Introduction to agricultural biodiversity

Biodiversity for food and agriculture includes the components of biological diversity that are essential for feeding human populations and improving the quality of life. It includes the variety and variability of ecosystems, animals, plants and micro-organisms, at the genetic, species and ecosystem levels, which are necessary to sustain human life as well as the key functions of ecosystems. Such diversity is the result of thousands of years of farmers’ and breeders’ activities, land and forest utilization, and fisheries and aquaculture activities combined with millions of years of natural selection. Most of the human population lives in areas where food production and nature co-exist together. Biodiversity for food and agriculture can be managed to maintain or enhance ecosystem functions to provide options for the optimization of agricultural production, and contribute to the resilience of ecosystems for risk mitigation. Indeed, biodiversity enhances ecosystem services because those components that appear redundant at one point in time become important when changes occur.

It is foreseen that developing countries will, in some areas, show a decrease in agricultural productivity between 20-40% due to the effects of climate change. This may lead to pressure on natural resources. The conservation and sustainable use of biodiversity for food and agriculture play a critical role in the fight against hunger, by ensuring environmental sustainability while increasing food and agriculture production. It is imperative to do so in a sustainable way: harvesting resources without compromising the natural capital, including biodiversity and ecosystem services, and capitalizing on biological processes. To cope with all these challenges and uncertainties a large reservoir of genetic and species diversity will need to be maintained and sustainably used. This diversity will further help maintain and rehabilitate productive ecosystems to supply future generations with abundant food and agriculture.

Biodiversity is an important regulator of agro-ecosystem functions, not only in the strictly biological sense of impact on production, but also in satisfying a variety of needs of the farmer and society at large. Agroecosystem managers, including farmers, can build upon, enhance and manage the essential ecosystem services provided by biodiversity in order to work towards sustainable agricultural production. This can be achieved though good farming practices which follow ecosystem-based approaches designed to improve sustainability of production systems. They aim at meeting consumer needs for products that are of high quality, safe and produced in an environmentally and socially responsible way.

The conservation and enhancement of biodiversity in cropping systems both above and below ground (e.g. soil biodiversity) are part of the foundation of sustainable farming practices. Such measures also lead to improved biodiversity in other parts of the environment which are adjacent to but not directly part of the cropland – such as water bodies and the broader agricultural landscape. The composition and diversity of planned biodiversity (for example selected crops) strongly influences the nature of the associated diversity - plant, animal and microbial. A challenge is to integrate, through ecosystem approach strategies, the planned biodiversity that is maintained with the associated diversity (for example, wild pollinators). Some ecosystem-based production practices:

• Conservation Agriculture (CA)
• Integrated rice management systems such as the System of Rice Intensification (SRI) 
• Integrated Pest Management (IPM) for plant and animal diseases 
• Integrated Production and Pest Management (IPPM) 
• Integrated Plant Nutrition Systems (IPNS) 
• Integrated Weed Management (IWM)

Maintenance of biodiversity, including crop-associated biodiversity, is necessary to ensure the continued supply of goods and services such as:

1. Evolution and crop improvement through breeding – the interaction between the environment, genetic resources and management practices that occurs in situ within agro-ecosystems ensures that a dynamic portfolio of biodiversity for food and agriculture (agricultural biodiversity) is maintained and adapts to changing conditions;
2. Biological support to production – support is provided by the organisms that make up the biological diversity of the agro-ecosystem. For example, soil fauna and micro-organisms, together with the roots of plants and trees, ensure nutrient cycling; pests and diseases are kept in check by predators and disease control organisms, as well as genetic resistances in crop plants themselves; and insect pollinators contribute to the cross-fertilization of outcrossing crop plants; and
3. Wider ecological functions – valuable ecological processes that result from the interactions between species and between species and the environment include the maintenance of soil fertility, water quality and climate regulation.

Why biological diversity is important to agriculture

Crop genetic diversity has a critical role to play in increasing and sustaining production levels and nutritional diversity throughout the full range of different agroecological conditions. Diverse organisms contributing to soil biodiversity perform a number of vital functions that regulate the soil ecosystem, including: decomposition of litter and cycling of nutrients; converting atmospheric nitrogen to an organic form, and reconverting this to gaseous nitrogen; and altering soil structure. Diversity in deliberate plantings on-farm- through crop rotations, crop species mixtures, permanent soil cover crops employed in conservation agriculture or agroforestry - are oft used techniques to increase yield stability, and increase soil fertility.

Grassland and pasture/crop systems that diversify and integrate ruminant livestock and crops tend to be more sustainable because they provide opportunities for rotation diversity, perennial cultivation, and greater energy efficiency. The introduction of grazing animals at certain points in farming cycles may help to break down plant material and increase nutrient availability. Predators and parasites which attack pest insects or pathogens on crops, or plant-feeding insects which attack crop weeds contribute to pest regulation. Beyond these direct trophic relationships, a web-like pattern of interactions amongst diverse life-forms on-farm can deliver additional benefits. For instance, crop production may benefit from benign micro-organisms which colonize crops and their habitats such that pathogens do not establish, or from non-crop plants which are attractive to pests and thereby reduce their numbers on crops. Taken together, this directly- and indirectly-acting biodiversity may create “pest suppressive” conditions.

Greater on-farm diversity of plants, greater closeness between crop plants and thus coverage of bare ground, and more perennial cultivation may be measures lending greater resistance to invasion of farming systems by noxious species, and assist in weed management. Pollinators are essential for orchard, horticultural and forage production, and contribute to improvements in quality of both fruit and fiber crops. Healthy pollination services are best ensured by an abundance and diversity of pollinators, in large part provided by wild biodiversity.

Plant genetic resources

About 7,000 species of plants have been cultivated for consumption in human history. The great diversity of varieties resulting from human and ecosystem interaction guaranteed food for the survival and development of human populations throughout the world in spite of pests, diseases, climate fluctuations, droughts and other unexpected environmental events.

Presently, only about 30 crops provide 95% of human food energy needs, four of which (rice, wheat, maize and potato) are responsible for more than 60% of our energy intake. Due to the dependency on this relatively small number of crops for global food security, it will be crucial to maintain a high genetic diversity within these crops to deal with increasing environmental stress and to provide farmers and researchers with opportunities to breed for crops that can be cultivated under unfavourable conditions, such as drought, salinity, flooding, poor soils and extreme temperatures.

Plant genetic resources are the basis of food security and consist of diversity of seeds and planting material of traditional varieties and modern cultivars, crop wild relatives and other wild plant species. These resources are used as food, feed for domesticated animals, fibre, clothing, shelter and energy. The conservation and sustainable use of PGRFA is necessary to ensure crop production and meet growing environmental challenges and climate change. The loss of these resources or a lack of adequate linkages between conservation and their use poses a severe threat to the world’s food security in the long term. The potential of plant genetic resources for food security, sustainable livelihoods, adequate nutrition and adaptation to climate change is enormous, if managed in a sustainable manner.

Crop and Crop-Associated Biodiversity

Plant genetic resources for food and agriculture (PGRFA) interacting with other dimensions of agricultural biodiversity - in particular crop associated biodiversity - provide multiple goods and essential ecosystem services such as nutrient cycling, pest and disease regulation, pollination, and other wider ecological services such as maintenance of water quality, waste removal, soil moisture retention with reduction of runoff, water infiltration and erosion control.

Crop associated biodiversity is the sum of non-crop living organisms found in agroecosystems. This includes the range of organisms above and below ground that can harm or help agriculture, such as pests, diseases, and weeds; pollinators and biological control organisms; and the many organisms controlling nutrient cycling. Together with crops and livestock that are intentionally introduced and maintained by the farmer, there are other resources, such as soil flora and fauna, herbivores, carnivores, decomposers or other species that already exist in, or colonise the agro-ecosystem, that are also part of agricultural biodiversity, and which contribute to a functioning agro-ecosystem.  Crop and crop-associated biodiversity benefits the ecosystems by providing nutrient cycling, pest and disease regulation, pollination, and other wider ecological services. For example, a well-managed biodiversity contributes to maintain water quality, enhance waste removal, soil moisture retention with reduction of runoff and control water infiltration and erosion. Other crop-associated biodiversity, such as pests, diseases, and competitors, is not so beneficial and requires wise management.

Because of the complex relationships that exist among systems and species in an ecosystem, crop associated biodiversity plays an important role in the in situ conservation of plant genetic resources, while its management can contribute to the sustainable utilization of plant genetic resources. Crop and crop-associated biodiversity (C-CAB) is an intrinsic and important part of agricultural ecosystems, and can be planned and unplanned.  Planned biodiversity includes crops and livestock purposefully introduced and maintained in an agro-ecosystem, by the farmer. Unplanned associated biodiversity includes all soil flora and fauna, herbivores, carnivores, decomposers and any other species that exist in, or colonise the agroecosystem. These diverse organisms interact with eachother, and with plants and animals, in a complex web of biologcal activity.

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