Agroecology: Searching in the wrong place

This paper presents a defence of ecologically based monodominance. The promotion of ‘agroecology’ has been validated by the belief that natural vegetation forms a multi-species ‘balance’ under pest pressure. Agroecologists consider monoculture crops as an artificial construct unknown in nature. To achieve this ecological balance crop fields should be re-diversified to species-diverse ‘polycultures’, as mimics of natural vegetation. This simple view of herbivorous insects forcing vegetation diversity held sway with various authors until around 1970. Post-1970 there was an increasing recognition of, and focus on, natural monodominant vegetation. The driving force behind natural plant monodominance, especially in herbaceous species, seemed to be seasonal ecological stress, including fire, flood, silt formation and soil nutrient deficiency. These abiotic stresses were capable both of winnowing out less adapted species, but also encouraging the evolution of adaptations to the stress (as seen, for example, in the distinctive features of monodominant mangroves and sea-grasses). The result was plant species with the ability to grow as monodominants, but, importantly, the evolved ability to resist any extra biotic pressure from herbivores – both features invaluable for monoculture agriculture. Agroecology never considered the possibility of adaptative evolution to biotic stress to allow monodominance (the ‘fight’ stratagem of plant species). In addition, agroecology only recognizes the ‘flight’ stratagem for short-distance escape (plant species ‘hiding’ in mixed-species vegetation). This ignores a major feature of modern agriculture, which heavily relies on long-distant crop introduction, through trans-oceanic crop introduction: the ultimate ‘flight’ mechanism to remove susceptible species from co-evolved herbivorous insects and disease by long-distant dispersal. In failing to understand the evolution of monodominance, current agroecological principles are without a solid scientific basis ecologically. There is still an opportunity to revise the current thinking to develop a more ecologically-based form of agroecology.