As a scientist that works in the field of urban evolution I often have to consider, “what makes an urban habitat?” While this seems like a fairly easy question to answer, there’s actually a lot of different ways that we consider urban habitats.
Are neighborhood parks considered urban habitat?
Technically, yes they are urban, they are found right in the middle of the city. But take a close look and this park has different features than the car lot down the street. In fact, urban parks, right in the middle of the park, can look more like the natural habitat than human built structures. So would you consider urban parks as non-urban habitat or urban?
Some of the most common ways to identify an urban habitat is to ask yourself, do people live there?
Yes! Great, but how urban is it?
We’ve got a few ways to measure this like looking at the percent impervious surface, where higher percentages are more urban because they have more concrete and asphalt. We can look at human population density as a measure as well, which starts to get a little dicey when you are looking at metropolitan areas vs single cities. Sometimes we look at canopy cover measures, which are typically lower in the city because we have replaced trees with buildings. This measure is great, but when you live in the desert, you might actually get more trees in the suburbs than non-urban areas because people plant in their yards. There’s so many factors to consider that make urban habitats!
Let us know in the comments what you consider to be urban habitat!
I am interested in urban ecology and evolution. Urbanization can have drastic impacts on local ecosystems, both negative and positive, and creates a new environment for organisms to experience. To understand the impacts that urbanization plays on organisms, I look through the lense of population genetics and molecular evolution.
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Great post – living in the city for the past 37 years and wondering about this for a while now. All the variables detailing urban habitat that you mentioned, such as % of impervious surface, % of tree cover, photosynthetic activity are important dimensions of every city, and will vary from city to city and will be strongly influenced by climate. I would argue that a synthetic index of urbanisation is often useful to compile these different dimensions of urbanisation, while sometimes specific variables are more appropriate. This topic will be covered in the chapter “How to quantify urbanisation when testing for evolution in the city?” , contributing to the book “Urban Evolutionary Biology”, to be published by Oxford University Press in early 2020. Any other thoughts on how to capture urbanisation? Please share!
Thanks for the comment, Marta! I’m excited to read that chapter when the text comes out. I’ve been wondering a lot lately about the best way to create urbanization indices. It seems that a simple PCA of various environmental variables – canopy cover, impervious surface, road intensity or density, housing density, land cover type – might be one approach. I would love to learn more about how people are addressing this problem rather than using simple paired urban to non-urban comparisons!