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'''0. Introduction/Summary'''
The 4 per 1000 Initiative aims to show that achieving food security, adapting to climate change and reducing atmospheric carbon dioxide concentrations are complementary through the preservation and increase of organic matter in soils leading to carbon sequestration. The 4 per 1000 initiative is a multi-stakeholder partnership with the goal of encouraging and supporting its partners on implementing actions to enhance the carbon content of soils with an aspiration rate target of 0.4% or 4‰, based on a transition towards productive and highly resilient agricultural and food systems.
'''1. Purpose and goals of the initiative'''
The 4 per 1000 Initiative aims to promote and deploy practical measures on the ground that benefit crop and livestock farmers through the implementation of practices favourable to the restoration of soils, to an increase in their organic carbon stock and to the protection of carbon-rich soils and biodiversity.
The Initiative aims to encourage their diverse partners to:
· implement training and outreach programs on agricultural management that preserves and builds up soil carbon
· fund projects that restore, improve and/or preserve carbon stocks in soils
· develop and implement public policies and appropriate tools
· adapt supply chains to ensure soil health-friendly agricultural products
'''2. The importance of soils for food security and climate'''
'''2.1 Soils as part of the global carbon cycle'''
Through the process of photosynthesis, vegetation uptakes CO<sub>2</sub> from the atmosphere, converting it to carbohydrate molecules used for plants' metabolism. After vegetation decay, dead biomass is not completely decomposed releasing all fixed carbon back to the atmosphere. It is partly transferred into the soil as litter and over time transforms to build up soil organic matter (SOM). The carbon contained in SOM is commonly referred to as soil organic carbon (SOC).
'''Soils represent the largest terrestrial reservoir of carbon'''. They are a key compartment of the global carbon cycle. An estimate of 829 Pg carbon were in the atmosphere in 2011, living biomass contained 450 to 650 Pg carbon and soils 1500 to 2400 Pg carbon (state: 2011).
The amount of carbon stored in soils is the result of the balance between carbon inputs and outputs. Carbon enters the soil mainly via plant residues representing a carbon flux from the atmosphere through biomass into the soil. Carbon is transferred into other reservoirs such as rivers and oceans in form of dissolved organic carbon. The release of carbon back to the atmosphere is mainly dependant on decomposition of dead biomass or SOM to its mineral components such as CO<sub>2</sub> (heterotrophic respiration) . There is a direct link between the amount of carbon stored in soils and atmospheric CO<sub>2</sub> concentration.
'''2.2 Importance for food production and adaptation'''
Soil C content can be considered as the general soil property reflecting soil fertility or productivity because soils rich in C generally contain higher amount of available nutrients for plants and have better soil physical and biological properties.
Soil is the most important natural resource for food production. Although soil organic matter, which is composed of carbon in 58-70%, comprises 5 to 10 % of most soils, it is essential for the formation and maintenance of soil properties that define soil quality and its capability to provide essential soil functions important for food production as well as for natural ecosystems. Among these functions are to store and provide plants with nutrients and water, filter rainwater that enters aquifers, provide habitat for soil fauna, flora and microorganisms, also essential environmental services. Usually the top 30 to 50 cm of soils is used directly for food production, but lower soil layers are also affected. Soils low in organic matter may be successfully used for food production by correcting soil acidity and applying plant nutrients, like nitrogen, phosphorus, potassium and other macro and microelements via synthetic fertilizers. However, soils that are low in the organic component, will gradually lose on physical and biological quality. Those soils, while providing nutrients, will have poor structure, thus will impede healthy root growth, water infiltration and storage, as well as support reduced and altered biological diversity. Unhealthy soils are unable to sustain economically viable food production in the long-term (> 20 years) and fail to provide environmental services. On the other hand, soils that are capable of maintaining essential functions, will enable agroecosystems to react to changes and external impacts in the environment maintaining or regaining their productivity. These are two fundamental behaviours, resilience and adaptation, of both natural and agroecosystems that enable environmental and economic sustainability.
'''2.3 Rationale behind “4 per 1000”'''
A simple calculation performed by scientists (Arrouays et al., 1999) shows that world soil carbon stocks are so large (860 Gigatons of organic carbon in the upper 40 cm of soils) that increasing them at an annual rate of 4‰ (i.e. 860 x 4 /1000= 3.4 Gigatons of C per year), would sequester an amount of carbon close to the current annual net increase of carbon as CO2 in the atmosphere (4.5 Gt C per year). Conversely, depleting the world soils’ upper C stocks by 4‰ annually would strongly accelerate the atmospheric CO2 rise.
This number, chosen as the logo/name of the initiative, intends to show that small changes in soil organic carbon do matter. 4‰ is not a normative target but is an aspirational goal. It should be made very clear and unambiguous here that this approach only makes sense in an environment where greenhouse gas emissions are drastically reduced in all sectors, including agriculture and forestry.
'''3. History of the initiative'''
The 4 per 1000 Initiative was launched in 2015 at COP21 in Paris, France. This initiative is part of the Global Climate Action Agenda, which follows on from the Lima-Paris Action Agenda. Its targets contribute to the goal of a land-degradation neutral world. Since its launch, 359 partners from diverse stakeholder groups have joined the initiative.
'''4. Organization of the “4per1000” Initiative'''
The structure and governance of the initiative is defined in the Declaration of Intention from 23 September 2016.
'''4.1 Forum of partners'''
The Forum of Partners is the initiative's body, in which partnerships and strengthened collaborative actions are built up. It brings together organizations that have signed the Declaration of Intention of Support for the 4 per 1000 Initiative. By signing the Declaration, all partners demonstrate that they share the principles and objectives of the initiative.
The Forum of Partners meets once a year, and also forms a digital community. The "4 per 1000" Forum has '''359 partners''' (as of December 2018). Diverse stakeholder groups are represented:
· Farmers' and land users organizations (40)
· States and provinces (42)
· International and regional organizations (12)
· Development banks and Foundations (14)
· Research and academic institutions (80)
· Civil society organizations (110)
· Private companies (61)
The full list of partners (as of 13 December 2018) can be downloaded here.
'''4.2 Consortium of Members'''
The Consortium of Members is the decision-making body of the "4 per 1000" Initiative. The Consortium determines, by consensus-based decisions, the work plan and budget of the initiative. Any non-profit and non-commercial Partner of the initiative can join the Consortium. As of December 2018, 183 organisms are contributing to setting the yearly road map of the 4 per 1000 initiative.
The Consortium of Members meets at least once a year on the occasion of the annual meeting of the Forum, but also at other times according to its own agenda. 4 per 1000 partners can sign the Marrakesh declaration of intention in request to become a member of the 4 per 1000 Initiative.
'''4.3 Scientific and Technical Committee'''
The Scientific and Technical Committee is the scientific body of the "4 per 1000" Initiative. The Scientific and Technical Committee (STC) was established in November, 2016 during COP22 in Marrakesh.
The STC is made up of 14 high-level scientists of high international reputation, selected by the Consortium of Members on the proposal of the Executive Secretariat. It is a multidisciplinary group, with a balanced composition of geographical origin and gender.
The STC has proposed the 4 per 1000 Research priorities as well as a set of Reference criteria and indicators for project assessment. Both documents have been adopted by the Consortium of Members as Guiding documents of the 4 per 1000 Initiative.
The STC meets several times a year to discuss ongoing and planned activities and provide scientific guidance to the work of the 4 per 1000 initiative. It also works on scientific publications to advance in the field of soil carbon sequestration and provides technical advice on field projects, actions and programs.
The main publications of the STC have been:
Rumpel, C., Amiraslani, F., Chenu, C., García Cárdenas, M., Kaonga, M., Koutika, L.-S. ..., Wollenberg, L. (In review). '''The 4p1000 Initiative for promoting increases in soil organic carbon stocks: finding common ground to stimulate policy-science-practice interaction'''. Ambio.
Rumpel, C., Amiraslani, F., Koutika, L.-S., Smith, P., Whitehead, D., Wollenberg, E., 2018: '''Put more carbon in soils to meet Paris climate pledges'''. Nature, 564, 32-34. <nowiki>https://www.nature.com/articles/d41586-018-07587-4</nowiki>
'''4.4 Executive Secretariat'''
The Executive Secretariat is the executive body of the 4 per 1000 Initiative.
Its mission is to provide support to the three governance bodies (Forum of Partners, Consortium of Members and Scientific and Technical Committee) and to coordinate and implement the activities of the Initiative, notably through the organization and documentation of meetings, the facilitated communication between the 4 per 1000 partners and the management of common tools (website including the collaborative platform and a digital resource center ...).
The Executive Secretariat is made up of the following team:
· Dr. Paul LUU, Executive Secretary of the “4 per 1000” Initiative since September 2016, is in charge of the coordination of the Executive Secretariat team, the mobilization of resources, implementation of the roadmap and organization of the statutory meetings of all bodies of the Initiative. His regional focus is Asia, Oceania and North America. He is based in Montpellier, France at the CGIAR System Organization.
· Dr. Paloma MELGAREJO-NARDIZ, is a Sciences Officer in charge of the link with the international research and scientific cooperation program with the STC. She is Professor of Reasearch at the Spanish Ministry of Agriculture, Fish and Food. She is based in Paris, France at INRA. Her regional focus is Central and South America.
· Mr. Marc BERNARD is involved in the coordination of the operational part of the International "4 per 1000" Initiative. He conceptualises and implements network activities for the development and implementation of the strategy, manages the electronic platform, promotes teamwork and partnerships and provides ideas to overcome complex challenges, such as the idea of "Twin Regions", the creation of working groups, the Delphi study... He is an agronomist and soil scientist, graduated from the Technical University of Munich.
· Ms Béatrice BRETON-ASKAR, Resource Mobilisation Senior Officer, is responsible for funder engagement. Her role within the Executive Secretariat is to develop networks, partnerships and funding for the International "4 per 1000" Initiative. She is based in Montpellier at the Executive Secretariat offices in France. She has a dual Franco-American background; she studied economics, management and international business at ESC Rennes, France and at Clemson University, USA, where she obtained a Master of Business Administration. She is employed part-time (60% Full Time Equivalent - FTE) by CIAT-Bioversity International Alliance on behalf of the Executive Secretariat of the Initiative.
· Ms Julia KLEMME works at the German Federal Office for Agriculture and Food (BLE), and is based in Bonn, Germany. She is responsible for communication in Germany, event organisation and moderation support for the collaboration platform. Julia KLEMME studied geography at the University of Bonn. She graduated with a Master of Science in 2016. She is employed part-time (50% FTE) by the BLE and works for the Executive Secretariat.
· Ms Brigitte CABANTOUS is in charge of the logistical organisation of the statutory meetings (Scientific and Technical Committee, Consortium of Members and Forum of Partners) and of the management of the Members. She also contributes to the updating of the website. She is employed by CIRAD in Montpellier (France) and collaborates with the Executive Secretariat for a Full Time Equivalent of 40%.
The human and financial resources allowing the operation of the Executive Secretariat, are provided on a voluntary basis, in form of secondments, by the Ministries of Agriculture of France, Germany and Spain as well as CIRAD.
'''5. Driving factors for soil organic carbon stock'''
In natural ecosystems, soil organic carbon maintains a steady state, which is disturbed by clearing forests and agricultural practices. The steady state content of carbon is governed by the balance between inputs and decomposition rates and the capacity of soil to protect soil organic matter from decomposition and erosion. Most agriculture soils maintain lower soil C stocks than natural ecosystems and tend to attain near steady state.
Inputs are driven largely by net primary productivity (plant biomass production) and, in agricultural lands, may also include organic amendments. Loss through decomposition of organic matter by microbial activity varies with soil moisture and climate variables such as temperature, and with soil properties. Soil type determines rates of turnover of organic matter as it cycles between living, decomposing and stable fractions in the soil, through factors such as clay content and nutrient status.
In addition to natural pedoclimatic conditions, agronomic practices and efficient use of water that maximise crop and pasture biomass production increase organic matter inputs and tip the balance towards higher soil carbon stocks. Practices that minimise loss include reducing exposure of previously protected organic matter in structured soils to microbial decomposition by minimising or stopping tillage, and by protecting soil surface from erosion, by use of cover crops and avoiding overgrazing pastures.
'''6. Benefits of maintaining and increasing the amount of soil organic carbon'''
Soil organic carbon (SOC) conservation or sequestration in agricultural or forestry systems lead to: (i) Improve soil overall health, function and fertility (physical, chemical and biological) and combat land degradation, desertification, biodiversity and water resources; (ii) Increase crop yields and alleviate the food insecurity, and (iii). Reduce Green House Gas (GHG) emissions i.e., contribute to mitigate climate change.
i) Improve soil overall health, function and fertility (physical, chemical and biological): There are interrelated. An increased soil organic carbon involves an improved soil physical properties i.e., aggregation, aeration and water holding capacity and reduce or alleviate soil degradation. This leads to an increase in overall faunal activity i.e., biological soil fertility e.g., bacterial, microbial etc.. This enhanced biological activity will lead to an improvement in soil chemical properties i.e., release of nutrients which will benefit to plant (crop or tree).
ii) Increase crop yields and secure food availability: SOC conservation and sequestration also have multiple co-benefits for food security. Improved soil fertility is directly linked to good plant growth and increase in crop yield and food availability i.e., alleviates food insecurity.
iii). Reduce Green House Gas (GHG) emissions i.e., contribute to mitigate climate change: Sequester carbon in both soil and biomass in agricultural landscapes (e.g., agroforestry) reduces CO2 emissions.
'''7. Practical solutions for maintaining and increasing soil organic carbon stocks'''
'''7.1. Scientific evidence'''
Long-term field experiments on soil organic matter (SOM) give us the evidence on what kind of SOM management can maintain or increase soil organic carbon (SOC) in a specific soil type under specific environmental condition. Long-term is needed because it is difficult to detect the changes in SOC in shorter period (less than 5 years). Soil C models developed based on these long-term experiments are useful, too, to predict what kind of SOM management can maintain or increase soil C in a specific soil type under specific environmental condition.
'''7.2 Examples from the ground'''
SOM management, which increases soil C can be divided into two; increasing SOM inputs and decreasing SOM decomposition in soils. For example, the use of green manure or cover crops are common management practices to increase SOM inputs to soils and no-tillage or reduced tillage are examples of reducing SOM decomposition in soils.
No-tillage or zero-tillage is a soil management system in which, instead of incorporating plant residues into the soil, by ploughing, as part of the process to prepare the soil to sow the next plant, the residues of the previous harvest (mulch) are maintained on the soil surface so that the soil not be disturbed physically. By maintaining the soil intact, the upper soil layer is not aerated, which keeps SOM decomposition rates lower than in the case of conventional tillage, in which case the soil is ploughed. Another benefit of creating and maintaining mulch is protection against soil erosion.
These two benefits of zero-tillage are especially important in soils of tropical and subtropical climate. Soils of the tropics are usually highly weathered, millions of years old, soils, which naturally have low concentration of nutrients and higher decomposition rate of organic matter than soils of colder and less humid climates. Due to the mineralogical composition of these soils, SOM is the principal source and carrier of nutrients for plants (Figure).
Figure: Major differences in the mineralogy and chemical properties of soils formed under tropical and temperate climate. CEC=cation exchange capacity: the quantity of cations (e.g. Ca2+, Mg2+, K+, Al3+, H+) on the surface of soil colloids, represents the capacity of the soil to store and provide nutrients. V% = base saturation: the proportion of cations of basic reaction, important plant nutrients (e.g. Ca2+, Mg2+, K+) within CEC. Soils with high CEC and high V% have high fertility potential. Nitrogen (N) availability depends on SOM and fertilizer N inputs. Phosphorus is strongly retained on oxide surfaces in tropical soils, while it is available for plants when adsorbed on organic colloids.
When these soils are barren or ploughed, they rapidly lose SOM by oxidation and by soil erosion. Conventionally managed soils of tropical regions often contain less than 1% SOM in the surface 20 cm layer, whereas soils under natural vegetation can contain as much as 5-8%, depending on the ecosystem. SOM management in tropical agro-ecosystems is, therefore, of utmost importance for agricultural production.
Studies on SOM dynamics in long-term experiments from humid temperate, humid subtropical to humid tropical savannah climate have shown that using zero-tillage is beneficial for maintaining or increasing SOM. The lack of ploughing itself can reduce the rate of SOM loss by promoting less oxidative soil environment. However to effectively gain SOM it is fundamental to combine zero-tillage with improved biomass (organic C and N) input into the system and the soil by including cover crops or green manure (nitrogen fixing leguminous plants) in the plant rotation (Figure) (Bayer et al., 2006; Boddey et al., 2010; Conceição et al., 2013; Sá et al., 2014; Corbeels et al. 2016).
Figure: Annual soil organic carbon (SOC) accumulation rate in tonnes per hectare due to changing soil management practice from conventional tillage to zero-tillage. Results from 33 long-term (10-26 years) experiments in Brazil.Carbon accumulation rates and the time to achieve a new SOC equilibrium as well as the capacity of the soil to maintain SOC levels depend on a variety of factors. Clay soils, for instance, would likely contribute to higher SOC stocks and to the maintenance of those (Zinn et al. 2007). The impact of the change in SOC stocks, however, may be more pronounced and measurable on the agronomic performance in light textured soils. The original SOC content of the soil and soil quality (Cardinael et al. 2017) is further influencing factors. The success of zero-tillage in promoting SOC accumulation and maintenance will largely depend on how successfully good management practices are followed over time. Some of these are the avoidance of mechanical soil disturbance, promoting or maintaining soil physical quality (soil aggregation, water infiltration and water retention), continued biomass inputs to ensure SOC buildup, constant soil cover to combat erosion and soil nutrients’ reposition to maintain nutrient balance (Oliveira et al., 2018).
'''8. Estimating the global and local potential of soil carbon sequestration and losses'''
Globally, the cumulative loss of soil carbon due to ecosystem management has been estimated as 115–154 Pg C<sup>[1],[2]</sup>. This loss defines a maximum soil C sink capacity but the attainable soil carbon sequestration will be less, perhaps at most only 50 to 66% of this technical potential<sup>[3]</sup>. Estimates<sup>[4]</sup> of potential rates of sequestration in Mg C ha<sup>-1</sup> year<sup>-1</sup> are 0.25–1.0 in croplands, 0.10–0.175 in pastures, 0.5–1.0 in permanent crops and urban lands, 0.3–0.7 in salt-affected and chemically degraded soils, 0.2–0.5 in soils physically degraded and prone to water erosion, and 0.05–0.2 for those susceptible to wind erosion. Based on a feasible area of 4,900 Mha<sup>5</sup>, the global technical potential SOC sequestration may be equivalent to 1.45–3.44 Pg C/year. Realistically long-term sequestration of carbon in soils is limited by biophysical factors, such as requirements for nutrients (particularly nitrogen and phosphorous), and social, economic and cultural constraints on adoption and effective implementation of new agricultural practices while increasing food production.
Actual rates of soil carbon sequestration are highly site dependent and vary over time generally approaching a new steady state<sup>6</sup>. Sequestration depends on soil texture and structure, rainfall, temperature, past soil management and on the adoption of regionally appropriate practices that add high amounts of biomass to the soil. Local data are essential for accurate estimates of potential sequestration at farm or regional scale, and to document co-benefits for soil health, production and climate resilience. For example, in tropical cropland regions soil carbon sequestration over an average period of approximately 14 years ranged from 0.24 to 0.83 Mg C ha<sup>−1</sup> yr<sup>−1</sup> depending on management practice and time since implementation[5].
'''9. Controversial issues/Addressing concerns related to “4per1000”'''
Several critiques have been addressed to the initiative, which resulted in improving its communication and pointing at research and assessments needs. First, it is important to state that the initiative does not propose to compensate for all fossil fuel emissions thereby allowing continuation of business as usual. Emission reductions are essential. It is imperative to change lifestyles in order to reduce fossil C consumption.
Sequestering carbon in soils is an additional action in a whole portfolio of measures that are needed to remove CO2 from the atmosphere in order to reduce warming of the planet (IPCC special reports: 1.5°C). Second, there are biophysical limits to storing additional carbon in soil, which need to be accounted for: SOC storage is limited as storage reaches a new equilibrium after several decades of maintaining a given SOC-storing management option. Biomass to return to soil may be locally limiting, as well as water, nitrogen and other nutrients needed to produce the biomass for transformation into soil organic matter. SOC storing management options must, therefore, be spatially diversified. Third, storing additional carbon in soils is only part of the story; a full balance of greenhouse gases is needed, as is now included in 4p1000 assessment criteria. Some SOC storing management options lead, in certain pedoclimatic conditions, to increased N2O emissions. N2O is a potent GHG and its emissions must be avoided. Finally, biophysical estimates of the local, regional and global SOC storage potential are much larger than economic potentials (when accounting for the cost of implementing the management options) and in-situ estimates, when accounting for adoption. A wide range of measures are needed to foster adoption of SOC storing management options.
'''10. Links and further reading'''
1. '''^''' "AR5 Climate Change 2013: The Physical Science Basis — IPCC". Retrieved 2019-02-21.
2. '''^''' Cotrufo, M. Francesca; Wallenstein, Matthew D.; Boot, Claudia M.; Denef, Karolien; Paul, Eldor (2013). "The Microbial Efficiency-Matrix Stabilization (MEMS) framework integrates plant litter decomposition with soil organic matter stabilization: do labile plant inputs form stable soil organic matter?". ''Global Change Biology''. '''19''' (4): 988–995. doi:10.1111/gcb.12113. ISSN 1365-2486.
3. '''^''' Intergovernmental Panel on Climate Change, ed. (2014), "Glossary", ''Climate Change 2013 - The Physical Science Basis'', Cambridge University Press, pp. 1447–1466, doi:10.1017/cbo9781107415324.031, <nowiki>ISBN 9781107415324</nowiki>, retrieved 2019-02-21
4. Boddey et al. Carbon accumulation at depth in Ferralsols under zero-till subtropical agriculture.
Global Change Biology (2010) 16, 784–795, doi: 10.1111/j.1365-2486.2009.02020.x
5. Bayer et al. Carbon sequestration in two Brasilian Cerrado soils under no-till. Soil and Tillage Research (2006), doi: 10.1016/j.still.2005.02.023
6. Conceição et al. Combined role of no-tillage and cropping systems in soil carbon stocks and stabilization. Soil & Tillage Research (2013) doi: 10.1016/j.still.2013.01.006
7. Sá et al. Long-term tillage systems impacts on soil C dynamics, soil resilience and agronomic productivity of a Brazilian Oxisol. Soil & Tillage Research (2014) doi: 10.1016/j.still.2013.09.010
8. Corbeels et al. Evidence of limited carbon sequestration in soils under no-tillage systems in the Cerrado of Brazil. Scientific Reports (2016) 6:21450, doi: 10.1038/srep21450
9. Zinn et al. Edaphic controls on soil organic carbon retention in the Brazilian Cerrado: texture and mineralogy. Soil Sci Soc Am J (2007) 71:1204–1214. doi:10.2136/sssaj2006.0014
10. Cardinael et al. Increased soil organic carbon stocks under agroforestry: a survey of six different sites in France. Agric Ecosyst Environ (2017) 236:243–255. doi:10.1016/j.agee.2016.12.011
----[1] Lal (2018) Digging deeper: A holistic perspective of factors affecting soil organic carbon sequestration in agroecosystems. ''Global Change Biology 24''(8), 3285-3301.
[2] Sanderman et al. (2017). Soil carbon debt of 12,000 years of human land use. ''PNAS'' ''114'', 9575-9580.
[3] Lal R. (2004). Soil carbon sequestration in India. ''Climatic Change'' 65, 277–296.
[4] Lal et al. (2018) "The carbon sequestration potential of terrestrial ecosystems." ''J. Soil & Water Con.'' 73, 145A-152A.
[5] Fujisaki et al. (2018). Soil carbon stock changes in tropical croplands are mainly driven by carbon inputs: a synthesis. ''Agriculture, Ecosystems & Environment'' ''259'', 147-158.
[[Catégorie:Événement en rapport avec le développement durable]]
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