Diversity in agroecosystems is the number and relative abundance of different species – both flora and fauna – that are found at a given site, or field. Diversity is generally considered a key factor in maintaining stable and resilient agroecosystems. Conventional agricultural systems are typically simplified from natural ecosystems to maximise the production of a limited number of crops or livestock. This has led to a significant loss of genetic diversity of domesticated plants and animals believed to be important for future food production and food security in the face of climatic and other shocks.
Studies investigating the relationships between diversity, stability and resilience have found that it is not the sheer number of species present that affects stability and resilience, but their nature, function within the systems, and the relationships they have with one another. Merely diversifying crops and livestock may not necessarily create the ecological variances and biotic interactions to support the full suite of ecosystem services needed for productive agriculture. Diversified farming systems (DFS) include functional biodiversity – the range of species that influence ecosystem functioning- that helps to maintain ecosystem services that are critical for agriculture, such as soil fertility, pest and disease control, water use efficiency, and pollination. Diverse agroecosystems can create multiple benefits when species are not in direct competition, encouraging beneficial relationships between species. For example, trees and shrubs provide shade for herbs, legumes provide nitrogen, essential for plant growth, and livestock furnish manure.
Mixtures of crops can provide for a diverse and healthier diet, deter pests and during times of crisis, such as drought or cyclone, provide a form of insurance when at least one crop out of many survives. Crop diversity has diminished significantly; out of a total of 300,000 plant species, only 10,000 have been used for human consumption since the origin of agriculture. Of these 10,000, only 150-200 species have been commercially cultivated and just 4 crops – rice, wheat, maize and potatoes – provide half of the world’s energy needs.
More than 800 million people globally are undernourished, whilst those with micronutrient deficiencies are estimated to number more than 2 billion. Although the direct link between agricultural biodiversity and human nutrition is difficult to make, the nutritional importance of a diverse diet is now widely recognised. In developing countries, this implies supplementing local staple crops with wild-harvested species or producing a greater variety of grains, legumes and vegetables through multiple cropping.
Opportunities to diversify agricultural production depend on a variety of factors from access to training, extension, seeds and crop varieties, to market conditions such as changes in consumer demand, market prices, government policy, trade opportunities and rural infrastructure. In general, diversification is relatively accessible to most farmers, despite their different needs, wealth or location, in comparison with more cutting-edge technologies. Multiple cropping, agroforestry and integrated pest management (IPM) are examples of practices that promote diversification for Ecological Intensification.