What is biodiversity?
Biodiversity can be described as "the planet's life-support system", or "the creative force of the planet", or "the accumulation of three and a half billion years of coexistence and experience of all life-forms". The quick two-word answer is "biological diversity", and single-word answers can also be found, such as "stability", "resilience" (the ability to withstand shock or pressure), or "beauty". But the widely accepted definition, as coined at the 1992 Rio Earth Summit, is:- "the variability among living organisms......and the ecological  complexes of which they are part: this includes diversity within species, between species, and of ecosystems". This rather dry definition takes into account genetic variation and the relationships between individuals, as well as the diversity of the species themselves and of the ecosystems of which they are part. But, to simplify things, biodiversity is usually taken to mean the number of species present within any given area. The more species present in any given area almost undoubtedly leads to a greater number of relationships between those species, and to greater genetic variation within those species. In this context the term "relationships" includes predation, pollination, competition, and grazing, for example.
Why do we need to safeguard biodiversity? Biodiversity has evolved over billions of years to reach the point it is at today, and it will never stop evolving (unless the planet is rendered permanently lifeless). Biodiversity is self-generating, the more there is the bigger the base from which more can evolve. Biodiversity is greater than the sum of its parts, all working together to achieve more than any individual species could on its own. This biodiversity is what makes the planet work, and therefore is what keeps us humans, and all other living things on Earth, alive. Animals and plants give us food to eat, oxygen to breathe, materials to use, the natural world to enjoy, and so on - but it is the diversity of those animals and plants that gives us so many different kinds of food, and a vast range of materials, and so much variety within nature. And as well as providing us with everything that we need to survive, it can be argued that biodiversity is worth conserving in its own right, from a moral point of view. However, as this is not the place for a philosophical discussion, we will return to earthier matters.
Biodiversity is important in farming, for six main reasons:
1 - natural pest control;
2 - pollinating species;
3 - a varied diet;
4 - more stability;
5 - a better place to work;
6 - nature conservation.
Natural pest control. - Biodiversity of wild species helps to control the pests that can affect and destroy crops, by allowing natural predators or parasites of those pests onto the farm to go about their business. Slow worms eat small slugs and snails, frogs eat slugs, ladybirds eat aphids, birds of prey eat rodents, and so on. By working with nature rather than against nature, we allow nature to do some of our work for us. - Biodiversity of (and within) crops helps contain any problem which may occur, because even a slightly different crop, or individual within the crop, may be less susceptible or even resistant to that particular problem. For example, by planting carrots and onions together we reduce the chances of carrot root-fly spreading amongst the carrots, because the root-flies don't like the smell of onions so will not lay their eggs near them. As another example, the larvae of the gooseberry saw-fly will strip gooseberry and redcurrant bushes of their leaves, but avoid the raspberries and other fruits, because they are species-specific and so target only the gooseberry and currant bushes. So even if one crop is lost, chances are the rest of the crops will survive. - Biodiversity of livestock helps control parasites. Chickens eat sheep-ticks (plus slugs and snails); the internal parasites of sheep may not be able to survive inside a horse, and vice versa, and the parasite will therefore die; and so on. One type of livestock permanently grazing one area can lead to a disastrous build-up of parasite numbers.
Pollinating species.
Many food crops require pollinating before they will produce, and so they need pollinators, most of which are wild. Pollination is not just performed by honeybees, although they are important - many other species pollinate crops and wildflowers, including bumblebees, flies, butterflies, moths, wasps, beetles, birds, and even some mammals. Some crops, such as the fig, rely on one particular specialised pollinator, in this case the "fig wasp". Our apple orchards rely chiefly on wild honeybees, bumblebees and hoverflies, although these may be assisted by domesticated honeybees from the local area. Healthy populations of pollinating species on or near the farm means better pollination, so a better crop. It is also important for those pollinators to have a wide diversity of wild flowers nearby, to feed them when the crops are not in flower. A varied diet. This refers not just to us humans that depend on the farm for our food, but to the livestock too. It may look as though the sheep are eating just grass, but on an "unimproved" pasture they could be eating 100 or 200 different herbaceous species, including 20 or 30 different species of grass, and the leaves of trees too. Many of these species will have medicinal as well as nutritional qualities. A varied diet is a healthy diet, for them as well as for us. Animals kept inside and fed on a small range of fodder (such as maize or soya) are usually given a constant stream of antibiotics to try and keep them healthy, because their diet and their environment are so lacking. More stability. Biodiverse systems are generally more stable and more resilient, meaning they can adapt more successfully when subjected to external stresses and pressures, such as drought. On our farm we always try to grow two or more varieties of any particular crop, each of which will perform differently under different conditions. Some may be more mildew-resistant than others (also see "natural pest control" above), some more drought-tolerant, some more waterlogging-tolerant, while others will stand up better to high winds, and so on. If we consider a monocrop, one particular external pressure can destroy all that year's harvest, such as a late spring frost killing the blossoms of apple trees. In a more biodiverse system, where apples are only one crop of many, we have the other crops to fall back on so all is not lost (in this example, the frost-tolerant crops, like blackberries and blueberries, or varieties of later-flowering apples whose blossoms were unaffected by the earlier frost).
A better place to work. The presence of biodiversity on the farm almost certainly arises from the minimal usage, or complete avoidance, of agricultural chemicals, therefore removing many of the dangers to health of modern farming. Not only will the farmers (and their neighbours) not be exposed to toxic chemicals, they will be able to see wild flowers, butterflies, birds, animals, and all the beauty of nature as they work, and who could fail to be happier (and more dedicated and productive?) as a result?
Nature conservation. Although for many people this may be the chief reason for promoting biodiversity on the farm, unfortunately nature conservation in itself offers little economic incentive (except for subsidies, and/or tourism). But farming is a livelihood, and must turn a profit. The first five reasons listed above can each make economic sense for the farmer, whilst nature conservation falls into the more woolly area of moral obligation. There is no doubt, however, that a farm with greater biodiversity contributes more to nature conservation. The opposite of a biodiverse system is a monocrop, more downsides of which are discussed in "How and Why - small-scale diverse organic farming versus monocropping".
How! Arguably the greatest boost we can give to biodiversity on the farm is to avoid using agricultural chemicals (pesticides and fertilisers). By not using pesticides, not only are we not killing the target pest, we are not killing its natural predators, nor are we killing the innocent bystanders that typically make up a high percentage of the death toll. It takes a lot longer for the predators to re-establish themselves than it does for the pests, plus the pests will sooner or later become resistant to that pesticide. So we are not solving a problem but creating one, and reducing biodiversity, and therefore nature's ability to solve the problem for us. Pesticides also kill pollinators, and are surely a major contributor to the drastic decline in bee numbers around the world (along with habitat loss). Artificial fertilisers, when used on pastures or meadows, reduce biodiversity by providing the nutrients necessary for the more vigorous species to proliferate and crowd out the less-vigorous species. On our farm we do not fertilise our meadows or pastures, which is why they are so biodiverse. In fact, by year after year cutting and removing hay from the meadows, we are reducing the fertility, thus allowing the less-vigorous species to flourish, and creating a less-competitive environment in which new species can establish themselves. This may give a lower quantity of grass or hay, but the varied diet it gives the livestock is of a higher quality (see above). Artificial fertilisers, when used on crops and in vegetable gardens, gradually lead to an impoverishment of the soil. Synthetic fertilisers contain no organic matter (unlike composts and manures), which leads to a lack of organic matter in the soil, poorer soil structure, and a decline in soil organisms, such as earthworms and micorhizae fungi. Loss of soil structure, organic matter, and soil organisms (and therefore biodiversity) gives a less fertile soil, so that more and more fertiliser is needed to produce crops, and sooner or later no amount of fertiliser will be enough. A high level of biodiversity within the soil is a good indicator of a healthy fertile soil. On an organic farm such as ours, no artificial pesticides or fertilisers can be used. Instead we rely on composts and manures for fertiliser, and local wildlife and our own knowledge to keep pests to a minimum.
Wild (or, more correctly, "semi-natural") areas within the farm, or adjacent to the farm, provide habitat for wildlife, and therefore biodiversity. These may be woodlands, hedgerows, ponds, rivers and streams, heathlands, wildflower meadows, or whatever, but they are areas with a minimum of human intervention (though many do require some management). Each of these will provide habitat for a different range of species, and add to the mosaic of habitats within the landscape, and the interactions between those habitats, all of which will boost biodiversity. Natural vegetation growing along waterways purifies the water a lot better than bare banks - another example of biodiversity working in our favour.
Growing a range of crops on the farm, in alternate areas or polycropped (more than one crop growing together), or in extensive mixed plantations, adds greater biodiversity than just one crop. Don't put all your eggs in one basket! For example, on our farm we have orchards planted with seven varieties of apple (most apple varieties require at least one other variety nearby, or the flowers will not be cross-pollinated and will therefore produce a lower yield of fruit), with an understorey of wild grasses and flowers, grazed in rotation by a mixture of sheep, horses, and chickens. This is a stable system, with minimal input, but high and varied output (apples, chicken eggs, and lamb meat). Managing the land with nature in mind also helps. Knowing what flowers when and where, and whether it is the food-plant of a particular caterpillar or other creature, should determine when we cut or graze that area. Managing the land to maximise biodiversity will help create a balanced productive system. If we are kind to nature, nature will be kind to us
Finally, some warnings must be mentioned. Biodiversity, especially when presented simply as a number, should not be considered an end point in itself. Every species, every ecosystem, every relationship is important in its own right. For example, some insect and lichen species can only survive in the darkest depths of an extensive forest. If the forest is broken up into a mosaic of habitats, including small patches of the original forest, those deep-forest species will become locally extinct, although the overall biodiversity of the area may have increased. Also, introducing exotic species may boost local biodiversity in the short term, but those exotics may run riot and crowd out the native species, damaging local biodiversity in the long term. Many of these damaging exotics are very difficult to control and/or eradicate. Some examples are Latin-American fleabane (currently a problem on one part of our farm), Japanese knotweed (which forms dense thickets where nothing else can grow, and is spreading along the banks of our local river), eucalyptus (widespread in Asturias and also a problem on one part of our farm), Sitka spruce (often favoured for northern tree plantations, it allows very little light through to the forest floor), and rhododendron (which covers the ground so nothing else can grow). Boosting biodiversity, like all things, should not be carried out to the nth degree. Further information. Whitefield, Patrick (2004); The Earth care manual. Permanent Publications.
Information sheet created by Hotel Posada del Valle. (