T6 Lewis- Agroecology: growing food sustainably

why is agroecology important?

• agriculture covers over a third of the ice-free terrestrial earth surface (including cropland and pastures)

agroecology needs to be considered to:

• tackle the problems of food security with exponentially increasing populations (and specific food demands, eg. meat, with wealthier populations)

  • until now, this has been met by intensification (particularly by inorganic fertilisers, pesticides, hedgerow removal and monoculture), funded by subsidies

• make yields more sustainable, by preserving ecosystem services and heterogeneity

• reduce the impact of agriculture on existing biodiversity (damaged by intensive farming methods, fragmentation + land conversion, particularly in the tropics and in soil organisms)

how does agricultural intensification affect soils?

• increasing input of fertilisers and disturbances (eg. tilling) has led to bacteria-dominated soil foodwebs

• these are more ‘leaky’ (less nutrient efficient), have high carbon emissions and are more dependent on repeated agricultural inputs

• healthy soils from low input management have more dominance of fungi, earthworms and microarthropods

• these are more efficient with nutrient cycling, produce fewer C emissions and are more self-sufficient

what are the potential solutions to tackle food security while maintaining biodiversity?

• organic farming, which uses crop rotation, green manure, compost and biological pest control and legally restricts inorganic fertilisers and pesticides

• agroforestry, primarily in the tropics, which integrates trees into crop systems (existing or planted) to improve biodiversity and better connect rainforest fragments

• agri-environment schemes, which incentivise wildlife-friendly farming and the delivery of public goods (eg. clean air + water, biodiversity + protection from hazards) eg. countryside stewardship schemes

there are three levels of diversity to consider:

• crop diversity by intercropping and rotation

• non-crop diversity by hedgerows, seminatural habitats and soil health

• soil diversity- inoculation of beneficial soil microbes, organic inputs and reducing disturbance (eg. tilling)

there is a land sparing vs land sharing debate:

• sparing- intensively farming some land to maximise yields, while protecting other land as a reserve

• sharing- farming a greater proportion of land in a wildlife-friendly way, despite lower yields per unit area

this is realistically a continuum, not a binary choice

j