Visualizing Environmental Science

PROCESS DIAGRAM^0

50

100

150

200

300

250

Municipal solid waste (1000 tons)

Total

yard waste

collected

Total

recyclables

collected

Before unit pricing

After unit pricing

Total land-

filled

garbage

Effects of Unit Pricing on Garbage Collection

and Waste Diversion Rates

Courtesy of Environmental ProtectionAgency (EPA).

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Graphs help scientists answer questions, test hypotheses, and generate new questions and hypotheses that can increase our basic

knowledge and help us solve important real-world problems. Analyzing graphs systematically can help you better understand and

interpret them and create your own scientific questions and hypotheses.

Some municipalities have tried to reduce their solid waste

by employing unit pricing, a system in which citizens are

charged according to how much garbage they generate,

but wastes that are diverted from the landfill through

recycling and composting programs are collected for

free. This graph shows how the total amount of landfilled

garbage decreased while recycling and compostable

yard waste collections increased after unit pricing was

implemented in San Jose, California.

(^1) Start by reading the graph’s title and caption. Note that the title
succinctly describes the subject matter of this graph, and that the
caption provides important background information and summarizes
the most important result portrayed in this graph.
(^2) Examine the graph’s descriptive components. The x-axis shows
the three categories of wastes described in the caption—landfilled
garbage, recyclables, and yard wastes—and the y-axis shows the
amount of waste collected. Note that the unit on the y-axis scale is
“1000 tons,” so the amount of landfilled garbage collected before
unit pricing is 250,000 tons, not 250 tons. The legend explains that
the green bars represent the “before unit pricing” data and the red
bars represent the “after unit pricing” data.
(^3) Study the graph’s data. Note how the amount of landfilled garbage
decreased after unit pricing was implemented while the amount of
wastes diverted from the landfill through recyclable and yard waste
collections increased after unit pricing.
(^4) Analyze the graph’s overall results and think about their larger
implications. For instance, these data suggest that unit pricing may
be an effective strategy for reducing the amount of landfilled solid
waste and increasing citizen participation in recycling and compost-
ing programs.
(^5) Build on the graph’s results and implications by thinking of addi-
tional questions to investigate and hypotheses to test. For example,
“Does the amount of waste diverted from landfills after unit pricing is
implemented decrease over time?” We might hypothesize that some
people may eventually decide that the money they save on their
garbage bill by recycling and composting is not worth all that extra
effort. We could investigate this question and support or refute our
hypothesis by quantifying the amount of garbage collected at regu-
lar time intervals after a unit pricing system is first implemented.
Would you hypothesize that unit
pricing would be an effective strategy for decreasing
the amount of landfilled garbage in poor countries?
Explain the reasoning behind your hypothesis, and
what you would do to rigorously test it.
Think Critically
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LEARNING OBJECTIVES

1. Review and synthesize the material presented in this
   Graphing Appendix.


2. Assess your overall understanding of this material and
   review any sections that remain unclear.

W

e have seen how useful graphs can be for visu-

alizing and interpreting data, answering

scientific questions and testing hypotheses,

and generating new questions and hypothe-

ses that may increase our knowledge and understan ding of

environmental science. The diagram below (Figure A.11)

presents a visual overview and synthesis of the material pre-

sented in this Graphing Appendix.