Urbanisation Flashcards
What is the ‘greying’ of urban areas?
→ conversion of gardens from vegetation to impervious surfaces e.g fake grass, paving
What is the relationship between urbanisation and biodiversity?
Studies show urbanisation tends to occur in areas of high biodiversity value and also has a disproportionate effect on species there
What is the predicted impact of urbanization on biodiversity hotspots by 2030?
- Dramatic increase
Examples: - Eastern Afromontane and Guinean Forests of West Africa: Predicted 300% increase in urban areas.
- Biodiversity hotspots with currently low urbanization: Predicted 900% increase in urbanization.
What selective pressures change along the rural-to-urban gradient?
- Green space: Changes in amount, type, and fragmentation.
- Urban heat island: Increased temperatures in urban areas.
- Pollution: Higher levels of air, water, and soil pollution.
- Disturbance: More frequent and intense human activity.
- Biotic interactions: Altered interactions among species (e.g., competition, predation).
What are the 3 main groups of species in response to urbanisation, and how are they doing?
- Avoider (in steep decline)
- Adapter
- Exploiter (high density at high end of urbanisation gradient)
What does it mean that urbanisation promotes biotic homogenisation
Urban assemblages tend to be quite similar regardless of global location
How has urbanisation affected native and invasive plant species richness?
Native species richness of plants declined
But non-native species increase
How has urbanisation affected population genetic structure
- Urban populations less diverse and often genetically distinct (-77% in genetic diversity in Japanese field mouse)
- Pops become stagnated / restricted = less likely to be able to adapt to new sel pressures (result from drift or selection)
Describe the urban selection pressure on Crepris sancta (Dandelion)
55% of dispersing seed land on concrete so cannot germinate
= Significant inc in proportion of non-dispersing seed
→ selection experiments suggest sort-term evolution over 5-12 gens
Describe how urbanisation has affected avian clutch size?
- Urban pops lay fewer eggs
- Mechanisms: Quality , Food abundance (urban environs bad at supporting inverts)
- Study suggests urban caterpillar pops would have to inc 250% for urban blue tits to have similar reproductive success to rural ones
What are the ecosystem services in urban spaces?
- Cultural services (recreation, aesthetic, spiritual)
- Regulating (climate, flood risk, disease)
- Supporting (nutrient cycling, soil formation)
- Provisioning (food, fuel)
Describe green medicine
Natural environs promote:
- Quicker surgical recovery
- Improved cognition
- Reduced mental fatigue
- Reduced stress
- Study into childhood exposure to greenspace and psychiatric disorder (Engemann et al. 2019) shows: greater risk of developing a psychoactive disorder if you’re living in a urbanised space
Describe The pigeon paradox
Species like pigeons play a key role in maintaining people in cities connection to nature, and therefore promoting conservation
How important are green spaces in urban areas for carbon storage
- 97% of above ground carbon stored in trees
- Low in domestic gardens = herbaceous vegetation
- If 10% council grassland planted with trees = 28,400 more tonnes carbon
- If 10% of gardens contained 1 more tree = 927 more tonnes carbon
- Overall, national estimates underestimated how important greenspaces in urban areas are for storing carbon
Aside from carbon storage, what are the direct effects of trees in green spaces?
- Add moisture increasing the airs specific heat capacity
- Evapo-transpiration
- Shade:
Reduces heat stroke deaths)
Cools buildings
Reduce heat island effects - Flood regulation
Describe urban sprawl
- Expansion of cities into surrounding rural or natural areas.
- Characterized by low-density development, large housing lots, and reliance on cars.
- Often leads to habitat fragmentation, loss of green spaces, and increased infrastructure demands.
Describe urban densification
- Increasing population density within existing urban areas.
- Achieved by building upward (e.g., high-rises) or repurposing land for compact housing.
- Reduces the need for expansion but can pressure existing green spaces and ecosystems.
What are the impacts of urban sprawl / densification on ecosystems?
- Densification increases flood risk (already raised by increases in peak river flows)
- Urban sprawl results in a 3.5x higher loss of carbon storage and agricultural production compared to densification.
- Decreased agricultural land under sprawl would require more imports, leading to higher carbon emissions elsewhere.
Summarise how urbanisation impacts evolution
Urban areas exert strong selection pressures that can drive evolution, restructure communities and cause local and global extinctions
What is a potential solution to the land sparing vs. land sharing debate?
The solution often involves a context-dependent approach:
- Land sparing: Intensive agriculture on smaller areas to leave more land for conservation.
- Land sharing: Wildlife-friendly farming that integrates biodiversity within agricultural landscapes.
- A hybrid model may be ideal, combining intensive farming in some areas with wildlife-friendly practices in others.
- The best approach depends on:
Local biodiversity.
Agricultural needs.
Socioeconomic and cultural contexts.
