Loss of Biodiversity

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Soil biodiversity is the term used to describe the variety of life below ground in the soil. It includes the genetic biodiversity, the species diversity and the diversity of the whole soil ecosystem. The biodiversity of soils is one of nature's most amazing assets. Imagine a spoonful of good garden soil - there are likely to be more organisms in that small amount of soil than there are people on the whole of planet earth! But it is not only the total numbers in soil that are amazing. It is also the number of different species that occur. There may be, for instance, in a one metre by one metre piece of garden soil 100 species of worms (earthworms, nematodes, enchytraeids); 100 species of mites; hundreds, even thousands, of species of bacteria and fungi). In fact for every type of organism present, there will be many different species. The variety and numbers of creatures that live in the soil is mind-boggling.

Together these organisms develop what is known as the food chain or food web. Each group of organisms has a well defined responsibility for the breakdown of plant material, the formation of humus, and the release and cycling of nutrients. Thus as soon as plant material falls to the surface, it is attacked by the larger soil fauna such as earthworms, mites, enchytraeids and these begin the process of breakdown and stimulate microbial activity. As the breakdown proceeds the microfauna come into action together with the microflora, both eventually enabling nutrients to be released and made available to plant roots as well as providing food for the organisms themselves. The breakdown of organic matter and the recycling of nutrients depends on a complex network of interactions between the larger organisms such as earthworms and mites and the microrganisms including bacteria and fungi. Although it is well known that this network occurs, we are still a long way from unravelling the complex network of interactions.

Each soil type and the vegetation it supports will have its own biodiversity. This biodiversity will be very different between, say a pine forest, a forest of oak trees and the tropical rainforest. The organisms will have adapted to the needs of the forest and in turn the forests and the soils in which they grow will be important in providing the habitat for these organisms. There will also be a significant difference between the biodiversity in a forest, a meadow or a farmer's cultivated field. The fact that there are these differences is well known but there are many things about biodiversity that we do not know. For example, we have very little idea of the numbers of organisms in soils, the number of species of organisms, the exact roles of the different species and what the impact of removing a particular species from the soil would be. The soil has been termed 'the last biotic frontier'. The danger is that until we know much more about the roles of the organisms and the effect that changing land use, for example, will have on them, we run a great risk of damaging for ever vital parts of the soil biotic system.

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