Urbanisation

Question 1

The rise in urban ecology

Answer 1

Several times more studies published in the last decade than in the last 100 years

Question 2

Why is urbanisation important?

Answer 2

Increasing extent as over 50% of human populations will live in a city in the upcoming decades

Urbanisation is increasingly intense, “hard surface” more prominent, lower biodiversity in loss of gardens and infilling of waste ground

Question 3

Current extent of urban areas

Answer 3

10% in some regions but >1% in some regions

Question 4

245 globally threatened birds in Africa

Answer 4

15% due to residential and commercial development

17% due to pollution, light pollution, urban waste water

20% due to human disturbance, recreational activities

16% due to transport and service corridors, shipping lanes, roads and railroads

Question 5

1995: 29 of 867 ecoregions are >33% urban

Answer 5

these contain 213 endemic vertebrates

Question 6

Urbanisation often develops in areas of high wildlife importance

Answer 6

Causes of threatened/endangered listings in the US are non-native species and urbanisation

Question 7

Urban expansion by 2030

Answer 7

300% increase

900% increase in some biodiversity hotspots with little current urbanisation (Turkey, Eastern Afromontane, Guinean forests of West Africa)

Question 8

Increasing extent of urban pressures surrounding natural areas

Answer 8

Protected areas will be much closer to urbanised areas

Question 9

Difference between rural and urban areas

Answer 9

Urban heat island, 3°C warmer in cities

Pollution

Disturbance

Biotic interactions

Question 10

Individual species abundance depends on elasticity of the species to adapt

Answer 10

Urban avoider (specialists) will decline
Urban adapter will do best at medium intensity urbanisation
Urban exploiter (generalists) will increase

Question 11

Urbanisation promotes

Answer 11

biotic homogenisation (regardless of their location urban assemblages will be similar)

Question 12

Assemblage structure and species richness

Answer 12

declines, but with increasing proportions of exotic species colonising new areas

Question 13

Population genetic structure

Answer 13

Genetic diversity decreases in urban populations with fewer polymorphic loci, allelic richness, and haplotypes

Question 14

Experiment on Crepis sancta flower

Answer 14

55% of seeds dispersed land on concrete and can’t germinate (0% in rural areas)
Evidence suggest short-term evolution (5-12 generations) changes species behaviour in Crepis

Question 15

Trait divergence in urban birds

Answer 15

Dong is higher dB in urban areas and of higher frequency. Unsure whether adaptive or not, or how it influences mate choice.

Question 16

Trait divergence in plant reproduction

Answer 16

Herkogamy in rural Centaurium erythraea where male anthers and female stigma are spatially isolated

No herkogamy in urban species adapted to dearth of pollinators, heritability 0.62

When rural adapted plants are put in urban environments then they have lower seed sets per fruit. Maladapted.

Question 17

Bird feeders

Answer 17

Controversial whether it increases population densities
May promote aggressive invasive or predatory species
Human-nature interactions

Question 18

Cat wars

Answer 18

cats probably limit bird population size in some locations

This indirectly, through fear of predation, reduces provisioning and leads to reduced chick growth rates and smaller clutch size.

On average cats reduced provisioning rates by one third.

Question 19

Trait mediated indirect effects

Answer 19

increased mobbing could increase risk of predators finding a nest

Question 20

The pigeon paradox

Answer 20

conservation may increasingly depend on the ability of people in cities to maintain a connection with nature

Question 21

97% above ground carbon stored in trees

No difference between public & private sites

Answer 21

Low in domestic gardens = herbacous vegetation
10% council grassland planted with trees 28,400 more tonnes carbon
10% gardens contain 1 more tree 927 more tonnes carbon

Question 22

Direct effect of trees

Answer 22

Shades hard surfaces reduces radiant heat gain

Adds moisture increasing the air’s specific heat capacity

Evapo-transpiration

Shading cools buildings

Flood regulation through transpiration, and infiltration into ground

Question 23

Impacts of future urbanisation

Answer 23

Loss in carbon storage and agricultural production 3.5 times higher under the sprawl than the densification scenario

Question 24

Summary

Answer 24

Urbanisation impacts:
1. Assemblage composition and structure:
large scale - extinction threat, urban avoiders
small scale - richness peaks at moderate intensities of urban
development
2. Traits of individual species:
communication, reproduction, behaviour etc. plasticity vs genetic adaptation
3. Urbanisation typically reduces ecosystem service provision:
With (often different) consequences for urban sprawl versus densification debate