Part 1: Carbon Cycle and Human Impacts
Photosynthesis brings both energy (from sunlight) and matter (from carbon dioxide) into ecosystems. It is also the basis of our economy, as we still largely run on fossil fuels, which are derived from ancient photosynthesis.
Recently, some concerns about carbon in the atmosphere have arisen. While plants and other photosynthetic organisms need carbon dioxide to make sugars, this molecule also plays a big role in regulating climate by trapping heat in the atmosphere.
We need to understand the carbon cycle before we can see how people impact it.
We will look at a diagram of the carbon cycle and analyze it see where carbon goes on our planet and follow the path of carbon through the various components of our environment.
The carbon cycle is an example of a biogeochemical cycle, which shows the various reservoirs and modes of movement for a particular substance on earth. Carbon is vital both as the basis of food chains and as a regulator of climate. Keep in mind that the largest reservoirs of carbon (such as rocks) are not necessarily the most important, as carbon in rocks is immobile. Vegetation has much less carbon but is much more dynamic, and so is more important for global carbon balance.
People influence the carbon cycle in several ways. We will highlight two: carbon loading and appropriation of photosynthate.
People add carbon to the atmosphere, which we call carbon loading. Carbon loading is disrupting global climates. People also appropriate a significant amount of the products of photosynthesis on earth, which can be destructive to ecosystems.
Use only the information shown on this Carbon Cycle diagram to answer the next four questions. Notice on the Carbon Cycle diagram where the important sinks (storage reservoirs) of carbon on our planet are located. One of the most important is the atmosphere. Notice also that for the land and the ocean, a gross uptake number of gigatons is shown at the beginning of each big white curved arrow. The net value given is much less. (GRAPH IS ON FILES )
1.According to the carbon cycle shown above, what processes on our planet remove carbon from the atmosphere?
2.According to the carbon cycle shown above, what processes add carbon to our atmosphere? .
3.The diagram shows that the land (terrestrial) + the ocean remove 210 Gt of carbon every year from the air.
How much of that carbon goes right back into the air?
Assume that the net uptake is at the maximum possible, so give the least amount of carbon returned to the air through natural processes.
Enter a number only, no words or units (e.g., Gt).
Part 2: Human Appropriation of the Products of Photosynthesis
How much of what plants produce on earth do humans use? To answer this question, we will read a scientific paper. You may never have read a scientific paper before, so to begin, check out the infographic on reading scientific papers
https://www.elsevier.com/connect/infographic-how-to-read-a-scientific-paper
The paper we will read is called Human Appropriation of the Products of Photosynthesis.
Here are some tips specific to the paper we are reading:
As the infographic suggests, do not read the paper from beginning to end in order. Instead, read the introductory section, then skim through each of the three estimates (low, intermediate and high), and then read the discussion.
Notice that the paper has three sections. Each of the sections has a brief intro and then an “Overall” at the end. These contain all the info you need (unless you want the nitty-gritty, you don’t need to read the details of how the estimates were made).
The paper will make more sense if you know what NPP is. The term is defined in the introduction, but you may want to look elsewhere (Google!) to fully understand what this means.
Pg means a Petagram, which is a quadrillion grams (which is a trillion kilograms or 2.2 trillion pounds). Peta- is a metric prefix. (Mega- = million; Giga- = billion; Tera- = trillion; Peta- = quadrillion)
A Pg is a big number, so in answering the questions in this case study, report how much of world’s NPP humans appropriate as a percentage rather than some number of Pg.
Read the paper Human Appropriation of the Products of Photosynthesis Download Human Appropriation of the Products of Photosynthesis (SEE FILES FOR PAPER)
4.What does the article mean by the products of photosynthesis?
List three different examples.
Although glucose, oxygen, and water are chemical products of photosynthesis, they are not relevant to this issue. Do not use them as examples.
5.In the article, the authors attempt to calculate how much of the world’s photosynthetic product we appropriate.
They give several estimates. Which estimate do you think is most appropriate to use?
Write your answer as a percent.
Explain why you think the estimate you chose is the appropriate estimate to use?
6.If you were writing a paper on photosynthesis, would this paper be an appropriate source to cite?
What features specifically makes this paper an appropriate and reliable source?
Are there any features that make this paper less appropriate as a reliable source for college?
7.Given the amount of the world’s photosynthesis that humans currently appropriate, write two to three paragraphs on the possible consequences for other species as our population grows to 8, 9, 10 or even 12 billion people. Specifically address how our appropriation of photosynthetic products would affect other species and our planet.
Part 3: Remote Sensing
To see how much and where photosynthesis is occurring on earth, let’s consult NEO! In this case NEO is not a character from the Matrix. NEO is the NASA Earth Observations, a fantastic resource maintained by NASA.
This NEO website compiles and makes available datasets from various NASA satellites. We can access the data and analyze global patterns of climate and vegetation at the NEO websiteLinks to an external site..
Let’s compare Net Primary Productivity https://www.khanacademy.org/science/biology/ecology/intro-to-ecosystems/a/energy-flow-primary-productivity
(NPP) from the region where the college is to another region, specifically the Amazon rain forest. (Look at the link to remind yourself of what NPP is.)
Here is how to accomplish this comparison using the NEO site:
On the home page find and click on Net Primary Productivity (look under the category Life or Land). Then do this:
Click on the most recent September for which there is data (by moving the slider).
The box on the top right side of the screen should now say: Currently Viewing: September [most recent year]
Click the blue Add to Analysis button at the top of the box. (Don’t worry if the “Currently Viewing” does not update.
The menu bar at the top right should indicate “1 IMAGE
Let’s compare September to March.
Move the slider and click on the most recent March available.
The box on the top right side of the screen should now say: Currently Viewing: March [most recent year]
Click the blue Add to Analysis button on the top right side of the screen.
The menu bar at the top right should indicate “2 IMAGES (You can click on this to see what images are loaded.)
Click ANALYZE on the far right side of the Menu bar at the top of the screen. Your computer may take a while to complete this command. Be patient! Eventually a map should load with the two months you chose on the right.
Below the map there should be a “Select Area (optional)” circle.
In the Select Area function, enter the following coordinates:
North: 40
West: -126 (include the minus sign)
South: 30
East: -110 (include the minus sign)
Click the Select button under the circle.
Click the blue LAUNCH ANALYSIS button. Give it time to load.
Note that September is shown in RED and March in GREEN at the top.
On the right, check the box Data Probe.
Now you can see NPP for both months, September and March, by pointing the Data Probe anywhere on the map. The red number is September, the green is March. The other number is the latitude/longitude coordinates of the probe’s location on the map.
Since the college is in San Jacinto, let’s use that as a standard location. Find San Jacinto on this map.
How can you find it on this map? Simply find the latitude and longitude of San Jacinto and move the probe to that latitude/longitude. Get as close as you can with your mouse Probe to the actual latitude and longitude.
