Chapter 1. Chapter 23: Ecosystem Ecology

1.1 Introduction

Welcome to the Interactive Study Guide for Chapter 23: Ecosystem Ecology! This Study Guide will help you master your understanding of the chapter's Driving Questions, using interactive Infographics and activities, as well as targeted assessment questions. Click "Next" to get started, or select a Driving Question from the drop-down menu to the right.

DRIVING QUESTIONS

• What are ecosystems, and how are ecosystems being affected by climate change?
• What is the greenhouse effect, and what does it have to do with global warming?
• How do carbon and other chemicals cycle through ecosystems?
• How are scientists able to compare present-day levels of atmospheric carbon dioxide with past levels, and why would they want to?

1.2 Driving Question 1:

Why should you care?

If you live in the United States, unless you live in New England, chances are good that you don't care about where your maple syrup comes from or that yields of maple syrup produced in the U.S. are declining. You should care because maple syrup production relies on cold winters, and the decline in US production is evidence that the climate is warming there. Changes to climate affect ecosystems, and we are connected to them, even in as mundane a way as what we put on our pancakes.

Does it really matter if a spring wildflower blooms a week earlier in the year than it used to? It might if that plant’s pollinators are still on the old schedule. Furthermore, early blooming is another indication of warming climates.

Mathematical models are among the best and most common tools that scientists have to predict what will happen. Unfortunately, the general public often doesn't know how to interpret them. People frequently respond to models in one of two ways: absolute skepticism since they are "only predictions", or blind acceptance since they are "scientifically based." You should know how models work and how experts use them so that you can make more-informed choices.

Humans are often apt to divide the planet into "nature" and "the real world," but they do that at their own folly. Humans are natural organisms too, and—although they may make more complex changes to their environment than most organisms—they are not immune to impacts to ecosystems.

What should you know?

To fully answer this Driving Question, you should be able to:

1. Interpret data to describe changes in plant flowering times.
2. Explain how changes in climate can affect the distributions of species.
3. Explain how the effects of climate change on the range of one species can affect the range and success of many more species.

Infographic Focus:

The infographics most pertinent to the Driving Question are 23.1, 23.2, 23.3, 23.6, and Up Close: Biomes.

Interpret data to describe changes in plant flowering times.

Question 1.1

Examine the graphs in Infographic 23.2 to answer the following questions:

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In the graphs, the flowering time is compared with the mean spring temperature. This would suggest that warmer spring temperatures correlate with earlier flowering times.

Question 1.2

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Yes, the data show a correlation between average spring temperature and flowering time. It is important to note, however, that the data show a CORRELATION and not CAUSATION, a difference we learned about in Chapter 1.

Question 1.3

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There are potentially other reasons we might be seeing earlier flowering times, including longer periods of sunlight (i.e., days becoming longer earlier than before) or the flowers’ pollinators arriving earlier than they have in the past, so it would be to the flower’s benefit to open earlier.

Explain how changes in climate can affect the distributions of species.

Question 1.4

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Predictions based on mathematical models are scientists’ best guess at what trends will be like in the future if the current affecting factors stay the same. They cannot definitively predict the future from these models, however, because the affecting factors may change and produce a different outcome than predicted.

Question 1.5

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Scientists can create these models by taking all of the data that have been collected in the past, leading to present day and use these data to plot a trend line on a graph. This trend line assumes that the changes in affecting variables continue in this pattern for the foreseeable future. Basically, they are saying that we predict X at some point in the future if W, Y, and Z remain the same.

Explain how the effects of climate change on the range of one species can affect the range and success of many more species.

Question 1.6

What are the underlying connections between climate change, flycatchers (birds), caterpillars, sugar maples, and forest fires? Using the blanks that correspond to the text balloons below, describe the underlying connections between climate change and increased forest fires in the northeast.

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A = As average temperatures increase, flycatchers will migrate north to cooler habitats.

B = As a result of their migration, flycatchers are no longer feeding on tent caterpillars.

C = Since they are no longer being preyed upon, the tent caterpillars can feed unchecked on sugar maple trees.

D = The uninhibited feeding by the caterpillars will kill many more sugar maple trees, which in turn is more fuel for forest fires.

Review Questions

Question 1.7

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2

Try again.

Correct.

Incorrect.

Question 1.8

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Correct.

Incorrect.

Question 1.9

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2

Try again.

Correct.

Incorrect.

1.3 Driving Question 2:

Why should you care?

Global warming (perhaps better described as global climate change) is one of the most contentious political issues of our time, and at the center of it all is the greenhouse effect. The greenhouse effect itself is not up for debate; without the normal greenhouse effect, our planet would be too cold for life. What is contentious is whether humans are adding extra greenhouse gases to the atmosphere and intensifying the effect. One way or another, you will be hearing about the global climate for the rest of your life.

Carbon dioxide is not the most potent greenhouse gas, but it is the most plentiful. The coincidence of rising carbon dioxide levels and rising global temperatures led some experts to investigate and document where the extra carbon dioxide was coming from.

Why care about rising temperatures in the Arctic, Antarctic, and Eurasia? Isn't it a good thing if the poles warm up a bit? Well, rising temperatures at the poles could lead to increased melting of polar ice and a rise in global sea level. Over half the people on Earth live in Eurasia; rising temperatures there could lead to crop loss, food shortages, and heat-related health issues.

What should you know?

To fully answer this Driving Question, you should be able to:

1. Explain how the greenhouse effect warms the planet.
2. Name some of the common greenhouse gases.
3. Describe the relationship between global temperature and carbon dioxide levels in the atmosphere for the last millennium.
4. List some of the methods used to estimate temperature and carbon dioxide levels in the past.
5. Describe the changes in average temperature at the polar ice caps.
6. Describe the relationship between climate change and the size of the polar ice caps.

Infographic Focus:

The infographics most pertinent to the Driving Question are 23.4, 23.5, 23.7, 23.8, and 23.11.

Describe the relationship between global temperature and carbon dioxide levels in the atmosphere for the last millennium.

Examine the graphs from Infographic 23.5; make sure to note the scale of time on the X axes.

Question 1.13

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They both have an upward trend. Over time, the concentration of carbon dioxide in the atmosphere and the temperature of Earth have increased.

Question 1.14

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It is likely not due to the change in technique used for measuring temperature because the temperatures calculated by the two techniques show the same trend (blue and red data lines in that time period).

Question 1.15

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The graph would likely look like the graph of temperature in the northern hemisphere during that time frame. Mainly, oscillating but relatively steady.

Describe the changes in average temperature at the polar ice caps.

Question 1.18

The map in Infographic 23.7 displays the changes in global temperature between the year(s) /5qxuCBevzs= and the year(s) 1Kln7Et3ymA=.

2

Correct.

Try again.

Incorrect.

Question 1.19

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The areas that had a temperature increase of 1°C or more were around the Arctic and northern hemisphere.

Question 1.20

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Temperatures remained the same around parts of Antarctica and the Pacific Ocean.

Question 1.21

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Temperatures decreased around Antarctica and the Pacific Ocean.

Question 1.22

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Temperature increases in the Arctic are more dramatic than other regions of Earth because, as the polar ice melts, it exposes open water, which, unlike ice, is an excellent absorber of solar radiation. The open water, now warmer, is exposed to the air and raises the air temperature as well. The increased temperature of the water and air leads to more ice melts, which leads to more exposed open water, which leads to increased temperatures… and the cycle continues.

1.4 Driving Question 3:

Why should you care?

Nowadays, terms like "carbon neutral" and "carbon footprint" get a lot of media time. Understanding the global carbon cycle is the best way to know what these terms mean.

It may be hard to get excited about nitrogen and phosphorus, especially since they largely cycle within soil. Nevertheless, the cycling of nitrogen and phosphorus are essential to the functioning of ecosystems and agriculture because, without them, plants wouldn't grow and animals wouldn't have food.

What should you know?

To fully answer this Driving Question, you should be able to:

1. Explain what sources add carbon dioxide to the atmosphere.
2. Explain what sources and processes remove carbon dioxide from the atmosphere.
3. Explain how nitrogen transforms as it cycles within ecosystems.
4. Explain how phosphorous transforms as it cycles within ecosystems.

Infographic Focus:

The infographics most pertinent to the Driving Question are 23.9 and Up Close: Chemical Cycles.

1.5 Driving Question 4:

Why should you care?

Scientists have made inferences about previous levels of carbon dioxide and global temperature from several different lines of evidence. The accuracy of these inferences has been debated by those opposed to policy changes based on the assumption that global warming is an imminent, real problem.

How do your daily actions contribute to the emission of greenhouse gases? In other words, what is your carbon footprint?

Carbon dioxide is produced when organic compounds are burned. Evidence suggests that when humans started increasingly using coal, petroleum, and natural gas (all of which are organic compounds) for fuel about three hundred years ago, they began to increase atmospheric levels of carbon dioxide faster than it could be drawn out through the action of photosynthetic organisms. Methane—also a carbon compound—is a more potent greenhouse gas than carbon dioxide, and is produced by the decomposition of organic material by microorganisms living in anoxic conditions (e.g., the soil of a flooded rice paddy or the gut of a farm animal).

The coincidence of rising carbon dioxide levels and rising global temperatures lead some experts to urge governments to curtail the burning of fossil fuels, but there is much resistance to change since the world's energy system is based largely on fossil fuels.

What should you know?

To fully answer this Driving Question, you should be able to:

1. Describe the methods used to establish carbon dioxide levels in the past.
2. Explain the seasonal variation in carbon dioxide levels measured directly from the atmosphere.
3. Describe the historic and recent trends in atmospheric carbon dioxide level.
4. Explain how various human activities increase atmospheric levels of greenhouse gases.

Infographic Focus:

The infographics most pertinent to the Driving Question are 23.5, 23.9, 23.10, and 23.11.

Explain the seasonal variation in carbon dioxide levels measured directly from the atmosphere.

Question 1.37

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There is a seasonal variation in the carbon dioxide cycle because carbon dioxide is removed from the air by the process of photosynthesis, which most plants perform during the summer months, when temperatures are optimal for the process.

Describe the historic and recent trends in atmospheric carbon dioxide level.

Question 1.38

Observe the graphs in Infographic 23.10 and answer the questions that follow.

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Carbon dioxide levels have gone down and come up about every 100,000 years.

Question 1.39

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The lowest level was about 180 parts per million, while the highest level was about 300 parts per million.

Question 1.40

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Around 400 parts per million

Thought Question: The historical cycling of carbon dioxide before 1800 correlated with ice ages. Why might this be, and do you think carbon dioxide levels were at their highest or lowest level in the cycle at the start of an ice age?