結論：NEW TREASURE（ニュートレジャー）Stage 2 Lesson 2のReadでは、外来種（non-native species）について『その地域にもともといたか』『人間の活動で持ち込まれたか』『悪影響が確認されたか』を区別すると、英文の因果関係を正確に理解できます。環境省の公式資料でも、すべての外来種が悪影響を及ぼすわけではないと説明されています。慶英会が制作した架空の自然観察・学校菜園の英文2題と独自24問、全問の根拠解説で、because／although／ifと筆者の主張を学びます。
慶英会 塾長
慶英グループ CEO
一般選抜にて慶應義塾大学合格（英語入試正答率97％）
成績優秀者（慶應義塾維持会奨学生）として
慶應義塾大学を卒業（2023年）
一般財団法人 慶應連合三田会
慶應義塾横浜三田会 会員
高校在学中に英検1級取得
公益財団法人 日本英語検定協会「成績優秀者」に選出
中高主要科目で「オール5」
（最高評価・高校偏差値70）
国内最高峰の英語スピーチコンテスト
「高円宮杯全日本中学校英語弁論大会」
横浜市大会入賞・神奈川県大会進出
米国高校留学中、唯一の日本人として
全米最大級の高校生リーダーシップ団体
「FBLA」主催の英語スピーチコンテストに出場
ニューヨーク州大会準優勝・全米大会進出
米国の在籍高校代表として
「シカゴ国際模擬国連会議」に出場
慶應義塾大学在学中より英語指導を行い
「英語個別指導オンライン塾｜慶英会」を設立
小学生から、現役英語講師・英検面接官を含む
社会人まで数百名以上を指導
（最前列左から2人目：塾長）
Ｚ会の2026年カタログでは、Third Edition Stage 2 Lesson 2のReadに外来種の影響を扱う説明文が位置づけられています。本記事はテーマが共通する慶英会独自の読解教材であり、教科書の本文・設問を転載したものではありません。教材のLesson進度と採用版は学校によって異なるため、学校の範囲表を優先してください。英文に登場する学校・植物の観察結果・活動は架空の事例です。
環境分野の読解を広げる：Lesson6スマトラ島の森林・UNESCOの公式資料を使った独自長文32問も公開しました。Lesson2の外来種で学んだbecause・although・事実と推測の区別を、森林保全の別題材へ応用できます。いずれも慶英会が独自制作し、設問・全解答を無料公開しています。
外来種と侵略的外来種を混同しない
non-native species は、人間の活動によって本来の自然分布域以外へ持ち込まれた生物を指します。一方、invasive alien species は、その中でも生態系や人の生活、農林水産業などへ悪影響を及ぼすものをいいます。『外国から来た＝すべて悪い』という単純化は不正確で、日本国内で本来の生息域を越えて人為的に持ち込まれた生物も外来種となる場合があります。環境省公式｜外来種の基本的な考え方を参考にしてください。
外来種被害予防の3原則
- 入れない：悪影響を及ぼす恐れのある生物を新しい地域へ人為的に持ち込まない。
- 捨てない：飼育・栽培している生物を野外に逃がしたり放したりしない。
- 拡げない：すでに野外にいる外来種を別の地域へむやみに移動・拡散しない。
自然観察では、知らない生物をその場で捕獲・除去・移動してよいとは限りません。法律上の扱い、対象の特定、専門家の判断が必要な場合があるため、授業では写真・既存資料・許可された観察記録を用いるなど安全な方法を選んでください。
Readで確認する接続詞・助動詞・推論
- because：観察や判断の理由を示す。It was not enough because the species was unknown.
- although：見た目と実際の影響など、対比・譲歩を表す。Although the plant was beautiful, its impact was unknown.
- if：実際に起きた事実とは限らない条件。If the species spreads, … の条件が成立したかを確認する。
- may／might／could：可能性を表す。The plant may affect others. は悪影響が確定したという意味ではない。
- should／have to：提案・必要性の違いに注意。適切な行動は公式情報と地域の指示に従う。
目次｜初見英語長文2題・24問
Read 1｜A Plant by the River: Look Before You Decide（約477語）
説明文・因果と仮説。英語の本文を読み、事実・推測・まだ分からないことに印を付けてから設問へ進んでください。
Students in a fictional town called Maple River visited a park for a science project. Near the river, they noticed a plant with bright yellow flowers. They had never seen it in that area before. At first, one student said, ‘This must be an invasive plant. We should pull it out today.’ Another student, Nao, was not sure. She had learned that a non-native species is a living thing brought by human activity to a place outside its natural range. She also knew that not every non-native species causes serious harm.
The science teacher asked everyone to step away from the plant. He said that a photograph could help them ask a question, but it was not enough to identify a species or decide how to manage it. The students took pictures from the path and recorded the date and location. They did not collect seeds, touch the plant, or move it to another place. The teacher planned to ask the appropriate local office for guidance before anyone took action.
Back in the classroom, the students read information from Japan’s Ministry of the Environment. They learned that some non-native species may compete with local plants, affect other animals, or harm farming. However, the introduction of a new species does not automatically mean that such damage has occurred. They also learned three principles for preventing problems: do not introduce harmful species into new areas, do not release species being kept or grown, and do not spread species already found outside their original range.
The group then made two lists. One was called ‘What we observed.’ It included yellow flowers, the place where they saw the plant, and the date. The second list was ‘What we still need to know.’ It asked what species the plant was, whether it had been brought there by people, and whether it was affecting native organisms. Nao explained that an unknown answer should remain a question, not become a dramatic headline.
The students prepared a short display for the school library. The first sentence said, ‘We observed an unfamiliar plant near the river.’ Another sentence explained what the term non-native species means. Their display did not call the plant invasive, because that had not been confirmed. They added a link to official guidance and advised readers not to move or release living things into new places. Some visitors said the display encouraged them to ask better questions, but the class did not measure whether anyone changed their behavior after reading it.
At the end of the project, the teacher asked what the students had learned. One student answered, ‘Science is not just finding interesting things. It is deciding what we can say from the information we have.’ Nao agreed. She still wanted to know the plant’s name, but she was pleased that her classmates had learned to separate an observation from a guess.
設問Q1〜Q12
- Q1. Where did the students first notice the unfamiliar plant?
- Q2. What color were the flowers?
- Q3. What did the first student want to do immediately?
- Q4. What is one key feature of a non-native species?
- Q5. Does the passage say all non-native species are harmful?
- Q6. What did students record without touching the plant?
- Q7. Which organization provided the official information they read?
- Q8. What three principles did the group learn?
- Q9. Was the plant identified as invasive?
- Q10. Why did the library display avoid calling the plant invasive?
- Q11. Explain the difference between observation and inference in one Japanese sentence.
- Q12. Retell in three English sentences.
Read 2｜A School Garden: How Should We Choose Plants?（約478語）
提案と反対意見・因果の限界。英語の本文を読み、事実・推測・まだ分からないことに印を付けてから設問へ進んでください。
A class at a fictional middle school wanted to improve its small garden. Each group was invited to suggest flowers that students could enjoy during the school year. One team chose a bright plant from an online photograph. They said it would probably grow quickly and need little care. Another team suggested asking a local specialist which plants were suitable for the area. Their ideas led to a discussion about what it means to make a responsible choice.
The teacher asked the students to explain their reasons. The first team said that the plant in the photograph looked beautiful and that a fast-growing plant could cover the empty soil. The second team asked whether fast growth was always helpful. Some plants that grow strongly may take space or resources away from other species, but this possibility does not prove that any particular plant will cause harm. The class decided not to order seeds until it had checked the plant’s identity and whether growing it was appropriate.
Students then interviewed a gardener invited by the school. The gardener explained that plant selection depends on several conditions, including the garden’s sunlight, water, soil, and local ecosystem. She also told the students not to move plants from protected natural areas into the school garden. When students wanted to share seeds with another school, she asked them to check the rules and risks before moving anything. The class understood that a friendly purpose did not remove the need for careful management.
Next, the teams created a decision table. They wrote down the name of each proposed plant, where reliable information came from, what conditions it needed, and which questions remained unanswered. One team had enough information about watering but did not know whether its chosen plant might spread beyond the garden. The group left that question open. Another team did not know how much shade the garden received, so they planned to measure it at different times of day.
After several discussions, the class made a provisional plan using plants suggested by the local specialist and suitable for the garden conditions. They did not publish a claim that the plan would improve biodiversity, because they had not studied biodiversity before or after planting. Instead, they said that the plan considered official guidance and local advice. The teacher called this a more honest statement because it described the process rather than promising a result.
In their final presentation, students discussed both the advantages and the limits of the plan. They said that gardens can be places for learning and enjoyment, but plant choice should involve more than appearance. A good decision needs reliable information, attention to local conditions, and willingness to change the plan when new evidence becomes available. The class finished with a question for its audience: ‘What would you need to know before recommending a new plant for your own town?’
設問Q13〜Q24
- Q13. What did the class want to improve?
- Q14. Why did the first team like the plant in the photograph?
- Q15. What was the second team’s first suggestion?
- Q16. Did fast growth prove that the chosen plant would harm local species?
- Q17. What did the class decide not to do until more information was available?
- Q18. Name two conditions the gardener said were important.
- Q19. Did the gardener recommend taking wild plants from protected natural areas?
- Q20. Why did the class make a decision table?
- Q21. What important question did one team leave open?
- Q22. Why did another team want to measure shade?
- Q23. Did the class prove the provisional plan improved biodiversity?
- Q24. Write a three-sentence English summary.
全24問の解答・根拠説明
Q1〜Q10／Q13〜Q22の内容理解は1問1点、各題最後の2問は自由記述として各2点を目安にすると、1題14点・2題28点です。英文要約・リテリングはモデルと同じ表現でなくても、事実と未確認事項を正確に区別できれば正答にできます。
Read 1の解答（Q1〜Q12）
- Q1. Near the river in a park. — Paragraph 1 identifies the place.
- Q2. Bright yellow. — Observation explicitly stated in paragraph 1.
- Q3. Pull out the plant. — This was a suggestion, not an approved action.
- Q4. It has been brought by human activity outside its natural range. — The passage provides a definition drawn from official guidance.
- Q5. No. — Not every non-native species causes serious harm.
- Q6. Photographs, the date, and the location. — Paragraph 2 explains the safe observation.
- Q7. Japan’s Ministry of the Environment. — The authority is named in paragraph 3.
- Q8. Do not introduce, do not release, and do not spread potentially harmful non-native species. — The principles are enumerated in paragraph 3.
- Q9. No. Its identity and effects were not confirmed. — The two lists distinguish observation from missing evidence.
- Q10. Because the class had not confirmed its identity or impact. — Paragraph 5 states the editorial reason.
- Q11. 観察は花の色や発見場所など確かめた情報であり、侵略的な影響があるという判断は追加の根拠が必要な推論です。 — Uses observed details and the unconfirmed impact.
- Q12. Students saw an unfamiliar plant but did not remove or move it. They recorded observations and read official information about non-native species. They made a display that separated confirmed facts from questions. — Preserves sequence, safe action, and epistemic limit.
Read 2の解答（Q13〜Q24）
- Q13. Its small school garden. — The purpose is introduced in paragraph 1.
- Q14. It looked attractive, and they thought it might grow quickly. — This was their opinion, not a measured property.
- Q15. Ask a local specialist which plants were suitable. — Paragraph 1 contrasts the two proposals.
- Q16. No. — Paragraph 2 notes a possible risk, not a proven effect.
- Q17. Order seeds. — It delayed ordering until identification and suitability were checked.
- Q18. For example, sunlight and soil (also water and the local ecosystem). — The gardener listed several conditions.
- Q19. No. She advised against moving them. — Paragraph 3 explicitly states this.
- Q20. To record reliable sources, plant needs, and unanswered questions. — Paragraph 4 describes the fields.
- Q21. Whether its plant might spread beyond the garden. — Unknown risks were not turned into assertions.
- Q22. It did not know how much shade the garden received. — Paragraph 4 states the knowledge gap.
- Q23. No. It had not measured biodiversity before and after. — Paragraph 5 distinguishes method from unmeasured outcome.
- Q24. Students compared possible plants for a school garden. They checked local advice and kept unanswered questions open before making a provisional plan. They did not claim a biodiversity improvement that had not been measured. — Covers deliberation, evidence, and limit.
事実と推測を切り分ける英語表現
We observed … と We believe … は同じではない
We observed yellow flowers. は見たことの記録ですが、We believe the plant is invasive. は評価・仮説です。評価を根拠付きで伝えるには、その地域での分布・影響・専門的な同定情報などを確認する必要があります。未確認の部分はwe do not know yetと書いて構いません。
All non-native species are harmfulという誤解
環境省は、すべての外来種が問題を起こすわけではないと説明しています。英語ではnot all non-native species cause harm のように部分否定で示します。all … notの語順だけで曖昧に書くより、not allを用いると誤読を減らせます。
7日間の復習方法
1日目はRead 1、2日目は本文中のbecause／although／may／not allを確認、3日目はRead 2、4日目は二つのReadから事実と仮説を2列に分けます。5日目は環境省公式の3原則を英語で各1文にまとめ、6日目に二題を英語3文で説明。7日目に24問を再テストし、本文にない種名・影響・成果を付け足していないか確かめてください。
よくある質問
これはNEW TREASURE Stage2 Lesson2の実際のRead本文ですか？
違います。外来種というテーマに対応させた慶英会のオリジナル英文2題です。出版社の本文を転載したものではありません。
見つけた植物が外来種かどうか自分で決めて除去してよいですか？
いいえ。写真だけでは同定できないことがあり、除去や移動には制度・地域のルールや安全上の注意が必要です。専門機関・学校の指示を確認してください。
外来種はすべて環境に悪いですか？
いいえ。環境省の公式資料でも、全ての外来種が悪影響を及ぼすわけではないと説明されています。
24問が解けたらどの教材へ進みますか？
同じReadの英文を3文でリテリングし、次に本文の論理関係・接続詞を変えた新しい英文でも読み分けられるか確認してください。
関連する無料教材・慶英会への相談
- Stage2のwhen・if・because・although接続詞
- Stage2の400〜600語初見Read2題30問
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- NEW TREASURE学習ガイド
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参考にした主な公式情報
公式情報確認：2026年10月26日。文章中の学校、発見した植物、活動、設問は慶英会が独自に作った架空の教材であり、学校の実際の観察記録やＺ会の教科書本文ではありません。