Soil change under different scenarios Joann K Whalen, Department of Natural Resource Sciences, Macdonald Campus of McGill University, Sainte-Anne-de-Bellevue, QC, Canada © 2022 Elsevier Ltd. All rights reserved. Introduction 1 Soil change due to erosion 1 Soil change due to erosion: The case of the Chinese Loess Plateau 2 Soil change due to loss of organic matter 6 Organic matter for soil stability 6 Soil change from organic matter loss after deforestation: The case of New Zealand pastures 7 Organic matter for soil fertility 9 Soil change due to organic matter loss following cultivation: The Great Plains prairie grasslands 9 Soil change due to element imbalance 13 Conclusions 15 References 16 Key points • Soil change is associated with geological processes and land use conversion for agriculture. • Soil erosion and loss of soil organic matter from fragile landscapes are associated with food insecurity, water shortages and ecological damage. • Loss of sediments and soil organic matter can be prevented by revegetating and stabilizing vulnerable areas with built control structures, and adopting conservation agricultural practices. • Element balances in soil are affected by improper fertilizer use and irrigation, as well as contaminants deposited from atmospheric pollution. • Judicious fertilizer and water use are needed to control the amounts of essential and non-essential elements that affect biological processes and abiotic reactions in soil. • Local, regional and national programs are needed to measure and monitor soil change. Introduction The United Nations declared 2021–2030 as the Decade on Ecological Restoration, which is a call for action to prevent, halt and reverse ecosystem degradation worldwide. We must rebuild ecosystems to achieve the sustainable development goals of food security, climate change mitigation, water and biodiversity conservation and eradication of poverty. This requires us to address issues related to land degradation, which affects an estimated 25% of the land surface and is estimated to reach 95% of the global land area by 2050. Land degradation is the change in the biophysical environment that causes deterioration or loss of productive soils. Such a change in the soil condition can limit the growth of desirable vegetation, which we use as food, fuel, fiber and depend upon for oxygen, regulation of hydrologic processes and other essential ecological services. Soil change can also diminish its biodiversity, capacity for biogeochemical cycling and ability to attenuate contaminants in the environment. Soil change is largely a human-induced phenomenon that has dire consequences for the world’s population. The erosion of about 24 billion tons of fertile soil each year impacts 3.2 billion people, approximately 40% of the world’s population. About 33% of soils worldwide have lost soil organic matter due to historical expansion of agriculture and pastoralism, which converted many native ecosystems (e.g., peatlands, forests, grasslands) for arable land use. Element imbalance due to soil salinization affects more than 830 million hectares of cultivated land worldwide and is expected to impact about 50% of arable land by 2050. These alarming trends must be stopped and reversed to ensure that soils continue to support vital ecosystem functions, creating a stable or improved land resource that can provide the necessary habitat and products that are needed to fulfil the Earth’s biological needs. This chapter explains the root causes of soil change due to human activities related to the conversion of natural ecosystems for agricultural use in the context of global climate change. Case studies are presented to explain the consequences of soil change, as well as the time needed for regional-scale restoration processes to be effective. These examples offer some concrete solutions to the problems that result from soil change, while explaining the necessity of stakeholder involvement, policies and economic investments to control soil change. Soil change due to erosion Erosion is part of the natural weathering process that leads to the physical and chemical degradation of rocks, sedimentary materials and minerals, moving smaller particles and dissolved substances from one location to another in the landscape. Soil erosion refers Encyclopedia of Soils in the Environment, Second Edition https://doi.org/10.1016/B978-0-12-822974-3.00123-3 1