Nature-Based Solutions (NbS) in Agricultural Soils for Greenhouse Gas Mitigation

Abstract

Greenhouse gases (GHG), accumulated in the atmosphere, are the main cause of climate change. In 2017, the increase in average temperature was about 1 °C (between 0.8 °C–1.2 °C) above pre-industrial levels. Global warming refers to the increase in air surface, sea surface, and soil surface temperature and according to IPCC (Intergovernmental Panel Climate Change), since the industrial revolution, C emissions are due to land use changes like deforestation, biomass burning, conversion of natural lands, drainage of wetlands, soil cultivation, and tillage. As the world population has increased, world food production has risen too with a subsequent increase in GHG emissions and agricultural production, which is worsened by climate change. Negative consequences are well known such as the loss in water availability and in soil fertility, and pest infestations which are climate change’s effects on agriculture activity. Climate change’s main aftermath is the frequency of extreme weather events influencing crop yields. As climate change exacerbates degradation processes, land management can mitigate its impact and aid adaptation strategies for climate change. About 21–37% of GHGs have been caused by the agriculture activity, so the application of Nature-based Solutions (NbS) like sustainable agriculture could be a way to reduce GHGs worldwide. The aim of this article is to review how NbS may mitigate GHG emissions from soil, with solutions defined as an integrated approach to tackle climate change and to sustainably restore and manage ecosystems, delivering multiple benefits. NbS is a low-cost tool working within and with nature, which holds many benefits for people and the environment.

1. Introduction

Carbon is considered a key parameter of many functions in soil, which is defined as a non-renewable resource on human scales [1,2,3,4]. Soil Organic Carbon (SOC) and land use play an important role in valuing the global carbon budget [5], it means to determine and quantify C sources and sinks. Five C pools have been distinguished: oceanic, geologic, pedologic (soil), biotic, and atmospheric pools. In the pedologic pool, the quantity of C is four times that in the biotic pool (trees, etc.) and about three times that in the atmospheric pool [5] (Figure 1 and Figure 2).

Soils hold the largest C pool, defined as SOC and Soil Inorganic Carbon (SIC). Soil quality can be enhanced by removing and storing atmospheric CO₂ [8]. Stored CO₂ shows variations in SOC and SIC amount and they are huge at the global level [9]; both are distinct components of soil carbon that coexist [10]. SOC plays a fundamental role in the C cycle, contributing to fertility, water storage, and crop production [11,12]; higher levels of SOC and N enhance biodiversity and improve soil quality, and nutrient supply ameliorates water reserves and soil structure, soil structural stability, and biogeochemical cycles of water and nutrients (C, P and N) [3,13].

Carbon emissions are based on improper crop management, deforestation and fertiliser overuse with a loss of SOM [14,15,16]. Soil is more enriched in C than in the atmosphere, and SOM is defined as a regulator of climate [17]. Indeed, SOM affects physical, chemical, and biological soil properties; it reduces erosion, improves water quality, and retains nutrients and water [18].

Global warming leads to an SOC decrease, C is oxidised and released in the atmosphere as CO₂ [12,19,20,21], and CO₂ varies according to time and environmental conditions [22]. Methane (CH₄), nitrous oxide (N₂O), and chlorofluorocarbons (CFCs) are emitted too; CO₂, CH₄, and N₂O are long-lived in the atmosphere [23]. According to IPCC [24,25], CO₂ is accountable for about 72% of global warming, CH₄ about 16%, and N₂ about 6% (Figure 3).

GHG flux’s main cause is anthropogenic activity, with emissions partially due to land use change in agricultural and industrial development [26]. Muñoz et al. (2010) [21] highlights the contribution of agricultural activity to GHG emissions depending on biophysical processes, on the incorporation/decomposition of organic residues in soil. Carbon dioxide is emitted in aerobic conditions, whereas CH₄ is emitted in anaerobic conditions; nitrification and denitrification processes lead to N₂O emission. Kirschbaum (1995) [20] pointed out that C and N are negatively correlated with temperature and precipitation. Low vegetation cover increases the risk of degradation and SOC depletion [27], inferring a relationship between vegetation cover and SOC in soil; this depends on the temperature and decomposition rate of SOM [20,28]. Carbon sequestration depends on soil C saturation deficit, recalcitrant C fractions, and aggregate physically associated with C, whereas organic C is a soil nutrient with a slow turnover in terrestrial ecosystems [11,29]. Accumulating C in soil could help in mitigating CO₂ in the atmosphere [11,30,31]; SOC stocks can raise passing from less to more complex systems [32].

IPCC (2021) [33,34] suggests that the terrestrial ecosystem can be a sink [35]; land was a C sink for about 30% of the anthropogenic emission from 2008 to 2017 [36,37], soil as a C sink can mitigate climate change, and SOC acts as indicator of soil quality and health [3,13]. Soil could also be a source of GHG emissions; the balance between the absorbance of C atmospheric and its release determines the net temporal status of soils [21]. Soil as a sink is one of the largest uncertainties in C biogeochemical cycles according to the climate models [38].

There are three high-level sustainable strategies to lower CO₂ emissions to mitigate climate change: decreasing the amount of energy, finding alternatives to fossil fuels, and sequestering CO₂ [39,40]. Skinner et al. (2014) [41] states that SOC is stabilised through physic-chemical processes and in soil’s structure within mineral surfaces and/or metal ions.

Soil can be a sustainable sink for CO₂ and, nature-based solutions (NbS) might be a valid tool to mitigate GHG emissions. The meaning of NbS is to enhance natural solutions to manage ecosystems and human wellbeing through storing carbon, flood control, shoreline stabilisation, landslide control, and increasing air and water quality. In the last few years, NbS have been considered cost-effective [42], through restoring degraded lands and practising sustainable agriculture through NbS and avoiding and/or mitigating GHG emissions and reducing soil degradation; preventing soil erosion through conservation will support C sequestration, enhance CH₄ consumption, manage N for crop production, and reduce N₂O emissions.

Furthermore, mitigation of GHGs can also occur through sustainable agricultural (SA). This practice can be divided into three components: reducing emissions from the agriculture activity by conservation agriculture (CA) with no-till farming and the use of organic manures; enhancing the photosynthetic input of C soil amendments like crop residue mulching; and avoiding emissions by using crops and residues from agricultural lands as a source of fuel [12,28,39,43].

This review examines the scientific knowledge of how NbS can exert control on land degradation to achieve sustainability, starting from the description of soil parameters such as Soil Organic and Inorganic Carbon (SOC and SIC), Soil Organic Matter (SOM), GHG emissions (nitrous oxide, carbon dioxide and methane) to assess soil health, being a key component of the Earth System [44,45], and being a leading tool to achieve sustainability of soil management. Agriculture activity raises GHG from lithosphere to atmosphere [46]. Soil can be a source or a sink according to the characteristics, but GHG’s storage capacity is finite [47].

2. Soil Organic Carbon (SOC)

Soil Organic Carbon is the sum of the interactions among photosynthesis, respiration, and decomposition, a balance between the amount of C from the growth and death of plant roots and from the transfer of carbon-enriched compounds from roots to soil microbes, assuring a continuous amount for microbial biomass and nutrients for plants [48]. Huang and Wei (2025) [10] asserts that SOC density is abundant in top soil; indeed, vegetation generally rises SOC pool than SIC pool. Its accumulation is higher in northern high latitude or peatlands, whereas it is inhibited in area with low temperatures or waterlogged conditions [10]. In effect, high precipitations increase vegetation and consequently SOM, wet conditions prevent SOC decomposition too. In particular, histosol and gelisol show more SOC; spodosol, ultisol, vertisol, and mollisol show more SOC on the top soil layer; aridisol and entisol have a low SOC amount whereas alfisol has large values in the top, middle, and bottom layers [10].

SOC stock incorporates the active, stable, and passive pools. The active pool is characterised by the presence of microbial biomass, is associated with nutrient mineralisation [49] and includes dissolved organic matter (DOM) [50], whereas the stable and passive pool contributes to soil health [11,51,52,53]. Carbon microbial biomass and mineralisable C are pools representative of biomass and activity of soil microorganisms [11], and there is a good correlation between SOC and microbial biomass C [54].

Indeed, CO₂ in soil is higher than in the atmosphere because of root respiration and organic material decomposition; depending on the climate and ecosystems [22], an increase in atmospheric CO₂ can produce an increase in subsurface CO₂ production. Lost carbon from soils is mainly CO₂ from decomposition processes [13], in particular, emissions are the sum of three processes: soil respiration (root respiration anaerobic and aerobic microbial respiration), ecosystem respiration, and net ecosystem exchange which is the difference between photosynthesis and ecosystem respiration [47]. Lal (2004) [5] stated that C emissions from land use changes are due to the decomposition of vegetation and mineralisation/oxidation of humus or SOC. A soil can sequester C according to vegetation, soil depth, drainage capacity, mineral composition, soil temperature, and the relative proportion of soil, water, and air [4,55]. From biomass decomposition, a small level of carbon is retained in the soil through the formation of humus [56,57]; these different origins make C more or less recalcitrant. Four types of soil degradation have been identified (physical, chemical, biological, and ecological), highlighting the reduction in water infiltration, runoff, wind and water erosion, depletion of nutrients, loss of cation exchange capacity (CEC) and biodiversity, and emission of GHGs [27]. Climate change can accelerate these phenomena; acidification and salinisation could also accelerate soil degradation processes. These changes affect all the ecosystem functions; mean annual temperature, seasonal temperature and mean annual precipitation are variables which can condition the amount of SOC and SIC in the soil layers [10]. Huang and Wei (2025) [10] states that less C in SOC and a reduction in SOC storage is caused by a loss of SIC reducing soil pH which controls nutrient availability, plant productivity, and soil microbial activity, also influencing plant and soil fertility. Managing SOC in the pedologic pool means to enhance soil quality, to stabilise soil structure, morphology, and geometry [11,27,48,58]. Improved management can reduce the amount of additional inorganic fertiliser, increasing vegetative cover and enhance infiltration water in soil. NbS are a first-rate way to enhance soil’s resilience, improving soil stability and pore geometry [12].

3. Soil Inorganic Carbon (SIC)

Huang and Wei (2025) [10] writes SIC higher in arid regions due to low soil water availability and limited leaching but, in arid and semi-arid land, SIC loss is caused by soil acidification due to the fertilisation phenomenon. Generally, SIC loss is reduced and it rises with soil depths, whereas SOC slightly decreases. SIC concentration is also high in cold and temperate humid regions close to lakes, rivers, and coastal areas because of the Ca-rich alluvial deposits or calcareous parent material; on the contrary, in high precipitation areas, SIC is easily leaching [10] (Figure 4).

Inter alia, SIC is high in aridisol and entisol in the top, middle and bottom layers; high SIC values are in the middle and bottom layers of spodosol, ultisol, vertisol, and mollisol. SIC dynamics are also affected by climate change, organic matter decomposition, microbial activity, and soil management such as irrigation, fertilisation, and afforestation.

SIC sequestration is considered a secondary one [4] with the formation of a paedogenic calcium carbonate [59,60]. A responsible irrigation leads to an SIC sequestration through leaching bicarbonates in groundwater [10,61,62]. Carbon sequestration in SIC requires interaction with Ca from silicates, an alkaline pH, and CO₂ [63]. Carbonate formation could sequester atmospheric C from Ca silicate mineral weathering [64] and can also be sequestered as bicarbonate through the dissolution of a pre-existing carbonate, and during the precipitation, CO₂ is released in the atmosphere. As a matter of fact, SIC is not considered a good sink [65,66], rather, a minor sink on a continental and/or global scale. The loss of SIC might be a sink or source for C, this unsolved point is due to the carbonate chemistry; certainly, this loss alters soil environment such as pH buffering capacity, structure, and chemical composition, which must be deeply studied in the near future [10]. Only a little amount has a biological origin and a significant role in C sequestration [11,67,68]. Actually, adsorption capacity is higher in SOC than in SIC, mainly in regions dominated by organic-rich soils; it is sensitive to the annual amount of CO₂ in soil [22].

4. Soil Organic Matter (SOM)

Soil Organic Matter means microbes such as bacteria and fungi, decaying material from plant and animal tissues, and faecal material [28,60,69,70,71,72,73,74]. Symbiotic arbuscular mycorrhizal fungi, found in the roots, are thought to contribute to C and SOM sequestration in soils [75]. SOM is highly enriched in carbon and SOC is directly related to the amount of it; its concentration is a clue to consider soil as a sink and not as a source [4].

Pataki et al. (2003) [76] states that high temperature leads to high levels of SOM decomposition and high CO₂ emissions [5,66]; in areas with high precipitation, SOM concentration is high because vegetation growth is favoured [10]. Soil productivity depends on SOM concentration; its decrease affects overall ecosystem health, reducing the water infiltration and soil moisture, increasing the erosion and consequently the depletion of nutrients, which could lead to the eutrophication phenomenon downstream [18]. Increasing SOM increases C and N in soil, soil aggregation, and aggregate stability [26,77,78,79,80,81]. Indeed, SOM has a key role in soil chemical properties such as pH, nutrient availability and cycling, and cation exchange capacity and buffer capacity [26].

5. Nitrous Oxide (N₂O)

Land use and land use changes affect N₂O emissions [21], nitrification and denitrification; soil microbial processes produced most of N₂O emission [82,83,84]. Fertilisers and animal manures are the first cause of N₂O emission from agriculture activity [26], providing a substrate for microbial nitrogen conversion through nitrification and denitrification [85]; these emissions may be greater from manure sources since they are strongly related to N-inputs [86].

The denitrification process of microbes occurs when nitrate is in anaerobic microsites, lacking oxygen, and under water saturation [87]. Anthropogenic activities have caused a disruption of N cycle, lowering the efficiency; N₂O emissions are higher in agricultural soil with availability of organic substrate [88].

Soil N₂O emissions increase because high soil moisture levels, restricted oxygen levels, abundant readily decomposable organic C, and high levels of soluble N (NH₄⁺ and NO₃⁻) occur together [89,90,91]. Cavigelli (2025), Reinbot (2015), Skinner (2014) [41,92,93] write that N₂O annual emissions from organically managed soils are lower than from the conventional treatment. In intensive agriculture N-cycling, processes of nitrification and denitrification have been shown to increase with synthetic N fertilisation and greater tillage intensity, which changes the bacterial and fungal communities involved in [94,95].

On the other hand, nitric oxide (NO) emissions from soil are less important; they were studied because of the acidic precipitation and ozone formation and destruction [47].

6. Methane (CH₄)

Methane is emitted in the atmosphere via methanogenic bacteria living in anaerobic soils, which may be a sink or source of CH₄ depending on moisture, N level, and ecosystem [75,96,97]. CH₄ is consumed by soil methanotrophic bacteria, which are ubiquitous in many soils [98], and it is also produced by methanogenic bacteria [99]. It favours the formation of methanogenic microorganism because of its formation under anaerobic conditions in flooded systems [21,100] (

Table 1. Potential mitigation methods for N₂O and CH₄ from the manure management continuum. Reprinted from Ref. [85].

	Methane	Nitrous Oxide
Animal house	Modify feeding strategy Removal of a slurry from beneath the house	Modify feeding strategy Adopt a slurry-based system compared to a straw or deep litter system
Manure store	Cooling slurry; e.g., below the slatted floor Modify feeding strategy Removal of slurry from the slurry store Minimising slurry volume stored in summer months	Modify feeding strategy Keep anaerobic (e.g., cover and compact) Adopt a slurry-based system compared to a straw of deep litter-based system Add additional straw to immobilise ammonium-N
Land spreading	Cooling slurry Aerate solid manure heaps-composting Anaerobic digestion Enhancing crust formation Modify feeding strategy	Modify feeding strategy Nitrification and inhibition Spring application of slurry Integrate manure N with fertiliser N Slurry separation Solid manure application

).

7. SOC and Erosion

The increase in agricultural activity affects natural erosion processes and causes a relevant and observable increase in soil erosion rates across landscapes [17,101], confirming the need to predict the consequences of soil erosion. Correlation between SL (soil loss rate) and R (annual runoff) is high in land use change and minimised in natural lands [102]. Water and wind erosion leads to the removal of soil fine fraction like clay and silt, resulting in partial loss of SOM which is bound with these fractions [57].

Soil erosion is the main factor in SOM removal and, consequently, the CO₂ increasing into the atmosphere [4].

Soil erosion affects C stocks; at larger-scale erosion, it may not represent a loss process per se, but rather a redistribution of soil C [103] over land (CO₂, CH₄, N₂O), deposition in channels (CO₂, CH₄, N₂O), and transportation/burial in the ocean (CH₄) [104]. This is considered the main cause for nutrient loss and carbon cycling, affecting land productivity, and is a threat to socioeconomic conditions worldwide [102,105,106,107,108].

Decreasing SOC increases erodibility and susceptibility in crusting, compaction, runoff, and erosion [5]. Sedimentologists affirm that soil erosion is a carbon sink; considering displaced C through the erosion phenomenon, part of SOC is released in valleys or surface depressions and accumulate in these sites [109], whereas agronomists state soil erosion is a loss in C. SOC depletion is enhanced by SOM erosion, and SOM is an indirect measure of soil quality and productivity [11,27]; it is affected by nutrient pollution and CO2, different precipitation regimes [110,111] and climate change. Soil moisture and modelling climate change lead to understanding the global carbon budget [22]. Part of the eroded C might be buried and redistributed and generate different feedback [112], partially emitted in the atmosphere as CO₂ or CH₄ because of methanogenesis [5]. When C is displaced from the erosion, it can be mineralised during transport and accumulate in different sites and be substituted from new photosynthates stabilised by the less C-saturated subsoil.

The erosion process redistributes particles according to the size; this phenomenon might change environmental conditions affecting plant growth and SOC decomposition [113,114]. Eroded soil shows a lower NPP than uneroded soil [109,115], and a linear correlation is observed between NPP and annual soil respiration. The temperature of soil respiration could differ from the temperature of organic matter decomposition, and it could be different from the root respiration temperature; the temperature of soil decomposition must be greater than the temperature of NPP [116]. Tillage increases temperature in the superficial soil horizon, whereas no-tillage procedure augments thermal diffusivity in the soil within depth [117]. Tillage is a normal practice after harvest and is a main contributor to the formation of colluvial deposits; it enhances soil erosion, but it hides the effect of water erosion [118]. One disadvantage from tillage practice is the exposure to freeze–thaw and wet–dry cycles enhancing the destruction of aggregates, whereas no-tillage practice might foster fungal growth, and fungal hyphae which enhances macroaggregate formation [119]. Oertel et al. (2016) [47] states that intensive tillage and fertilisers enhance GHG emissions in croplands.

SOC and N amounts are positively correlated with rainfall and negatively correlated with increase in temperature [20,120,121,122]. Soil water content and temperature vary during the year, high temperature does not necessarily mean high soil decomposition, as the rate of soil decomposition varies according to the soil water content, and decomposition is consistent with the loss of SOM [20]; SOM is mineralised and about 20–30% of SOC is emitted in the atmosphere.

8. GHG Emissions from Soil

Greenhouse gas emissions will rise by about 50% between 2000 and 2030, impacting weather, climate, and agriculture activity [85]. Lamb et al. (2021) [123] states that GHG emissions are caused by five economic sectors such as energy, industry, buildings, transport, and all land uses. Food production and agriculture activity produce more than 20% of greenhouse gas emissions [124]. In developed countries, GHG emissions are quite stable from 1990 to 2015, whereas in developing countries like China, the emissions have been doubled, mainly for the mechanisation in agriculture activity [124]. In 2017, agriculture emissions were 11.1 Gt CO₂eq/year, about 6.1 Gt CO₂eq/year stands for crop and livestock, and about 5.0 Gt CO₂eq/year are for agriculture land use [125].

The main emissions from land change used are caused by deforestation, peat drainage, wood harvesting, transformation between croplands and pasture, and CO₂ soil emissions from grassland and cropland management [123] (Figure 5).

The application of fertiliser increases N₂O emission, the application of manure release CH₄ and N₂O, and forestry and other land use stand for CO₂ emissions [126] (Figure 6 and Figure 7).

Generally, CO₂ is emitted when the assimilation is less than the mineralisation phenomenon in the soil [46]. Soil humidity affects GHG emissions controlling microbial activity. Parameter water-filled pore space (WFPS) rules emissions; a value of about 20% stands for the maximum emissions. If WFPS is lower than 10% NO emissions decrease because of the inhibition of nutrient supply, CH₄ and N₂O require an anaerobic system, N₂O is good with a value of WFPS about 60% and decreases with a value of 30% [47]. CH₄ emissions are correlated with anaerobic conditions. Granulometry affects the amount of water in pores; in aerobic conditions, large pores cannot retain water fostering GHG emissions, whereas in anaerobic conditions, fine pores emit more CH₄ and N₂O—CO₂ emissions are also higher (

Table 2. Key drivers of GHG emissions from soils. Reprinted from Ref. [47].

Land use	Transformation Ecosystem resilience
Land cover	Forestlands, grasslands, barren lands, croplands, wetlands, other land covers
Vegetation	Age and type Distribution Leaf area index
Nutrients	C/N ratios Land use management Atmospheric deposition
Humidity	Soil water content (SWC) Water-filled pore space (WFPS) Precipitation/drought
Temperature	Radiation Exposure (Soil cover, exposition) Corg Soil colour (mineralogy) Wildfires

).

In acidic conditions, emissions from soil are lower, in a pH range between 4 and 7, methanogenesis produce high CH₄ emissions, whereas at neutral values, CO₂ emissions are highest and N₂O emissions are reduced in acidic conditions; nitrification raises at high pH [47].

Agricultural intensification, eutrophication, and contamination of groundwater exert a significant influence on GHG emissions; the management of soil resources and SOC is extremely important [127] (Figure 8,

Table 3. Emissions data from land change use. Reprinted from Ref. [128].

Agriculture category (MtCO2 eq/yr)	1961	1990	2000	2005	2010
Enteric fermentation	1375	1875	1863	1947	2018
Manure left on pasture	386	578	682	731	764
Synthetic fertiliser	67	434	521	582	683
Rice cultivation	366	466	490	493	499
Manure management	284	319	348	348	353
Crop residues	66	124	129	142	151
Manure applied to soils	59	88	103	111	116
Total (MtCO2 eq/yr)	2604	3883	41,361	4354	4586
Net deforestation		4315	4296	3397	3374
Combined total		8198	8432	7751	7960

).

Carbon dioxide emissions and removal are influenced by land use changes such as reduction in forest cover, conversion to permanent cropland/waste lands, and land for conversion to forestry (including plantations) and from erosive processes [21,39,129]. These emissions are an index of root respiration and decomposition of organic matter by the microorganisms, an indicator of the mineralisation of nutrients and rate of decomposition. This activity is influenced by root systems, microbial process, crop residues, litter content, microclimate, and soil characteristics [130]. Considering total CO₂ emissions, it is possible to define

CO_{2 tot-emission} = E_FF + E_LUE + G_R + S_O + S_L

where E_FF is the emissions from fossil fuels and industry, E_LUE emissions from land use change, G_R rate of growth of CO₂, S_O mean ocean CO₂ sink, and S_L global residual terrestrial CO₂ sink [4]. CO₂ emissions can decrease by using energy-efficient technology and through capture and storage within long-lived pools [40] (Figure 9).

9. Solutions

Solutions will involve SOC sequestration through crop and grassland management and the improvement in soil quality and productivity, and consequently food security [126].

SOC sequestration enables management of biomass, minimum soil disturbance, and improvement in soil structure and microbial activity [5]. Sustainable and organic agriculture may reduce GHG emissions through a lower fertiliser use and a low level of carbon-based inputs, and it can contribute to SOC sequestration [131,132]; so, organic production systems are more resilient [133] (Figure 10).

Blanco-Canqui and Lal (2008) [135] underlined the importance of establishing a relationship between soil erosion and water, wind, and tillage; valuing C dynamics and storage in soils at different climatic conditions; modelling the fate of C transport by erosion; valuing if soil is a source or a sink and the importance of biochar in sequestering and mitigating climate change. Restoring SOC enhances soil quality; this improves food production and maintains clean water [53]. Amount of CH₄ and N₂O might change the mitigation by the management practice, and this must be considered along with SOC sequestration [5]. Lal (2015) [27] suggests conservation agriculture (CA) as a suitable management, that is, the retention of crop residue mulch (increasing SOC) [30,136,137,138]; incorporation of cover crop in the rotation cycle, the use of integrated nutrient management and organic amendments, no-till (mechanical tillage is an energy-intensive process), limited use of synthetic fertilisers and herbicides highlighting benefits such as a significant C sequestration and reduction in fuel consumption [139].

A resilient agriculture system is suggested to maintain and improve economic, ecological, and social benefits [84]. A stable SOC sequestration path might be achieved through agricultural system and management practice and by conversion of degraded land [140].

10. Nature-Based Solution (NbS)

Nature-based Solutions have been defined as a way to find a solution for mitigating and adapting to the climate change effects, whilst simultaneously protecting biodiversity and improving sustainable livelihoods [14,141,142,143], to manage natural systems balancing the benefits for both nature and society [144]. Seddon et al. (2021) [145] states that NbS may enhance synergies and tackle more challenges due to the flexible and integrated approach (Figure 11). Adil et al. (2022) [146] states that for NbS, like non-removal crop residues, conservation tillage increases SOC, in particular, mineral associated organic carbon, mineral associated organic matter, and microbial biomass carbon components.

Nature-based Solutions can provide multiple benefits for living organisms and biodiversity, economy, society, and environment; they are cost-effective and efficient than engineering solutions [147].

The main idea of NbS is to improve land management, to improve C storage and sequestration, to protect soil from erosion, and to avoid the changes in land use [124] (Figure 12).

Nature-based Solutions are considered a cost-effective long-term solution for soil and water; they are considered a holistic approach which can tackle problems more efficiently [135,149,150,151] and mimic natural processes, improving vegetation and water availability, restoring biodiversity, and raising agricultural productivity [152]. They are based on natural processes to recover services such as goods and resources and having their fundamentals in the concept of soil health [62,144,150]. Eight criteria have been defined: address societal challenges, landscape scale of intervention, biodiversity gain, economic viability, governance capability, equitably balance trade-offs, adaptive management, and mainstreamed within an appropriate jurisdictional context [144] (

Table 4. Specific types of NbS implemented within ecosystem. Reprinted from Ref. [147].

Type of Nature-based Solutions
Green	Blue	Mixed (Green-Blue)	Hybrid (Green-Blue-Grey)
Urban parks	Ponds	Mangroves	Bioswales
Heritage parks	Wetlands	Vegetable wetlands	Rain gardens
Green strips	Rivers	Coral reefs	Green roof
Plains grass cover	Lakes and streams	Seagrass	Permeable surface channels
Trees and shrubs	Seas and oceans	Riparian buffer zones	Live pole drains
Forest orchard	Aquifer protection	Submerged dams or weirs	Live cribwalls
Hedges/shrubs/green fences	Room for the river	Beach nourishment	Live ground anchors, etc.
Street trees(s)	Constructed flood storage, etc.
Agroforestry Forest protection Reforestation Optimised forest Managements, etc.

).

The implementation of long-term sustainable solutions requires a better and deeper, more comprehensive understanding of the coupled natural and human systems and the causal mechanisms, impacts, and feedback inherent in this complex interaction [141]. Indeed, ref. [147] raises that NbS must be achieved the considering ecosystem services and trade-offs; therefore, NbS advantages will be largely leveraged.

Eggermont et al. (2015) [153] proposed some typologies of NbS; the first type is of no or minimal intervention in ecosystems, to maintain or improve the delivery of a range of ecosystem services both inside and outside of these preserved ecosystems. A second type corresponds to the definition and implementation of management approaches developing sustainable and multi-functional ecosystems and landscapes. A third type consists of managing ecosystems in very intrusive ways or even creating new ecosystems.

Seddon et al. (2021) [145] has classified NbS as soil-vegetation and landscape solutions. The former solution enhances soil health and resilience [154] such as vegetation cover, mulch to avoid soil erosion and runoff, and to improve porosity, aggregate stability, organic matter content and water holding capacity, whereas the landscape solutions are geomorphological parameter like hillslope morphology and runoff pathways. These solutions may mitigate flooding, droughts, soil erosion, carbon emissions, and can enhance biodiversity.

Actually, NbS are site-specific so that the success of a solution is bounded with socioeconomic and environmental conditions, this is the reason why the choice of an NbS is with population and stakeholders too. Indeed, Debele et al. (2023) [147] underlines that NbS must be designed to be measurable, sustainable and cost-effective.

Nature-based Solutions applied to the agriculture landscape have the carbon sequestration as a main goal, including water and disaster-risk management [28,103,155,156,157]. Conversion to invigorating land uses and implementation of NbS can enhance SOC concentration in soil [39].

Some NbS practices are based on the use of trees and plants reducing the environmental impact of the production [157], like grass strips’ control on soil erosion and return crop yields [157,158], and vetiver to trap phosphorous [157,159].

Organic agriculture, silvo-pasture, cover cropping, and agroforestry are methods which show positive impacts on SOC. On the contrary, tillage and grazing management are activities which show different N₂O emissions and different impact on SOC storage [17].

Agroforestry, an NbS based on land use management, may be an opportunity to counter the adverse impacts of climate change through adaptation and mitigation [102,160]. As a matter of fact, agroforestry cropping systems tend to be resilient, pest-resistant, nutrient conserving and providing multiple benefits [161], like improving carbon sequestration and storage [162,163]. The application of agroforestry may be a tool to enhance resilience for food supplies to pests, diseases, and extreme climate events [42,164,165,166]. Indeed, NbS are fundamental in reducing the cost of climate mitigation solutions to achieve the goals from the Paris Agreement [167]. Griscom et al. (2020) [168] suggests that the application of NbS will reduce the emission of CO₂ through the forest protection, wetland, and grassland, whereas the global carbon sink is through the management of timberland, croplands, grazing land, and with the restoration of native forests and wetlands.

Agriculture practice and forestry may be a significant way to mitigate CO₂ sequestering of C so soil can act as a sink [32,169]. Specifically, conservation agriculture is a mix of conservation tillage, crop rotation, and cover crops, pointing out the potential to increase crop yields [157]. Indeed, trees enhance the resilience of small farmers to face climate risks through crop and income diversification, soil and water conservation, and efficient nutrient cycling and conservation [132,170]. It is fundamental to select the suitable tree species leading to the management of pest control, spacing and width of hedgerows, sustainable forest management to conserve soil and water resources, developing protocols for assessing C pools and assessing the potential of C sequestration [135] (Figure 13 and Figure 14).

The postulation of NbS encompasses climate change mitigation as well as the sustainable agriculture [145]; actually, NbS can be very helpful in reducing the consequences due to flooding, erosion, drought, and poor agricultural productivity phenomena [173].

11. SOC Sequestration

Borrelli et al. (2021) [17] defined SOC as a natural climate solution via C restoration in soil (sink) and avoiding and/or reducing CO₂ emissions, considering land use change and climate change and pointing out that SOC’s loss is quicker than its storage in soil. SOC makes soil more resilient to fire, pests, and winds. (Figure 15).

Soil can sequester C in two ways, direct transformation (transformed in SIC) and indirect fixation of atmospheric CO₂ (transformed in SOC during the photosynthesis reaction) [32,175].

SOC sequestration is a cost-effective and environmentally friendly practice; atmospheric CO₂ is transferred into long-lived pools, C is stored in soil mainly through photosynthesis [18], and it depends on the turnover time and physical or chemical protection against microorganisms and soil erosion [48]. After a period of 10 to 40 years, C attains a steady state [84]; it is not reemitted and SIC is also increased [53]. The time to reach the steady state varies with the soil type, management intervention, climate regime, and previous SOC depletion [17]. Soil as a sink can sequester SOC through recommended management practices: no-till on agricultural and forest soils, leaving residues as mulch and cover crop, crop rotations, and agroforestry [13] (Figure 16).

The potential SOC sequestration is in the following order: degraded soils and desert ecosystems > cropland > grazing lands > forest lands and permanent crops [177]. Effectively, Borrelli et al. (2021) [17] states that forest system SOC is mainly in the above-ground tree biomass whereas in wetland system, SOC is the main way to reach climate mitigation. Furthermore, Oertel et al. (2016) [47] highlights that reforestation of croplands shows reduction in CO₂ emissions, not in CH₄ and N₂O emissions. These recommended strategies might affect N₂O emissions [39,178,179] since the reduction in these emissions seems to depend on soil and climatic conditions [180]. Nitrification seems to affect soil CO₂ sink and nitrogen cycling in CO₂ sink and reduces CO₂ emissions due to soil respiration. Nitrification is considered an energy-yielding reaction, enabling the use of CO₂ as a carbon source and, to reduce CO₂, it is necessary for the energy from nitrification processes and N-cycling to be repeated several times. When increasing NH₄⁺ concentration in soil, a decrease in CO₂ emission is observed until a limit; beyond this limit, nitrification is inhibited even though NH₄⁺ is supplied and CO₂ is emitted [181]. Emissions may be caused by a retarded respiration or inhibition; another hypothesis is that the NH₄⁺ excess may cause a stabilisation of the CO₂ minimum without significant CO₂ release.

SOC content in soil depends on interacting mechanisms such as the formation of passive humus fraction, formation of stable micro-aggregates, and deep placement of SOC; it is fundamental to understand how much and how long C could be in soil [11,182,183]. Turnover time depends on SOC fractions; labile or decomposable fractions have a turnover time of less than 5 years; fraction with particulate or light fractions have a time between 5 and 20 years; humus and light fractions between micro-aggregates show a time of 20–50 years; passive or non- labile fractions have a time of 50–100 years [28,48,184,185]. Determining the amount of C in soil compared to its saturation capacity leads to fixed C being sequestered in the soil [186,187]. Soil can also be a sink depending on SOM concentration, climate, soil profile, and soil management [5]. Improving SOC and SOM enhances soil sustainability and, the management of land may help reduction in GHG emissions from soil, particularly leaving the crop residues on soil and increasing N efficiency [21,188,189]. There is a potential for C sequestration through the management of crop residues [190]; C from annual crops undergoes its fastest turnover in the wet, warm season, whereas carbon returned by woody species resists decomposition and carries over into the cooler, drier periods [4,191,192]. Instead, the management of land use bears on the stability of soil aggregates and C concentration and its dynamics in these aggregates. Soil primary particles form stable aggregates due to the presence of humic substances and/or complexes with polyvalent cations forming micro-aggregates [4,80], whereas macro-aggregates are formed by polysaccharides, fungal hyphae and plant roots. Stable micro-aggregates are the main mechanism for C sequestration in soil. In particular, Ca²⁺ is considered a persistent linking agent with the formation of clay-cation polyvalent-organic material complex [5,193]. Application of Ca²⁺ leads to the formation of stable aggregates in soil [99,194]; sesquioxides show the same influence on the soil aggregates and influence the stability of SOM too. It has been observed that C in micro-aggregates is older but more labile than C in macro-aggregates [195].

Moisture, temperature, clay content, and mineralogy are also fundamental parameters and, in general, SOC is mostly associated with clay fraction [196]. Macro and micro-aggregates make soil more resistant to C decomposition by enzymes and microorganisms. In these aggregates, organic material is protected from enzyme and/or microorganism attacks; the lesser amount of oxygen reduces microbial activity [197]. The formation of soil aggregates is a strategy to sequester C in soil, so C mineralisation is reduced [64,198,199]. Moreover, SOM could act as a binding agent to form stable macro-aggregates and enhance C sequestration [190]. During climatic conditions of high precipitation and frozen soil in the winter, SOM is higher and leads to higher C sequestration than in warmer and drier climates, while crop rotation allows a high C sequestration in sub-humid climates than drier ones [200,201].

Six et al. (2002) [64] distinguishes four SOM pools: a biochemically protected C pool, a silt- and clay-protected C pool, a micro-aggregate-protected C pool, and an unprotected C pool. The silt- and clay-protected C pool is protected by the mineral particles, and it is hydrolysable and depends on the amount of silt and clay in the soils. The micro-aggregate-protected C pool is exerted by SOM at the micro-aggregates level (SOM physical protection), the biochemically protected C pool is associated with the non-hydrolysable fraction, and the unprotected C pool is labile; it is a nutrient source and very sensitive to the management practice.

In addition, Six et al. (2002) [64] defines three major mechanisms to stabilise SOM: physical, chemical, and biochemical processes. Physical mechanism is the formation of aggregates to protect SOM from microbes and enzymes; it is mainly protected in free micro-aggregates and in micro-aggregates within macro-aggregates [202,203,204]. Chemical mechanism is the binding between SOM and soil minerals since C is associated with primary organo- mineral complexes; therefore, they are chemically protected; silt and clay content underpins this mechanism [64,205,206,207]. Biochemical SOM stabilisation is a mechanism because of its own complex chemical composition [64]. Microbial-derived C binds micro-aggregates into macro-aggregates and it seems that macro-aggregates protect SOM [80,208].

12. Tillage

Ploughing and tillage lead to a moisture decrease and an increase in soil temperature and of SOC mineralisation. The most suitable tillage system is one which leads to the restoration of soil quality, reduces soil erosion, and allows the efficient use of rainwater and fertilisers [60]. Cover vegetation avoids the overgrazing and reduction in water infiltration, soil erosion, and runoff; biomass is related to SOC pool, to restore biodiversity; fauna and flora (micro, meso, and macro) is one other important aspect to improve.

Ploughing accelerates erosion and is responsible for about 1 Gt/year of C loss; tillage increases SOC mineralisation with CO₂ release and crop residues are closer to microbes favouring mineralisation too [5,27]. Daniels (2022) [124] states that tillage accelerates soil erosion and consequently impoverishes soil health with the leaching of N and P heightening the erosion; tilling races up CO₂ emissions because of the soil disturbing. In a wetland system, CO₂ emissions are also reduced in the case of a no-tillage system [47].

Conservation tillage (CT) is a tool for soil and water conservation through crop residues and enhancing soil quality; it is an instrument for mitigating the greenhouse effect and for improving environmental quality [28,209]—response from conservation tillage differs by regions, climates, and soil types [89]. The evolution of weed control technology and farm gear facilitated the application of CT [85].

Tillage removes soil aggregates, a physical barrier between SOC and microbial degradation [146], reducing the amount of SOC in all the fractions and particularly in fine clay and sand [193], ploughing decreases particulate SOC and the light fraction. Through CT, the added SOC is in inter-macro-aggregate material; this may increase macro-aggregation and their stability; showing a positive impact on sequestering C in agricultural soil [146,188,210]. The increase in SOC amount is close to the soil surface and seems to protect erosion and microbial decomposition. Conversely, Baker et al. (2010) and Johnson et al. (2007) [26,211] underline that tillage may redistribute and mix plant material and SOC throughout the profile. In a short-term, tillage enables CO₂ emission proportional to the volume of disturbed soil and, CT raises C sequestration based on the depth of soil sampling [26].

Generally, reduced tillage or no-tillage allow C sequestration, whereas in some cases, a C loss is caused by the soil disturbance due to the accelerated decomposition and erosion [85]. No-tillage is suggested as a practice to reduce soil erosion and, at the same time, it betters soil’s physical conditions and cuts down GHG emission but does not affect the yield [85,116,212].

Adil et al. (2022) [146] writes that NT increases all the various SOC fractions comparing to CT. Reducing tillage makes SOC increase, in particular, easily oxidised organic carbon and particulate organic carbon components; in a minor measure dissolved organic carbon and microbial organic carbon components.

Actually, no-tillage or conservative tillage enhances carbon sequestration and storage; at the same time, with a minor use of tractors, fewer fossil fuels will be used [124]. Duda et al. (2014) [213] also states that no-tillage, mulch and rotations ameliorate markedly soil properties with a less amount of emitted CO₂. However, conservative tillage shows good results in improving soil’s physic parameters, reducing soil erosion and increasing infiltration and, in some cases, even increased productivity. Concerning conservative tillage, results suggest overlaying land with 15–30% of plant debris; in the case of minimal tillage the cover is over 30%; in a no-tillage system, seeds are put in the stubble or the ground is protected by plant debris from the previous yield.

The amount of SOC leads to stable aggregation due to dominant fungal microflora, earthworm activity, and formation of platy structure with high bulk density [193,214,215,216]. Ploughing leads to aggregate breakdown and conversion to CT can enhance the aggregate dimensions [217,218,219,220]. The goal is to improve the physical, biological, and ecological components of soil to achieve good soil health [53].

Lal (2007) [221] highlights that reducing tillage to sequester C may increase the frequency or duration of denitrifying conditions in soil, because soil remains wetter and additional N fertiliser may be used; high amount of N₂O emissions is emitted under non-tillage (NT) than conventional tillage [222,223]. Blanco-Canqui et al. (2008) [135] developed a model to value soil transport by tillage, to discriminate the difference between soil loss by tillage, by water erosion, and by wind erosion, and the consequences on C sequestration in soil.

Three activities might restore soil quality, including minimising losses from soil, creating a positive C content in soil, and strengthening the water and nutrient supply [27]. Under no-tillage, soil C sequestration occurs in the upper-soil layers but declines in deeper layers; therefore, the total soil C content remains unchanged [8,224].

Carbon and SOM accumulate in soil when no-tillage is applied; according to [225], it may increase the denitrification process and N₂O emissions, whereas it is helpful in reducing CH₄ emissions; [226] stated that comparing no-tillage and plough tillage, CH₄ emissions were reduced. The advantage of no-tillage practice is a pore continuity and a niche for methanotrophic bacteria, therefore a CH₄ absorption. According to [213], reduction in tillage led to improve qualitative and quantitative agriculture activity and soil fertility.

13. Water Management

Agricultural water management may decrease GHG emissions; sustainable agriculture (SA) improves infiltration, water capacity, and water retention, consequently allowing the development of root system, restoring aerobic soil condition and reducing flood impacts [227,228]. Restoring the ecosystem through water regulation leads to biodiversity conservation, carbon sequestration, pollination enhancement, and generation of livelihoods [229,230,231,232].

Calderón Cendejas et al. (2021); McDowel et al. (2021) [233,234] highlighted a correlation between land use and water quality and the different impact on the water of crop, forest, and population. Agricultural practices have a negative impact on water quality, showing a positive correlation with higher levels of turbidity, hardness, total nitrogen, nitrates, and ammonium [233,235].

Duda et al. (2014) [213] highlights that sustainable water management with innovative agriculture could mitigate climate change effects; innovative agriculture stands for a sustainable agriculture based on the enhancing of crop rotation and reduction in energy consumption. Liu et al. (2020) [236] asserts that Mulched Drip Irrigation (MDI) reduces the amount of water and GHG emissions, whereas a wrong irrigation can race up N₂O emissions because of the denitrification and the breakdown of SOM, which causes CH₄ emissions.

14. Organic Agriculture

Organic agriculture may help in mitigating climate change by reducing GHG emissions [4,237,238]; cover crop practice points out positive results in C sequestration [239]. Organic agriculture application has increased, reaching about 70 million hectares for crops like dry pulses, vegetables, and olives [85]. Conservation agriculture (CA) can play a crucial role in the development of sustainable agricultural systems in view of growing food demand and environmental changes [8]. FAO (2017) [240] is promoting CA for more sustainable land management, environmental protection, and climate change adaptation and mitigation; CA results in an improvement in fertility and yield [127,241]. Soil carbon sequestration and the adoption of conservation agriculture depend on climate conditions, especially in arid regions. In dry areas, CA enhances soil moisture mostly during fallow time; reduction in soil temperature, increase in water infiltration, evaporation and C emissions are impeded by mulch residual [8]. Intensive agriculture means a high loss of SOC [4,11,242,243,244,245,246,247]. Sun et al. (2020) [8] states that the humidity index (HI) affects the SOC value. In semi-arid to humid areas (40 ≤ HI ≤ 100), conservation agriculture leads to an increase in SOC, whereas in cool, humid, and tropical humid areas, the decreasing temperature and mulch cover waterlogging might be a disadvantage for early seed germination and crop growth.

Organic agriculture leads to the reduction in manure, to avoid the application of organic fertiliser before irrigation; hence, to diminish nutrient depletion, crop rotation and organic fertilisers might reduce contaminants concentration in soil [4,135]. Animal manures may be decomposed by soil microorganisms and contribute to the SOM pool; cover cropping and animal manures can contribute to SOC sequestration [26,248].

15. Biochar

Biochar can be a soil conditioner and/or a soil amendment improving soil quality, a sink for nutrients enhancing plant growth, and have a great potential to mitigate soil emissions [157,249]. Biochar has a high C content; it fosters the ability to store and recycle C in an efficient way [26,249,250,251] and decreases N₂O and CH₄ emissions and enhances soil sustainability and fertiliser concentration [40,252,253,254,255,256,257]. Carbon sequestration is high if biochar is produced from plants because of the high C/N ratio; the pyrolysis conditions influence C content and potential sequestration in biochar. Biochar application provides SOC content in the long term and high stability, and it increases the availability of nutrients and water, yield, microbial biomass, and diversity. Biochar enhances long-term carbon storage due to the high rate of C sequestration; microbial decomposition is very low, making biochar a very powerful recalcitrant amendment [40,258]. H/C value must be lower than 0.7 and O/C value must be lower than 0.4 to reach a good quality and high stability in biochar [40,259]. Converting biomass to biochar can store about 50% of original C and persist for a long time, interacting with organic matter reducing its decomposition [13,40]. Gupta et al. (2020) [40] suggests valuing the carbon sequestration potential of biochar (CSB) by

CSB (%) = (M × Ch × C_ch × R₅₀)/(M × C_F)

where M = mass of feedstock (g); Ch = yield of biochar (%); C_ch = carbon content of the biochar, R₅₀ = recalcitrant index; and C_F = carbon content of feedstock.

Implementing the annual biochar application leads to a higher C stock in soil. Soil mineralogical composition affects the results of biochar application; increasing clay content increases SOC stability. Gross et al. (2021) [260] states that tillage enhances C biochar migration to low horizons, fostering soil aeration and decay; tillage practice and biochar application should maximise SOC sequestration. It may reduce CO₂ emission so the system is C-neutral, and under proper conditions, it may increase soil CEC, water storage, and soil fertility [26,250]; it could act as a slow fertiliser and potentially decrease leaching and runoff [26,249,261]—these favourable effects can be provided for a long time [206,262,263]. Methane emissions are reduced during methanotrophic activity according to soil lithology, biochar physico-chemical characteristics, and water management [40,264]. Methanotrophic activity is enhanced increasing the aeration and via methane adsorption on biochar which shows a high surface area [253]. In addition, some biochar characteristics like porosity, pH, and surface area are profitable in reducing N₂O emissions. Its application in soil lowers NO₃⁻ and NH⁺₄, limiting microbial activity and emissions as well as concentration for nitrification and denitrification reactions.

16. Agroforestry

Agroforestry is a cost-effective way to sequester C over a long time period, combining trees, shrubs, and agronomic crops. Bangroo et al. (2013) [39] highlights the importance of afforestation and reforestation as a mitigation strategy for C sequestration and a resource for wood production, too. The presence of trees increases C sequestration and their residues (leaves and branches) increase SOM. Reforestation–afforestation of non-forest lands and/or brownfields will prevent land degradation, as well as sequestering and reducing the net C emission [39]. To succeed in afforestation protocol, the choice of the correct tree species is imperative; different tree species generate litter with differentiated characteristics which affects soil formation and properties like texture and pH [265,266]. Further parameters, which can affect its success, are clay content past land use and climatic zone [32,267]. This practice is considered a good natural-based solution to sequester C in soil; increasing C residence time enhances SOM stabilisation in the aggregates. Deforestation leads to a C release from biomass decomposition and SOM; part of this C could be restored through reforestation [18]. Forests are considered an atmospheric CO₂ sink according to the net aerial primary production rise; after harvest or a natural catastrophe, vegetation can be regenerated [35], but the carbon balance might be negative because of constant SOM decomposition. Forests turn out to be a very good sink for atmospheric CO₂ during the active phase of regeneration, whereas at a maturing stage, the CO₂ adsorption is less due to the established balance between the rates of net production and net decomposition. Miralles-Wilhelm (2021) [157] identifies that reforestation has highlighted co-benefits, including biodiversity habitat, air and water filtration, flood control, and enhanced soil fertility. Furthermore, land change from agriculture to agroforestry increases SOC in soil up to a depth of 100 cm [32].

Ontl and Schulte (2012) [18] suggests the creation of wetlands and ponds to sequester a massive amount of C, because decomposition is greatly reduced in waterlogged soils from the lack of oxygen. Tubiello (2010) [268] pointed out that the positive impact of forests in mitigating atmospheric CO₂ will be lower. Particularly, average productivity increases in young trees under elevated CO₂, whereas a lower stimulation in stem growth of older tree stands has been observed. Additionally, species competition, disturbance, pollutants, and nutrient availability may limit stand-level response to elevated CO₂ (Figure 17).

Further conservative practices to reduce soil erosion are grassed waterways and vegetated riparian buffer strips; therefore, floods could be absorbed and C sequestered [212].

17. Future Hints

Compare short-term versus long-term effects of conventional tillage and conservative tillage systems to identify which practice is sustainable.

Evaluate how soil properties, climate, and management interactions modify outcomes over time, and determine whether practices such as no-tillage, reduced tillage, conservation agriculture, and agroforestry consistently lower GHG emissions and improve soil health when observed on multi-decadal scales.

Short-term studies often show variable or contradictory results for no-tillage and other conservation practices. There is a scarcity of long-term experiments that track how the environmental context and time shape sustainability metrics.

Important unresolved questions include whether soil depth plays a role in long-term CO₂ stabilisation, how extreme climate events alter trajectories, and whether agroforestry provides durable co-benefits for food, timber, and climate mitigation.

Hypotheses to test in long-term studies on more multi-site, multi-decadal experiments with standardised protocols and open data are needed to resolve context-dependent effects.

To better understand the longevity and stability of SOC gained under different tillage systems, especially the role of depth and mineral association.

Quantification of how extreme climate events change SOC trajectories and how tree cover in agroforestry mitigates these effects.

Economic and social assessments to evaluate adoption barriers and co-benefits of long-term conservation strategies.

Long-term evaluation is essential to determine whether conservation tillage and agroforestry reliably deliver sustainable outcomes.

Soil depth, climate, management interactions, and ecosystem processes all shape the final result; therefore, comprehensive, depth-resolved monitoring, integrated GHG accounting, and site-tailored practices are required to establish robust, scalable recommendations for climate-smart agriculture.

18. Conclusions

NbS play a critical role in climate mitigation by enhancing carbon sequestration, protecting ecosystems, preventing carbon release from deforestation and degradation, and improving land management. NbS can be more cost-effective than engineered solutions for climate adaptation. NbS could contribute up to 10 Gt of CO₂ equivalent per year by 2050, under the effective implementation of NbS for climate mitigation. More data is needed on long-term impacts, especially on biodiversity and ecosystem health.

In particular, C and N sequestration in soils are suitable within soil and water management as well as the protection of biodiversity, natural systems filter pollutants, coastal wetlands, and mangroves buffer storm surges and stabilise shorelines. The amount of C sequestered in soil relies on the vegetation, soil depth, its drainage capacity, mineral composition, soil temperature, ongoing and former land use, and the relative proportion of soil, water, and air.

NbS such as conservation tillage, organic farming, crop rotation, cover crops, and green manures lead to the reduction in compaction and improved water management, avoiding the erosion and depletion of nutrients. These solutions lead to the maintenance of biodiversity, to sustain ecological processes providing a healthy ecosystem including pest control, pollination, and restoration of soil nutrients connected to management procedures, mitigating GHG emissions from the agricultural system.

In particular, CA and CT are deeply interconnected in improving soil health, retaining SOM, reducing erosion, and promoting microbial activity. No-tillage has been found to be a viable alternative for improving soil health in some industrial agricultural systems due to its potential in enhancing sustainability, reducing costs, and improving long-term productivity. Industrial agriculture typically involves large-scale monoculture, heavy machinery, and intensive input use, and its benefits are as follows: it prevents erosion and degradation across vast fields, improves infiltration and retention, and reduces irrigation needs by up to 30%.

Agroforestry systems might lead to an increase both above- and below-ground C stocks, reducing soil erosion and degradation and mitigating GHG emissions. Conservation and cover crops and elimination of synthetic pesticides may help to offsets GHGs and restore the nutrient cycling mechanisms of natural systems.

Good agricultural practices may mitigate GHG emissions, such as soil conservation, reducing the use of inorganic fertilisers and pesticides; the diversification of the crops will help in mitigating climate change. The synergy between climate-change mitigation and agriculture adaptation is a great opportunity for developing win–win strategies in the GHG sequestration. Management of agriculture and forestry have the same importance for GHG mitigation through increasing carbon sequestration and sustainable agricultural and forestry practices within the protection of soil health.

Nature-based solutions can crucially reduce greenhouse gas emissions by enhancing the natural capacity of ecosystems to capture and store carbon.