Urbanization
and Wildlife
Why do we care about urbanization?
• Globally
– Roughly 39-50% of land has been converted to
human uses
– The world’s urban population was 50% in 2000 and
is expected to reach 70% by 2050
– About 17% of land is protected
• In the U.S.
– Urban land increased by 1.1 million acres per year
between 1960-1980
– By 1989, 74% of the population lived in urban areas
• In Central Puget Sound
– The population has increased by 2 million people
since 1960
More and more people are living in urban areas
DeStefano et al (2005)
Location of cities exaggerate impacts:
coasts, river mouths, lakes, fertile inland areas.
Natural resource production is displaced and therefore a larger area of
more intensively used area is needed for wood and agricultural products
Puget Trough Ecoregion (2)
Occupies 8% of the land area of the state, but
contains over 70% of Washington's human
population.
• Amount of land and water area a
human population requires to
produce the resources it consumes
and to absorb its wastes
• A larger, more intensively used area
is needed to support urban areas
• Urban footprints can be highly
dispersed: Chicago’s famous pizza
– cheese from Wisconsin
– flour from Kansas
– oven from Japan
Ecological footprint (# earths)
Urban areas have large
ecological footprints
23% too high
Urban Sprawl
A form of urbanization distinguished by
– Large areas of single-use
development (residential)
• Heavy reliance on automobiles
– Minimal public open space
– Leapfrog patterns
– Commercial strips
– Low density
4% population increase drove
49% increase in developed
land
Urban sprawl in eastern King County
(1974  1998)
A Tidal Wave of Sprawl is Likely to
Come from Developing Areas
(WRI 1996)
Becoming More
Urban
Sprawling From
Urban Centers
Contrasting Various Land Covers
High
Urbanization
Effect of
Agriculture Fragmentation
Persistence
of
Change
Low
Timber
Harvest
High
Low
Similarity of Matrix to Natural Habitat
(Marzluff and Ewing 2001)
Where is Urban?
URBAN IN INDIA
URBAN IN JAPAN
URBAN IN CHINA
URBAN IN PANAMA
URBAN IN CANADA
URBAN IN THE US
URBAN IN BOTSWANA
The World’s Urban Centers
CITY
POPULATION
(millions)
Tokyo, Japan ..........................................................
Mexico City, Mexico ...............................................
New York-Newark, USA .........................................
São Paulo, Brazil ....................................................
Mumbai (Bombay), India .........................................
Calcutta, India .........................................................
Shanghai, China .....................................................
Buenos Aires, Argentina .........................................
Delhi, India ..............................................................
Los Angeles-Long Beach-Santa Ana, USA ............
34.450
18.066
17.846
17.099
16.086
13.058
12.887
12.583
12.441
11.814
Regional Comparison
URBAN AREA
Land area within city limits
SHANGHAI
Area: 6200 km² (2418 sq mi)
Population: 14 million
MEXICO CITY
Area: 1,487 km² (574 sq mi)
Population: 9.8 million
SEATTLE
Area: 217.4 km² (83.9 sq mi)
Population: 570,800
URBAN GRADIENT
Land Cover Classes
The Urban Gradient
urban
suburban exurban
• Shift in
Imperviousness (paved)
Forest cover
Exotic species
Biodiversity
wildland
r
te le m etry s tudy s ite s
r
2002 c las sified lan dco ve r
heav y-m ed iu m u rb an
ligh t u rb an
cleared la nd
grass
m ix ed fo re st
clearc ut fo re st
re gene ra tin g forest
agriculture
nonfo re sted w e tla nds
open w a ter
bare rock /sn ow /ic e
sho re lin e
999
N o D ata
r
r
r
r
r
suburban
urban
r
r
r
exurban-rural
Seattle
r
r
r
r
r
r
r
r
r
0
10
20
r
wildland
30
40 K ilo m eters
Settlement Affects Native Habitat
• Habitat Loss
• Reduced connection
among remaining patches
• Perforation of large
patches
• Increased edge &
degradation of remaining
habitat
• Introduction of nonnatives
Settlement has varying effects on
wildlife species
Some benefits:
• Reduced predation
• Reduced climatic
extremes
• Available water
• Supplemental food
• New nest sites
• Increased edge and
vegetative diversity
Some costs:
• Increased predation
• Reduction in nest sites
• Reduced food
• New disturbances
• Increased edge and
vegetative diversity
Diversity patterns associated w/ urbanization
Species richness peaks
w/ moderate
development then
decreases.
Blair & Johnson (2008)
Why?
Marzluff (2005)
Effects of Urbanization
• Convenient to think of wildlife in
three categories
– urban avoiders
– urban adapters
– urban exploiters
Effects of Urbanization
• Declining and threatened/endangered
species are usually native urban avoiders
suffering from
– habitat loss, fragmentation
– interaction with non-native species (predation
and competition)
Effects of Urbanization
• Urban avoiders in Puget Sound
Settlement Benefits Some
Wildlife
•
•
•
•
•
Reduced predation
Available water
Supplemental food
New nest sites
Increased edge and vegetative diversity
Effects of Urbanization
• Urban adapters can benefit from urbanization if
sufficient native habitat remains
– able to live in small patches and/or
– adapt to altered environment
Effects of Urbanization
• Urban exploiters increase with urbanization and
exploit new & altered environment
– Both native and non-native
– Serve to homogenize species in cities
Loss of native specialists (avoiders) and gains in generalist and
synanthropic species (adapters and exploiters) explain diversity
patterns
Marzluff (2005)
Marzluff & Rodewald (2008)
Other general trends associated w/ urbanization
Blair & Johnson (2008)
Marzluff & Rodewald (2008)
Other general trends associated w/ urbanization
Blair & Johnson (2008)
Some birds found consistently in cities
around the world
Global
homogenization
of some wildlife
communities a
concern.
Wildlife communities change along
the urban to wildland gradient
Loss and fragmentation of original habitat
Shift in vegetative structure and composition of
habitat fragments and the urban matrix
Alteration of population dynamics processes
(reproduction, survivorship, dispersal)
Species losses and gains
Effects of Urbanization
• Other organisms in cities:
– More non-native plants, insects with increased
urbanization
– Greater plant diversity in larger habitat patches
– Small mammal diversity and density decrease with
urbanization
Primary Problems for Urban Wildlife
• Loss of habitat (amount and
•
•
connectivity)
Simplification of habitat (quality,
exotics)
Invasion by exotic species
(competition, disease)
Primary Problems for Urban Wildlife
• Predation by domestic animals (cats,
•
•
dogs)
Predation by wild animals (corvids,
squirrels, rats)
Increase in accidents (cars, windows,
power lines, fences)
Raptors as City Dwellers
Some raptor species can thrive in urban areas
• able to use artificial nest platforms
• find abundant prey
• relatively free from persecution
Suburban v Rural Eastern Screech Owls in Texas:
Nested earlier (urban heat island)
Larger clutches (more food)
More and larger fledglings (food and low predation)
More recruits into population
Higher fitness
Controlling Sprawl
• Sprawl is a strong driver of the urban footprint
– results in loss, fragmentation, and degradation of
habitat
– increases energy use
– increases pollution from commuting
• Growth Management is needed to control it
– Limits most future growth inside Urban Growth
Boundary
– May just displace the problem if regional planning is
not incorporated (leapfrogging)
Growth Management Act - King County Comprehensive
Plan
Subdivision Planning
Clustered subdivision has
• smaller lots
• higher density of homes
• majority of the site left
as open space
Gillham 2002
standard
clustered
Wildlife Conservation in Urban
Areas
1. Preserve large areas of habitat
 the area, numbers, and connectivity of reserves
should be maximized
 buffers should be maintained around reserves
 the amount of edge and degree of fragmentation
within reserves should be minimized
 the scale of reserve planning should be expanded
beyond the local area to include entire watersheds
and bioregions
(Marzluff and Ewing 2001)
Wildlife Conservation in Urban
Areas
2. Enhance habitat locally
• Retain as much natural habitat
as possible (especially new
housing)
• Plant native plants, fruitproducing exotics
• Retain understory and snags
• Minimize lawn cover
Wildlife Conservation in Urban
Areas
3. Provide essential resources:
 Places to breed (nest boxes, platforms,
trees)
 Feeding stations (squirrels, birds)
 Water
 Cover (vegetation)
4. Provide protection from domestic
predators
• control dog and cat behavior
Wildlife Conservation in Urban
Areas
5. Reduce accidental mortality:
• Birds crashing into windows
• 3.5 million birds/yr
• Birds hitting buildings, towers, etc.
• 1.5 million birds/yr
• Avoid planting fruit-bearing plants/trees
next to highways
• Clean bird feeders frequently
(Salmonella)
Wildlife Conservation in Urban
Areas
6. Support urban planning
initiatives and education
• Clustered development
• Growth management
• Open space preservation