Sabtu, 29 Desember 2012

Global Warming Effects on Adelie Penguins

Data:     Our data was collected from numerous scientific journals to aid our analysis of the Adelie penguin population decline. The combination of graphs and charts is used to test our project's hypothesis and act as useful visual aids. Each of the following charts and graphs is accompanied by a brief explanation relating it to the overall study.

Temperature Information:
The graph below shows the global temperature change over the course of 140 years.  The rapid increase in temperature since the Industrial Revolution is predominantly due to the swell in CO2 concentration in our atmosphere.

                                                                                        (Kling, 2006)

This first graph (above) shows the global temperature change over a long period of time, while the table below shows the changes over a short time-span specifically on the Antarctic Peninsula. Though the change of only a few degrees may seem insignificant, it is a rapid escalation relative to past climate trends spanning thousands of years. This increase has resulted in the warming of the ocean water surrounding the peninsula, which leads to the subsiding of pack ice and glaciers in the region.

The annual temperature measured at Bellingshausen Station on the Antarctic Penninsula demonstrates the warming trend in the area. This data shown below was measured from 1944 to 2005.

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The Temperature and Adelie Relationship:

The following two line graphs explicate the ice dependence of the Adelie penguins for persistence. The first of the two graphs below compares the relationship of sea ice extent and Adelie abundance over time.

                                                               (Forcada, 2006)

Over the course of 20 years, the sea ice has shown a diminishing trend (grey line) correlated with ensuing declines of Adelie penguins (shown in the dark lines).
This correlation reflects the Adelie's extreme reliance on pack ice for survival. Compared to other species of penguins in the same area, the Adelies are experiencing the greatest struggle.  The Chinstrap and Gentoo penguins have greater foraging capability as well as more flex in their diet which explains their successful adaptation to warming (Forcada, 2006).

In the graph below, Adelie population is compared with the Chinstrap and Gentoo penguins.

                                                                                                 (Forcada, 2006)

Connection with Krill:

To fully understand why this decline occurs you must consider the beginning of the food chain. We found that with a deterioration of winter sea ice came a decline of sea algae, which in turn led to the reduction in Antarctic krill. This shrinkage is demonstrated in the graph below.

                            (Atkinson, 2004)

There is much evidence to support this sequence of trends. One source, The Los Angeles Times, cautions, “Krill—the heart of the rich Antarctic food chain nourishes whales, seals and penguins—have declined by more than 80% in the last 25 years in key ocean regions, according to a new study that links the loss to warming temperatures.” The result of the higher temperatures, writes reporter Usha Lee McFarling, “is a diminished ice cover in some parts of the waters surrounding Antarctica.” No ice means no krill. She reports: “Krill larvae require sea ice to survive the winter….Without sea ice, the larvae starve.”
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The Food Chain:

      (sea algae)                                       (krill)                                    (Adelie penguins)

The algae upon which the krill feed inhabit the nutrient-rich substructure of sea ice (first picture above). Ninety-nine percent of the Adelie penguins' diet consists solely of Antarctic krill (Roach, 2004).  This sequence of pictures displays the interconnected relationships on the Peninsula.

After our group's analysis of these relationships, we recognized the bottom up effect present in this ecosystem. We decided that the best way to represent these interconnected relationships was through a Stella Model.

The Adelie Population Decline as it Relates to Temperature Increase on the Antarctic Peninsula:stella_model.jpg

In this model, multiple assumptions were made in order to express these relationships. We assumed that...
-There were 1 billion sea algae in the region.
-The algae birth rate = ice melting rate * 0.3
-The rate of physiological efficiency for the krill's consumption of algae = Birth of Algae * 3.
-The chance of an Adelie encountering a krill while foraging is 0.0005.
-The krill death rate is 0.2 krill/yr.
-The Adelie Birth rate = 0.4 Adelie/yr.

*These assumptions were derived from previous models demonstrating the predator vs prey relationship*

Our Stella Model:
The three stocks shown in this model represent the population of three species in a food chain. Due to the rise in temperature, the pack ice melting rate will increase, affecting the birth rate of sea algae. This, in turn results in a decrease of the Antarctic krill's food source, which leads to the reduction of krill in the area. There a positive correlation between each stock. When the population of a prey diminishes, their predator population also lessens. Therefore, the initial decline in temperature will eventually cause a subsequent decrease in Adelie population.

We created two graphs to clearly demonstrate these relationships. The first graph shows the inverse relationship between temperature and the penguin population.

Here you can see the rapid rise in temperature (red line) from 1945 to 2005, which correlates to the data found from the Bellingshausen Station on the Antarctic Peninsula (above). The blue line shows the dramatic decline of the Adelie population in reaction to this temperature change.The second graph we made included the other two factors affected in this ecosystem: the sea algae and the Antarctic krill.chart_2.bmp

This graph indicates that a rapid temperature rise (green line) correlates with a decrease in the sea algae, krill, and penguin populations. We contribute the anomalies (drastic spikes in krill and algae populations) in this graph to the assumptions made in the design of our Stella model. However, the overall trend of the graph correctly represents our hypothesis.

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