How Soil Security is Important to Biodiversity.

Biodiversity is in crisis around the world. As a result of numerous pressures, including land use intensification, pollution and expansion of urban areas, the diversity of organisms from microbial to mammal continues to be diminished in native and managed habitats around the world (CBD, 2014). Current rates of extinction are estimated at about 1000 times background with future rates poised to increase (Pimm et al 2014). What is clear that despite more than 30 years of active conservation measures initiated by the Convention on Biological Diversity (CBD), alongside many 1000’s of regional and national conservation activities, global rates of extinction are outpacing local conservation successes. Losses in biodiversity are now attracting greater attention as awareness increases about the requirement for biodiversity to safeguard a myriad of ecosystem goods and services that are fundamental to human health, wealth and well-being (MEA, 2005). These can be illustrated by the role of microbial organisms in supporting plant growth to the importance of forests in regulating the global climate.

This fundamental requirement for biodiversity is now encapsulated in the CBD’s Strategic Plan for Biodiversity 2011-2022 which was adopted by Governments under the Nagoya Protocol in 2010 (CBD, 2011). Key to this plan is the Aichi Biodiversity Targets which include enhancing the benefits of biodiversity and ecosystem services alongside improving the status and promoting the sustainable use of biodiversity and reducing pressures on biodiversity. These serve to highlight a philosophical shift in conservation towards the functional importance of biodiversity as summarised by Mace and colleagues (2014) who state that “biodiversity’s role in supporting a safe operating space for humanity may lie primarily in its interactions with other boundaries” which requires a move towards conserving “functional type” biodiversity and the “genetic library of life” that underpins this diversity alongside the condition and extent of biomes.

How can soil security contribute to the need to halt the loss in and enhance biodiversity to meet the aims of UN’s decade of biodiversity and, ultimately, to safeguard humanity? A review of the twenty Aichi Targets identifies soil to be at the core of 12 Targets. For example, Target 7 states that areas under agriculture, aquaculture and forestry must be managed sustainably by 2020 thereby ensuring conservation of biodiversity. Since soil is the fundamental resource for the majority of the world’s agriculture, it is implicit that sustainable management of the soil resource is required to achieve this Target.  In parallel, Target 15 states that ecosystem resilience and the contribution of biodiversity to carbon stocks should be been enhanced by 2020 thereby contributing to climate change mitigation and adaptation and to combating desertification. Since soils are the greatest terrestrial carbon store, it is questionable whether Target 15 can be achieved successfully without positive action to halt loss in, and restore, soil carbon stocks (Scharlemann et al., 2014).

Soil is the primary media for terrestrial plant growth thus the nutrient and water status of soil have a profound influence on the germination and establishment of plant species and hence plant community structure and habitat extent. It is widely acknowledged that conservation of plant species or restoration of habitats can be limited by excess soil nutrients or inadequate soil-water regime (c.f. Hobbs and Harris, 2001). It is not only terrestrial biodiversity that is affected; concerns with freshwater biodiversity can be linked to excess soil nutrients and soil erosion. Soil is a primary energy source for the terrestrial food chain with many birds, mammals and amphibians reliant directly or indirectly on soil-based food sources e.g. insects, small mammals. Widely used conservation strategies to support bird populations aim to increase the abundance of soil invertebrates through land management (c.f. Bradbury and Kirby). Soil is also a key stage post in the life cycles of many plants, insects, birds, mammals and amphibians, for example as a seed-bank, incubating environment and habitat for hibernation. It is the diversity of the soil as well as the extent and status of the soil that are important to biodiversity. Different types of soil have different fundamental capacities for supporting biodiversity. Halting biodiversity losses and sustainable use of biodiversity will require greater consideration of these aspects of the soil resource.

It can be argued that conservation and sustainable use of biodiversity need to extend beyond the emphasis on the above-ground and start to pay far more explicit attention to the biodiversity in soil itself. Soil is the most important habitat for the greatest proportion of the world’s terrestrial biodiversity. The “genetic library of life” (c.f. Mace et al 2014) in soil far exceeds anything recorded above-ground (Trange et al., 2005). While the vast diversity of soil organisms is being uncovered using DNA-based approaches, we have little idea of the rates of extinction of species below-ground, or the implications for ecosystem function. The multi-functional nature of soil is now recognised as essential to the survival of humanity as well as biodiversity in general (MEA, 2005). Soil is fundamental supporting food production, water flow and climate regulation as well as supporting biodiversity species and habitats.

While biodiversity is dependent on soil, soil is also dependent on biodiversity. The array of microorganisms, invertebrates, amphibians and animals that make up soil biodiversity are vital to maintenance of numerous ecosystem functions (Brussaard et al., 1997). Many plants have evolved indispensable symbiotic relationships with soil organisms to access nutrients. Soil microorganisms fix nitrogen from the atmosphere and releasing minerals from rocks making them available for plant growth. Soil organic matter is a fundamental ecosystem property influencing, for example, energy transfers through the food web, ecosystem water dynamics and climate regulation. The formation and turnover of soil organic matter requires soil microbes and invertebrates. Atmospheric concentrations of greenhouse gas emissions are regulated in a large part by the dynamics of soil microorganisms. Ultimately the formation of soil itself involves the action of soil organisms which breakdown minerals, move particles and form pores and channels to aid the movement of water and gases. Sustainable management of the soil resource and effective restoration of soil will therefore require close consideration of soil biodiversity. In correspondence with approaches for freshwater and above-ground terrestrial habitats, what is the requisite ecological status of soils to halt biodiversity loss and to sustain multiple ecosystem goods and services?

In the current situation, where halting biodiversity loss is a global priority with greater emphasis on restoring habitats and enhancing ecosystem goods and services, it is difficult to see how these can be achieved while soil degradation continues. The functioning of soil has been significantly compromised by degradation from pollution, nutrient enrichment, loss in organic matter, erosion and a significant loss in the global stock of soil. The implications of climate change add to the risk of loss in soil functions and hence add yet more risk to maintaining numerous ecosystem goods and services.  In contrast, restoration ecosystems and ecosystem functions, with the enhancement of ecosystem goods and services, can be extremely effective when the importance of soil is adequately addressed (c.f. Banwart, Noellemeyer and Milne, 2014).

References

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