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May 18, 2023

Leveraging Dirt: Soil as Southeast Asia’s Under

HOME ARTICLES Leveraging Dirt: Soil as Southeast Asia’s Under-explored Solution for Carbon Mitigation and Food Security A farmer sprinkles manure on his land in Sunju Village, Sigi Regency, Central

HOME ARTICLES Leveraging Dirt: Soil as Southeast Asia’s Under-explored Solution for Carbon Mitigation and Food Security

A farmer sprinkles manure on his land in Sunju Village, Sigi Regency, Central Sulawesi Province, Indonesia on May 2, 2020. (Photo by Basri Marzuki/NurPhoto)

Published 7 Aug 2023

Elyssa Kaur Ludher

The world’s soils are under threat due to deforestation, urbanisation, agriculture, and pollution. Southeast Asia should prioritise sustainable soil management to reap the benefits of carbon mitigation and enhance food security.

Author’s note: The author would like to thank Aditi Punj Sood, Education Lead and Curriculum Cultivator for Living Soil Asia for assisting in this article. Living Soil Asia seeks to bring awareness to regenerative practices in Singapore and South East Asia.

As heat waves ripple across the world, one often overlooked “victim” lies under our feet: soil. Elevated temperatures degrade lands by reducing soil moisture and depopulating soil biodiversity.

Healthy soil is key to food security, and is also one of the most cost-effective mitigation and adaptation solutions. Soil captures three times more carbon than forests and greenery. Healthy soils also retain moisture and protect against drought.

The world’s soils, however, are under threat; half of our topsoil has been lost in the last 150 years due to deforestation, urbanisation, agriculture, and pollution. The United Nations Food and Agriculture Organisation (FAO) has warned that “90 per cent of earth’s topsoil will be at risk by 2050”. The #SaveSoil movement has argued —not without controversy — that at current attrition, soils can only support another 80 to 100 crop cycles, after which there will be a serious food crisis.

The reason is that the current rate of soil loss exceeds natural regeneration capacity. It takes 500 years to generate 2.5 centimetres of topsoil under “normal agriculture conditions”, according to a study by the University of Sheffield. The lengthy period is due to soil’s complex composition of minerals, organic matter, biological organisms, gas, and water, which changes based on location and depth. Erosion and use of chemical inputs in conventional agriculture disturb the balance of soil composition, resulting in impoverished soils.

Healthy soils crucially rely on organic matter and living biological organisms — including microbes (such as bacteria), fungi, arthropods, algae, and protozoa. A teaspoon of healthy soil may contain 1 billion bacteria, of which scientists have documented only 5 per cent. The living organisms are vital for the decomposition of organic matter into humus and bio-available nutrients; use of fertilisers, pesticides, herbicides, and fungicides’ impacts on this biodiversity. Microbes are essential for the formation of humus (which gives carbon-rich soils their dark colour), while mycorrhizae fungi have been found to be a main actor for soil carbon storage, as a result of a symbiotic relationship with plants. Another fungi group secretes glomalin, a type of “glue” that binds soil particles together into aggregates and strengthens soil structures against erosion and drought by establishing air pockets where air and water are held. Healthy soils can boost farm production by up to 58 per cent and reduce the need for chemical inputs, according to the FAO.

Fortunately, soil rehabilitation can be hastened through human action. Increasing carbon in the top 30 to 40 centimetres of soil by 0.4 per cent a year can “significantly reduce the annual increase of CO2 in the atmosphere”. In recognition of this, the soil rehabilitation initiative – “4 per 1000” – was launched during COP21 in 2015 by the French government. The initiative has raised awareness and spurred soil rehabilitation projects worldwide.

Southeast Asia’s warm and humid climate has contributed to carbon-rich, fertile soils. However, intensifying storms, precipitation, and floods as a result of climate change have hastened topsoil loss (Figure 1). Soil fertility is also diminishing from salinisation caused by rising sea levels, sea storm surges (Figure 2), droughts and landslides.

Figure 1: Present soil erosion due to water (rains, floods etc.) as of 2019, with areas experiencing higher water erosion shown in orange and red.

Figure 2: Areas in red showing land up to 10 meters above sea level which will likely experience salinisation from sea level rise, storm surges and groundwater intrusion.

Time is short. According to the #SaveSoil movement, we can turn things around if we take action in the next 15 to 25 years, after which it would take hundreds of years to recover healthy soils.

Fortunately, sustainable soil management provides avenues for Southeast Asia to reverse the decline in soil fertility and reset the conservation trajectory. The region can adopt practices in regenerative agriculture — such as conservation tillage, intercropping, cover cropping, and crop rotation — and utilise soil amendments that can “bury” carbon into the soil, such as biochar, microbes, mulch, manure, compost and others.

Southeast Asian nations have developed policies, laws and guidelines relating to soil management, the most comprehensive of which is the ASEAN Guidelines on Soil and Nutrient Management, and the Indonesian Soil and Water Conservation Law. Most policies, however, prioritise pollution avoidance, land use maximisation and agricultural productivity.

These are important objectives, but inadequate for the long haul, as Europe has learned. Recognising the necessity of soil management, the European Commission has proposed a ‘Directive on Soil Monitoring and Resilience’, commonly termed the “Soil Monitoring Law”, in mid-2023 to elevate soils to have the same legal basis as clean air and water. While this proposed law has stopped short of mandating the promotion of healthy soils, if passed, it will contribute to better soil outcomes due to improved monitoring.

Table 1: A non-exhaustive list of relevant laws or guidelines relating to soil in Southeast Asia

Nations also have the opportunity to support sustainable soil management or “carbon farming“, through carbon offsets — units that can be sold on the carbon market to fund such programmes. FAO calculated that up to 40 million tonnes of carbon could be sequestered in soil in Southeast Asia, which could unlock up to US$2.5 billion at a conservative carbon price of US$60 per tonne. However, reaching this potential requires as-yet under-developed mechanisms to monitor, report and verify changes in soil carbon stock.

Table 2: Sequestration potential under the FAO’s Sustainable Soil Management scenario 3 (SSM3), as well as potential value to each Southeast Asian nation at US$18.5 and US$60.

A regional cooperative effort by Southeast Asian nations, as a potential initiative of Indonesia as ASEAN Chair for 2023 under its stated priority for Food Security, could catalyse the development of satellite and other aerial sensor technologies for detailed soil carbon data capture. Actions should be focused on areas with high carbon sequestration potential, which are present in nearly all Southeast Asian nations (Figure 3, map on left). FAO has found that it is possible to increase soil carbon sequestration by 20% (SSM3 scenario, over business as usual) over 20 years by adopting sustainable soil management practices focusing on key areas (map on the right).

Figure 3: Southeast Asia current (left map) and future potential (right map) for organic carbon, the latter based on FAO’s SSM3 scenario.

Time is short. According to the #SaveSoil movement, we can turn things around if we take action in the next 15 to 25 years, after which it would take hundreds of years to recover healthy soils. As we enter the next few months of extreme weather threatened by El Nino exacerbated by climate change, we will continue to lose life-giving soil. Furthermore, increases in soil temperatures could exacerbate carbon dioxide and methane released through increased soil respiration.

It is thus in Southeast Asia’s best interest to swiftly secure its soil health to gain not only the benefits of carbon mitigation, but also for greater food security.

2023/180

Elyssa Kaur Ludher is Visiting Fellow with the Climate Change in Southeast Asia Programme, ISEAS - Yusof Ishak Institute. Prior to joining, Ms Ludher contributed to food policy research at the World Bank, Centre for Liveable Cities Singapore, and the Singapore Food Agency.

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