Ireland's State of the Environment Report 2024

143 Chapter 6: Soil Soil 1. Introduction While we might not immediately think of soils when we think of nature, soils are the Earth’s largest habitat. They are essential for life: they support terrestrial plant life used as food by humans and animals. Soil health is vital to biodiversity, plant growth and food production, climate control and water quality regulation. The value of soils is not limited to supporting plant growth: they also provide a wide range of essential services (Baer and Birgé, 2018; Smith et al. , 2021). Maintaining soil health is essential to enable soils to continue to supply the important services they provide (Figure 6.1). “Too few know that the thin layer that lies below our feet holds our future. Soil and the multitude of organisms that live in it provide us with food, biomass and fibres, raw materials, regulate the water, carbon and nutrient cycles and make life on land possible. It takes thousands of years to produce a few centimetres of this magic carpet.” EU Soil Strategy for 2030 (EC, 2021a) Figure 6.1  Soil services Climate and air quality regulation Soils hold the largest terrestrial carbon stocks and are an important carbon sink. Carbon storage as soil organic carbon is important as a carbon sink. Soils can be a source of greenhouse gases (GHGs) such as carbon dioxide, methane and nitrous oxide. Regulation of water flow and quality Healthy soil can help regulate the water cycle (Keesstra et al, 2021). "Green" water is the water that is available in soil for plants. “Blue” water is the water available in groundwater and in surface water bodies like rivers and lakes. This water is replenished by infiltration through soils. If plant cover is low, or the soil structure is insufficiently able to cope with rainfall, then water can run off leading to flooding, loss of soil nutrients (which can impact water quality) and soil erosion (Keesstra et al, 2021). Healthy soils can play an important role in regulating floods and droughts (Saco et al, 2021). Soils & human health There is evidence that exposure to soil micro-organisms can lessen the prevalence of allergies and atopic health conditions like asthma (Thiele-Bruhn, 2021). Micro- organisms in soil can be used to produce antibiotics (Waksman, 2010). Support for terrestrial ecosystems As well as providing a habitat for life below ground, soils impact on habitats above ground by influencing the diversity of plants that grow and the fauna that depend on the plant life. Soil life has a complex interaction with plant life, which in turn drives the formation of soil in the long term (De Deyn Gerlinde and Kooistra, 2021). Supply of food, fuel and material Soil is essential for plant growth, which is essential for food and raw materials (Baer & Birge, 2018). Nutrient cycling Nitrogen (N) and Phosphorus (P) are two of the main sources of water pollution in Ireland (EPA, 2023a). Soil biota can remove N from the ecosystem. Levels of P in rivers can be abated by the strategic use of wetlands (Baer & Birge, 2018). Soil as a habitat Soils are the largest habitat, being home to the majority of all living species on Earth (Thiele-Bruhn, 2021). Soil contains an abundance of bacteria, fungi, insects, isopods, earthworms, spiders, centipedes, millipedes and other invertebrates. While soil is an ecosystem in its own right, this ecosystem is vital to plant health and agricultural production (Baer & Birge, 2018).