This chapter examined the ways in which land degradation affects global agricultural productivity, with profound implications for environmental sustainability and socioeconomic well-being. The impacts of accumulated land degradation, relative to conditions that would likely prevail in the absence of human activity, undermine the capacity of land to support sustainable agricultural production, and lead to growing yield gaps and increased vulnerability. A comprehensive approach to assessing land degradation – including indicators measuring changes in soil organic carbon, soil erosion and soil water – within a debt-based framework helps to distinguish between human-induced and natural degradation, offering a clearer picture of the land’s health and its potential for productivity.
Assessing the causal linkages between land degradation and yield gaps requires consideration of multiple factors, including management practices, agroecological conditions and socioeconomic circumstances. While establishing a direct causal link is challenging, the costs of degradation in terms of larger yield gaps – manifested in the loss of potential calories, revenues and production – are clear. Around 1.7 billion individuals live in areas where crop yields have been significantly impacted. Reversing just 10 percent of this degradation could restore sufficient production to meet the annual caloric requirements of 154 million people.
These figures understate the true scale of the impact of land degradation for three reasons:
- First, they relate only to cropland and exclude pastureland. However, the degradation of pastureland negatively affects both human and animal health, reducing income and productivity for dependent livelihoods, and potentially increasing the risk of conflict.12
- Second, they quantify the impacts on provisioning services derived from land that are mostly borne by private land users, and these only constitute a small share of the total cost of global land degradation. Other effects of cropland degradation not measured here, including decreased carbon sequestration, intensified biodiversity loss and increased pollution, impose much larger costs on the global community. Many people outside degraded croplands depend on the ecosystem goods and services those lands provide, making action to address degradation a public good.30
- Third, most of the global cost of land degradation is attributed to LUCC (not quantified here). The costs of the yield losses on cropland quantified herein, combined with the possibility that they could lead to land abandonment, in conjunction with population and market pressures, can incentivize LUCC if not addressed.
The findings in this chapter underline the contributions of historical land degradation to crop yield gaps across all levels of economic development. In intensively managed agricultural systems in high-income countries, per hectare production losses due to historical land degradation are particularly high. This likely reflects the long-term consequences of intensive agriculture including monoculture, and excessive use of synthetic fertilizers and heavy machinery. In other words, current practices are maintaining high yields in these regions by increasingly compensating for the negative effects of land degradation. However, while agricultural intensification can mask yield gaps temporarily, it cannot indefinitely prevent productivity losses if land degradation continues. Thus, while the private benefits of compensatory practices may exceed private costs, farmers implementing these practices face increasing overall costs and are contributing to the intensification of land degradation.
The relatively weak causal relationship between land degradation and yield loss, observed across the African continent, should not be interpreted as evidence that soil health interventions are not beneficial for closing yield gaps in this region. Rather, it indicates that other constraints – for example, unavailability of inputs and labour, poor infrastructure, and lack of access to markets, credit or information – are equally or more important than biophysical land degradation in terms of causing yield gaps. Nonetheless, soil health matters in its own right; it therefore remains a fundamental component of agricultural productivity, particularly in predominantly low-input systems, where soils respond poorly to increased input use. Given the very high current yield gaps, doubling crop yields in Africa would have a substantial impact on local livelihoods, even if the contribution to closing the global yield gap is relatively modest.97 Accordingly, the findings presented here suggest the need for a holistic assessment of the complementary factors, in addition to land degradation, that constrain yield gaps in this region.
Such an approach would also address poverty and food insecurity challenges in the Indo-Gangetic plain and parts of sub-Saharan Africa. Closing yield gaps through sustainable management of croplands would improve not only livelihoods but also ecosystem services, and create positive spillover effects on other types of land cover.79, 86 This would significantly decrease the global costs of land degradation, which are mainly driven by changes in land-use and land-cover, including conversion of forest land to grazing land in Latin America and the Caribbean, grassland to barren land in Asia, and grassland to cropland in sub-Saharan Africa. The costs of these transitions are borne by society as a whole, while the incentives of private land users are driven by the value of provisioning services (crop yields), making land degradation a global problem that requires both global and local solutions.30
Given the need to promote sustainable land management in areas with both small and large yield gaps,98 it is essential to understand the decision-making processes of the full range of farming systems, whose day-to-day land-use decisions affect global outcomes. Farms of all sizes contribute to global food production and land degradation to a varying extent. Accordingly, the global distribution of farm sizes is subject to scrutiny as part of the discourse on the future of farms (especially smallholders), food production and food.99
The following chapter presents the latest estimates of the global distribution of farm sizes, using data from the most recent available agricultural censuses; it explores the extent to which farms control global agricultural land and contribute to food production. It also highlights the particular challenges farms face in addressing land degradation and food security, and the underlying drivers. Farmers’ incentives and their ability to invest in reducing and reversing land degradation and ultimately restoring land – while improving productivity – can differ significantly depending on farm size, land conditions and socioeconomic factors. Larger farms often have more resources to invest in advanced technologies that optimize input use and productivity, but may also exacerbate land degradation. However, these farms may also have greater incentives to maintain land quality if clearly linked to long-term profitability. Conversely, smaller farms often contend with more vulnerable land conditions, and struggle with limited resources and multiple market constraints. These interact with socioeconomic and environmental conditions in different ways to shape incentives for addressing degradation. Farm size, therefore, while not the only factor influencing land management and food production, shapes all other determinants in important ways. This feature is assessed systematically using the most recent data and methodologies in the next chapter.
