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.

Source: Seattle Audubon Society’s BirdWeb

Urban areas have large ecological footprints

• 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

Eco

logi

cal f

ootp

rint

(# e

arth

s) 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)

Becoming MoreUrban

Sprawling From Urban Centers

Wor

ld P

opu

lati

on (

Bil

lion

s)A Tidal Wave of Sprawl is Likely to Come

from Developing Areas(WRI 1996)

Persistenceof

Change

Similarity of Matrix to Natural HabitatHigh Low

Low

High

Agriculture

TimberHarvest

Urbanization

High

Low

Effect ofFragmentation

Contrasting Various Land Covers

(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

Tokyo, Japan .......................................................... 34.450 Mexico City, Mexico ............................................... 18.066 New York-Newark, USA ......................................... 17.846 São Paulo, Brazil .................................................... 17.099 Mumbai (Bombay), India ......................................... 16.086 Calcutta, India ......................................................... 13.058 Shanghai, China ..................................................... 12.887 Buenos Aires, Argentina ......................................... 12.583 Delhi, India .............................................................. 12.441 Los Angeles-Long Beach-Santa Ana, USA ............ 11.814

CITY

POPULATION

(millions)

Regional Comparison

URBAN AREA

Land area within city limitsArea: 6200 km² (2418 sq mi)Population: 14 million

SHANGHAI

Area: 217.4 km² (83.9 sq mi)Population: 570,800

SEATTLE

Area: 1,487 km² (574 sq mi) Population: 9.8 million

MEXICO CITY

Land Cover Classes

URBAN GRADIENT

urban suburban exurban wildland

The Urban Gradient

• Shift inImperviousness (paved)Forest coverExotic speciesBiodiversity

r

rr

r

r

rr

r

r

rr

r

r

r

r

rr

rr

2002 classified landcoverheavy-medium urbanlight urbancleared landgrassmixed forestclearcut forestregenerating forestagriculturenonforested wetlandsopen waterbare rock/snow/iceshoreline999No Data

r telemetry study sites

0 10 20 30 40 Kilometers

urban suburban

exurban-rural

wildland

Seattle

Settlement Affects Native Habitat

• Habitat Loss

• Reduced connection among remaining patches

• Perforation of large patches

• Increased edge & degradation of remaining habitat

• Introduction of non-natives

Settlement has varying effects on wildlife species

• Reduced predation

• Reduced climatic extremes

• Available water

• Supplemental food

• New nest sites

• Increased edge and vegetative diversity

• Increased predation

• Reduction in nest sites

• Reduced food

• New disturbances

• Increased edge and vegetative diversity

Some benefits: Some costs:

Diversity patterns associated w/ urbanization

Blair & Johnson (2008)

Marzluff (2005)

Species richness peaks w/ moderate development then decreases.

Why?

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

Marzluff (2005)

Loss of native specialists (avoiders) and gains in generalist and synanthropic species (adapters and exploiters) explain diversity patterns

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

Clustered subdivision has • smaller lots• higher density of homes• majority of the site left as open space

Gillham 2002

Subdivision Planning

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, fruit-producing exotics

• Retain understory and snags

• Minimize lawn cover

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

Wildlife Conservation in Urban Areas