4.1.8 Natural and Managed Ecosystems 

Key Knowledge: natural and managed ecosystems including the importance of biodiversity to the sustainability of agriculture and/or horticulture 

The Importance of Biodiversity to Agriculture

Biodiversity is the variety of all living things, including plants, animals, and microorganisms. In agriculture, biodiversity is not a luxury; it provides critical ecosystem services that keep the farm running.

Biological Pest Control

In a monoculture, a pest population can explode because there are no natural predators. A biodiverse farm maintains insect hotels, native vegetation, and multi-species shelterbelts. These areas house predatory wasps, ladybirds, and birds that hunt crop pests, reducing the need for chemical sprays.

Pollination Services

Most horticultural crops (such as almonds, berries, and stone fruits) rely entirely on insects for pollination. Maintaining native vegetation around orchards ensures that wild bees, butterflies, and hoverflies have a food source year-round, securing high pollination rates and fruit set when the crop flowers.

Soil Health and Nutrient Cycling

A biodiverse soil is full of life: bacteria, fungi, earthworms, and protozoa.

• Mycorrhizal fungi form symbiotic networks with crop roots, helping them access water and phosphorus from deep in the soil.

• Rhizobia bacteria fix nitrogen from the air into a form plants can use. A diverse soil microbiome breaks down organic matter faster, keeping nutrients flowing naturally.

Genetic Diversity and Resilience

Cultivating a single variety of a crop makes the industry vulnerable. Maintaining genetic diversity—such as preserving heritage seed varieties or breeding varied livestock lines—ensures that if a new strain of disease emerges or temperatures spike, some individual plants or animals will possess the genes needed to survive.

PRACTICE  Use the marking scheme to evaluate your work 

Question (4 Marks)

An almond grower in the Sunraysia region clears all native vegetation within a 5-kilometre radius to maximise their planting area. Analyse the long-term impacts of this decision on pollination security and pest pressure.

Exam Tip: 

When an exam question asks you to compare a natural ecosystem to a managed agricultural ecosystem, do not just list definitions. You should frame your answer around the flow of resources.

Examiners look for a specific cause-and-effect chain showing why managed ecosystems are inherently less stable:

• The Cause: Monoculture production requires the regular removal of biomass (the harvest).

• The Biological Effect: This disrupts the natural decomposer pathway, preventing nutrients from returning to the earth.

• The Management Consequence: The system becomes dependent on artificial human interventions, such as synthetic fertilisers and chemical additives, to replace the natural ecosystem services that were lost.

SAC Tip: 

Be Specific! If a SAC question asks how biodiversity improves sustainability, avoid using broad or vague terms like it helps the environment or it makes nature healthier. Instead, name a precise ecosystem service and its direct financial or biological benefit to the farmer.

Use this structure to guarantee full marks:

1. The Action: Planting native flowering shrubs along orchard boundary lines.

2. The Ecosystem Service: Provides a year-round pollen and nectar source for beneficial predatory insects like hoverflies and lacewings.

3. The Practical Benefit: These insects control populations of destructive aphids, reducing the farm's reliance on chemical insecticides and lowering input costs.