US cityscapes show consistent patterns of 'urban evolution'

September 10, 2014, University of Maryland
Eroding stream banks and aging sewer lines contribute to evolving water pollution problems in cities. In this photo from Baltimore, Maryland, a sewage pipe that was originally placed in a stream bed developed leaks, and is now surrounded by a concrete casing. Credit: Tamara Newcomer Johnson, University of Maryland

Most people think of city landscapes as simpler, diminished versions of the wild forests and free-flowing streams found in remote places. But in a series of studies published Sept. 10, 2014 in a special issue of the journal Biogeochemistry, scientists specializing in urban ecosystems say just the opposite is true. Urban landscapes are more complex than they seem, and from coast to coast these ecosystems can work in surprisingly similar ways, regardless of local conditions. And they have the potential to change quickly – for better or worse – depending on how people manage them.

In 14 studies, scientists from across the U.S. examined the impacts of human actions on the geology, chemistry and biology of . The studies were carried out in a broad range of climates from Boston and Baltimore to San Juan, Puerto Rico;Tucson, Arizona; and Southern California, including sites in the National Science Foundation's Long Term Ecological Research (LTER) network. Results were published in a special issue of Biogeochemistry exclusively devoted to urban ecosystems, edited by University of Maryland geologist Sujay Kaushal and University of New Hampshire ecologists William McDowell and Wilfred Wollheim.

"Urban ecosystems change relatively quickly in response to human activities," says Kaushal. "These changes can result in rapid losses of ecosystem functions, like flood protection and pollution filtration, or they can result in progress toward ecological health and productivity. The difference depends in large part on how they are managed."

In an overview article, Kaushal, McDowell and Wollheim point out some key factors that affect the evolution of urban ecosystems. For example, the streams, lakes and land surfaces that make up cities' watersheds show consistent patterns of change over time:

  • They are becoming saltier, partly due to road salt used for de-icing, and partly because the salt that people eat ends up in . Excess salt in the human diet is excreted in human waste, and captured by sewer systems. Crumbling sewage pipes leak this chloride-laden waste into groundwater, where it eventually mingles with surface water, say the authors of the overview paper. The researchers propose that one way to track the spread of urbanization is by looking at the chloride content of cities' freshwater rivers and streams.
  • They carry the chemical signature of dissolving concrete, a major building material in urban areas since the mid-20th century. Most concrete contains cement made of powdered limestone, which weathers easily when exposed to acid rain or chemicals. The authors say many cities now have their own human-made geology: concrete surfaces that mimic a type of limestone called karst. This "urban karst" is constantly breaking down into its constituent elements, including calcium and carbonate minerals, which flow into urban streams and affect their pH content, and therefore their ability to sustain aquatic life.
  • Urban ecosystems develop "hot spots," like road crossings where automobile exhaust, litter, de-icing salt and other human-made substances can sharply alter downstream water quality. They also experience "hot moments," such as heavy rainstorms that wash large pulses of organic matter and manufactured chemicals into streams, or cause sewage overflows. These hot moments can suddenly change water chemistry in ways that shock natural systems.
  • The networks that supply cities with water evolve and expand over time, including not just surface waters, but also storm drains, leaking water and sewer pipes, roofs and gutters, groundwater, and waste water that humans bring into the area from other watersheds. The boundaries between nearby cities' watersheds are blurring, making it hard to define, study and manage them.

This stream restoration project in Baltimore, Maryland is in an early stage of evolution towards sustainability. A concrete channel that enclosed the stream has been removed, and native tree seedlings have been planted along its banks. Credit: Tamara Newcomer Johnson, University of Maryland
"There is a lot of good urban restoration work underway," says McDowell, "but often it only has a short-term effect, because urban watersheds follow their own evolutionary paths. For example, utility managers may build a stormwater retention pond to capture polluted runoff, such as excess nitrogen from urban runoff. And it may work very well for a few years. But then it fills in with sediment, and becomes a wetland, and it's no longer working the way the engineers designed it to work."

"We hope scientists, managers and citizens will work together to make decisions that allow for what we call 'urban evolution,' – that is, changes in the ecology of cities over time, " says Kaushal. "If we do that, we can find effective ways to understand and manage the trajectory of urban ecosystems, from decline towards sustainability."

In this stream restoration project in Baltimore County, Maryland, a suburban stream and its floodplain have been reconnected to help control erosion and protect nearby bridges and sewer lines from floods. Credit: Paul Mayer, US EPA
"This synthesis brings the power of evolutionary biology to understanding ecosystem processes in urban environments, some of the most rapidly changing habitats globally," says Saran Twombly, NSF's LTER program director. "Merging evolutionary biology with ecosystem sciences is an exciting frontier for long-term ecological research, beginning with this issue on biogeochemical cycles."

Explore further: Study suggests expanded concept of 'urban watershed'

More information: Copies of all 14 papers in the special issue on urban biogeochemical cycles will be available free of charge for 30 days, beginning September 10, 2014, at the Biogeochemistry website:

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1 / 5 (3) Sep 10, 2014
Let's not dumb-down ecological adaptations by comparing them to evolution.

Nutrient-dependent amino acid substitutions differentiate the cell types of all cells in all individuals of all species. The substitutions link the biophysically-constrained chemistry and molecular biology of urban ecosystems from quantum physics to quantum biology via RNA-mediated events. For comparison to those RNA-mediated events, no evolutionary events have been described in terms of biologically-based cause and effect.

Those who accept use of the term "urban evolution" may not realize that the availability of nutrients determines the pheromone-controlled physiology of reproduction of all species. The species manifest differences in chemical ecology in their morphological and behavioral phenotypes.

Population geneticists who tout the pseudoscientific nonsense of mutations and natural selection have never described an evolutionary event that can be linked to biodiversity in species from microbes to man.
5 / 5 (3) Sep 10, 2014
JVK is obviously using that bays-inference word generator I also used to create advertisement fillers back in 1999. About 30 lines of python code. He employs enough techno jargon to sound as if something meaningful is being said, while it is just meaningless bullshiyte strung together by word frequency probabilities using Markov chains. Obviously an xtian script kiddie
1 / 5 (2) Sep 10, 2014
Nutrient-dependent/pheromone-controlled adaptive evolution: a model

Approximately 100 cited references like my other published works.
5 / 5 (2) Sep 11, 2014
Cited by 100 other xtian script kiddies without a university degree, doubtless. Otherwise known as a circle-jerk or echo chamber. Add a senile septuagenarian scientist for sport
5 / 5 (1) Sep 15, 2014
Nah, JVK cites 100 people but nobody cites back, check his link. No biologist ever cites him and for good reason - James V Kohl is a charlatan.
1 / 5 (1) Sep 15, 2014

Human pheromones: integrating neuroendocrinology and ethology
JV Kohl, M Atzmueller, B Fink… - Neuroendocrinology …, 2001 -
The effect of sensory input on hormones is essential to any explanation of mammalian
behavior, including aspects of physical attraction. The chemical signals we send have direct
and developmental effects on hormone levels in other people. Since we don't know either ...
Cited by 80

From fertilization to adult sexual behavior
M Diamond, T Binstock, JV Kohl - Hormones and Behavior, 1996 - Elsevier
Research has established the broad mammalian developmental plan that genes on the sex
chromosomes influence gonad development which determines gonadal hormone
production (or its absence) leading to modification of the genitalia and simultaneously ...
Cited by 31
5 / 5 (1) Sep 15, 2014
Not cited in 13 years huh.

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