Our discussion began with the Collins et al. 2012 manuscript. We contemplated the role Vitousek's work has played in establishing the importance of human dominated ecosystems to global ecological functioning. Students then evaluated the PPD diagram (Figure 1 from Collins et al. 2012), valuing the interdisciplinary connections. Pulse and press events were a focus of our conversation: What is the difference between the two? In some instances there may not be a clear boundary between the two types of events, and it seems that it might be useful to consider a potential gradient of environmental phenomenon. Nonetheless, everyone agreed acute incidents with extreme impacts that can be defined in space and time are pulse events. Although these events may be important in linking social and ecological systems it was not obvious why this framework was named PPD, instead of highlighting the role of ecosystem services in connecting coupled human and natural systems. We suspect that pulse and press events was a new addition to the socio-ecological concept and that defining this particular framework as an ecosystems services conceptualization would be controversial to some economists and ecologists.


We then attempted to fit our own research questions into the PPD framework - Attached below are the individual frameworks, including short summaries of the lesson learned during this exercise.

Kelly Suttles: I chose this to explain the human behavior of loving a wild place so much that they have to go move there, thereby forever changing the place. I found this exercise challenging/interesting because by the time I got to the biophysical template I was showing the effects. I'm sure it works the other way when you begin on the other side.

Scott Beck: Sorry! My scanner wouldn't work -- this is the best I could do until I get the issue resolved. Hypothesis: Grass cover contributes to water quality decline in urban systems. I placed this in the social template under Human Behavior because grass cover doesn't occur naturally in urban areas in the Triangle -- it is placed there by people for aesthetic purposes (Ecology of Prestige?). I'm sure it could also go in the biophysical box because it involves land cover, specifically modified land cover, which contributes to the heterogeneity of cities and subsequently alters ecosystem processes/function (Alberti 2005; Cadenasso et al. 2007). When approached from a social perspective, I believe the primary external drivers are both natural & geopolitical -- where pulses are rain events & governance structures (who is in charge every 2 or 4 years?), and presses are cultural identity, economics, & the climate system of a given region. I learned that you can approach this model from a variety of angles, and that I still don't quite get it right no matter what angle I take. Don't like how the feedback loops are one directional.

Rene Valdez: For this assignment I chose to test the hypothesis that the removal of an invasive rodent from an island ecosystem would improve the health of that ecosystem. This action would clearly be a human behavior and would reflect human values of biodiversity which underpin conservation biology and restoration ecology. The original cause of many invasive species on islands has been globalization, the ability to remove invasive species can be linked with technological advances. The ensuing press would be the loss of pressure on the ecosystem from an invasive species. As a result I would expect an increase or stabilization of diversity and density of species in the community. The ecosystem processes would then more closely resemble historical processes. When writing in ecosystem services I focused too heavily on services for people and not enough on the actions that would benefit the ecosystem itself, which would likely include stability and improvements of nutrient retention and cycling.

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Eric Thompson: My hypothesis is that children who experience wildlife-related recreation (e.g. fishing) will place higher value on wildlife as adults, thereby increasing their political and economic support for wildlife habitats. This hypothesis exists at the site of H5 in the model, which is that "changes in human outcomes, such as quality of life or perceptions, affect human behavior." In this case, the behavior is conservation and restoration-based actions, which create the presses and pulses that increase the quality of the biophysical template. In turn, the quantity and quality of wildlife-related recreation experiences are increased for the next generation of children.

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Julia : My hypothesis was that Sprawl Development is primarily motivated by economic factors (i.e. not because the sprawl environment is itself considered desirable). I worked through the chart starting with Human Behavior and ending with Human Outcome. I thought this was appropriate since this development pattern is so people-focused. I forgot all my arrows, but they should be the same as the original diagram.

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Janet Felts: My hypothesis is that migration to urban areas ultimately decreases migration away from urban areas. I chose this topic because migration is a key part of globalization today and is an increasing global phenomenon which we must address in order to maintain the sustainability of urban areas. Due to increased globalization and opportunity to migrate, migration into urban areas is increasing around the world. Long-term disturbances to land use and increased resource consumption as well as short-term drought and pollution interact to alter ecosystem structure and function. Ecosystem services ensure that resources are regulated to maintain the health and well-being of the people living in these urban areas. In turn, people will feel happier and remain in the urban areas.