urbanisation

Question 1

what is the current extent of urban areas

Answer 1

1% of earths land area , up to 10 % in some regions

Question 2

What is an example of an area with relatively constant urban extents

Answer 2

London has had a relatively constant level of urbanisation since the 1950’s

Question 3

what is an example of how urbanisation is increasing in intensity

Answer 3

I.E. Garden types, has become much more common to have paved gardens now reducing green space

• urban areas are increasingly “covered” up/ Tarmacs cement etc.

Question 4

Example of how urbanisation affects biodiversity

Answer 4

Example: Africa (1% urban cover)

• 245 globally threatened bird species in Africa, 29 of which (10%) are directly linked to urbanisation.
• 1 % urbanisation cover threatens 10% of bird species

Question 5

What are some of the other main factors affecting African bird species

Answer 5

• Commerical + industrial areas
• Light pollution
• Roads and railroads
• Transport
• almost all have direct links to urbanisation

Question 6

to what extent does urbanisation affect ecoregions and threaten species (1995)

Answer 6

• 29/867 ecoregions are >33% urban
• These regions contain 213 endemic vertebrates (threatened by urban sprawl)
• 8% of vertebrates on IUCN red list primarily threatened with urban sprawl ( only 1 % urban cover)

Question 7

Example of a species significantly affected by urban sprawl

Answer 7

• I.E. Wimmer tree shrew , endemic to ivory coast
• has not been recorded since 1976
• originally found in “shrub” habitat on urban fringes , these spaces have now been covered by urban sprawl

Question 8

Why does urbanisation have such strong conservation effects

Answer 8

1. At broad spatial scales there is a strong correlation between number of species and human population
   (explanation - humans are another species- just settled in most productive areas)
2. At small spatial scales urban development often is focused in areas of high wildlife importance

Balmford et al .(2001) + Gonzales- Abraham (2007) `

Question 9

Effects of urbanization in the USA

Answer 9

urbanisation is the 2nd largest cause of threatened species in the UK `

Question 10

What is the projected urban expansion by 2030

Answer 10

• 300% increase in urban cover
• 900% increase of urban cover in biodiveristy hotspots (areas with low current urbanisation)

E.g. eastern afromontane + guinean forests of west africa

Question 11

Proximity to urban areas has the following effects on ecoregions

Answer 11

• fragmentation of green space
• urban heat island
• pollution
• disturbance
• biotic reactions
• these all affect species composition

Question 12

(local scale) effects of urbanisation

Answer 12

Graph shows that for uk birds as housing density increases , species number first increases up to a point and then plummets

For example: Blackbird population grew with housing density (0-1555), then plummeted as housing increased further (1555-9799)

Question 13

Why do we see this trend in species number vs housing density

Answer 13

Depends on the habitat type.

• i.e. agriculture vs woodland cover
• gardens more diverse then agriculture monoculture , facilitates higher species richness
• However when you move to high density housing , richhness goes down

Question 14

What are the three types of species response to urbanisation

Answer 14

• Urban avoider (population decreases with urbanisation)
• Urban adapter (population increases initially and then returns to normal levels as urbanisation increases)
• Urban exploiter (population increases with urbanisation)

Question 15

what does urbanisation promote

Answer 15

-urbanisation promotes biotic homogenisation

I.E. urban assemblages similair regardless of their location

Question 16

How was the assembly structure of Adelaide changed with increasing urbanisation

Answer 16

Over time plant species have increased, natives have decreased and exotics have increased

• this is indicative of a characteristic of urbanisation (intro of exotics)

Question 17

How dangerous is the introduction of new species to a habitat

Answer 17

Invasion of alien species is as large a driver of extinctions as urbanisation.

Question 18

Genetic structure of urban populations

Answer 18

• On average genetic populations are less diverse and often genetically distinct from other populations

Question 19

Species example of urban and rural trait divergence

Answer 19

Crepir sancta

1. 55% of seeds land on cement (cant germinate)
2. Shift -> Significant increase in proportion of non-dispersing seeds

• selection experiments suggest short term evolution over 5-12 generations

Question 20

2nd example of urban vs rural trait divergence (communication)

Answer 20

• Birds are singing at higher frequencies in urban environments
• Most urban sounds are low freq
• Adaptive however unknown if females will begin to select for higher pitched voices

Question 21

3rd example of urban vs. rural trait divergence in plant reproduction

Answer 21

• Rural pollinator (rich) - herkogamy spatially isolated male anthers and female stigma
• Urban pollinators (few) - no herkogamy , heritability index H2 = 0.62

Evolutionary response in urban populations due to reduced availability of pollinators

*Good example of adaption and reduced success of plants in urban areas

Question 22

What are the effects of bird feeders

Answer 22

• there is mixed evidence that it increases population densities
• May promote aggressive or invasive species (grey squirrel)

Question 23

Affects of domesticated cats on wildlife

Answer 23

• Direct mortality
• probably limits population size
• hard to estimate rates in some locations
• Sub lethal affects of predation
• another secondary affect can be drawing attention to nest sites through the birds mobbing the cat

Question 24

What are the sub-lethal effects of predation

Answer 24

Fear of predators -> reduced provisioning -> smaller clutch size / reduced chick growth rates I.e.

Question 25

Additive and compensatory mortality

Answer 25

Not all predation increases mortality

I.e. if a cat kills a bird that was going to starve anyway it does not matter