Agroecosystems

Types of Agroecosystems

Agroecosystems have been used for thousands of years among indigenous societies - they recognised the important connection between agriculture and natural systems. Only in the 20th century did agroecology come about as a discipline in western science.

The types of agroecosystem vary depending on:

• Location
• Natural community
• Agricultural focus

Polyculture (Intercropping)

Polyculture differs greatly from modern, industrial monocultures. Instead of huge expanses of one plant, different complementary crops are interspersed, producing mutual benefits.

Polyculture strategies can save land area by up to 29% compared to monocultures - making them very useful in the journey to sustainable agricultural expansion.

Permaculture

Permaculture systems create synergies and imitate natural systems. These systems apply holistic techniques to support ecosystem function, integrating a range of functions (e.g. hydrology, livestock, waste management).

Permaculture has been adopted as a design system in many other aspects of life. It's about working with, rather than against, nature. The permaculture philosophy focuses on earth care, people care, and fair shares.

Permaculture designs can be applied to urban areas, finance, technology, culture, education, and health and well-being.

Agroforestry

Agroforestry encompasses the growth of trees and crops, and managing animals for mutual benefit.

Silvopastoral Systems

Silvopastoral systems combine livestock with mixed plants such as trees, grasses and shrubs.

These systems are common in Latin America, and typically combine grazing pastures and trees - such as timber plantations or fruit trees. These pastures are incorporated among trees or using rows of trees to provide borders. Grazing is rotated between different pastures to allow time for recuperation.

Trees provide shade and shelter, providing favourable conditions for the livestock and improving their welfare, while animals provide manure that fertilises the land.

When compared to modern farming methods, silvopastoral systems show improved animal welfare, increased biodiversity, and increased production of meat and dairy. Furthermore, silvopastoral systems also support climate mitigation.

Agrisilvicultural Systems

Agrisilvicultural systems combine crops and trees.

Agrosilvopastoral Systems

These systems combine all three elements of crops, forests and pasture.

Pigs wandering freely in a Spanish dehesa.

Components of Agroecosystems

Agroecosystems consist of two components: abiotic and biotic.

Abiotic Components

• Climate: temperature, light intensity, day length, CO₂
• Resources: water availability, nutrient supply
• Landscape: topography, relief
• Soil: fertility, salinity, pH

Biotic Components

• Pests: parasites, herbivores
• Competition: between plants
• Symbiotic relationships: subterranean organisms, pollinators
• Farmers: includes their management of (a)biotic factors

Characteristics of Agroecosystems

Agroecosystems are categorised by types of diversity.

Interactions between Planned and Unplanned Diversity

Planned diversity can impact overall ecosystem functioning. Modern industrial agricultural systems have much lower diversity (including genetic diversity) than traditional systems. Reduced genetic diversity leaves plants and animals susceptible to pests and diseases, which have often adapted to exploit the most common varieties.

A potential mitigation strategy is genetically engineering agricultural products to have increased resistance to these diseases and pests.

Alternatively, promoting increased diversity can help reduce these problems and increase overall resistance. Furthermore, increasing planned diversity also increases unplanned diversity. This benefits agricultural production by delivering services such as pollination, pest control and soil health.

Biodiversity in Agroecosystems

Agroecosystems support a greater level of biodiversity compared to monocultures. This helps agroecosystems perform a range of services outside of food production - nutrient cycling, regulating climate and hydrology, detoxification, and many more.

Agroecosystem Biodiversity Components

• Productive Biota: another term for planned diversity. Productive biota plays a key role in determining the complexity and diversity of the agroecosystem.
• Resource Biota: organisms contributing to the agroecosystem's productivity through services such as pollination and decomposition.
• Destructive Biota: weeds, insects and pathogens. Farmers aim to limit their effects through management.

Restoring Biodiversity in Agricultural Landscapes

Restoring the functional biodiversity of agricultural landscapes is an important step toward expanding sustainable agriculture. This improves soil fertility and ecosystem productivity.

It has been proven that increasing the diversity of an agricultural system promotes increased yields, production and stability. A higher diversity also suppresses weed and pest species - a study found that 53% of pest species were less abundant in a more diverse system.

As monoculture yields continue to decline or decelerate, increasing diversity could become key for sustaining production and maintaining ecosystem services.

I hope that this has clarified agroecosystems for you. Remember that an agroecosystem is a natural community modified for agricultural processes and that it encompasses the interactions between species and the environment too.

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