Biodiversity generally increases as the olive groves become more extensive, until finally scrubbing over of abandoned groves fundamentally changes their open 'parkland' habitat. Particularly important for biodiversity are old trees, wide spacings, limited tillage and human activity, as well as an absence of the pesticides used in the more intensive plantations.
The traditional production systems, which harbour the richest wildlife communities, use occasional cultivation or grazing to control weeds between the trees and, in upland areas, use terracing with supporting walls to reduce soil erosion on slopes. Under more intensive systems, terracing is less usual and the combination of frequent mechanical weed control, thin soils and steep slopes often leads to very serious problems of soil erosion, with figures quoted for losses of up to 80 tonnes of topsoil per hectare per year in parts of Spain. The most modern systems, using newer dwarf varieties at over 200 trees per hectare, tend to be sited on flatter land and to use herbicides for weed control; this reduces the problem of soil erosion but establishes a virtual monoculture with minimal biodiversity. The final stage in intensification is to use irrigation, allowing higher tree densities and increasing yields by almost 50% compared with intensive dryland systems. Irrigation brings with it a new environmental impact, through the exploitation of scarce water resources and the construction of reservoirs to store irrigation water.