The Green Revolution was a mid-20th-century shift in agriculture (roughly starting in the 1940s and accelerating through the 1960s–1970s) that used new strategies to dramatically raise crop yields. Key features were high-yielding varieties (HYVs) like dwarf wheat (Rht genes) developed by Norman Borlaug, IR8 rice from IRRI, and work at CIMMYT; plus mechanization, synthetic nitrogen fertilizer, expanded irrigation, pesticides, and later genetic modification. It boosted food production and reduced famine in many places but also caused problems: salinization from irrigation, monoculture and agrobiodiversity loss, pesticide resistance, and greater fossil-fuel reliance. This topic is in Unit 5 (Land & Water Use) and appears on the AP Exam (see EK EIN-2.C.1–2). For a quick AP-aligned review, check the Green Revolution study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and more Unit 5 review or practice problems (https://library.fiveable.me/ap-environmental-science/unit-5; https://library.fiveable.me/practice/ap-environmental-science).

It started because countries needed a fast, big boost in food production. After WWII and into the mid-1900s, world population rose quickly and famines (especially in Asia and Mexico) made higher yields urgent. Scientists like Norman Borlaug developed high-yielding varieties (HYVs)—dwarf wheats and improved rice (IR8)—and institutions (CIMMYT, IRRI) helped spread them. Those seeds worked best with synthetic nitrogen fertilizer, expanded irrigation, pesticides, and mechanization, so agriculture shifted to those practices (EK EIN-2.C.1). The goal was to produce more food per hectare quickly; the result was huge yield increases but also tradeoffs: monoculture, loss of agrobiodiversity, pesticide resistance, salinization, and greater fossil-fuel use (EK EIN-2.C.2). This topic is tested in Unit 5 (Land & Water Use) and ties to learning objective EIN-2.C—so review the Green Revolution study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Traditional farming relies on local, low-input practices: diverse crops, manual labor or animal power, saved seeds, little synthetic fertilizer or pesticides, and often rain-fed irrigation. The Green Revolution shifted agriculture to high-yielding varieties (HYVs like dwarf wheat and IR8 rice), mechanization, synthetic N fertilizer, expanded irrigation, and heavy pesticide use—plus monoculture planting and sometimes GMOs. That made food production much higher (Norman Borlaug’s work) but introduced downsides: fossil fuel dependence, salinization from irrigation, pesticide resistance, loss of agrobiodiversity, and more runoff/ pollution. For the APES exam, recognize EK EIN-2.C.1–2: list specific Green Revolution strategies (mechanization, fertilizers, irrigation, pesticides, GMOs) and link them to impacts (monoculture, salinization, pesticide resistance). Review the Topic 5.3 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Mechanization increases farm profits and efficiency by letting a farm do more work faster with fewer people. Machines (tractors, combines, planters) speed up planting/harvesting, lowering labor costs per hectare and reducing crop loss from delayed harvest. They enable larger fields and economies of scale—the cost to produce one unit (kg of grain) falls as you farm more land with the same machines. Mechanization also allows timelier operations (planting and fertilizing at optimal windows), which raises yields. Modern mechanization + precision tech (GPS-guided equipment) cuts waste of seed, fertilizer, and fuel, improving profit margins. Trade-off: higher upfront costs and greater reliance on fossil fuels and maintenance (noted in the CED). For AP review see the Topic 5.3 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g), the Unit 5 overview (https://library.fiveable.me/ap-environmental-science/unit-5), and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Short answer: GMOs aren’t simply “good” or “bad”—they’re a tool with environmental trade-offs. Genetically modified crops (part of Green Revolution strategies alongside HYVs, irrigation, fertilizers, and pesticides) can increase yields and reduce the need to convert more wild land to agriculture, which lowers habitat loss and can cut CO2 from land-use change. Some GMOs also reduce pesticide use (e.g., Bt crops), which can lower chemical runoff. But they can contribute to monoculture and agrobiodiversity loss, encourage pesticide resistance in pests, and increase reliance on certain inputs or seed companies—so local context matters. For AP exam connections, EK EIN-2.C.1 and related keywords (HYVs, monoculture, pesticide resistance, agrobiodiversity loss) are what graders expect you to mention. For a quick review of Topic 5.3, check the Fiveable study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Main Green Revolution strategies: switching to high-yielding varieties (HYVs) and later GMOs (e.g., dwarf wheat with Rht genes, IR8 rice), heavy use of synthetic fertilizers—especially nitrogen—to boost growth, and widespread chemical pesticides to cut pest losses. Other key practices: mechanization (tractors, combines), expanded irrigation (which can cause salinization), and planting large monocultures. These changes raised yields but introduced problems: increased fossil fuel use, pesticide resistance, loss of agrobiodiversity, soil degradation, and water issues. Know the names and tradeoffs (Norman Borlaug, CIMMYT, IRRI; EK EIN-2.C.1–2) for the exam. For a quick topic review, use the Fiveable Green Revolution study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g), the Unit 5 overview (https://library.fiveable.me/ap-environmental-science/unit-5), and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Mechanization means replacing human and animal labor with machines (tractors, combine harvesters, irrigation pumps). Those machines need energy—mostly diesel or electricity produced from fossil fuels—so fuel must be bought and burned to run, maintain, and transport them. Mechanization also lets farms scale up (monoculture, bigger fields), which raises demand for other fossil-fuel–intensive inputs like synthetic fertilizers (Haber–Bosch fertilizer production relies on natural gas) and long-distance transport of larger harvests. Together, that creates a feedback: more machines → more fuel use for field work, irrigation, repairs, and processing → more reliance on fossil-fuel supply chains. This is exactly why the CED links mechanization to increased fossil-fuel dependence in the Green Revolution (EK EIN-2.C.1 and EK EIN-2.C.2). For a quick review on this topic, see the Green Revolution study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and more practice questions at (https://library.fiveable.me/practice/ap-environmental-science).

The Green Revolution raised crop yields worldwide by introducing high-yielding varieties (HYVs like dwarf wheat and IR8 rice), mechanization, synthetic nitrogen fertilizers, expanded irrigation, and pesticides. Positives: huge increases in food production (helped prevent famines), higher farm efficiency and profits, and greater short-term food security (Norman Borlaug’s work). Negatives: reliance on fossil fuels for machinery and fertilizer; soil degradation and salinization from intensive irrigation; increased pesticide use leading to resistance and health/ecosystem harms; loss of agrobiodiversity from monocultures; and nutrient runoff causing eutrophication. For APES, know the trade-offs (EK EIN-2.C.1–2) and key terms (HYVs, IRRI, CIMMYT, salinization, pesticide resistance). Review the Topic 5.3 study guide on Fiveable for concise notes (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and practice more with AP-style questions (https://library.fiveable.me/practice/ap-environmental-science).

Irrigation moves water to crops when rainfall isn’t enough—pumping groundwater or surface water through canals, drip lines, sprinklers, or flood systems so plants get consistent moisture. Modern systems (center pivot, drip irrigation) improve efficiency by delivering water directly to roots or using timed pulses, which raises yields and enabled the Green Revolution’s high-yielding varieties to reach their potential. Irrigation’s important because it increases food production, allows multiple cropping seasons, and reduces reliance on variable rainfall (CED EK EIN-2.C.1: irrigation expansion). But overuse causes problems like salinization, waterlogging, aquifer depletion, and greater energy use for pumping (connects to mechanization and fertilizer reliance). For AP exam prep, know trade-offs: irrigation boosts yield but can degrade soil and water resources—a common FRQ theme in Unit 5 (see Topic 5.3 study guide: https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g). For extra practice, check unit resources (https://library.fiveable.me/ap-environmental-science/unit-5) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

GMOs are made by changing a crop’s DNA to give it new traits. Scientists identify a useful gene (like drought tolerance or a Bt gene for insect resistance), cut it out of one organism, and insert it into a plant using bacteria (Agrobacterium), a gene gun, or gene-editing tools like CRISPR. The modified gene is expressed in the plant so it shows the trait (e.g., herbicide tolerance so farmers can kill weeds without harming the crop, or pest resistance to reduce insect damage). On farms, GMOs increase yields (part of the Green Revolution idea of high-yielding varieties), can reduce some pesticide use, and enable mechanized practices—but they can also lower agrobiodiversity and create resistance issues. For APES, know examples (Bt, herbicide-tolerant crops), pros/cons, and links to monoculture and pesticide resistance (CED EK EIN-2.C.1). Review Topic 5.3 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

The Green Revolution (HYVs, synthetic N fertilizer, irrigation, pesticides, mechanization—think Norman Borlaug and IRRI/CIMMYT) massively raised crop yields per hectare. That jump in food supply reduced famines and death rates, so more people survived and global population climbed—in effect raising Earth's short-term carrying capacity. On the APES exam you should link cause → effect: new agricultural techs increased production → lowered mortality/increased food security → population growth. Also note the trade-offs listed in the CED (salinization from irrigation, agrobiodiversity loss, pesticide resistance, fossil-fuel reliance) that can limit long-term sustainability and create feedbacks affecting future food supply and population trends. For a quick topic review, see the Green Revolution study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

Pesticides help by directly reducing crop losses—killing insects, fungi, or weeds so high-yielding varieties (HYVs) from the Green Revolution can produce more food. That’s why farmers use them: faster, predictable increases in yield and profit (EK EIN-2.C.1). But they also cause problems: they can kill non-target species (reducing agrobiodiversity), contaminate soil and water, and select for pesticide-resistant pests that reproduce faster (pesticide resistance). Overuse and monoculture amplify those negatives, increasing chemical inputs and ecosystem harm (CED keywords: chemical pesticides, monoculture, pesticide resistance, agrobiodiversity loss). On the AP exam, you might be asked to explain both benefits and trade-offs and propose sustainable alternatives (e.g., integrated pest management, crop rotation). For a focused review, check the Topic 5.3 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

The Green Revolution massively increased global food production by introducing high-yielding varieties (HYVs) like dwarf wheat (Rht genes) and IR8 rice, plus mechanization, synthetic nitrogen fertilizer, irrigation expansion, and chemical pesticides. Led by scientists like Norman Borlaug and centers such as CIMMYT and IRRI, these changes boosted yields enough to avert famines and support growing populations. But there were trade-offs: widespread monoculture and loss of agrobiodiversity, increased reliance on fossil fuels for mechanization, irrigation-induced salinization, pesticide resistance, and runoff from fertilizers causing eutrophication. Socially, benefits were uneven—wealthier farmers gained most, which increased inequality. For APES, focus on EK EIN-2.C.1–2.C.2: list the strategies (HYVs, GMOs, fertilizer, irrigation, pesticides, mechanization) and both positive (higher yields, food security) and negative (environmental degradation, resistance, agrobiodiversity loss) outcomes. Review Topic 5.3 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g) and practice questions (https://library.fiveable.me/practice/ap-environmental-science) for exam-style examples.

You see Green Revolution tech all over modern agriculture. Real-world examples: high-yielding dwarf wheat and IR8/modern rice varieties developed by CIMMYT and IRRI (bred for higher yields and disease resistance), heavy use of synthetic nitrogen fertilizers and chemical pesticides, expanded irrigation systems (canals and center-pivot irrigation), and mechanization with tractors/combines. Today many farms also use GMO crops (herbicide- or pest-resistant varieties) and precision-agriculture tools (GPS-guided tractors, variable-rate fertilizer application) to boost efficiency. These changes map to the CED’s EIN-2.C (mechanization, GMOs, fertilization, irrigation, pesticides). Remember tradeoffs the exam likes: salinization from irrigation, pesticide resistance, monoculture and agrobiodiversity loss, and increased fossil fuel use. For more review, see the Topic 5.3 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g), the Unit 5 overview (https://library.fiveable.me/ap-environmental-science/unit-5), and practice questions (https://library.fiveable.me/practice/ap-environmental-science).

You need to know agricultural practices because Topic 5.3 (EIN-2.C) is core to Unit 5 (Land & Water Use), which is 10–15% of the exam—questions can show up in both multiple choice and free-response. The CED expects you to describe Green Revolution changes (mechanization, GMOs/HYVs, synthetic N fertilizer, irrigation, pesticides) and their impacts (salinization, monoculture, pesticide resistance, agrobiodiversity loss, fossil fuel reliance). On the exam you’ll be asked to explain processes, analyze data, do calculations (Practice 6), and propose/justify solutions (Practice 7)—for example, FRQs often ask you to evaluate irrigation impacts or fertilizer trade-offs and calculate application rates. Learn the keywords (Norman Borlaug, IRRI, Rht genes, salinization) and cause–effect links so you can describe, justify, and calculate quickly. For focused review, use the Topic 5.3 study guide (https://library.fiveable.me/ap-environmental-science/unit-5/green-revolution/study-guide/peuUQ0oN39WWAmVQVC2g), Unit 5 overview (https://library.fiveable.me/ap-environmental-science/unit-5), and practice problems (https://library.fiveable.me/practice/ap-environmental-science).