An ecosystem is a community of living organisms (plants, animals, fungi, microorganisms) interacting with each other and with the non-living components of their environment (soil, water, air, sunlight) in a defined area. Ecosystems are characterised by flows of energy (through food chains and webs) and cycles of matter (through biogeochemical cycles such as the nitrogen, carbon and water cycles).
KEY TAKEAWAY: Agricultural and horticultural systems are simplified, managed ecosystems. The health and sustainability of these systems depends on the ecological services provided by biodiversity — both within the farm and in surrounding natural ecosystems.
| Feature | Natural Ecosystem | Managed Ecosystem (Farm/Orchard) |
|---|---|---|
| Species diversity | High — many interacting species | Low — focused on target species |
| Energy input | Solar energy only | Solar + fossil fuels (machinery, fertiliser) |
| Nutrient cycling | Closed — nutrients recycled on-site | Open — nutrients exported in products, replaced by fertiliser |
| Pest/disease regulation | Self-regulating through natural predators | Relies on chemical/physical interventions |
| Stability (resilience) | High — diverse systems recover from disturbances | Lower — monocultures vulnerable to pests, climate variation |
| Productivity per unit area | Lower | Higher for target products |
EXAM TIP: A key VCAA concept is that simplification of ecosystems for production reduces their inherent resilience and ecological function, making them more dependent on external inputs. Biodiversity restoration in and around farms partially restores ecological functions.
Biodiversity (biological diversity) has three levels:
COMMON MISTAKE: Students sometimes assume biodiversity only refers to large, visible animals. Soil biodiversity (microorganisms, invertebrates) is arguably more important for agricultural sustainability than above-ground biodiversity, and is more directly threatened by intensive management practices.
| Strategy | Benefit |
|---|---|
| Revegetation with native species | Habitat for pollinators, natural enemies; carbon sequestration |
| Riparian zone protection | Water quality; habitat corridors; bank stabilisation |
| Shelter belts / windbreaks | Wind erosion control; habitat; microclimate improvement |
| Cover crops and diverse rotations | Soil biodiversity; natural pest and disease suppression |
| Reducing pesticide inputs (IPM) | Protects beneficial insects; maintains natural enemy populations |
| On-farm habitat strips and insectary plantings | Food and shelter for beneficial insects adjacent to crops |
STUDY HINT: The concept of ecosystem services is a useful framework for explaining why biodiversity matters to farmers in practical, economic terms. Pollination, pest control, soil health and water regulation all have dollar values — making biodiversity conservation an economic as well as ecological decision.
VCAA FOCUS: Be prepared to explain the mechanism by which biodiversity provides a specific service (e.g. how insect biodiversity supports pest regulation), not just state that it does. Linking mechanism to consequence demonstrates higher-order understanding.
APPLICATION: A market garden operation could increase on-farm biodiversity and reduce pesticide inputs by: establishing a flowering habitat strip along fence lines to support native bees and parasitic wasps; retaining mulched pathways to encourage earthworm activity; implementing a four-season crop rotation (including a legume phase) to disrupt pest cycles and improve soil biology; and avoiding broad-spectrum insecticides during flowering times.
