Soil and Climate Change
Effects of Climate Change on Soil
The drivers of climate change such as temperature, precipitation (amount and frequency), and carbon dioxide levels in the atmosphere are the major driving forces which can alter soil properties and its processes. Climate change will affect soils, leading to changes in soil organic carbon; soil flora; soil erosion; soil acidification and salinization; soil fertility and nutrient availability.
Soil Organic Carbon
Organic matter is important for many soil properties, including structure formation and maintenance, water holding capacity, cation exchange capacity, and the supply of nutrients to the soil ecosystem. Organic carbon incorporated into soil organic matter may play a major role in controlling soil behavior as a sink or source for atmospheric carbon dioxide, thus contributing significantly to the global carbon cycle. One of the biggest questions concerning climate change and its effects on soil processes and properties involve how potential changes in the carbon cycle will influence the productivity of agricultural soils. The maintenance of soil organic carbon stocks in croplands and grasslands of the world is thus of upmost importance for ensuring global food security and the prevention of substantial carbon dioxide emissions.
Soil Flora
Higher levels of atmospheric carbon dioxide, warming, and changes in precipitation regimes simultaneously can have direct or indirect, positive or negative impacts on soil fauna and soil flora. Precipitation and soil moisture changes may alter the ratio of bacteria and fungi, as well as shift their community composition. The role of soil organisms in decomposing organic matter means they are an integral part of the global carbon and nitrogen cycles, which influence the concentrations of greenhouse gases in the atmosphere. The effect of climate change on soil flora is not easy to determine.
Soil Erosion
Soil erosion is a complex process that depends on soil properties, ground slope, vegetation, and rainfall amount and intensity. Global warming is expected to lead to a more vigorous hydrological cycle, including more total rainfall and more frequent high intensity rainfall events. Soil erosion under climate change is most directly affected by changes in extreme precipitation. Extreme precipitation is projected to increase as a result of the increasing moisture-holding capacity of a warmer atmosphere, resulting in a more vigorous hydrological cycle.
Soil Acidification and Salinization
While temperature increases are forecast for most parts of the world, there is less certainty about precipitation changes. Significant increases in rainfall will lead to increases in leaching, loss of nutrients and increasing acidification, depending on the buffering pools existing in soils. The direction of change towards increased leaching or increased evaporation will depend on the extent to which rainfall and temperature change and consequent changes to land use and its management. In either case the situation could lead to important changes in soils. Increased salinization and alkalization would occur in areas where evaporation increased or rainfall decreased.
Soil Fertility and Nutrient Availability
Soil warming can increase nutrient uptake from 100 to 300 percent by enlarging the root surface area and increasing rates of nutrient diffusion and water influx. Since warmer temperatures increase rates of transpiration, plants tend to acquire water soluble nutrients (nitrate, sulfate, calcium, magnesium) more readily as temperature increases. Temperature increases in the rhizosphere can also stimulate nutrient acquisition by increasing nutrient uptake via faster ion diffusion rates and increased root metabolism.
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