Sarah Lambson
Introduction
It is well known by conservationists that urbanization is a major cause of decreasing biodiversity
in the world today. More and more land is developed over and used for agriculture, new homes,
businesses, etc. While the growth of human population and the continuing need for this
development cannot be ignored, the need to preserve the natural world must also be prioritized.
As stewards of this planet, the human race must take responsibility for the changes being
wrought on the earth and attempt to work in harmony with our natural counterparts. What
habitat fragments that exist in urban areas are becoming more and more important for wildlife.
Urban greenspaces such as parks, trails, and cemeteries offer wildlife small “islands” of habitat
where they can safely nest and reside amongst foreign and unlivable cities.
Urbanization
Urbanization is simply the conversion of any area into a more urban landscape. With regards to
natural resources this usually means the conversion of natural habitat into urban development
(Vallejo, 2009). This destroys habitat for many species, but also modifies habitat for species and
in some cases can create new useable habitat. So while urbanization is often seen as a negative
occurrence, it is unavoidable and can be managed in such a way that it can have some positive
effects (Adams, 2005). In a world that continues to grow in population, there is a constant need
for urban development. There is also a need to maintain a sustainable developmental lifestyle. It
is important to take into account ecological processes in developing new areas. Urban planners
and urban ecologists should work together in an attempt to meet the goals of both parties
(Marzluff, 2005).
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Decreasing Diversity
The decrease in wildlife diversity is the driving factor behind most urban wildlife studies. All
literature on the subject shows that as habitat decreases due to urbanization and fragmentation,
wildlife diversity also decreases. Though in many cases, this fragmentation can increase species
density. Diversity is an important measurement when considering the impact of fragmentation
and urbanization. There are several different measurements of diversity and many ways of
obtaining the data needed. In this case, Simpson’s index of diversity is used (Krebs, 1989).
Most literature in which bird counts were conducted used some form of line transect walk
whether it be random or systematically selected. Few used a point method. Due to the favoring
of the line transect method (Sutherland, 2006); this is the method that is used in this study.
Intermediate disturbance theory suggests that rather than have very high or very low disturbance,
having an intermediate level of disturbance creates greater diversity (Marzluff, 2005). There are
some species that favor very high disturbance levels and some that favor very low disturbance
levels. Finding a happy medium between the two could increase diversity, especially in urban
cases.
How about adding examples of high disturbance and low disturbance.
Habitat in Urban Settings
The dividing of land into developed spaces with spotty natural habitat is known as
fragmentation. While it is normally frowned upon, in most urban cases it can now no longer be
avoided. Why? The spaces where habitat can be found are considered urban greenspaces. These
include parks, trails, and cemeteries. Most, if not all literature on the subject agrees that diversity
of species found in these greenspaces is highly dependent on the size of the greenspace
(Jokimaki, 1999). This correlates with the idea of Island Biogeography, which in simple terms
states that as the size of an “island” of habitat decreases so does the diversity and as the distance
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that island is from a large “landmass” of habitat increases, the diversity decreases (MacArthur &
Wilson, 1967 in Jokimaki, 1999). Plant type also greatly affects the kind of species and the
diversity of species found in these patches of habitat. A diverse matrix of plants can greatly
increase the number of species found in an area (Azerrad, 1999). Along with this, edge effects
should also be taken unto account. Edge is the boarder between two habitat types and while
many species suffer from increased predation near edge habitat, there are some species, which
thrive in these places (Jokimaki, 1999). Many papers on urban wildlife are centered around the
idea that urban planners should take into account all of the things previous in order to create a
more wildlife friendly urban environment (Vallejo, 2009). Studies like this have important
information for these planners as well as landowners looking to enrich their property.
Cemeteries
As an urban greenspace, cemeteries can provide essential habitat to urban wildlife. Along with
other greenspaces they are considered “Islands” within urban settings where wildlife can find
refuge (Lussenhop, 1977). This is especially true for bird species. In some cases, it is suggested
that cemeteries could be locations for outdoor recreation (Thomas, 1973 in Noyes, 1974). There
are obvious social disagreements with this idea but that does not mean that cemeteries cannot
play a vital role in connecting the public with the natural world. High levels of human
disturbance tend to decrease diversity and nesting in an area. Flushing distance, which is the
distance at which a bird will fly away from an invader, increases as the disturbance levels in an
area decresase (Fernandez-Juricic, 2001). Cemeteries are not heavily visited my large numbers
of people often which is one major difference between them and other greenspaces. This
increases their appeal to many species especially since reserved levels of disturbance can
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sometimes increase nestedness in bird populations (nestedness being a measure of community
structure) (Fernendez-Juricic, 2002).
Conclusion
Most of the papers cited agree on the fact that urbanization generally decreases diversity in
wildlife species unless utilized properly. Articles by Fernandez-Juricic, Jokimaki, and Marzluff
seem to span many of the topics being explored and provide vital information to this study.
Other papers are also useful and support the information provided by these three authors.
Information in this study can add to the information already present and help urban planners and
urban ecologists in their attempts to create a more nature friendly and sustainable urban
environment in the world’s cities.
Works Cited
Azerrad, Jeremy M. Avain community characteristics of urban greenspaces n St. Louis
Missouri. Thesis. 1999. 59p.
Fernandez-Juricic, Esteban and Jukka Jokimaki. A habitat island approach to conserving birds
in urban landscapes: case studies from southern and northern Europe. Biodiversity and
Conservation. 2001. 21p.
Fernandez-Juricic, Esteban. Can human disturbance promote nestedness? A case study with
breeding birds in urban habitat fragments. Oecologia. 2002. 9p.
Jokimaki, Jukka. Occurrence of breeding bird species in urban parks: Effects of park structure
and broad-scale variables. Urban Ecosystem. 1999. 13p.
Krebs, Charles J. Ecological Methodology. New York. Harper & Row Publishers, 1989. Print.
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Lowell, Adams W. Urban wildlife ecology and conservation: A brief history of the dicipline.
Urban Ecosystems. 2005. 18p.
Lussenhop, John. Urban Cemeteries as Bird Refuges. The Condor. 1977. 6p.
Marzluff, John M. Island biogeography for an urbanizing world: How extinction and
colonization my determine biological diversity in human-dominated landscapes. Urban
Ecosystems. 2005. 21p.
Noyes, John H and Donald R. Progulske. A Symposium on wildlife in an urbanizing
environment. Massachusetts. Amherst, 1974. Print
Sutherland, William J. Ecological Census Techniques. 2nd Edition. New York. Cambridge
University Press, 2006. Print.
Vallejo, Benjamin M; Aloy, Alexander B; Ong, Perry S. The distribution, abundance and
diversity of birds in Manila’s last greenspaces. Landscape and Urban Planning. 2009. 10p.
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