multilateral environmental agreements and the SDGs.

Table 12.10 collates risks, impacts and opportunities associated with different mitigation options that occupy land.

'''Table 12.10 | Summary of impacts, risks and co-benefits associated with land occupation by mitigation options considered i''' '''n Section 12''' '''.''' '''5.'''

{| class="wikitable"
|-
! Mitigation option

! Impacts and risks

! Opportunities for co-benefits

|-
| colspan="3"| '''Non-bio-based options that may displace food production'''

|-
| '''Solar farms'''

| Land use competition; loss of soil carbon; heat island effect (scale dependent) (Sections 12.5.3 and 12.5.4)

| Target areas unsuitable for agriculture such as deserts ( [[#12.5.3|Section 12.5.3]] )

|-
| '''Hydropower (dams)'''

| Land use competition; displacement of natural ecosystems; CO 2 and CH 4 emissions (Sections 12.5.3 and 12.5.4)

| Water storage (including for irrigation) and regulation of water flows; pumped storage can store excess energy from other renewable generation sources ( [[#12.5.3|Section 12.5.3]] )

|-
| colspan="3"| '''Non-bio-based options that can (to a varying degree) be integrated with food production'''

|-
| '''Wind turbines'''

| May affect local/regional weather and climate (scale dependent); impacts on wildlife; visual impacts ( [[#12.5.3|Section 12.5.3]] )

| Design and siting informed by visual landscape impacts, relevant habitats, and flight trajectories of migratory birds ( [[#12.5.3|Section 12.5.3]] )

|-
| '''Solar panels'''

| Land use competition ( [[#12.5.3|Section 12.5.3]] )

| Integration with buildings and other infrastructure; integration with food production is being explored ( [[#12.5.2|Section 12.5.2]] )

|-
| '''Enhanced weathering (EW)'''

| Disturbance at sites of extraction; ineffective in low rainfall regions ( [[#12.3.1.2|Section 12.3.1.2]] )

| Increased crop yields and biomass production through nutrient supply and increasing pH of acid soils; synergies with biochar ( [[#12.5.3|Section 12.5.3]] )

|-
| colspan="3"| '''Bio-based options that may displace existing food production'''

|-
| '''Afforestation/reforestation (A/R)'''

| Land use competition, potentially leading to indirect land use change; reduced water availability; loss of biodiversity ( [[#12.5.3|Section 12.5.3]] )

| Strategic siting to minimise adverse impacts on hydrology, land use, biodiversity ( [[#12.5.3|Section 12.5.3]] )

|-
| '''Biomass crops'''

| Land use competition, potentially leading to indirect land-use change; reduced water availability; reduced soil fertility; loss of biodiversity ( [[#12.5.3|Section 12.5.3]] )

| Strategic siting to minimise adverse impacts/enhance beneficial effects on land use, landscape variability, biodiversity, soil organic matter, hydrology and water quality ( [[#12.5.3|Section 12.5.3]] )

|-
| colspan="3"| '''Bio-based options that can (to a varying degree) be combined with food production'''

|-
| '''Agroforestry'''

| Competition with adjacent crops and pastures reduces yields ( [[IPCC:Wg3:Chapter:Chapter-7#7.4.3.3|Section 7.4.3.3]] )

| Shelter for stock and crops, diversification, biomass production, increases soil organic matter and soil fertility; increased biodiversity and perennial vegetation enhance beneficial organisms; can reduce need for pesticides (Sections 7.4.3.3 and 12.5.3)

|-
| '''Soil carbon management in croplands and grasslands'''

| Increase in nitrous oxide emissions if fertiliser used to enhance crop production; reduced cereal production through increased crop legumes and pasture phases could lead to indirect land use change (Sections 7.4.3.1 and 7.4.3.6)

| Increasing soil organic matter improves soil health, increases crop and pasture yields and resilience to drought, can reduce fertiliser requirement, nutrient leaching and need for land use change ( [[IPCC:Wg3:Chapter:Chapter-7#7.4.3.1|Section 7.4.3.1]] )

|-
| '''Biochar addition to soil'''

| Land use competition if biochar is produced from purpose-grown biomass. Loss of forest carbon stock and impacts on biodiversity if biomass is harvested unsustainably. ( [[#12.5.3|Section 12.5.3]] )

| Facilitate beneficial use of organic residues, to return nutrients to farmland. Increased land productivity; increased carbon sequestration in vegetation and soil; increased nutrient-use efficiency, and reduced requirement for chemical fertiliser (Sections 7.4.3.2 and 12.5.3)

|-
| '''Harvest residue extraction and use for bioenergy, biochar and other bio-products'''

| Decline in soil organic matter and soil fertility ( [[#12.5.3|Section 12.5.3]] )

| Nutrients returned to soil e.g., as ash; reduced fuel load and wildfire risk (Sections 7.4.3.2 and 12.5.3)

|-
| '''Manure management (i.e., for biogas)'''

| Risk of fugitive emissions

Can contain pathogens (Sections 7.4.3.7 and 12.5.3)

| Biogas as renewable energy source, digestate as soil amendment ( [[#12.5.3|Section 12.5.3]] )

|-
| colspan="3"| '''Options that do not occupy land used for food production'''

|-
| '''Management of organic waste (food waste, biosolids, organic component of municipal solid waste)'''

| Can contain contaminants (heavy metals, persistent organic pollutants, pathogens) ( [[#12.5.3|Section 12.5.3]] )

| Processing using anaerobic digestion or pyrolysis produces renewable gas and soil amendment, enabling return of nutrients to farmland. (Note that some feedstock nitrogen is lost in pyrolysis) ( [[#12.5.3|Section 12.5.3]] )

|-
| '''A/R and biomass production on degraded non-forested land (e.g., abandoned agricultural land)'''

| High labour and material inputs can be needed; abandoned land can support informal grazing and have significant biodiversity value. Reduced water availability ( [[#12.5.3|Section 12.5.3]] )

| Application of biochar can re-establish nutrient cycling; bioenergy crops can add organic matter, restoring soil fertility, and can remove heavy metals, enabling food production (Sections 7.4.3.2 and 12.5.3)

|}

'''Cross-Working Group Box 3, Figure 1 | Left:''' High-input intensive agriculture, aiming for high yields of a few crop species, with large fields and no semi-natural habitats. '''Right:''' Agroecological agriculture, supplying a range of ecosystem services, relying on biodiversity and crop and animal diversity instead of external inputs, and integrating plant and animal production, with smaller fields and presence of semi-natural habitats. Source: Reprinted by permission from Springer Nature Customer Service Centre GmbH: Springer Nature, Nature Sustainability , Towards better representation of organic agriculture in life cycle assessment, Hayo M. G. van der Werf et al. © 2020.

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