Urban Climates (continued from 10/11)

Our class began (and ended) with clarifications from last week's lecture on urban climates and a continued discussion on the urban heat island. Key points included:
-Anthropogenic heat factors are only relevant in urban areas where density of people is high enough to make an impact, people produce ~ 100 - 300 watts depending on activity
-Water sources or vegetation in cities can result in pockets of cool islands
-Tree planting can help make urban heat island smaller, however we have to keep in mind oppotunity cost such as trucks used for planting
-There is an positive exponential relationship between air temperatures and ability to hold water. This factor may perpetuate climate change due to rising temperatures and water vapor being the number one greenhouse gas
-There is a time lag between air temperature and absorbed insolation in regards to radiant energy flow
-Rural areas have cooler nights due to less re-radiation of heat absorbed during the day
-Buildings can create a sort of 'canyon effect' - promoting short wave absorption from reflections and increased surface areas and a decrease in long wave absorption
-HW help - we were encouraged to take the differences in the yearly and seasonal means to help with our homework due 11/1

NCSU class: Our discussion before the Dan Childers presentation focused on the Glaeser/Khan and Seto articles.

There was a general consensus that ‘The Greenness of Cities’ was an admirably thorough effort, but also a difficult read. The authors were very careful in their attention to detail, explaining each decision as to carbon calculations and assumptions. While the charts and tables listing performance by city were an interesting comparison, the class was left wondering as to the applicability of the effort.

The social context seemed to be missing. At several points in the paper, the authors referenced ‘appropriate’ decisions, recommended tax levels, preferred regions to live in, or best-performing home ages. While some people may be able to consider energy usage when deciding where to live, it is far more likely that they need to prioritize economic or family responsibilities. White the analysis can lead us to understand WHERE energy policy change is most needed, leaving out the social framework (or at least some context) does not help us determine WHAT that change may be.

The ‘Global Forecasts of Urban Expansion’ also led to an interesting conservation on applicability. Some in the class with experience working in South Africa questioned the forecast conclusions presented in the paper. Aside from the questions of forecast validity, the class also discussed the use of these global projections. Is environmental work productive on this global scale?

Speaker: Dr. Dan Childers, Global Institute of Sustainability at ASU

Dr. Childers is a professor of sustainability whose research focuses on urban wetland ecosystems and sustainability sciences. He began his speech with his idea of the 3 spheres of sustainability:
1. Environment
2. Society
3. Economy
He elaborated on how he believes the factors are nested within one another going down the list (environment being the largest, economy the smallest). He disagrees with a similar view that these are independent ideas that partially overlap like in a Venn Diagram. By utilizing the nested web approach, systems can be more appropriately studied to address sustainability. He argues that all aspects of society and the economy are impacted by the environment, so if one was to view them as independent entities it would be ignoring environmental impacts.

Dr. Childers then went on to discuss his wetland study on the effectiveness of urban wetlands in ecosystems services, in particular surface water filtration. The primary goal of the research was to see if evapotranspiration from plants in the wetland was so strong that it was resulting in evapoconcentration of nitrogen and other substances in the water. The results showed that while evapotranspiration was high, the wetlands were still extremely successful in water filtration. While the evapotranspiration appears large on the small scale, on a whole-systems scale it actually has little impact. The evapotranspiration is, on the other hand, creating a sort of 'biological tide' of water being pulled towards the shore during high periods of high uptake by the plants. Dr. Childers finished with briefly explaining his approach in building partnerships to help research turn into policy. He believes good sustainability starts with having a basic knowledge in the environment, society, AND the economy. By focusing too much on one aspect, your views are narrowed and the overall goals of sustainability can be lost.

Expanding on Dr. Childers' emphasis on partnerships, the end of his presentation had some key priorities to remember for staying relevant in future work:
  • partnership goals: legitimacy, credibility, knowledge base about system function comes first, built trust with partner agency, efficiently package information.
  • partnership approach: identify key managers, ask key players questions to stay relevant, organize charrettes, clearly address challenges.


Dr. Childers' findings on the 'biological tide' in the Tres Rios constructed wetland are encouraging. It's incredible that this ecosystem was not present a few years ago, but now the wetland is able to provide effective water filtration. I look forward to hearing further results from this study!

A question following the talk from Dr. Childers: how does the high nitrogen levels in the inflow water affect ecosystem functioning in the open water? More specifically, does the high nitrogen and high amounts of sunlight lead to seasonal blooms of phytoplanktonic algal species or dense mats of larger plants in the open water? (Please let me know if Dr. Childers covered this in his talk and I missed it!). There have been issues with high nutrient levels and resulting algal blooms in Narragansett Bay in Rhode Island. The summer of 2003 had high rainfall, and runoff carried nutrients from human and animal waste into the bay. Warm temperatures and sunlight, combined with the high nutrient levels, led to large phytoplankton blooms. When the phytoplankton died, they sank to the bottom and were decomposed by microbes. This process depleted oxygen near the bay floor. Though winds can sometime mix water layers and restore oxygen levels, this did not happen in August 2003. Dissolved oxygen levels dropped at the deeper water layers, and fish, crabs, shrimps, and eels had no air to breathe and began dying. This was a historic "fish kill" for Narragansett Bay - an estimated 1 million fish were killed by the lack of oxygen.

Does anyone know if such phytoplankton blooms could occur in a constructed wetland such as the Tres Rios ecosystem? While high growth of algae may lead to additional N-uptake by plants, it could lead to low dissolved oxygen and negative consequences for other aquatic species. Though, in this system, perhaps the in- and outflow of the water creates enough movement to mix water layers and prevent dramatic drops in dissolved oxygen levels. I am no expert on wetlands, so please let me know if anyone has some insight on this.

I really enjoyed the Glaeser and Kahn reading this week. Before taking this class and looking into studies like this one in which researchers must scavenge for indirect data sources to estimate carbon emissions, I never appreciated the complexity of producing such estimates. I assumed some governmental agency actively and directly monitored these carbon emission values. It was particularly exciting to see the Glaeser and Kahn data presented in full within the text because it allowed me to more closely look at information regarding cities of special interest to me. I did not feel like there was a full exploration or defense of the arbitrary choice of using a $43/ton social cost, so I was mainly interested in seeing the actual carbon emissions data in Table 2. Unfortunately, the table does not provide a total annual standardized household CO2 emission value for each city, but that can essentially be found by summing the first three columns and the product of the fourth and fifth columns in Table 2. As mentioned in the text, home heating accounts for a large proportion of CO2 emissions in New England. Yet, even if we omit home heating emissions, the West Coast still has slightly lower emissions than New England. For example, San Diego’s total combination of CO2 emissions from driving, public transportation, and electricity but not home heating is 32,693 lbs/year, while Boston’s total without home heating is 34,531 lbs/year. I found this surprising because I thought heavy driving on the west coast would reorder the list when home heating was removed. I guess what I’m saying is, I was bitterly looking for ways to slice the data where the West Coast would lose to Boston, but San Diego kept topping the list. Finally, the last take-home number that I think of as a useful figure to keep in mind when driving or filling the gas task is the estimate of 23.46 lbs CO2 emissions per gallon of gas discussed in the methods.

Sravya- Just a few quick thoughts: I was thinking about the Professor Hutyra's questions regarding the effects of pharmaceuticals being dispersed into the environment and I thought I would share a relevant reading from my behavioral biology class. The paper is about physchotherapeuttic drugs in natural waters and fish behavior. In a nutshell, scientists screened Swedish surface water and analyzed drug concentrations. It found that the concentration of the drug, in this case, oxazepam, was about 6 times higher in the fish due to bioaccumulation. The researchers went on to discover that fish exposed to dilute concentration of psychotherapeutic drugs exhibited altered behavior including increased activity, reduced gregariousness, and an alarmingly high feeding rates. Needless to say, this can have an array of ecological consequences, especially because the concentration of these substances are projected to increase.

On another note, here is the link to London's Walkie Talkie tower/car melting video.

Dan's work with the City of Phoenix is a very interesting case of a human created ecosystem to provide services (cleaning nutrients/pollutants). Unintended consequences abound, but most of it is arguably "good" being that it is literally a desert oasis with rich avian and aquatic species biodiversity. I am curious how the City came to the decision to install the engineered wetland and what other possible solutions they explored. I am studying a policy framework in another class, so understanding the process that led to that conclusion interests me.
I liked the article selection offering several different viewpoints on urban sustainability. Each in its way had a "call to action" on a policy level, which to me is somewhat unusual in the papers I tend to read. I liked the calls to action because it showed a usefulness for the research. I was disappointed that we did not talk about the article on SITES though Dan's work is a great example of green infrastructure. I think the authors preferred the term 'functional ecological infrastructure' better, but I don't see that one catching on. Whatever you call it, it is a necessary component to urban infrastructure and one thing I will enjoy learning more about.
Mary - I have about the same understanding that you do, so I would appreciate it, if anyone could explain a little further.

To sort of build off Mary, I would like to know a little more pertaining to the types of species they used in the created ecosystem to provide these services and how they monitored and maintained them. It would be interesting to see or know if the introduction of invasive species could possibly effect the services and how negative of an effect invasive species could have to these ecosystems.

I thought Dan Childers’ presentation on Phoenix’s urban wetland was thought provoking and an interesting way to take a potential hazard to the environment and turn it into something good. Phoenix, AZ is an interesting case because of its sources of available water. The local climate has very warm annual temperatures and very little annual precipitation that falls mostly during a short “monsoon” season in late summer to early fall. I believe I remember hearing somewhere that most of the water that is brought in to the city comes from exotic rivers diverted from the Colorado and Gila Rivers. There is a large (and growing) population of people in Phoenix and its suburbs and people need water for biological needs. I’m sure a good amount of the incoming water is diverted to things like golf courses, lawns, swimming pools, etc.

I began thinking about the local hydrologic cycle, outgoing water and the creation urban wetland. The presentation focused on many of the good things that this wetland can bring to the issues of nutrient cycling and sewage treatment. I was curious if this is at all a bad thing for the local environment.

First, does this huge flux of water into a dry, arid climate have any effect? In terms of the atmosphere, this would increase evaporation and potential alter the precipitation patterns. The higher temperatures would allow for more water vapor to be held in the air. This could lead to more precipitation? Would all this additional water affect soil/geology?

Second, engineers have converted a portion (albeit a small portion) of the SonoranDesert into a lush wetland. I would think the desert provides some ecosystem service(s). My question is would this wetland diminish those services? I would also think that an issue with overpopulation might occur in the future. The wetland may attract animals that can only live in this wetland environment. If the biodiversity increases, it would be difficult to accommodate all these species. There really isn’t anywhere else for the animals to go in the local area since it is all desert surrounding the wetland.

Lastly, did the engineers actually create a river from the treatment plant to a local waterway? I was under the impression that wetlands develop within existing ecosystems (lacustrine in lakes/ponds, riverine in rivers, etc.).