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How have human activities transformed the phosphorus cycle? Active Listening Questions: • What does Dr. Crews point to as the fundamental driver of change to the phosphorus cycle in the last century? W H A T: In this clip from the public 2009 presentation “Agriculture After Norman Borlaug, ” Dr. Crews describes how the rise of fossil fuels has enabled large scale extraction of concentrated reserves of phosphorus through mining. This has enabled farmers, primarily in industrialized countries, to apply increasing amounts of phosphorus to soil, far beyond what was possible in the past with techniques of phosphorus concentration. The result of this phenomenon is a major transformation of the global phosphorus cycle. “Fossil fuels] allowed us as a
H O W : Dr. Crew's draws his conclusions from species to discover and exploit
existing studies and reports produced by reliable highly concentrated reserves
sources, such as the scientific report from Cordell et of Phosphorus and other
al1, which shows an increase in the use of phosphate elements -- and in many cases
rock based fertilizers. just use them once."
1Cordell, D., et al., "The story of phosphorus: Global food security and food for thought." Global Environ. Change (2009), doi:10.1016/j.gloenvcha.2008.10.009 W H Y: The tremendous increase in fossil fuel consumption is a trend that has been well documented by industry data. One example is the accompanying rendering based on data compiled by Vaclav Smil (Smil, 20101). Similar data is available on the use of mined phosphate rock based on data compiled by academics and organizations over the last 40 years (Cordell, 20082). 1
Smil, Vaclav. Energy Transitions: History, Requirements, Prospects. Santa Barbara: 2010, Praeger. Cordell, D., et al., "The story of phosphorus: Global food security and food for thought." Global Environ. Change
(2009), doi:10.1016/j.gloenvcha.2008.10.009
2
SO W H A T: Dr. Crews’ research highlights some of the profound ways in which fossil fuels have
transformed systems in society and nature in profound ways. The transformation of the global phosphorus
cycle is just one example. As another example, fossil fuels have enabled the industrial-scale production of
nitrogen as fertilizer. While enormous societal benefits have resulted from these transformations, a range
of challenges have also arisen. For example, increased runoff of nitrogen and phosphorus into freshwater
ecosystems and oceans causes a rapid rate of eutrophication.
BIO: Tim Crews is the Director of Research and Research Ecologist at The Land Institute. His research focuses on how prairie ecosystems maintain soil fertility and how these insights can be applied to minimize the need for fertilizer inputs. horsesmouth.agci.org
How have human activities transformed the phosphorus cycle? TA KIN G TH E REIN S D iscussion Q uestions:
Discuss with a friend or record your thoughts in a journal.
• How have human changes to the phosphorus cycle impacted human lives and the ecosystems in which we live?
• What are some of the benefits of these changes to the phosphorus cycle, and what are some of the downsides? Q uiz Q uestions:
Quiz 1. How has the discovery of fossil fuels changed the way humans acquire phosphorus for agriculture? a) Fossil fuels enable efficient manufacturing of phosphorus in factories. b) Fossil fuels are rich in phosphorus and can be applied to croplands to enrich the soil. c) Fossil fuels power equipment to mine and distribute phosphorus reserves found in rocks and minerals nature. d) Fossil fuels enable the extraction and distribution of diluted phosphorus found in oceans and rivers. Quiz 2. Which statement is most accurate in regard to the role of fossil fuels in human history: a) Fossil fuels have always been heavily exploited, but a significant increase in use is identifiable in recent years. b) Almost all of the fossil fuels consumed in human history have been burned over the last 70 years. c) Fossil fuel use has declined over the last 70 years. d) There has been no significant trend in fossil fuel use in the past century. Glossary Term: Reserve
Quiz 3. What was one of the primary limitations to the amount of phosphorus available to pre-­‐industrial agriculture? a) ability to locate and identify phosphorus b) quantity of available labor c) dilution of phosphorus over large bodies of
land and water d) rates of geologic weathering When discussing cycles and systems in science, a reserve is an untapped source of the item in question, here, phosphorus. For example, areas of land rich in phosphorus are reserves, and they are utilized through mining and extraction of this desirable resource. horsesmouth.agci.org
How have human activities transformed the phosphorus cycle? G o Beyond: Thinking in Systems, Part 3 Transformational Changes in a System Recall the simple system you developed in Part 1 and augmented in Part 2 of “Thinking in Systems.” The example system in this activity is a city bike share system. In this exercise, you will be asked to consider how transformational changes may alter your system -­‐-­‐ in either positive or negative ways. Instructions: 1. Think about conditions that would lead to a transformation of your system—what could cause a sudden and enormous change in the quantity of inputs/outputs or the speed of processes within the system? Make a list of possible drivers of transformational change as well as possible positive and negative consequences of that change. 2. Select one of the transformational changes you identified and alter your system map to characterize the changes to your system. 3. Evaluate your transformed system to determine whether it still behaves in a manner consistent with the original goals of your system. Also evaluate the extent to which transformations in the system carry external consequences that positively/negatively affect other systems. 4. What might be some transformation changes that occur in the system of phosphorus cycling? Examples: • New city policy limits vehicle traffic thus pushing a significantly larger share of the population towards riding bikes. Consequences: o For a period, demand overwhelms supply of shared bicycles o More diverse routes are added to the system which enable easier rebalancing between redocking systems • Bikes are retrofitted with small motors, which increase the speed of trips and enable longer routes Consequences: o A entire new set of individuals begin to bike, leading to a dramatic increase in demand for bikes o Longer routes lead to a much larger demand for distribution of docking stations o Shared motorized bicycles begin to replace cars on roadways horsesmouth.agci.org
How have human activities transformed the phosphorus cycle? A ssociated G raphs
Graph 1 Graph 2
Further Reading: Graph 1: Cordell, D., et al., The story of phosphorus: Global food security and food for thought. Global Environmental Change. (2009), doi:10.1016/j.gloenvcha.2008.10.009 Graph 2: Smil, Vaclav. Energy Transitions: History, Requirements, Prospects. Santa Barbara, (2010), Praeger. Crews, Timothy E., Kanehiro Kitayama, James H. Fownes, Ralph H. Riley, Darell A. Herbert, Dieter Muller-­‐Dombois, and Peter Vitousek. 1995. “Changes in Soil Phosphorus Fractions and Ecosystem Dynamics across a Long Chronosequence in Hawaii,” Ecology, Vol.76, No. 5 (July, 1995). Ecological Society of America, pp 1407-­‐1424. http://www.jstor.org/stable/1938144