Soil biodiversity and soil organic carbon: keeping drylands alive

Abstract

By the year 2050 the global population is projected to be 9 billion and the world will need to produce an estimated 60% more food, while 1.8 billion people will be living in water scarce areas. While food production is increasing globally, the land on which agriculture depends is degrading at an alarming rate, jeopardising future progress. Soil biodiversity and soil organic carbon are vital to the way ecosystems function and they largely determine the role of land in producing food, storing water, and mitigating climate change. They are the key to unlocking the multiple economic and environmental benefits—the multi-functionality—of land. Globally, soil biodiversity has been estimated to contribute between US$ 1.5 and 13 trillion annually to the value of ecosystems services. Yet despite its global importance, soil biodiversity is often neglected in public policy and is being lost at a considerable rate through unsustainable land management practices, soil erosion and other land degradation processes. Between one quarter and one third of all land worldwide is estimated to be degraded, resulting in lower agricultural production, disrupted water cycles, and release of sequestered greenhouse gases. Dryland soils make an important contribution—roughly one third—to global stocks of soil biodiversity and soil organic carbon, and they can contribute strongly to global food production and to climate change mitigation. They account for 42% of the world’s land, providing 44% of all cultivated land and 50% of the world’s livestock. Drylands are particularly valuable for carbon storage due to their high degree of permanence—the duration that carbon is stored in the soil—compared to humid areas. The proportion of degraded land in the drylands is similar to the global proportion, but the solutions may be different to those suitable for more humid lands. The comparatively high level of poverty and under- development in drylands means that drivers of degradation are different and the nature of policies and investments to address desertification should differ accordingly. Restoring or preserving soil biodiversity and soil organic carbon requires increased inputs of organic matter or a reduction of carbon losses, or both. It is particularly important to maintain soil organic carbon (SOC) and to increase it where possible. In dryland soils SOC levels are often low and close to the tipping point where restoration is no longer possible, giving way to irreversible land degradation. However, measures to increase soil biodiversity and SOC can take many years. Restoration of degraded land can be costly and it is preferable to avoid degradation in the first place, through adoption of sustainable land management practices and protection of sustainably managed agricultural landscapes. Many farming practices are known to increase soil biodiversity and SOC, mostly revolving around integrated management of soil water and nutrients, erosion control measures, and maintaining groundcover. Sustainable farming practices that have been used widely in the drylands include agroforestry, conservation agriculture and pastoralism. However, adoption or maintenance of these practices is low in the world’s poorest drylands, where population growth and the demand for greater agricultural productivity and water security are highest. These regions will face future land degradation unless sustainable land management becomes central to agricultural development programs. Sustainable land management often demands investment of labour and energy and requires new skills, knowledge, equipment and inputs. Innovative policies and investments are therefore needed to encourage adoption by land users. An important part of the solution lies in rewarding or otherwise incentivising the multiple benefits of sustainably managed land, or “multi-functionality”, at scale, rather than maximising individual goods or services. This includes those values that are enjoyed as externalities by the wider society. The 2030 Agenda for sustainable development increases the demand on soils to provide food, water and energy security, protect biodiversity, and mitigate climate change, increasing the centrality of soils in global environmental and development politics. Target 15.3 on Land Degradation Neutrality, reflects the growing awareness that land, and by extension soil biodiversity and soil organic carbon, is both a natural resource and a public good that underpins wider sustainable development. For good governance of our shared Land Resources, governments should aim at protecting and promoting the multi-functionality of land: to ensure that land users employ sustainable approaches that are measured against the delivery of multiple goods and services. Achieving this goal requires a number of priority measures: 1. Evaluate land management against the sustainable delivery of multiple goods and services; 2. Build on policies and legislation to enable scaling-up of sustainable land management and landscape restoration or rehabilitation; 3. Enhance local governance mechanisms that support land users in sustainable land management practices; 4. Strengthen land information to support landscape-scale planning and monitoring; 5. Establish effective extension services that support land users to adopt sustainable land management practices; 6. Create enabling conditions for private investment in sustainable land management.