Agriculture and Biodiversity
Laura Armstrong & Joe Wolfensohn
Teachers


Contents
Recall Questions
This topic requires prior knowledge of biodiversity. You can test your knowledge on this below.
Why does monoculture reduce biodiversity?
Growing only one crop variety means a reduced variety of plant species. This will lead to a reduction in the diversity of animals due to fewer different food sources and a smaller variety of habitats.
In what other ways can human activity reduce biodiversity?
Through habitat destruction, pollution, overexploitation, introduction of invasive species, and climate change.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains agriculture and biodiversity or read the full notes below. Once you've gone through the whole note, try out the practice questions!
Balancing Yield and Biodiversity & Monoculture
Balancing Yield and Biodiversity
- Growing population = increased demand for food.
- Farmers aim to increase yield per hectare (a hectare is a unit of area 100m x 100m).
- This often comes at the expense of biodiversity.
Monoculture
- Growing a single crop over a large area.
- Decreases species diversity:
- Fewer plant species: fewer food sources.
- Also reduced habitat diversity.
- Leads to decline in herbivores, predators, and pollinators.
Increasing Field Size & Cereal Crops and Ploughing
Increasing Field Size
- Hedgerows and field margins are the areas around the edge of the field. They provide important habitats for animal species as well as areas for wild flowers to grow.
- Hedgerows and field margins are removed to make room for larger machinery like tractors, and to grow more crops.
- Removing hedges may also help to remove any natural pests that are potentially damaging the crop and reducing its yield.
- Removing hedgerows and field margins leads to:
- Loss of habitat for birds, insects, and small mammals and reduced plant diversity.
- Fewer nesting sites and food sources.
- More soil erosion.
Cereal Crops and Ploughing
- Cereal crops (like wheat and oats) are sown (planted) in the autumn and harvested the following July.
- The land is ploughed between harvest and sowing, this loosens the soil making it easier to sow crops. It also aerates the soil to maintain oxygen concentrations.
- Ploughing exposes the insects living in the soil and are an important food source for birds and other animals.
- Fields only remain ploughed for 1 month reducing the time that the soil invertebrates are available as a food source.
Draining Wetlands & Pesticides and Fertilisers
Draining Wetlands
- Wetland areas are drained for farming- to graze animals and grow crops.
- Destroys aquatic and semi-aquatic habitats.
- Reduces biodiversity of species adapted to wet conditions (e.g., frogs, dragonflies, aquatic plants).
Pesticides and Fertilizers
- Pesticides:
- Kill pests to reduce damage to crops, but also non-target species like pollinators (e.g., bees) and natural predators (e.g., ladybirds). These natural predators may have been useful as a form of biological pest control- killing pests that damage the crops and reducing the need for chemical pesticides.
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Fertilisers:
- Harvesting removes biomass from the field, important mineral ions (such as nitrates and phosphates) are not recycled into the soil by decomposition.
- The mineral ions can be replaced by using fertilisers.
- Mineral ions (especially nitrates) run off into water - Eutrophication:
- Algal bloom - blocks sunlight - death of aquatic plants.
- Decomposition of dead plants uses up oxygen - death of aquatic animals.
Organic Farming & Biodiversity vs Profit
Organic Farming
- Avoids synthetic chemicals.
- Uses organic fertilisers (e.g., compost, manure which contain organic molecules from decomposing waste material).
- Nutrients are released slowly as material decomposes:
- Less runoff / leaching - reduced eutrophication risk.
- Encourages natural pest control (e.g., ladybirds, birds).
- Supports higher biodiversity but lower yields.
Biodiversity vs Profit
- Farming practices that reduce biodiversity often increase short-term profits.
- However:
- Loss of pollinators and natural pest control can reduce long-term sustainability.
- Biodiversity is essential for ecosystem stability and resilience.
- Sustainable practices (e.g., maintaining field margins) can balance biodiversity and yield.
Key Terms
- Monoculture: Growing only one type of crop.
- Eutrophication: Mineral enrichment of water - algal blooms and oxygen depletion.
- Biodiversity: The variety of life in an area, including species, genes, and ecosystems.
- Organic Farming: Farming without synthetic chemicals, using natural processes instead.
Exam Tip
Don't just say "Biodiversity Decreases" — explain how and why (e.g., loss of habitat, fewer food sources, pesticide use).
Explain how agricultural practices reduce biodiversity. (5 marks)
- Monoculture reduces plant species variety.
- Removal of hedgerows and field margins reduces the variety of habitats for birds and insects.
- Pesticides kill non-target species, including pollinators and predators.
- Fertilisers lead to eutrophication, decreasing aquatic biodiversity.
- Draining wetlands destroys unique habitats and reduces ecosystem diversity.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!