Urbanisation

Question 1

What is the ‘greying’ of urban areas?

Answer 1

→ conversion of gardens from vegetation to impervious surfaces e.g fake grass, paving

Question 2

What is the relationship between urbanisation and biodiversity?

Answer 2

Studies show urbanisation tends to occur in areas of high biodiversity value and also has a disproportionate effect on species there

Question 3

What is the predicted impact of urbanization on biodiversity hotspots by 2030?

Answer 3

• 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.

Question 4

What selective pressures change along the rural-to-urban gradient?

Answer 4

• 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).

Question 5

What are the 3 main groups of species in response to urbanisation, and how are they doing?

Answer 5

• Avoider (in steep decline)
• Adapter
• Exploiter (high density at high end of urbanisation gradient)

Question 6

What does it mean that urbanisation promotes biotic homogenisation

Answer 6

Urban assemblages tend to be quite similar regardless of global location

Question 7

How has urbanisation affected native and invasive plant species richness?

Answer 7

Native species richness of plants declined

But non-native species increase

Question 8

How has urbanisation affected population genetic structure

Answer 8

• 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)

Question 9

Describe the urban selection pressure on Crepris sancta (Dandelion)

Answer 9

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

Question 10

Describe how urbanisation has affected avian clutch size?

Answer 10

• 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

Question 11

What are the ecosystem services in urban spaces?

Answer 11

• Cultural services (recreation, aesthetic, spiritual)
• Regulating (climate, flood risk, disease)
• Supporting (nutrient cycling, soil formation)
• Provisioning (food, fuel)

Question 12

Describe green medicine

Answer 12

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

Question 13

Describe The pigeon paradox

Answer 13

Species like pigeons play a key role in maintaining people in cities connection to nature, and therefore promoting conservation

Question 14

How important are green spaces in urban areas for carbon storage

Answer 14

• 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

Question 15

Aside from carbon storage, what are the direct effects of trees in green spaces?

Answer 15

• Add moisture increasing the airs specific heat capacity
• Evapo-transpiration
• Shade:
  Reduces heat stroke deaths)
  Cools buildings
  Reduce heat island effects
• Flood regulation

Question 16

Describe urban sprawl

Answer 16

• 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.

Question 17

Describe urban densification

Answer 17

• 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.

Question 18

What are the impacts of urban sprawl / densification on ecosystems?

Answer 18

• 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.

Question 19

Summarise how urbanisation impacts evolution

Answer 19

Urban areas exert strong selection pressures that can drive evolution, restructure communities and cause local and global extinctions

Question 20

What is a potential solution to the land sparing vs. land sharing debate?

Answer 20

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.