Low-intensity grazing is increasingly used in nature conservation because many nature reserves and special sites have relict vegetation communities from a former pastoral landscape.
If we start from the assumption that large herbivores are a natural component of the ecosystem and that most present day so-called "natural" habitats developed under their influence, logically it is unrealistic to try to perpetuate these habitats and all their functional components, without grazing animals. For example, in woodlands cattle can create structural diversity, and in grasslands, heaths and marsh they encourage conditions which favour floristic diversity and the micro-habitats needed by invertebrates, mammals and birds. Essentially they introduce small scale perturbations to the vegetation resulting in an increase in biodiversity. Their herd behaviour can introduce seasonal and cyclic pressures which are virtually impossible to produce in any other way – not only through their grazing but through their trampling, dunging and resting and ruminating in favoured places and selecting foraging areas in relation to the seasonal availability of herbage.
Once common across all of Europe, low intensity arable systems are now mainly confined to the Mediterranean region. Non-irrigated cereal production is the most important for nature conservation, and is often practised in combination with seasonal grazing by sheep of stubbles and fallows. The use of chemicals, especially herbicides, is low, and a large proportion of the land is usually left fallow each year. Large areas occur in central Spain, the interior of Portugal and southern Italy. Smaller areas remain in Greece, southern France and in parts of central Hungary. Other systems include remnants of traditional flood-irrigated rice production in the Mondego valley of central Portugal, and small amounts of organic arable cultivation in north-west.