Landscapes shaped by humans Flashcards
(25 cards)
How much of the earths surface has been altered by humans?
2/3rds
How are humans niche constructors?
- Domestication
- Resource management
- Controlled burning of forests
What is the main process of human transformation of the natural environment?
Land clearing
What does clearing forests provide for humans?
- Wood for fuel and shelter
- Food - fruit and nuts
- Deep, fertile soil
- Land for cultivation
What is evidence of prehistoric clearing?
1) The invasion of early succession forest taxa
- Birch, fir and spruce
2) Distribution of fruit trees
3) Spread of weeds that accompanied cultivation
How does land conversion effect local richness of biodiversity?
Meta analysis of 284 studies found local species richness by 75% in worst areas, 10% solely due to land use change
Losses of local species richness over 20% are likely to impair the contribution of biodiversity to ecosystem function
What is the worlds most threatened biome?
Temperate grasslands
How much of lands surface is temperate grassland?
8% - over 50%converted for crop production, plantation and urbanisation
Where are grasslands found?
Found in mid-latitudes with seasonal climates
What are temperate grasslands affected by?
- Habitat fragmentation/loss
- Biodiversity loss
- Desertification
When and why did deforestation occur in Europe?
- Massive population increase and the dissolution of the Roman Empire in 400 AD
- The Black Death in 1350
- Great clearances occurred in 11th-13th centuries AD
How much does woodland-pasture cover in the Mediterranean?
Covers 1/4 of Portugal and 1/6 of Spain
Where are woodland-pastures found?
Typically found in areas of 400-700mm/year rainfall
What trees dominate woodland pastures in the Mediterranean?
Dominated by evergreen Oaks - Quercus ilex and Q. suber (holm and cork oak).
Densities of around 20-40 mature trees/ha
Small, tough, thick and waxy leaves prevent water loss during drought
What are woodland pastures in the Mediterranean managed for?
They are managed for acorn production, livestock grazing (liberal ham), wood and charcoal production and cork harvesting
Are Mediterranean woodland pastures biodiverse?
They are highly diverse
- Protected under a pan- European network called Natura 2000
- Over 130 species in every 0.1 ha of cork oak woodland
How are woodland pastures formed in the Mediterranean?
- Climatically controlled
- Wet conditions creates forests
- Drought conditions prevent any trees
- Can be natural or man made
Describe classical reasons for deforestation
- Substantial wood clearing
- Primarily to grow food and graze
- Also for fuel, ship building and metal smelting
Problems with deforestation to soil
- Soil erosion means reforestation cannot occur
- Caused by surface run off from lack of canopy over and over grazing
What controls species dominance in Med woodland pastures?
- Disturbance-drought interactions
- Time since last disturbance indicates amount of light hitting the ground
- This defines the successional stage and the types of species the will flourish
What can suppress fire frequency in the Med woodland pastures?
Management through clearing, browsing and firewood collection
Whats another name for woodland pastures?
Savannah
What human activity occurs in Med woodland pastures?
- Extermination of large herbivores
- Grazing of livestock
- Alteration of fire regime
- Woodcutting and forestry
What are the modern threats to Med woodland pastures?
- Rapid change in human land use after history of rural economies - ecosystems cannot adapt quickly enough
- Changing fire frequency can past ecosystems past tipping point - some species cannot survive
- Reforested land - introduction of new species - original species becoming endangered
- Encouraged over grazing prevents tree regeneration
- Land abandonment due to cork price dropping
