The below-surface biodiversity ranges from the ’invisible’ bacteria, fungi, microbes and microscopic invertebrates to large invertebrates such as ants, earthworms and termites in soils and crayfish, shrimps, mussels, worms and other organisms in freshwater and marine ecosystems.
Because the majority of soil and sediment biodiversity is hidden beneath lands, freshwaters and oceans, these species’ richness remains mostly unknown, poorly mapped and rarely considered in management decisions.
Yet, this vast biodiversity is critical to the well-being of all life, both below and above the surface, as it provides ecosystem services such as filtering air and water, and regulating the global cycles of carbon, nitrogen and phosphorus.
Worldwide degradation and destruction of soil and sediment habitats diminishes the biodiversity of below-surface and the associated above-surface biotic communities.
Because the soils and sediments of fresh and marine waters are intertwined, effects on biodiversity in one habitat can affect the others.
Losses of below-surface biodiversity result in cascading effects on ecosystem processes and services, increased societal costs and widespread impacts on local and national economies. Once these species and the services they provide for ecosystems and humans are lost, the damage will require long periods for remediation and restoration, while the loss of some species might be irreversible.
In many cases, the broad scales of impact mean that active restoration is extremely costly and remediation may not even be possible.
In order to ensure the long-term sustainability of soils and sediments and the biodiversity they support, the identification and implementation of integrated management practices are urgently needed. Soils, like sediments, vary in chemical and biological composition, sometimes within the length of a metre.
Some regions have extremely productive, high-fertility soils (e.g. the Nile Delta region), but other regions have soils underlain by permafrost, or very shallow and less productive soils.
Because of the demand for food and fuel, and increasing global changes leading to degraded soils (e.g. desertification, droughts and floods), many regions are losing their productive lands. Marginal lands are increasingly being impacted, as well as sediments in lakes, streams, rivers and oceans.
All sub-surface and above-surface organisms depend on soil and sediment biodiversity for food and habitat.
Human health and wellbeing and national economies are largely based on the benefits provided by soils, freshwater and marine sediments because they provide rich, fertile habitats for food (e.g. fish, crustaceans, grains, fruit) and fibre (e.g. firewood, paper).
Soil biodiversity is also crucial to biologically control human, animal and plant pests and pathogens, flood and erosion, waste processing, soil fertility and water purification. There is increasing recognition that it is economically important to protect soils across landscapes and watersheds as source areas for drinking water. Reducing the downstream transport of nutrients and sediments saves costly expenditure by industry, municipalities and consumers by reducing the costs of water treatment.
Because the soil and sediment biodiversity metabolise toxins and transforms harmful chemicals and excess nutrients, less chemical and filtration treatment is needed, resulting in a higher quality of water at a lower cost.
Despite the fundamental role played by soils and sediments for the Earth system and society, these cryptic below-surface habitats with their numerous species in complex food webs are being damaged at an unparalleled rate, affecting their ability to provide the services necessary for the sustainable functioning of all the Earth’s ecosystems.
Disturbance, spread of invasive species, acidification of soils, increased nitrogen deposition and chemicals (pollutants, fertilisers and pesticides), and climate and land use change, severely and in some cases irreversibly impact soil and sediment communities and their ability to provide ecosystem services.
Soils and sediments are natural resources that once damaged often retain a long-term legacy of mismanagement.
In addition to soils and sediments being major sinks for sequestering carbon, their disruption, through ploughing or trawling, releases CO2 to the atmosphere.
Certainly, any new venture to sequester carbon in soils and sediments, or to develop alternative energy such as biofuels, will need to include the careful management of the connections among soil and sediment habitats.
Soils and sediments and their biodiversity cannot be easily sustained in the future without a major coordinated effort involving the integration of multiple disciplines and a combination of theory, rigorous hypothesis testing, long-term experiments and the involvement of scientists and stakeholders in establishing best management practices. Attention to the sustainable management of soil and sediment biodiversity is urgently needed.
Recommended actions to manage this biodiversity could ensure ecosystem services for the long term.