Carbon farming
Carbon farming is a set of agricultural methods that aim to store carbon in the soil, crop roots, wood and leaves. The technical term for this is carbon sequestration. The overall goal of carbon farming is to create a net loss of carbon from the atmosphere.[1] This is done by increasing the rate at which carbon is sequestered into soil and plant material. One option is to increase the soil's organic matter content. This can also aid plant growth, improve soil water retention capacity[2] and reduce fertilizer use.[3] Sustainable forest management is another tool that is used in carbon farming.[4] Carbon farming is one component of climate-smart agriculture. It is also one way to remove carbon dioxide from the atmisphere.
Agricultural methods for carbon farming include adjusting how tillage and livestock grazing is done, using organic mulch or compost, working with biochar and terra preta, and changing the crop types. Methods used in forestry include reforestation and bamboo farming.
Carbon farming methods might have additional costs. Some countries have government policies that give financial incentives to farmers to use carbon farming methods.[5] As of 2016, variants of carbon farming reached hundreds of millions of hectares globally, of the nearly 5 billion hectares (1.2×1010 acres) of world farmland.[6] Carbon farming is not without its challenges or disadvantages. This is because some of its methods can affect ecosystem services. For example, carbon farming could cause an increase of land clearing, monocultures and biodiversity loss.[7] It is important to maximize environmental benefits of carbon farming by keeping in mind ecosystem services at the same time.[7]
Aims[edit]
Modification of agricultural practices is a recognized method of carbon sequestration as soil can act as an effective carbon sink and thus offset carbon dioxide emissions.[8]
Agricultural sequestration practices may have positive effects on soil, air, and water quality, be beneficial to wildlife, and expand food production. On degraded croplands, an increase of one ton of soil carbon pool may increase crop yield by 20 to 40 kilograms per hectare of wheat, 10 to 20 kg/ha for maize, and 0.5 to 1 kg/ha for cowpeas.[9]
Scale[edit]
Carbon farming can offset as much as 20% of 2010 carbon dioxide emissions annually.[8] Organic farming and earthworms may be able to more than offset the annual carbon excess of 4 Gt/year.[20]
As of 2016, variants of carbon farming reached hundreds of millions of hectares globally, of the nearly 5 billion hectares (1.2×1010 acres) of world farmland.[6]
However, the effects of soil sequestration can be reversed. If the soil is disrupted or intensive tillage practices are used, the soil becomes a net source of greenhouse gases. Typically after several decades of sequestration, the soil becomes saturated and ceases to absorb carbon. This implies that there is a global limit to the amount of carbon that soil can hold.[21]
Methods used in forestry[edit]
Reforestation[edit]
Forestry and agriculture are both land-based human activities that add up to contribute approximately a third of the world's greenhouse gas emissions.[33] There is a large interest in reforestation, but in regards to carbon farming most of that reforestation opportunity will be in small patches with trees being planted by individual land owners in exchange for benefits provided by carbon farming programs.[34] Forestry in carbon farming can be both reforestation, which is restoring forests to areas that were deforested, and afforestation which would be planting forests in areas that were not historically forested.[4] Not all forests will sequester the same amount of carbon. Carbon sequestration is dependent on several factors which can include forest age, forest type, amount of biodiversity, the management practices the forest is experiences and climate.[35][36] Biodiversity is often thought to be a side benefit of carbon farming, but in forest ecosystems increased biodiversity can increase the rate of carbon sequestration and can be a tool in carbon farming and not just a side benefit.[36]
Bamboo farming[edit]
A bamboo forest will store less total carbon than most types of mature forest. However, it can store a similar total amount of carbon as rubber plantations and tree orchards, and can surpass the total carbon stored in agroforests, palm oil plantations, grasslands and shrublands.[37] A bamboo plantation sequesters carbon at a faster rate than a mature forest or a tree plantation.[38] However it has been found that only new plantations or plantations with active management will be sequestering carbon at a faster rate than mature forests.[39] Compared with other fast-growing tree species, bamboo is only superior in its ability to sequester carbon if selectively harvested.[40] Bamboo forests are especially high in potential for carbon sequestration if the cultivated plant material is turned into durable products that keep the carbon in the plant material for a long period because bamboo is both fast growing and regrows strongly following an annual harvest.[37][41]
While bamboo has the ability to store carbon as biomass in cultivated material, more than half of the carbon sequestration from bamboo will be stored as carbon in the soil.[41] Carbon that is sequestered into the soil by bamboo is stored by the rhizomes and roots which is biomass that will remain in the soil after plant material above the soil is harvested and stored long-term.[38] Bamboo can be planted in sub-optimal land unsuitable for cultivating other crops and the benefits would include not only carbon sequestration but improving the quality of the land for future crops and reducing the amount of land subject to deforestation.[38] The use of carbon emission trading is also available to farmers who use bamboo to gain carbon credit in otherwise uncultivated land.[38] Therefore, the farming of bamboo timber may have significant carbon sequestration potential.[42][43][44]
Costs and financial incentives[edit]
Many factors affect the costs of carbon sequestration including soil quality, transaction costs and various externalities such as leakage and unforeseen environmental damage. Because reduction of atmospheric CO
2 is a long-term concern, farmers can be reluctant to adopt more expensive agricultural techniques when there is not a clear crop, soil, or economic benefit.
Carbon farming methods might have additional costs. Individual land owners are sometimes given incentives to use carbon farming methods through government policies.[5] Governments in Australia and New Zealand are considering allowing farmers to sell carbon credits once they document that they have sufficiently increased soil carbon content.[22][45][46][47][48][49]
Approved practices may make farmers eligible for federal funds. Not all carbon farming techniques have been recommended.[27]
Challenges[edit]
Carbon farming is not without its challenges or disadvantages. When ecosystem restoration is used as a form of carbon farming, there can be a lack of knowledge that is disadvantageous in project planning.[7] Ecosystem services are often a side benefit of restoring ecosystems along with carbon farming, but often ecosystem services are ignored in project planning because, unlike carbon sequestration, is not a global commodity that can be traded.[7] If and how carbon farming's additional sequestration methods can affect ecosystem services should be researched to determine how different methods and strategies will impact the value an ecosystem service in particular areas.[7] One concern to note is that if policy and incentives are only aimed towards carbon sequestration, then carbon farming could actually be harmful to ecosystems.[7] Carbon farming could inadvertently cause an increase of land clearing and monocultures when species diversity is not a goal of the landscapes project, so there should be attempts to balance the goals of carbon farming and biodiversity should be attempted.[7]
Critics say that the related regenerative agriculture cannot be adopted enough to matter or that it could lower commodity prices. The impact of increased soil carbon on yield has yet to be settled.
Another criticism says that no-till practices may increase herbicide use, diminishing or eliminating carbon benefits.[27]
Composting is not an NRCS-approved technique and its impacts on native species and greenhouse emissions during production have not been fully resolved. Further, commercial compost supplies are too limited to cover large amounts of land.[27]
Carbon farming may consider related issues such as groundwater and surface water degradation.[2]
By country or region[edit]
Australia[edit]
In 2011 Australia started a cap-and-trade program. Farmers who sequester carbon can sell carbon credits to companies in need of carbon offsets.[26] The country's Direct Action Plan states "The single largest opportunity for CO
2 emissions reduction in Australia is through bio-sequestration in general, and in particular, the replenishment of our soil carbons." In studies of test plots over 20 years showed increased microbial activity when farmers incorporated organic matter or reduced tillage. Soil carbon levels from 1990 to 2006 declined by 30% on average under continuous cropping. Incorporating organic matter alone was not enough to build soil carbon. Nitrogen, phosphorus and sulphur had to be added as well to do so.[44]
North America[edit]
By 2014 more than 75% of Canadian Prairies' cropland had adopted "conservation tillage" and more than 50% had adopted no-till.[53] Twenty-five countries pledged to adopt the practice at the December 2015 Paris climate talks.[26] In California multiple Resource Conservation Districts (RCDs) support local partnerships to develop and implement carbon farming,[2] In 2015 the agency that administers California's carbon-credit exchange began granting credits to farmers who compost grazing lands.[26] In 2016 Chevrolet partnered with the US Department of Agriculture (USDA) to purchase 40,000 carbon credits from ranchers on 11,000 no-till acres. The transaction equates to removing 5,000 cars from the road and was the largest to date in the US.[26] In 2017 multiple US states passed legislation in support of carbon farming and soil health.[54]
Other states are considering similar programs.[54]