D2.Geo.10.9-12: How Melting Sea Ice and Changing Diets Reshape Trade and Land Use
In plain English: D2.Geo.10.9-12 is the C3 Framework geography indicator for grades 9-12 that asks students to evaluate how changes in a place's environmental and cultural characteristics influence spatial patterns of trade and land use. Students weigh evidence on two changes, shrinking Arctic sea ice and rising U.S. demand for avocados, and judge how much each one moved trade routes and farmland.
Evaluate how changes in the environmental and cultural characteristics of a place or region influence spatial patterns of trade and land use.
C3 Framework for Social Studies (NCSS) · Dimension 2: Applying Disciplinary Concepts and Tools · Discipline: Geography · Global Interconnections: Changing Spatial Patterns · Official standard
D2.Geo.10.9-12 asks students to evaluate how changes in the environmental and cultural characteristics of a place or region influence spatial patterns of trade (where goods are shipped from and to, and by which routes) and land use (what land, and here also water, is used for). Evaluating means judging how strong the influence is and what else helped cause the pattern, such as government rules, prices or safety.
The lesson uses two contrasting cases. In the first, an environmental change, the shrinking of Arctic sea ice measured by satellites since 1979, has opened the Bering Strait and the Arctic coast to more ships; students read two U.S. Coast Guard notices that plan shipping routes while weighing the needs of Alaska Native communities, and they analyze a map and NOAA@NSIDC sea-ice data. In the second, a cultural change, the rising place of avocados in the American diet, appears in USDA data on consumption, imports and farmland; students read a 2004 USDA rule that opened more U.S. states to avocados from Michoacán, Mexico, in two stages, and judge whether changing tastes drove the trade or the trade changed tastes.
Learning Objectives
By the end of this lesson, students will be able to:
Analyze satellite sea-ice data and a map to describe how an environmental change is reshaping shipping routes and the planned use of Arctic waters.
Explain how a cultural characteristic (subsistence hunting and fishing) shapes how new sea routes are planned.
Analyze USDA data to describe how a change in diet is linked to changes in trade patterns and in where avocados are grown.
Evaluate how strongly each change influenced trade and land use, compared with other causes such as government rules, prices and safety.
Prior Knowledge Required
Students should already be comfortable with:
Analyzing how cultural and environmental characteristics vary among regions D2.Geo.10.6-8
Explaining how the environment and production of goods shape world trade D2.Geo.11.6-8
Reading line graphs and calculating percent change
"Name a food that was rare in your grocery store a generation ago but is common now, or a route that ships or trucks use now but could not use before. What changed: nature, people's habits, or the rules?"
List answers in three columns: environmental change, cultural change and rules or prices. Most answers will need more than one column. Tell students that today they will test two cases where one change gets most of the credit, and decide whether it deserves it.
Direct Instruction20 minutes
Part 1: Key terms. A spatial pattern of trade is the arrangement of where goods come from, where they go and the routes between. Land use is what an area is used for; at sea, geographers speak of marine spatial planning, deciding which waters are used for shipping lanes, fishing or protection. Sea ice extent, as the National Snow and Ice Data Center (NSIDC) measures it, is the total area of ocean map cells in which at least 15 percent of the surface is covered by ice. Subsistence is the noncommercial harvest of fish, marine mammals and plants for food and culture. A vessel routing measure is a charted rule for ships, such as a two-way route or an area to be avoided.
Part 2: Case A, the Arctic. Show Diagram 2 and Table 1. September is the month of least ice. The Bering Strait, between Alaska and Russia, is the only sea gate between the Pacific and the Arctic Ocean. Show Diagram 1 and the communities near the strait.
Part 3: Case B, avocados. Show Table 2. Per capita availability is the amount available per person in a year, a common USDA stand-in for how much people eat. Bearing acreage is the land in U.S. orchards old enough to produce fruit.
Table 1. Arctic sea ice extent in September, average by period, million square kilometers (real data: NOAA@NSIDC Sea Ice Index, version 4, monthly extent)
Period
Average September extent
1980-1989
7.21
1990-1999
6.66
2000-2009
5.65
2010-2019
4.66
2020-2025
4.55
Table 2. Fresh avocados in the United States (real data: USDA Economic Research Service, Fruit and Tree Nuts Yearbook, Tables A-1, A-4, G-3 and H-1; imports are for the season beginning in the year shown; import share is the percent of U.S. fresh avocado availability, from Table H-1)
Year
Available per person (pounds)
Imports (million pounds)
Imports as share of U.S. availability
U.S. bearing acres (thousands)
1990
1.41
37.6
10.5%
83.5
2000
2.23
162.1
25.7%
65.2
2010
4.00
915.6
73.4%
59.9
2020
9.22
2,674.4
87.3%
52.1
2023
8.60
2,683.5
91.7%
52.2
Measuring the environmental change
Use Table 1. By what percent did the average September extent fall from 1980-1989 to 2010-2019?
Result: (7.21 - 4.66) / 7.21 = 0.354, a drop of about 35 percent. Diagram 2 shows the change is not smooth; single years such as 2012 (3.57) dip far below the trend.
Reading the map
Use Diagram 1. Which of the communities shown lie within the latitude and longitude limits of the 2010 study area (62°30′ to 67°30′ N, west of 167°30′ W)?
Result: Gambell, Savoonga, Diomede and Wales. Nome, Kotzebue, Shishmaref and Point Hope lie outside it. Any new shipping route through the strait would pass close to these four communities.
Measuring the cultural change
Use Table 2. How many times as many pounds of fresh avocados were available per person in 2020 as in 1990?
Result: 9.22 / 1.41 = 6.5, so about six and a half times as much. That is a large change in diet in thirty years.
Linking trade and land use
Use Table 2. How did U.S. bearing acreage change from 1990 to 2023 while imports rose?
Result: (83.5 - 52.2) / 83.5 = 0.375, a fall of about 37 percent, while imports rose about 71 times (2,683.5 / 37.6). The growing demand was met by orchards abroad, not by more U.S. orchards, so the pattern of trade and the pattern of land use moved together.
Guided Practice20 minutes
Read Sources 1 and 2 with Diagrams 1 and 2. Both are U.S. Coast Guard notices in the Federal Register, the federal government's daily journal of rules and notices. Words to know: aids to navigation (buoys, lights and markers), TSS (traffic separation scheme, a set of one-way lanes for ships), EEZ (exclusive economic zone, the ocean area up to 200 nautical miles from a country's coast), Northwest Passage and Northern Sea Route (Arctic shipping routes along the coasts of North America and Russia).
1The Coast Guard is always seeking ways to enhance the safety of life at sea. Since 2007’s record minimum for summer sea ice cover in the Arctic, international attention has been focused on the region and its potential accessibility for shipping and natural resource exploration. One significant study released in April 2009 by the Arctic Council entitled ‘‘Arctic Marine Shipping Assessment’’ noted both the sparse nature of aids to navigation in the United States Arctic as well as the absence of vessel routing measures in the Bering Strait. According to the study, significant increases in shipping are not expected in the near term. However, the U.S. Coast Guard desires to begin its study process so that essential safeguards are in place in advance of any future shipping increase. The Coast Guard has identified a potential safety enhancement by increasing predictability of vessel traffic patterns in this area with an established vessel routing system. When vessels follow predictable and charted routing measures such as a TSS, congestion may be reduced, and mariners may be better able to predict where vessel interactions may occur and act accordingly. This study will assess whether the creation of a vessel routing system is advisable to increase the predictability of vessel movements, which may decrease the potential for collisions, oil spills, and other events that could threaten the marine environment.
U.S. Coast Guard, Department of Homeland Security (Federal Register, 75 FR 68568), Port Access Route Study: In the Bering Strait, “Necessity for a New Port Access Route Study” (Source 1) (2010). US government work (17 U.S.C. 105). Source text.
1Sea ice extent in the Arctic Ocean, Chukchi Sea, and Beaufort Sea is declining. These changes in the arctic are affecting the people, wildlife and habitat of the region which in turn has resulted in increased levels of government attention, media attention, scientific research, natural resource exploration, eco and adventure tourism, and increasing commercial use of the Northwest Passage and the Northern Sea Route as alternative shipping routes. As the federal agency most responsible for coastal and marine spatial planning, the Coast Guard, via the PARS process, is initiating the study to analyze current vessel patterns, predict future vessel needs and balance the needs of all waterway users by developing and recommending vessel routing measures for the arctic coast.
[...]
2The study will encompass the entire EEZ of the United States Arctic coast from the border between the United States and Canada to Cape Prince of Wales on Alaska’s Seward Peninsula. As part of the study, the Coast Guard may analyze commercial vessel traffic, fishing vessel traffic, subsistence hunting and fishing activities, recreational activities, military activities, existing and potential outer continental shelf activities, port activities, environmental factors, economic effects and impacts, as well as other topics that may arise during the study process.
U.S. Coast Guard, Department of Homeland Security (Federal Register, document 2018-27604), Port Access Route Study: Alaskan Arctic Coast, two paragraphs (Source 2) (2018). US government work (17 U.S.C. 105). Source text.
Find the environmental change and its date. Ask: what event does Source 1 name as the trigger for international attention? Check it on Diagram 2.
Compare the two notices. Ask: how does the 2018 notice describe shipping differently from the 2010 notice? What changed in eight years?
Find the cultural characteristic. Ask: which activities in Source 2, paragraph 2, belong to the communities on Diagram 1? Why would a shipping route need to account for them?
Draw the pattern. On a copy of Diagram 1, sketch where students think a shipping route through the strait would run, and circle the communities it would pass.
Independent Practice15 minutes
Read Source 3 with Table 2. Source 3 is a 2004 USDA rule on avocados grown in Michoacán, a state in western Mexico. Words to know: phytosanitary (protecting plants from pests and disease), certified acres (orchard land inspected and approved for export), APHIS (the USDA's Animal and Plant Health Inspection Service). Remember that paragraphs 2 and 4 are claims made by commenters, which the rule prints, not findings of the agency.
1The regulations in 7 CFR 319.56–2ff (referred to below as the regulations) have provided for the importation of fresh Hass avocado fruit grown in approved orchards in approved municipalities in Michoacan, Mexico, into specified areas of the United States, subject to certain conditions. Those conditions, which include pest surveys and pest risk-reducing cultural practices, packinghouse procedures, inspection and shipping procedures, and restrictions on the time of year (October 15 through April 15) that shipments may enter the United States, are designed to reduce the risk of pest introduction. Further, the regulations have limited the distribution of the avocados to 31 northeastern and north central States (Colorado, Connecticut, Delaware, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New York, North Dakota, Ohio, Pennsylvania, Rhode Island, South Dakota, Utah, Vermont, Virginia, West Virginia, Wisconsin, and Wyoming) and the District of Columbia.
[...]
2Comment: The USDA import program has grown exponentially since 1997, from approximately 3,700 to over 53,000 certified acres, stretching USDA resources and increasing the probability of human error. [...]
[...]
3Response: As noted previously, APHIS has decided, based on the comments we received on the issue, to implement a limited distribution plan that would delay the importation of Hass avocados from the Mexico State of Michoacan into the commercial avocado producing States of California, Florida, and Hawaii for 2 years from the effective date of this final rule. [...]
[...]
4Comment: [...] We believe that the increase in consumption of 10.4 percent utilized in the model may be overly conservative. The introduction of Mexican grown avocados over a period of 7 years has resulted in an increase of over 400 percent in the consumption of avocados in the approved States. We believe that the quality of Mexican avocados, coupled with targeted promotional activities, may likely yield a higher growth in consumption than is assumed within the model.
Animal and Plant Health Inspection Service, U.S. Department of Agriculture (Federal Register, 69 FR 69748), Mexican Avocado Import Program, final rule: background, two comments and a response (Source 3) (2004). US government work (17 U.S.C. 105). Source text.
Causal-chain organizer. For each case, students fill four boxes, change, trade pattern, land or sea use pattern, other causes, and then rate the influence of the change (strong, partial or weak) with one piece of evidence. For Case B, they must also answer: did the change in diet cause the trade, did the trade cause the change in diet, or both?
Closure10 minutes
Exit ticket. "Which change had the stronger influence on a spatial pattern: shrinking sea ice on shipping in the Bering Strait, or changing diets on where avocados are grown? Give one piece of data and one other cause."
Teacher note. Keep the discussion on evidence and patterns. Sea-ice decline and trade rules are both subjects of current public debate; the lesson asks students to evaluate influences on spatial patterns, not to take positions on climate or trade policy. Present Alaska Native subsistence as the sources do: a living cultural practice that the Coast Guard lists among the uses its study must weigh. Most communities on Diagram 1 are Alaska Native villages: Gambell and Savoonga, on St. Lawrence Island, are St. Lawrence Island Yupik communities, and Wales, Diomede, Shishmaref, Kotzebue and Point Hope are Iñupiat communities. Name the peoples rather than treating them as one group.
Differentiation Strategies
For Struggling Students
Provide the causal-chain organizer with the change box filled in for both cases.
Pre-highlight the sentences in Sources 1-3 that describe a change, and have students find the effect.
Let students use a calculator template for percent change: (new - old) / old.
For Advanced Students
Download the full September series and compute the average change per decade with a linear fit.
Use USDA data to compare avocados with another food whose import share rose, and test whether the same causal chain applies.
Write a short memo, in the Coast Guard's neutral voice, listing the trade-offs a Bering Strait routing measure must balance.
Assessment Guidance
What to Look For
Strong answers describe a spatial pattern (where, from where, by which route), not just a total; use the data accurately; and separate the change being evaluated from other causes. The best answers judge strength with evidence, treat commenters' claims in Source 3 as claims, and notice when the arrow of cause may run both ways. Watch for answers that call any trend a cause without showing the link.
02
Classroom Activities
3 Activities
1
Two Changes, Two Causal Chains
15 minPairs
Pairs build a causal chain for each case on a strip of paper: change → trade pattern → land or sea use → other causes. Each link must cite a source, a table or a diagram.
Chain Prompts
Case A: What changed in the environment, and how do we know (Diagram 2, Table 1)?
Case A: Which routes and waters are affected (Sources 1-2, Diagram 1)?
Case B: What changed in culture, and how do we know (Table 2)?
Case B: Where did trade come from and go to, and which land changed use (Source 3, Table 2)?
Both cases: name one cause that is neither environmental nor cultural.
Teacher Check
A complete chain has evidence on every link. Watch for links that skip a step, such as "ice melted, so the Arctic became a trade route," without the evidence on ship traffic or planning. For prompt 5, accept any cause the sources support, such as safety rules, pest rules or the actions of other governments.
Discussion
Ask pairs to compare their two chains. Which chain has more links supported by data, and which relies more on statements of expectation or claims?
2
Plan a Route Through the Strait (Simulation)
20 minGroups of 4
Groups play a planning team and sketch one vessel routing measure for the Bering Strait on tracing paper over Diagram 1. This is a classroom simulation; students do not contact any agency.
Roles
Shipping planner: shortest, safest path for cargo ships.
Community representative: how the communities on the map use nearby waters for food.
Safety officer: distance from shores and islands in case of engine failure or oil spills.
Recorder: writes the group's reasons and the trade-offs.
Tasks
Draw a two-way route from the Bering Sea to the Chukchi Sea inside the study area.
Mark at least one "area to be avoided" and explain who it protects.
Use the 50-mile scale bar to estimate how close the route passes to the nearest community.
Write a three-sentence justification that names one trade-off.
Debrief
Compare routes across groups. Ask: which groups put the route close to the communities, and why? How does the plan change the pattern of sea use, not just the pattern of trade? Score the reasoning: a route that names its trade-offs and uses the map accurately earns full credit wherever it is drawn.
3
Which Way Does the Arrow Point?
15 minWhole class, then pairs
Write two claims on the board: A. "Americans' changing taste for avocados drove the growth of imports from Mexico."B. "Opening U.S. markets to Mexican avocados changed what Americans eat." Pairs decide how much evidence supports each claim and place a marker on a line from "mostly A" to "mostly B."
Evidence to Weigh
Table 2: availability per person by decade, and imports and import share.
Source 3, paragraph 1: where and when Mexican avocados could be sold before 2004.
Source 3, paragraph 4: a commenter's view on consumption and promotion.
Source 3, paragraph 3: which states had to wait.
Scoring
Score the reasoning, not the position: an accurate use of two pieces of evidence, a fair statement of the other claim, and a judgment that says how strong each direction of influence is. A middle position can be the best supported.
Variation: Add a Third Cause
Ask pairs to add a third arrow for a cause that is neither taste nor trade rules, such as prices or year-round supply, and explain what evidence they would need to test it.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: The Bering Strait Region and the Coast Guard's 2010 Study Area
Alaska outline: U.S. Census Bureau 2023 cartographic boundary file (1:5,000,000). Community points: 2023 Census Gazetteer. Red dashed line and corner points: the study-area positions listed in the Coast Guard's 2010 notice (62°30′ N, 173°00′ W; 62°30′ N, 167°30′ W; 67°30′ N, 167°30′ W; 67°30′ N, 168°58′37″ W; and 63°40′ N, 173°00′ W). The study area's western edge, from 67°30′ N, 168°58′37″ W south to 63°40′ N, 173°00′ W, follows the Russian Federation/United States maritime boundary line, as the notice describes; that edge is not drawn, so the dashed line stops at those two corner points. The Russian coast is not drawn either. Equirectangular projection; the scale bar is true at about 65° N.
Diagram 2: Arctic Sea Ice Extent Each September, 1979-2025
Real data: NOAA@NSIDC Sea Ice Index, version 4 (Fetterer and others, National Snow and Ice Data Center), file N_09_extent_v4.0.csv. Each point is the September average extent for the Northern Hemisphere.
04
Homework Assignment
~30 min
D2.Geo.10.9-12 Homework: The Port of Kellan Bay
Directions: Kellan Bay is an invented northern port at the mouth of the Kellan Valley, and all data below are invented for this homework. Use them, and the evidence from class, to evaluate what moved trade and land use.
Ice-free shipping days per year: 1990, 175; 2000, 186; 2010, 199; 2020, 214. Port shipments (thousand tons): 1990, 820; 2000, 990; 2010, 1,310; 2020, 1,640. Kellan Valley farmland (thousand acres): cattle pasture, 410 in 1990 and 280 in 2020; lentil and pea fields, 60 in 1990 and 205 in 2020. Households eating meatless protein meals at least weekly (national survey): 18 percent in 1990; 41 percent in 2020. Other facts: In 2008 a new rail line linked the valley to the port. In 2012 a trade agreement cut taxes on lentils and peas shipped to an overseas market.
Part 1: Measure the Changes (Problems 1-3)
Find the percent change from 1990 to 2020 in ice-free shipping days and in port shipments. Show your work.
Find the percent change in cattle pasture and in lentil and pea fields from 1990 to 2020, and the change in total farmland of these two kinds.
Sketch a simple map of the valley and the port, and describe the spatial pattern of trade and land use in 2020 compared with 1990.
Part 2: Evaluate (Problems 4-6)
Evaluate this claim: "The longer ice-free season caused port shipments to double." Use the timing of the data and at least one other fact.
Evaluate this claim: "A change in diet turned cattle pasture into lentil and pea fields." Is the arrow of cause clear? What other cause would you need to rule out?
Write a paragraph of 6-8 sentences comparing Kellan Bay with one class case (the Bering Strait or avocados). Which change, environmental or cultural, had the stronger influence on spatial patterns in each place, and why?
Rubric
Criterion
Full Credit (3 pts)
Partial Credit (2 pts)
Minimal Credit (1 pt)
Accurate Calculations
All percent changes correct with work shown
Most correct
Few correct or no work
Describes Spatial Patterns
Map and description show where goods move and how land use shifted
Pattern described but not located
Totals only, no pattern
Evaluates Causes
Weighs the change against the rail line or trade agreement with timing evidence
Names another cause without weighing it
Treats one change as the only cause
Compares with a Class Case
Accurate comparison using a source or table from class
General comparison
No comparison
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Questions 3, 4, 15 and 20 use Source 1, and questions 5, 6, 15, 16 and 20 use Source 2 (both in Guided Practice). Questions 10-13 and 17-20 use Source 3 in Independent Practice. Questions 7, 8, 14, 15, 17, 19 and 20 use Tables 1-2 and Diagram 2, and questions 9, 16 and 19 use Diagram 1. Choose the best answer, then check it.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
Which statement describes a spatial pattern of trade?
Answer: B
A spatial pattern of trade is about where goods come from and go, so naming the source region is spatial. Choices A, C and D describe totals, prices and rank, which are not spatial.
Question 2 of 20 · Multiple Choice
Which of these is a change in a cultural characteristic of a place?
Answer: C
What people choose to eat is part of culture, so a shift in diet is a cultural change. Choices A, B and D are environmental changes.
Question 3 of 20 · Multiple Choice
According to Source 1, what focused international attention on the Arctic as a region for shipping?
Answer: B
Source 1 says: "Since 2007's record minimum for summer sea ice cover in the Arctic, international attention has been focused on the region and its potential accessibility for shipping." Choices A, C and D are not in the source.
Question 4 of 20 · Multiple Choice
According to Source 1, what did the 2009 Arctic Council study expect about shipping in the near term?
Answer: C
Source 1 reports that "significant increases in shipping are not expected in the near term," yet the Coast Guard began planning anyway "in advance of any future shipping increase." This matters for evaluation: in 2010 the influence of the ice change on trade was expected, not yet observed. The other choices are not in the source.
Question 5 of 20 · Multiple Choice
How does Source 2, paragraph 1, describe the Coast Guard's role?
Answer: A
Source 2 calls the Coast Guard "the federal agency most responsible for coastal and marine spatial planning," which is why its routing study shapes how Arctic waters are used. Choice D describes the satellite data in Diagram 2, which come from NOAA@NSIDC, not from the Coast Guard.
Question 6 of 20 · Multiple Choice
Which of these does Source 2, paragraph 2, list as something the Coast Guard may analyze in its study?
Answer: B
Source 2 lists "subsistence hunting and fishing activities" among the topics, along with commercial and fishing vessel traffic. That is a cultural characteristic of the region entering a plan for sea use. The other choices are not in the list.
Question 7 of 20 · Multiple Choice
Use Diagram 2. By about what percent was the 2012 September extent smaller than the 1979 extent?
Answer: D
(7.05 - 3.57) / 7.05 = 0.494, about 49 percent smaller. Choice C (51 percent) is the share that remained (3.57 / 7.05). Choice B confuses the difference in million square kilometers (3.48) with a percent, and choice A is the decade-average drop from Table 1, not the 1979-2012 change.
Question 8 of 20 · Multiple Choice
Use Table 1. Between which two periods did the average September extent fall the most?
Answer: C
The drops are 0.55 (1980s to 1990s), 1.01 (1990s to 2000s), 0.99 (2000s to 2010s) and 0.11 (2010s to 2020-2025). Choice B is very close but slightly smaller, so careful subtraction matters.
Question 9 of 20 · Multiple Choice
Use Diagram 1. Which community shown lies farthest south within the study area?
Answer: A
Savoonga is at 63.68° N, slightly south of Gambell (63.78° N). Wales and Diomede are near 65.6-65.8° N, in the strait itself.
Question 10 of 20 · Multiple Choice
According to Source 3, paragraph 1, during which part of the year could Mexican Hass avocados enter the United States before the 2004 rule?
Answer: A
Source 3 lists "restrictions on the time of year (October 15 through April 15) that shipments may enter the United States." Choice D describes the change the 2004 rule made, not the earlier rule. Choice B reverses the dates.
Question 11 of 20 · Multiple Choice
According to Source 3, paragraph 1, where in the United States could the avocados be distributed before the 2004 rule?
Answer: C
Source 3 says distribution was limited "to 31 northeastern and north central States ... and the District of Columbia." Choice A is not supported by paragraph 1. Choice B describes nationwide, year-round sales, which the earlier rule did not allow.
Question 12 of 20 · Multiple Choice
According to Source 3, paragraph 3, which states had to wait two more years for Mexican avocados?
Answer: D
Source 3 says the plan "would delay the importation of Hass avocados ... into the commercial avocado producing States of California, Florida, and Hawaii for 2 years." The other choices are not in the source.
Question 13 of 20 · Multiple Choice
According to the commenter in Source 3, paragraph 2, by how many certified acres did the import program grow after 1997?
Answer: D
53,000 - 3,700 = 49,300 acres. Choice A adds the two numbers, choice B is the ratio (53,000 / 3,700 is about 14 times), and choice C is the starting figure. Remember that this is a commenter's figure that the rule prints, not an agency finding.
Question 14 of 20 · Multiple Choice
Use Table 2. By how many percentage points did imports' share of U.S. fresh avocado availability rise from 2000 to 2020?
Answer: A
87.3 - 25.7 = 61.6 percentage points. Choice B adds the two shares. Choice C is the ratio (87.3 / 25.7). Choice D is the percent change in the share, about 240 percent, which is a different measure from percentage points.
Question 15 of 20 · Short Answer
Using Sources 1 and 2 and Diagram 2, explain how the decline in sea ice has influenced the planned spatial pattern of shipping and sea use. What changed between the 2010 and 2018 notices?
Model answer: Diagram 2 shows September extent falling from 7.05 million square kilometers in 1979 to a record low of 3.57 million in 2012, and no September since 2007 has been above 5.3 million. In 2010, the Coast Guard began a study of routing through the Bering Strait, tying it to the Arctic's changing ice (Source 1). By 2018, it described "increasing commercial use of the Northwest Passage and the Northern Sea Route" and widened its study to the whole Arctic coast (Source 2). The environmental change first prompted planning, then an observed shift in routes, and the planning itself (routing measures) is a new pattern of sea use. Full credit: data, both notices and the change between them.
Question 16 of 20 · Short Answer
Explain how a cultural characteristic of the Bering Strait region shapes the planning of new routes. Use Source 2 and Diagram 1.
Model answer: Source 2 lists "subsistence hunting and fishing activities" among the topics the study may analyze; harvesting food from the sea is a cultural characteristic of the region. Diagram 1 shows communities such as Gambell, Savoonga, Wales and Diomede inside or beside the study area, so a route through the strait passes near the waters these communities use for food and culture. Planners must place routes and any areas to be avoided so that shipping, a new trade pattern, does not displace or endanger subsistence, an older pattern of sea use. Full credit: names the cultural characteristic and links it to where routes go.
Question 17 of 20 · Short Answer
Source 3, paragraph 4, prints a comment that the introduction of Mexican avocados "has resulted in an increase of over 400 percent in the consumption of avocados in the approved States." Using this and Table 2, evaluate whether the change in diet drove the trade or the trade drove the change in diet.
Model answer: The evidence points both ways. The comment claims that opening states to Mexican avocados raised consumption there, so trade rules and supply helped change diets; it also credits "targeted promotional activities." Table 2 shows availability per person rising from 1.41 pounds in 1990 to 9.22 in 2020 while import share rose from 10.5 percent to 87.3 percent, which fits either direction. Because the 400 percent figure is a commenter's claim, it is weaker evidence than USDA data. A strong judgment: diet and trade reinforced each other, with the opening of markets as a trigger. Full credit: uses both pieces of evidence, treats the comment as a claim and makes a reasoned judgment.
Question 18 of 20 · Short Answer
Describe the spatial pattern of avocado trade that Source 3 sets out, and explain why the producing states were treated differently.
Model answer: Before the 2004 rule, Mexican avocados from approved orchards in Michoacán could be sold only in 31 northeastern and north central states and the District of Columbia, and only from October 15 to April 15 (paragraph 1). The 2004 rule opened more states and all months, but delayed California, Florida and Hawaii, the "commercial avocado producing States," for 2 years (paragraph 3). The pattern kept imports away from U.S. orchard regions first, The rule says the delay lets APHIS further confirm that its pest safeguards work; in effect, it also delayed competition for those states' orchards for a time. Full credit: describes where and when, and gives a reason for the producing states' treatment.
Question 19 of 20 · Short Answer
Compare the land-use (or sea-use) effects of the two changes. Use Table 2, Source 3 and Diagram 1.
Model answer: In the avocado case, land use shifted across borders: U.S. bearing acres fell from 83.5 thousand in 1990 to 52.2 thousand in 2023 (Table 2), while a commenter in Source 3 reports Michoacán's certified orchards growing from about 3,700 to over 53,000 acres after 1997. In the Arctic case, the change is in planned sea use: routes, possible areas to be avoided and the balance with subsistence waters near the communities on Diagram 1. One case moved farmland from one country to another; the other is creating new uses of water that was once ice-covered. Full credit: one accurate point for each case and a clear comparison.
Question 20 of 20 · Short Answer
Evaluate: in which case did the change (environmental in the Arctic, cultural for avocados) have the stronger influence on spatial patterns of trade and land use? Support your judgment with data and name at least one other cause for each case.
Model answer (either case can earn full credit): The avocado case shows the stronger observed influence. Imports grew about 71 times from 1990 to 2023 and supplied over 90 percent of avocados, while U.S. orchard land shrank (Table 2). But trade rules were a major cause too: the 2004 rule opened states one group at a time (Source 3). In the Arctic, sea ice has clearly declined (Diagram 2), yet the main effect so far is planning (Sources 1-2) and some new commercial use (Source 2), alongside other causes such as safety concerns and resource exploration. Full credit: a clear judgment, data from both cases and another cause for each.
0 of 20 answered · 0 correct
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Frequently Asked Questions
10 Questions
What does D2.Geo.10.9-12 mean?
D2.Geo.10.9-12 asks high school students to judge how changes in a place's environment or culture affect where trade flows and how land is used. Students trace a change, such as melting sea ice or a new food habit, to new routes, new sources of goods or new uses of land, and weigh it against other causes such as rules, prices and technology.
What is a spatial pattern of trade?
It is the arrangement of where goods come from, where they go and the routes between. A pattern can change even when the total amount traded stays the same, for example when a country switches suppliers or ships begin using a new passage.
How can environmental change affect trade routes?
It can open, close or change the cost of routes. Less sea ice can lengthen the shipping season in Arctic waters; low river levels can limit barges; storms or droughts can shift where crops are grown and from where they are bought.
How can cultural change affect land use?
Changes in what people eat, wear or value change what farmers and businesses produce. When demand for a food grows, land somewhere is planted with it, and that place may be far from where the food is eaten.
Is D2.Geo.10.9-12 about climate policy or trade policy?
No. The indicator asks students to evaluate influences on spatial patterns using evidence. Policies appear in this lesson as documented facts, such as a federal rule or a study notice, and students are not asked to take positions on current policy debates.
Which courses teach D2.Geo.10.9-12?
It is usually taught in high school human geography or world geography, and it fits economics units on trade and environmental science units on the Arctic. It pairs well with RH.11-12.7 on integrating information from data and text.
What is the difference between D2.Geo.10.6-8 and D2.Geo.10.9-12?
The middle school indicator asks students to analyze how cultural and environmental characteristics vary among regions. The high school indicator adds change over time and asks students to evaluate how those changes influence patterns of trade and land use.
Why use Federal Register documents in a geography lesson?
They are primary sources that record what agencies planned and why, in their own words. They also show how agencies hear from the public, since rules print comments and responses, which lets students practice telling an agency's findings from a commenter's claims.
What mistakes do students make with D2.Geo.10.9-12?
Many students describe totals instead of patterns, or assume that because two trends rise together one caused the other. Others forget to name other causes. Asking "where, from where, by which route, and what else changed?" keeps answers spatial and evaluative.
How should I assess D2.Geo.10.9-12?
Use data questions on change, a mapping or planning task and a written evaluation that rates the strength of an influence and names other causes. Rubrics should reward accurate data use and reasoning about cause, and accept more than one well-supported judgment.
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Related Standards
6 standards
These standards connect to D2.Geo.10.9-12: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
D2.Geo.10.6-8Prerequisite
Analyze how cultural and environmental characteristics vary among world regions
Evaluate how human-made and natural catastrophes affect trade, politics and migration
Lesson coming soon
Standard text: National Council for the Social Studies (NCSS), The College, Career, and Civic Life (C3) Framework for Social Studies State Standards: Guidance for Enhancing the Rigor of K-12 Civics, Economics, Geography, and History (Silver Spring, MD: NCSS, 2013). NCSS was not involved in the production of this lesson and does not endorse it.
