Introduction to the ecological olive grove

According to Monserrat —veteran ecologist and researcher— «agrobiosystems are such ecosystems in which humans simplify their structure, specialises their community, closes material cycles and directs the flow of energy to valued products». This definition contains one of the few valid recipes for ecological agriculture. It consists in taking an ecosystem, or recreating one —bearing in mind what it is—, and applying the four steps mentioned above: simplifying the structure, specialising the community, closing the nutrient cycles and directing the flow of energy to the olives and the oil, in our case. It may seem simple, but there are some practical difficulties,

To make land arable we must start by «simplifying the structure» of the ecosystem. We have to remove any living beings or groups of living beings which are a problem: because they compete with the farmer for the crop; or because they compete with the crop for nutrients, water, light or living space; or simply because they hamper access to harvesting or tending to the crop; or whatever the reason. What is clear is that since humans started to farm, they have always begun by simplifying, and that they have carried on doing so throughout history, following the initial simplification or developing it further.

When simplifying an ecosystem by eliminating many of its original components (flora and fauna) and thus reducing the relationship between them, we also reduce the diversity/complexity of its structure and, as a result, the maturity/stability is also reduced. It is inevitable. To manage an ecosystem and get sufficient production it is essential that we simplify its structure while specialising its community. There is no other way. It is difficult to produce anything in a mature and complex ecosystem like a forest or a swamp, as everything that is produced gets consumed by the ecosystem itself. To put it simply, there is nothing left over in a mature ecosystem, everything is used. If we want to take something from it, and in sufficient quantities, it is essential that we simplify the system to some degree.

In classical ecology terms, agriculture represents a regression in ecological succession to less mature stages, where the production/biomass relation is higher (larger rate of renewal), which allows for an easier yield extraction.

As a general rule, more simplification corresponds to more production, but also to a greater loss of stability. We try to remedy this loss of stability by introducing energy and materials from outside the ecosystem (human and animal labour, fossil fuels, organic or mineral fertilisers, natural or chemically synthesised phytosanitary products), and we need to introduce more, the greater the state of regression, the greater the loss of diversity.

When simplification is excessive, there can be undesirable consequences such as a proliferation of phytophagous insects (usually referred to as crop pests). If the problem arises from an excess reduction of diversity, the solution will entail –in all likelihood- the restoring of the lost diversity. But not any diversity which randomly increases the number of species present. We will have to rebuild a functional and useful diversity which allows us to maintain stability without affecting yield.

There are no universal recipes, we still have a lot to learn, but there is one rule we can use as a starting point: diversity is rebuilt from the base of photosynthetic producers, green plants; if we have a base of varied producers, it is much easier for a diverse trophic pyramid to take shape, also including organisms (of all sizes) that live on the ground, not only auxiliary fauna, but also what are called «beneficial insects».

Traditional olive groves –in particular dry land ones- are extensive crops with a relatively low need for external agents. This is a relative advantage for ecological farming. If simplification is not excessive, it is likely there will be enough stability and we can go ahead with the only precaution that we do not reduce existing diversity. This is the case in some ecological olive groves in many mountainous provinces, in which there is a state of intermediate maturity, with some complexity and stability in the «olive grove agrosystem», to which we must add the special landscape structure of the olive groves, with many discontinuities in the shape of spontaneous vegetation, shrubs and even trees, which grow on the edges, gorges, escarpments and, generally speaking, in any of the many topographically irregular areas. This structure offers a solution to the dilemma of «conservation-exploitation», through the spatial location of areas where stability appears –fragments of vegetation- next to areas where the priority is production. This solution is very similar to the hedge system found in other farming landscapes.

The situation is very different when the landscape is an uninterrupted blanket of olive groves, with no variety, as we can see in many areas, to which are added bare soils as deserts (they usually call them clean). There is nothing to conserve, diversity must be rebuilt, starting with plant diversity: the sowing of herbaceous ground cover or, in some cases, simply leaving the grasses which appear spontaneously.

Manuel Pajarón Sotomayor is a retired agricultural engineer. His professional life was practically spent in the Sierra de Segura (Jaén), first as an agricultural consultant at the Agencia Comarcal de Beas de Segur, and later, in the same area, as Director of the Oficina Comarcal Agraria (Provincial Agriculture Office) for the Sierra de Segura. He has devoted his professional life (preferably but not exclusively) to ecological olive groves from their beginning, over 35 years ago. He is a founding member of the Sociedad Española de Agricultura Ecológica (Spanish Society of Ecological Agriculture) (SEAE).