Agroecology: growing food sustainably Flashcards
Agriculture covers … of the ice-free terrestrial earth surface
35-40%
… of agriculture is cropland
15,000,000 km2 (14%)
Describe cropland
‘arable’ + ‘permanent crops’
… of agriculture is pastures
30,000,000 km2
Most of the cultivatable land is…
already exploited
… of the planet’s terrestrial net primary productivity is appropriated by humans
~30%
What is agroecology?
- application of ecological understanding and principles to agriculture
- study of ecological processes that operate in agricultural production systems
- can be applied to a variety of farming models
List some farming models
– organic
- conventional
- intensive
- extensive
- arable
- pastoral
What is the importance of agroecology?
- make yields more sustainable
- reduce impact of agriculture on biodiversity outcomes
What links yields and biodiversity
ecosystem service provision
Describe agricultural intensification
linked to the green revolution
Describe the green revolution
Increase production and productivity
Give some UK examples of agricultural intensification
- land drainage
- hedgerow removal
- new crop types (e.g. oilseed rape)
- ‘improvement’ of pasture
- increased agrochemical inputs
Describe the policy underlying agricultural intensification
- EU’s Common Agricultural Policy
- subsidizes production and supports farmers’ income
- costs ~€60bn/year (38% of the total EU budget), even though agriculture generates just 1.6% of EU GDP and employs only 5% of EU citizens
Describe some of the effects of agricultural intensification
- fragmentation of natural and seminatural habitats
Describe fragmentation of natural and seminatural habitats
- large populations with easy dispersal become small, fragmented extinction-prone populations
- low connectivity inhibits recolonisation
- induces range shifts in response to climate change
The food system is responsible for … of global greenhouse gas emissions
25 to 30%
Give some examples of agricultural greenhouse gas emission
- 5% from land conversion
- CH4 from ruminants and irrigated rice
- N2O from fertilisers
Describe agriculture-dependent species
- long history of agriculture
- arable weeds
- butterflies in early successional (grazed) habitats
Describe the Adonis Blue butterfly (Polyommatus bellargus)
dependent on traditional grazing of chalk and limestone grasslands
Describe the Shepherd’s Needle (Scandix pecten-veneris)
- abundant until the 1950s
- controlled as a weed
- now conserved as a priority species through the UK Biodiversity Action Plan.
Anthropogenic intensification reduces
the diversity of soil organisms
Give some soil organisms that have been depleted due to anthropogenic intensification
- nematodes in Cameroon
- macrofauna in Peru
- termites in West Africa
- microbes in Wales
Describe the general pattern for intensification on soil processes
alters the relative importance of bacterial versus fungal-based pathways of decomposition
Describe the effect of intensive management (fertilizers, tillage) on soil
- bacteria-dominated foodwebs
- relatively inefficient nutrient use
- more ‘leaky’ nutrient cycling
- high carbon emissions
- dependence on repeated inputs
Describe the effect of low input management on soil
- greater importance of fungi, earthworms and microarthropods
- more similar to natural ecosystems
- relatively efficient nutrient use
- tighter recycling of nutrients
- lower C emissions
- less need for management inputs
Describe the effect of intensification on pollination
- erode above-ground ecosystem services
- pollination increases with richness of wild bees and proximity to natural habitat
- fruit set of open pollinated flowers is strongly positively correlated with bee species richness
- number of social bee species is strongly negatively correlated with forest distance
Describe organic farming
- a form of agriculture that relies on ‘natural’ techniques
- uses fertilisers and pesticides if they are considered ”natural”, but excludes or strictly limits the use of synthetic petrochemical fertilizers and pesticides
- often regulated and legally enforced
- 30% higher species richness than conventional farms
Give some ‘natural’ agricultural techniques
– crop rotation
– green manure
– compost
– biological pest control
Organic plots have…
- more diverse microbial communities
- correlated with more efficient functioning
Describe earthworm biomass and abundance in organic plots
higher by a factor of 1.3 to 3.2
Describe agroforestry
- integration of existing or planted trees into crop farming systems
- traditional part of many farming systems e.g. ‘home- gardens’
- biodiversity benefits
Describe the biodiversity benefits of agroforestry
- (partial) replacement for forests – can support more than 2/3 of
forest species - favourable matrix between forest remnants
- livelihood benefits for local people
Describe agri-environment schemes
- farmers incentivized to farm in a wildlife-friendly way
- entry level: ‘good agricultural and environmental condition’
- higher level: more complex management; agreements are tailored to local circumstances
- £400M/year to farmers in England
- 60% of the land
Give an example of an agri-environment scheme
Countryside Stewardship Schemes (Natural England)
Describe the Environment Act 2021
Farmers and other land managers paid for delivering the following public goods:
* clean air
* clean and plentiful water
* thriving plants and wildlife
* protection from environmental hazards
* beauty, heritage and engagement with the environment
* reduction of and adaptation to climate change
Describe land sparing
some land is farmed intensively to maximise yields while other land protected as a reserve
Describe land sharing
All the land is farmed, but using wildlife-friendly techniques which may reduce yields
Describe land sharing v land sparing
- compared crop yields and densities of bird and tree species across gradients of agricultural intensity in southwest Ghana northern India
- more species were ‘losers’ (negatively affected by agriculture) than ‘winners’ (benefiting from agriculture)
- for most taxa in both countries, land sparing seems a more promising strategy
Describe the problems with land sparing
- lack the means to effectively protect areas in the long run
- long record of sustainable land sharing
- situations where both yields and biodiversity are high or where biodiversity depends on agriculture e.g. Mediterranean
- vast regions with shallow soils or low rainfall are only suitable for non-intensive use
Describe heterogeneity
- loss of ecological heterogeneity is a universal consequence of agricultural intensification
- the best predictor of biodiversity outcomes
- future policy and management should aim to recreate
heterogeneity as the best way of restoring and sustaining biodiversity in temperate agricultural systems.
Agricultural diversification practices generally have a …
positive impact on biodiversity and ecosystem services, without compromising yield
