'Respect dirt and dung' to combat desertification
- 70 per cent of world’s forests threatened by conversion to cropland and urbanisation
- Essential soil organic carbon (SOC) stocks are being depleted
- UN report calls for better monitoring and maintenance of SOCs
Decomposing animal and plant matter are vital for drought resistance, writes Ranjit Devraj.
[NEW DELHI] “Dirt is wealth — we must respect the dung and the rotting leaves if there is to be a future,” said Sadhguru Jaggi Vasudev, a speaker at the 14th Conference of the Parties (CoP14) of the UN Convention to Combat Desertification (UNCCD) in the Indian capital.
Vasudev, founder of the Isha Foundation, a non-profit and spiritual organisation that works on nature conservation, was not alone in warning against the loss of soil organic carbon (SOC) to conserve land resources and ensure food security for all.
“SOC is made up largely of decomposing animal and plant matter, and is key to drought resistance, soil stability and organic crop production,” explained Ermias Aynekulu Betemariam, a Kenya-born land health scientist who works with World Agroforestry and co-authored a science-policy interface report, released at CoP14 (2-13 September).
“Because of its multifunctional roles and its sensitivity to land management, SOC is one of the three main global indicators of LDN [land degradation neutrality], the other two being land cover and land productivity,” Betemariam told SciDev.Net.
“The only way we can get water to stay in the soil is by ensuring that the soil has rich organic content — basically by making use of fallen leaves and animal dung,”
Sadhguru Jaggi Vasudev, Isha Foundation
Land degradation neutrality, one of the UN sustainable development goals (SDGs), refers to a state where the world’s land resources are stable or increasing sufficiently to support ecosystem services and food security.
According to the UNCCD, 70 per cent of the world’s forests are now threatened by conversion to cropland and urbanisation — the main processes which deplete organic carbons in the soil. Particularly at risk are tropical forests, which declined at a rate of 5.5 million hectares annually between 2010 and 2015.
‘A fragile web’SOC is also lost through poor land use management in agriculture. A Food and Agriculture Organization of the UN (FAO) publication, ‘SOC – the hidden potential’, attributes loss of these carbon stocks in farmlands to unsustainable agricultural practices such as “monocultures, extensive tillage and use of chemical inputs that degrade the fragile web of community interactions between pests and their natural enemies”.
Discussions at CoP14 focused on the power of SOC to improve soil aggregate and structural stability, important for soil aeration and the infiltration and retention of water. This enhances the capacity of the soil to store water, on which the world depends for farming.
Organic carbon also produces nitrogen, phosphorous, sulphur and other nutrients that are vital for the growth of plants and for crop productivity. Overall, the fertility and functioning of soils depend on interactions between the soil-mineral matrix, plants and microbes which help preserve soil nutrients.
Barron Joseph Orr, lead scientist for the UNCCD, told SciDev.Net: "Our new report will help member countries of the Convention identify sustainable land management technologies and monitor SOC for the achievement of land degradation neutrality as well as other SDGs such as zero hunger, health and sanitation, climate action and gender equality."
Monitoring and modellingThe report calls on governments to maintain SOC levels and to share these recommendations with farmers and other land managers.
It stresses the need to accurately assess SOC levels, noting that this currently varies markedly between countries. Efforts must be stepped up, the report says, to improve the measurement and modelling of SOC to address data gaps and limitations in existing tools and models.
A spatio-temporal study carried out by EnvirometriX Ltd, an environmental science consultancy firm based in the Netherlands, indicates that the greatest loss of SOC between 2000 and 2015 took place in the northern hemisphere and in Brazil, Central Africa and Indonesia, where large swathes of natural forests have been converted to croplands.
According to Marioldy Sanchez Santivanez, an observer to the UNCCD Science-Policy Interface and forest evaluator for Peruvian NGO AIDER, better soil sampling, measuring and monitoring “has the potential to contribute greatly to restoring soil carbon in many of the world’s land degraded areas”.
Among simple tools now available to evaluate SOC on the ground is the open-access Soil Organic Carbon App developed by researchers at the International Center for Tropical Agriculture. It is capable of determining the amount of sequestered SOC and also assessing the impact of good conservation practices over time.
Warding off droughtHimanshu Thakkar, who leads the South Asia Network on Dams, Rivers and People, a Delhi-based NGO, believes that retaining SOC is vital for South Asia, which is estimated to lose 80 per cent of the rainfall it receives to the sea, leaching away valuable organic carbon and contributing greatly to desertification. “This is an area that needs urgent attention since more than 30 per cent of the South Asian landmass is now degraded,” he said.
“The UNCCD report on SOC is especially important for South Asia because [of] its many and varied agro-climatic zones, each requiring specific interventions to prevent loss of SOC and retain moisture in the soil to nourish vegetation roots,” Thakkar told SciDev.Net. “All that remains is for the governments to pick up the detailed guidelines and decision trees in the report and follow them.” A study published in May says at least a third of the area around 18 river basins of the Indian sub-continent have become vulnerable to “vegetation droughts”, indicating drastic loss of soil moisture.
Vasudev and his Isha Foundation are presently driving Cauvery Calling, an ambitious programme in South India that supports farmers to plant 242 million trees in the Cauvery basin over an 83,000 square kilometre area. “We expect to retain nine trillion litres of water, which is more than 40 per cent of the water flowing in the river, by providing shade and building SOC,” Vasudev said.
Vasudev believes that the proven success of Isha’s strategy can be replicated in India’s other river basins. “The only source of water India has is the monsoon, which is 60 days of rainfall,” he said. “And the only way we can get that water to stay in the soil is by ensuring that the soil has rich organic content — basically by making use of fallen leaves and animal dung.”