An Example of an ESS Analysis - 1986 Yellowstone FiresBasic ESS Analysis Typical Student ESS Response
After looking at the interactions that occurred between and among the event and spheres, you will now focus on looking at how to write ESS analyses that explore the “why” and the “how” of the science behind the various interactions that occur.
Check out the examples below. Pay attention to the various ways that you can post your interactions. These examples represent a few of the many interactions that could have been discovered during an ESS analysis of the Yellowstone forest fires event. Review the Yellowstone ESS analysis interactions you found in terms of this example. How do your interactions compare to those below? Are some of yours the same? Are they different? Look at how the examples below include more detail and explanation than the ones in the “An Introduction to an ESS Analysis” reading and think about how you could now revise your ESS analysis so that your explanations go deeper into the science behind the interactions.
The examples below address sphere to event and event to sphere interactions. When doing ESS analyses in the future, you can include your event to sphere and sphere to event interactions under one heading called “Event <--> Sphere Interactions.”
Event and Atmosphere
E > A
The forest fires could cause acid rain. As with industrial pollution, CO2 from the fire would combine with the moisture in the atmosphere to form carbonic acid, or H2CO3.
E > A
Intense fires create their own upward air movement. Forest fires make "updrafts" of air like the warmth you can feel if you hold your hand about 12 inches above a candle flame.
A > E
I heard that lightning is a common cause of forest fires. This makes sense to me because the high temperature of a lightning bolt combined with the dry biomass often found in Yellowstone is a recipe for a forest fire.
Event and Hydrosphere
E > H
Burning pine needles, wood, and other plant material can produce an ash that may come down in nearby streams and change (either up or down) the pH of water.
H > E
Precipitation can naturally extinguish wildland fires. On September 11, 1988, two inches of wet snow covered a large portion of Yellowstone National Park. The snow put out some of the flames and prevented the fire from spreading. http://www.nps.gov/yell/naturescience/wildlandfire.htm
Event and Biosphere
E > B
Removal of leaf litter and other debris, as well as plant competitors such as non-natives, makes it easier for native plants and pioneer plants (fireweed, lodgepole pine, etc.) to germinate.
E > B
Forest fires are sometimes needed in the life cycle of some living things. For example, some pinecones, like the lodgepole pinecones, need the heat of a fire to open them and release their seeds.
E > B
Animals that couldn't flee the flames were killed. Even those who could flee had trouble surviving after the fire because their habitat was severely altered.
B > E
Future fires will be less likely to occur after all the fuel (biomass) in an area has been combusted. For instance, when the plant litter on the ground is burned off, there is no more fuel for a new fire. And we know that a fire needs fuel. This makes sense to me because I read that leaf litter and other "burnables," which had collected on the Yellowstone forest floor since the previous fire 75 years ago, provided the fuel for the 1988 fire.
Event and Lithosphere
E > L
Intense heat from the fires may have caused some rocks to break apart as I have seen happen in campfires.
E > L
Heat from the fires can affect the topsoil. As an illustration, the fires baked out a lot of the living, nutrient-rich organic matter, called humus.
In the future, as you list event > sphere, sphere > event, and sphere > sphere interactions, it is important that you be able to explain why or how the interactions occur. For example, the E > A interaction above doesn’t merely state, “The forest fires could cause acid rain.” It gives the reason, "As with industrial pollution, CO2 from the fire would combine with the moisture in the atmosphere to form carbonic acid, or H2CO3.” Such explanations display your understanding of the science behind the interactions. These explanations are valuable for you and others because they make your "Why?" or "How?" thinking visible, and they often lead you to think of additional ESS interactions.
Below are some of the sphere > sphere interactions that could have occurred during the ESS analysis of the Yellowstone forest fires event.
Pay attention to how the "Why?" or "How?" for the interactions is made visible in the examples below. Make the “why” and “how” visible in your interactions by including, “What you really believe to be true, ‘I think...’” supported by reasons, “Because...” and, when possible, including "These reasons come from..."
Lithosphere and Biosphere
L > B
Burned plant debris that did not blow away becomes the new soil that can provide some nutrients for pioneer plants. By comparison, gardeners prepare their soil with ashes from a fireplace.
Because soil moisture is extremely low due to the fires, surviving seeds of all types, plus windblown seeds and spores, cannot germinate until new rains fall in the area.
B > L
A decrease in vegetation may have resulted in increased erodibility of soil because there were fewer roots to hold the soil in place. In the area where I live, the roots from good plant cover appear to help keep the topsoil from washing away during heavy rains.
Lithosphere and Hydrosphere
L > H
Erosion increases from runoff following the fire and changes the turbidity, temperature, and pH of the streams and rivers. A similar circumstance occurs in the strip mining areas near where I live. Following hard rains, the nearby streams become very muddy. An article in the local paper said such "erosion and drainage creates acidic conditions in the streams."
Lithosphere and Atmosphere
L > A
Blackened areas can absorb heat faster, increasing the rate of convection in cells. An increase in convection may move air masses through a burned area quicker and/or cause moist air to move vertically faster, increasing rain further downwind.
A > L
Ash particles in the air could have been carried by the wind and dropped on the ground miles away from the forest fires; the ash particles--which have a high pH--could have changed the pH of the soil.
Atmosphere and Hydrosphere
A > H
Ash may be carried by winds many miles from the fire and then dropped into streams. A similar thing happens when ash from an erupting volcano is carried by the winds to other regions.
A > H
There may have been more precipitation in neighboring areas because ash particles in the air could have become condensation centers upon which raindrops could form.
Atmosphere and Biosphere
A > B
Smoke and noxious fumes could have coated the lungs of animals and people, affecting their ability to breathe.
Biosphere and Hydrosphere
B > H
Destruction of waterside habitat (and cover) can raise water temperatures because the ponds and streams are exposed to more radiant energy from the sun.
Remember, these are NOT all the possible event > sphere, sphere > event, and sphere > sphere interactions that could have occurred as a result of the Yellowstone forest fires event. These are merely a few examples of what seem to be some reasonable causes and effects. There are many other possibilities.
Note that many of the above interactions between the Yellowstone forest fires and the spheres result in negative environmental impacts. For example, smoke from the fires can coat the lungs of animals. However, positive environmental effects could occur as the result of the fires. Such positive effects include the removal of excess fuel material in the forests and the preparation of the seeds of some plant species for germination.
Some of the interactions also establish feedback loops. For example, the E > H interaction leads to the continuation of the fire. As the fires burn, they dry vegetation around them, thus creating more fuel for the fire. This positive feedback loop reinforces the burning of the forest fires. A negative feedback loop that lessens the intensity of the fires is established when ash from the fires is carried into the atmosphere and forms condensation particles for water vapor. These condensation particles eventually form clouds that release precipitation. The precipitation can put out the forest fires.
Remember to keep in mind as you list event > sphere, sphere > event, and sphere > sphere interactions that it is important for you to be able to explain why or how the interactions occur. For example, the above lithosphere > biosphere interaction does not merely state, "a decrease in vegetation may have resulted in increased erodbility of soil." It gives the reason, "because there were fewer roots to hold the soil in place." Such explanations display your understanding of the science behind the interactions. These explanations are valuable for you and others because they make your "Why?" or "How?" thinking visible, and they often lead you to think about additional ESS interactions.
The interactions that occur within Earth's system actually occur as a series of chain reactions, which ripple through Earth's spheres like waves that spread out from a pebble tossed in a still pond. This means that an event often leads to a change in one sphere, which leads to a change in another sphere, which leads to a change in yet another sphere. For example:
- A forest fire destroys all the plants in an area (E > B).
- The absence of plants could lead to an increase in erosion of soil (B > L).
- Increased amounts of soil could enter streams, which could lead to increased turbidity, or muddiness, of the water (L > H).
- Increased turbidity of stream water could have a negative impact on the plants and animals that live in the stream (H > B).
The four interactions above can be written as a causal chain to synthesize the results of the ESS analysis and to describe how the event can lead to a ripple of effects throughout the Earth system. Causal chains show the interdependence of Earth's spheres. The causal chain for the forest fire event outline above can be summarized in the narrative form below:
E > B > L > H > B
The fire consumed the vegetation. A decrease in vegetation could have resulted in increased soil erosion because there were fewer roots to hold the soil in place. Increased erosion of loose soil could have led to increased soil particles, or sediments, in streams. This would make stream water "muddier." Sediments in the water could have clogged the gills of fish and other aquatic organisms and choked them.
Some simple causal chains would be:
A > B > E
I read that more than eight weeks of warm to hot, low humidity air masses drew moisture out of grasses and trees in Yellowstone National Park prior to the 1988 fires.
E > A > E
The intense fires created their own upward air movement, increasing the wind velocity and drawing in oxygen at the base of the flames to continue to feed the fire.
Notice that in the case above the causal chain goes from the event to a sphere then back to the event. Causal chains don’t always have to go just from an event to one sphere then another sphere. They can also go back to the event.
Finally, a more complex illustration of an ESS causal chain would be:
E > L > B > L > B > L > H > B
Heat from the fires can affect the topsoil. As an illustration, the fires baked out a lot of the living, nutrient-rich organic matter, called humus. This may make it more difficult for many of the plants to start growing again. However, burned plant debris that did not blow away becomes part of the new soil and can provide some nutrients for pioneer plants, much like gardeners prepare their soil with ashes from a fireplace. However, because soil moisture is extremely low due to the fires, surviving seeds of all types, plus windblown seeds and spores, cannot germinate until new rains fall in the area.