Soil, the uppermost layer of Earth’s crust, is a complex living system. It consists of minerals, water, air, and a vast array of organisms. Soil is fundamental for supporting life, playing a crucial role in processes like food production, water filtration, and nutrient cycling. Climate change, a global phenomenon characterized by long-term shifts in temperature and weather patterns, poses significant challenges to this resource.
Shifts in Soil Temperature and Water
Global temperatures are rising, leading to warmer soil temperatures. A study in the United States showed that soil temperature at a depth of 10 cm increased by 0.32 °C over a decade. Researchers also found that soil hot extremes are increasing faster than air hot extremes, by 0.7 °C per decade in Central Europe. These temperature shifts influence almost all other soil processes.
Climate change also alters precipitation patterns, leading to more intense rainfall events and longer droughts. While some regions may experience increased overall rainfall and rising soil moisture, others face significant drying. Increased temperatures can accelerate evaporation from the soil surface, reducing moisture levels, particularly in drier conditions. Conversely, intense rainfall can lead to waterlogging, where soil becomes saturated, restricting oxygen supply to plant roots.
Consequences for Soil Organic Matter and Nutrients
Shifts in soil temperature and moisture affect soil organic matter (SOM) and nutrient cycling. Warmer temperatures accelerate SOM decomposition by microorganisms, leading to a rapid release of carbon dioxide into the atmosphere. This process, known as soil respiration, creates a feedback loop that intensifies global warming.
A reduction in SOM diminishes soil fertility and its capacity to support plant growth. Altered water availability also influences nutrient accessibility. Intense rainfall can cause nutrient leaching, washing away essential nutrients from the root zone. Conversely, prolonged droughts can slow down microbial processes that convert organic nitrogen into plant-available forms, making nutrients less accessible to plants.
Effects on Soil Life
Climate change impacts the diverse community of organisms living in the soil, from microscopic bacteria and fungi to larger invertebrates like earthworms. Changes in temperature and moisture directly affect microbial activity, species composition, and overall biodiversity. Higher temperatures can activate dormant bacteria, accelerating the release of carbon.
A decline in soil biodiversity can impair soil functions. These include nutrient cycling, where microbes transform elements for plant uptake, and disease suppression, where beneficial organisms help control plant pathogens. Physical disturbance from extreme weather events can also disrupt the habitats of soil organisms.
Accelerated Soil Degradation Processes
Climate change contributes to several soil degradation processes. More intense rainfall events increase soil erosion, where water carries away nutrient-rich topsoil. This reduces soil fertility and can lead to flash flooding due to reduced water infiltration. Global soil erosion rates could increase by 2070, with climate change being a primary driver.
Prolonged droughts can lead to desertification, transforming fertile land into arid or semi-arid areas. This process is intensified by factors like vegetation loss, which depletes soil nutrients and makes the land more vulnerable to wind and water erosion. Coastal soils face salinization due to sea-level rise and saltwater intrusion. This increased salt content reduces soil fertility and can impact crop yields. In Arctic regions, thawing permafrost releases stored carbon dioxide and methane, contributing to greenhouse gas emissions and causing land subsidence.