Agroecology Flashcards
The problems with global agriculture
- Agriculture covers 35-40% of the ice-free terrestrial earth surface (pastures + crop land)
- Most of the cultivatable land is already exploited
- ~30% of the planet’s terrestrial net primary productivity is appropriated by humans
Yeild gap:
- until now the green revolution (dwarf crops + fertiliser) have allowed crop production to keep pase with population growth
- But many negative effects on biodiversity which actually improves crop production
- Yield increases not matching increase in demand, even for most productive crops such as wheat thar are subject to intensive breeding programs (breeding may not be enough)
- Must increase yeild
Biodiversity problem:
- intensive farming methods have negative effects on biodiversity
GG problem:
- ~15bn mature trees chopped a year to create new farms
- ~40bn mature trees worth of co2 added to atm each year from agricultural expansion + energy production and only ~3bn trees worth of Co2 from rest of human activities
- Not enough land to plant all trees needed to reabsorb co2 – as most is farmland
trade off between yeilds and biodiversity
agro ecology
Agroecology = study of ecological processes that operate in agricultural production systems
often misdefined as be env-friendly farming
May help make yields more sustainable and decrease impact of agriculture on biodiversity
The effect of agriculture on biodiversity
Modern farming: tilling, fertiliser, insectisides/ herbicides/ pesticide, large fields, fences
Impact on species Diversity:
Reduction in hedges
- farmland support 50% of European bird populations but many are threatened and in decline (e.g. Turtle dove and Skylark)
- Reduction in insect dievrsity (e.g. 2/3 of butterfly species are in declines, 30% reduction in moth abundance, Adonic blue butterfly is dependent on traditional grazing of chalk and limestone grassland)
fragmentation
- small extinction prone populations in isolated habitats with little dispersal
- small populations-> demographic stochasticity, envrionemntal stochastisity, allee effect (e.g. group defences break down), genetic drift
- dp/dt= cp(1-p)-ep -> high rate of colonisation and large populations
**Impact on ecosystem functioning: **
- Less efficient nutrients cycling (fungi dominated food web shifted to bacteria dominated with less efficient nutrient cycle and leaking requiring constant inputs)
- reduction in pollination (e.g. wild bee richness depends on prixmity to natural haitats -> study in coffee plantations)
- Example: Greater Prairie-Chickens declined to near extinction
Land use change to agriculture has more drastic effect than intensficiation -> study showed that most species had decline richness (some generalists thrive-> Dung beatle)
Solution: envrinmentally friendly farming
Environmental farming
- may not be organic but pushing to increase biodiversity
- Intercropping, crop rotation -> crop diversity
- Flower strips, hedgerows -> heterogeneity
- Inoculation of beneficial soil microbes eg. mycorrhizal fungi + N2 fixing bacteria to increase soil diversity
- Organic inputs eg. manure + crop residues to increase soil div
- decrease soil disturbance eg. reduce tillage
Study: Hope Farm RSPB
Methods:
- reducing how many times hedgerows are cut
- providing insect-rich flower habitats, and seed-rich habitats
- a safe nesting spaces with lapwing and skylark plots,
- use no insecticides
- reduced pesticide and inorganic fertiliser.
- soils are managed to promote richer habitats for invertebrates
Results:
- 226% increase in breeding farmland birds
- 15 times more wintering farmland birds
- As profitable as “control” farms -> is this as they are getting subsitidies to cover the cost of the reduced yeild? Need to consider the fact that yeild per hectare needs to improve as land conversion is major biodiversity threat?Maybe has no negative effect on yeild?
Subsidies: Environmental act 2021 pushing farmers to be more environmental
Farming and emissions
The food system is responsible for 25 to 30% of global greenhouse gas emissions of which:
- 5% from land conversion
- CH4 from ruminants and irrigated rich
- N2O from fertilizers
- 1.7% of CO2 emissions
Is environmtal farming feasible?
High income countries
- strategies possible
- Limited population growth and little potential for futher intensification and land conversion
Low income cournitries
- strategies not feasible as come at expense of economic develeopement
- more concentration in improving yeilds and feeding the country
Case study: oil palm
Facts:
- 10-50% of all items in a UK shopping basket contain palm oil
- used to make biofuel
positives:
- Grown in poorest countries and brought many out of poverty and allowed developement due to exports (80% of production of SE Asia, Malaysia and Indonesia)
- >30x more employment per ha than other large scale farming
- > 2-3million employed by the sector in Indonesia
- Cheap, versatile, high yeilding (4-10x more efficient to other oil seed crops), more environmentally friendly (less fertiliser, pesticides needed and perrenial ‘tree like’ crop)
- > to boycott Oil palm would intensify the problem with a worse crop
Drawbacks:
biodiversity loss
- Oil palm grown where biodiversity peaks and many species are threatened (54% of mammals)
Fragmenetation
Deforestation
- In Borneo, oil palm = biggest drive of deforestation since 2005 (~50% of all deforestation)
- Globally = oil palm causes <0.5% of all deforestation, most is for cattle
Climate change
- Land clearance releases CO2 especially on peat land
- 27% burned as bio fuels -> only sustaible if crop grown on abandoned land
Solutions:
Priortisation: Convert land with low biodiversity and avoid deforestation
- Study: Converting cattle pasture to oil palm in the Neotropics increases biodiversity in ants, dung beetles and herpetofauna
- problem: RSPO have strict criteria for deforestation but can lead to leakage into other habitats -> grasslands with high ecological value (e.g. Guinean Savanna in West at risk)
Land sparing
- Must prioritise areas for biodiversity as little diversity possible in plantations (unlike with UK agriculture where crops and animals have evolved for centuries)
retaining habitats within
- areas of “high conservation value” are maintained and/or enhanced in plantations
- Forest patches must be over 200 Hectares to support healthy tree regenerations -> 60-70%of biodiversity as found in continuous forest
- Study: 70 plantations digitalized and found most HCV areas were too small to have dignificant benefits for biodiversity but do improve connectivity
Riparian reserves
- Strips of forest retained alongside rivers through plantations (ideally >200m)
- Increase diversity and dispersal
- Example: Gray’s study on butterflies.
Land sharing vs land sparing crop
Land Sparing
o Some land is farmed intensively to maximize yields while other land protected as a reserve
Land Sharing
o All the land is farmed, but using wildlife- friendly techniques which may reduce yields
Overview
The effects of agrviculture on
Biodiversity
- Reduction in hedgrows
- Fragmentation
Ecosystem funcitoning
- Pollinators
- nutrients cycling
- fewer species = lower productivity (lack of niche complenetation)
Solution:
- environmetally fridnly farming
Case study: Oil palm
- facts
- benefits
- problems
- solutions
Drawbacks of environmentally friendly farming/ organic farming
Lower yeilds meaning more land conversion is required
- Requires 40-50% more land to produce same amount of food = more land clearance
Higher costs
Lengthy transition process from standard to sustainable farming
Limited Scalability:
- Some environmentally friendly farming practices may be difficult to scale up to large commercial operations.
Market Access:
- food prices from organic farming are higher
- may not be feasible in low income coountries
Extra facts
~15bn mature trees chopped a year to create new farms
= ~40bn mature trees worth of co2 added to atm each year from agricultural expansion + energy production and only ~3bn trees worth of Co2 from rest of human activities
Not enough land to plant all trees needed to reabsorb co2 – as most is farmland
Environmetal schemes
Environmental scheme/ stuardship schemes are important to incenstivise farmers to farm environmentally
Pre-brexit
- Single farm payment -> paid depending on how much land can be used to grow crops (gaurunteed income for farmers)
Post brexit
- Single farm payment is slowely being removed (gone by 2027) -> this is being protested
- Introduction of more stuardship schemes insentivising biodiversity friendly farming-> beneficial for biodiversity but less secure income for farmers -> e.g. Environmental land management scheme (not a guraunteed payment-> requires money to be put in)
- No longer get money for cropable land -> many farmers are moving away from crop production and rewilding farms (e.g. Hepple estate Northumberland)
- While this is good for the environment it is threatening food security
- New rules being brought in limiting how much of farmland can be re-wilded at once
Will incenstivising re-wilding lead to increased inports which also have negative environmental effect. -> airmiles
