Change is a Constant
Our Earth, due to species interference and the life cycles, experiences constant changes. Some are slow and always evolving, some are fast and sporadic, and some are somewhere in the middle. Effects that these processes have can be drastic or negligible to certain ecosystems, and can happen to have short-term or longer-term effects. Manmade, or anthropogenic, disasters may be equal to any natural counterparts.
These alterations in Earth's happenings can be random (like a lightning strike from one storm), seasonal (the months in which hurricanes occur to form a hurricane season), or by episode (like stages of a volcanic eruption). For example, glaciers and climate change are contributing to sea level rise, which increases flooding in coastal cities or communities. These are manmade disasters that can have great effects on ecosystems. Naturally, disasters such as the cold can cause migrations, such as geese in Canada finding similar conditions further south to escape snow and ice storms during winter.
Resistance and Resilience
Resistance is a measurement of how much an ecosystem changes after a disruption (forest fire, invasive species...). If there is little change, the ecosystem has a high resistance and is considered to be quite stable. That is to say, this ecosystem would bear the brunt of the disaster without experiencing much internal damage.
Resilience is the measure of how quickly the ecosystem can ‘bounce back’ from the disturbance. It is a measure of how quickly an ecosystem can recover and rebuild its environment.
Intermediate Disturbance Hypothesis
Maximum species diversity is reached when an ecosystem experiences an intermediate level of disturbance. It is because both early and late succession species are able to survive at the same time. An early succession species (grasses, shrubs) is one that is able to exist in an ecosystem first, requiring fewer nutrients and existing with less interspecies competition. A late succession species is the opposite, and has found the ecosystem more recently. So, an ecosystem with a moderate amount of disturbance (detectable, not destructive!) will allow all succession levels to survive the best they can. 🎥 Watch: AP Environmental Science Streams
Frequently Asked Questions
What are natural disruptions to ecosystems and how are they different from human-made ones?
Natural disruptions are nonanthropogenic events or processes that change ecosystems suddenly or over long timescales—examples: volcanic eruptions, wildfires, hurricanes, droughts, floods, El Niño, Pleistocene glaciations, sea-level change, tectonic uplift, asteroid impacts (Chicxulub), coral bleaching, and permafrost thaw. They can be short-term (hurricane, wildfire) or long-term (glaciation, climate shifts) and often trigger ecological succession, habitat loss, migration, or even mass extinctions. Important: some natural disruptions can have impacts as large as or larger than human-made ones (CED EK ERT-2.G.1–.6). Human-made disruptions (e.g., deforestation, pollution, greenhouse-gas emissions) differ because they’re driven by human activities, often are continuous or cumulative, and can alter the frequency/intensity of natural disturbances (e.g., climate change increasing wildfire risk). For AP exam practice, be ready to explain short vs. long time scales, link processes to ecosystem responses (succession, migration, refugia), and use examples from the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU). For more review and practice problems check the Unit 2 overview (https://library.fiveable.me/ap-environmental-science/unit-2) and practice bank (https://library.fiveable.me/practice/ap-environmental-science).
Why do natural disruptions sometimes cause more damage than human activities?
Natural disruptions can cause more damage than human activities because they often act suddenly, affect huge areas, and change fundamental environmental conditions. Events like volcanic eruptions, asteroid impacts (Chicxulub), major wildfires, hurricanes, or Pleistocene glaciations can remove or radically alter habitat across thousands to millions of hectares, trigger mass extinctions, and force large-scale ecological succession and species migration. They also operate on different time scales (episodic or random vs. many human impacts that are chronic), so recovery can take centuries to millions of years (EK ERT-2.G.1, ERT-2.G.2, ERT-2.G.5). Some processes—sea-level shifts from glaciation or rapid climate swings (ENSO, permafrost thaw)—change physical baselines (temperature, pH, salinity), creating cascading effects like coral bleaching or loss of climate refugia. For AP exam prep, know examples, timescales, and outcomes (mass extinction, succession, migration) and review Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU). For more practice, see the Unit 2 overview (https://library.fiveable.me/ap-environmental-science/unit-2) and 1,000+ practice questions (https://library.fiveable.me/practice/ap-environmental-science).
I'm confused about the difference between periodic, episodic, and random Earth processes - can someone explain?
Think of Earth processes by how often they happen: - Periodic: predictable, regular cycles. Examples: seasons, El Niño–Southern Oscillation (periodic multi-year shifts), tidal cycles. They operate on known time scales so ecosystems often adapt (e.g., seasonal migration, breeding). - Episodic: irregular but caused by known processes and somewhat repeatable over years to centuries. Examples: volcanic eruptions, large wildfires, major droughts. They’re not on a strict schedule but are tied to drivers (tectonics, climate patterns) and can cause big short-term disruption and long-term succession. - Random: truly unpredictable, rare events with no clear timing pattern. Example: asteroid impacts (Chicxulub). These can produce massive, often catastrophic changes (mass extinctions) that ecosystems can’t anticipate. For the AP exam, you should be able to classify events and explain short- vs. long-term ecosystem impacts (ERT-2.G, EK ERT-2.G.2). Review Topic 2.5 study guide on Fiveable for examples and practice (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU).
What's the difference between short-term and long-term natural disruptions?
Short-term natural disruptions are events that happen quickly (hours to years) and cause immediate changes—think volcanic eruptions, hurricanes, wildfires, floods, or El Niño. They can cause large, sometimes local losses (mortality, habitat destruction) but ecosystems often recover through ecological succession, species migration, or rapid adaptation. Long-term disruptions operate over decades to millions of years (permafrost thaw, Pleistocene glaciations, sea-level change, tectonic uplift, or mass extinctions like the Chicxulub impact). These change climate or landscape at scale, shift biomes, alter sea level, and can drive long-term species migrations, loss of biodiversity, or new climate regimes. AP focus: know time-scale differences (periodic/episodic/random; EK ERT-2.G.2–5), examples (coral bleaching, permafrost thaw vs. hurricane, wildfire), and typical ecological responses (succession, refugia, migration). For a focused review, check the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).
How has Earth's climate changed over geological time and what causes these changes?
Over geological time Earth’s climate has swung between warm “greenhouse” and cold “icehouse” states because of several natural drivers. Major causes include plate tectonics (changing ocean/atmosphere circulation and volcanic CO2), large volcanic eruptions (short-term cooling from aerosols), asteroid impacts (rapid, severe short-term change—e.g., Chicxulub), Milankovitch orbital cycles (periodic changes in tilt, eccentricity, precession driving ice ages), solar output variability, and natural changes in greenhouse-gas levels (CO2, CH4, N2O). Those changes alter sea level (glaciations lock water in ice; melting raises seas), shift habitats, force species migration, and can trigger mass extinctions or long-term succession. For AP exam answers, name specific mechanisms (e.g., volcanic CO2 vs. volcanic aerosols, Milankovitch cycles, Chicxulub) and link climate shifts to habitat loss, migration, and biodiversity change (CED EK ERT-2.G.3–EKT-2.G.5). Review Topic 2.5 on Fiveable for concise notes (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).
Why does sea level change when glacial ice melts or forms?
When glacial ice melts or forms, global sea level changes for two main reasons: (1) redistribution of water between land and ocean and (2) changes in ocean volume. Ice that sits on land (continental glaciers and ice sheets, e.g., Greenland, Antarctica) stores freshwater; when it melts, that water runs into the ocean and raises sea level. By contrast, melting sea ice (floating ice) doesn’t change sea level much because it’s already displacing ocean water. (3) Also, warming that accompanies ice melt causes ocean water to expand (thermal expansion), which raises sea level further. Over geologic time, larger continental glaciations lock up water and lower sea level; when glaciers retreat, sea level rises (EK ERT-2.G.4). For AP review, see the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).
Can you give me examples of major environmental changes that cause habitat loss?
Major environmental changes that cause large-scale habitat loss include: volcanic eruptions (ash/lava bury habitats), large wildfires (remove vegetation and alter succession), hurricanes/storm surges and floods (destroy coastal and inland habitats), prolonged drought (loss of wetlands, tree die-off), and sea-level change from glacial cycles or modern warming (coastal habitat loss). Bigger, rarer events: Pleistocene glaciations (shifted ranges), tectonic uplift or subsidence (change local habitats), asteroid impacts like Chicxulub (mass extinction), and long-term climate change (warming, permafrost thaw, ocean warming → coral bleaching). These disturbances drive ecological succession, force species migration, create climate refugia, and can trigger mass extinctions (CED EKs ERT-2.G.1–EKT-2.G.6). For exam prep, know examples + mechanisms (how they alter abiotic factors and species distributions). Review Topic 2.5 study guide on Fiveable for concise examples and practice (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU) and try practice questions (https://library.fiveable.me/practice/ap-environmental-science).
What causes animals to migrate and how do natural disruptions affect migration patterns?
Animals migrate for resources, reproduction, and survival—think food, water, suitable breeding sites, and avoiding harsh seasons. Migration can be short-term (seasonal bird movements) or long-term (range shifts over decades). Natural disruptions—wildfires, droughts, hurricanes, volcanic eruptions, El Niño, Pleistocene glaciations, sea-level change—change habitat availability, resource timing, and cues animals use (temperature, day length, ocean currents). That forces changes in timing (phenology), routes, destinations, or causes population declines if suitable habitat disappears. Examples: reduced upwelling during El Niño decreases food for seabirds, shifting their migratory success; sea-level rise floods coastal breeding sites, pushing species to new areas or creating climate refugia. These effects tie directly to EK ERT-2.G.1–6 (habitat change, succession, migration). For AP prep, be ready to explain specific disruptions and link them to migration outcomes on free-response prompts. Review Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU), unit overview (https://library.fiveable.me/ap-environmental-science/unit-2), and practice problems (https://library.fiveable.me/practice/ap-environmental-science).
I don't understand how natural disasters can be worse than pollution - is this actually true?
Short answer: yes—natural disasters can be as bad or worse than pollution, depending on scale and timing (this is exactly what EK ERT-2.G.1 says). Why: some natural events (volcanic eruptions, major hurricanes, asteroid impacts like Chicxulub, large wildfires, glaciation/sea-level shifts) cause rapid, large-scale habitat loss, mass mortality, and long-term ecosystem change (succession, migrations, even mass extinctions). Those are episodic or random earth system processes that operate at big spatial and temporal scales (EK ERT-2.G.2, ERT-2.G.5). Pollution tends to be chronic and local-to-regional, but it’s cumulative and persistent (so severe in different ways). For the AP exam, be ready to compare short vs long term impacts, give examples (volcano, drought, El Niño, coral bleaching), and explain recovery via succession and migration (ERT-2.G objectives). For a focused review see the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).
How do volcanic eruptions or earthquakes impact entire ecosystems?
Volcanic eruptions and earthquakes can reshape entire ecosystems both quickly and for centuries. Short-term effects: ash, lava, and pyroclastic flows bury plants, kill animals, reduce light for photosynthesis, and contaminate water with ash and toxins. Earthquakes cause landslides, soil liquefaction, and sudden habitat loss. Those are episodic disturbances that can cause big immediate mortality (EK ERT-2.G.1, ERT-2.G.2). Long-term effects: new land from lava and ash starts primary ecological succession—pioneer species colonize, soil develops, and biodiversity gradually increases or changes (EK ERT-2.G.5). Tectonic uplift or subsidence can alter coastlines and create or remove habitat; repeated upheaval can force species migration or create climate refugia (ERT-2.G.6, keywords: tectonic uplift, ecological succession, species migration). Large events can contribute to regional extinctions if habitats vanish. For AP review, focus on cause → immediate impact → succession/migration → long-term community change. For a deeper recap, check the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU) and try related practice problems (https://library.fiveable.me/practice/ap-environmental-science).
What happens to wildlife populations when their habitat gets destroyed by natural events?
If a natural event (wildfire, hurricane, volcano, flood, drought, etc.) destroys habitat, wildlife populations often drop quickly—individuals die, reproduction falls, and carrying capacity for that area falls. Short-term responses include immediate mortality, displacement/migration to refugia, and altered species interactions (more competition, opportunistic species expand). Long-term outcomes depend on disturbance severity and frequency: ecological succession can gradually rebuild habitat and allow recolonization, but repeated or massive changes can cause local extinctions or even contribute to broader declines (think Pleistocene glaciations or mass extinctions). Some species recover fast (r-selected, generalists); others (specialists, low reproductive rates) may not. For AP purposes link this to EK ERT-2.G.1 and ERT-2.G.5: natural disruptions can equal or exceed human impacts and commonly change large swaths of habitat. For more review see the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU), Unit 2 overview (https://library.fiveable.me/ap-environmental-science/unit-2), and extra practice (https://library.fiveable.me/practice/ap-environmental-science).
Why do some species survive natural disruptions better than others?
Some species survive natural disruptions better because of their traits, life history, and where they live. Key factors: being a generalist (broad diet/tolerance) vs. a specialist, high reproductive rate (r-selected species bounce back faster), large or connected populations (more genetic diversity), mobility or ability to migrate to climate refugia, and physical adaptations (thick bark for fire, burrowing for floods). Habitat factors matter too: intact refugia or nearby undisturbed areas let recolonization happen, and ecosystems with more biodiversity recover faster through succession. On the APES exam, you should tie these ideas to CED concepts like ecological succession, species migration, and mass extinction (Topic 2.5 keywords: wildfire, hurricane, coral bleaching, permafrost thaw). For extra review, see the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU) and practice questions (https://library.fiveable.me/practice/ap-environmental-science).
How long does it take for ecosystems to recover from major natural disruptions like hurricanes or wildfires?
Short answer: it depends—recovery can take from months to centuries. After a disturbance like a wildfire or hurricane, most ecosystems undergo ecological succession. Secondary succession (soil intact) often shows visible recovery in years–decades (grasses and shrubs in 1–5 years, young trees in decades), but full mature forest structure can take 50–200+ years. Severe disturbances that remove soil or kill foundational species (e.g., intense crown fires, coral bleaching) may require decades to centuries or lead to a different stable state. Primary succession (no soil) takes much longer—centuries to millennia. Drivers that set recovery time: disturbance severity, life histories of key species, climate, connectivity (migration/refugia), and human impacts. This ties directly to the CED ideas on ecological succession and natural disruptions (ERT-2.G; keywords: wildfire, hurricane, ecological succession). For AP review, see the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU), the Unit 2 overview (https://library.fiveable.me/ap-environmental-science/unit-2), and extra practice problems (https://library.fiveable.me/practice/ap-environmental-science).
What's the connection between ice ages and sea level changes throughout Earth's history?
When large ice sheets form during ice ages, lots of Earth’s water gets locked up as continental glacial ice, so global sea level falls; during the Last Glacial Maximum (~20,000 years ago) sea level was roughly 120 meters lower than today. When the climate warms and glaciers melt, that water returns to the oceans and sea level rises—flooding coastal habitats, changing shorelines, and forcing species migrations or local extinctions. This is exactly EK ERT-2.G.4: sea level varies with glacial ice volume and EK ERT-2.G.5: major environmental change reshapes habitats. For AP prep, remember time scales matter (Pleistocene glaciations are long-term, periodic disruptions) and link to ecosystem impacts like shifts in coastal wetlands and migration corridors. For more review, see the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU), the Unit 2 overview (https://library.fiveable.me/ap-environmental-science/unit-2), and practice problems (https://library.fiveable.me/practice/ap-environmental-science).
Can natural disruptions actually be beneficial for ecosystems in some cases?
Yes—natural disruptions can be beneficial in many cases. Disturbances like wildfire, flooding, volcanic eruptions, or storms often reset ecosystems, start ecological succession, recycle nutrients, create new habitat mosaics, and increase long-term biodiversity (EK ERT-2.G.1, ERT-2.G.5). For example, some plants need fire to release seeds or clear competing vegetation; floods deposit nutrient-rich silt that boosts productivity; tectonic uplift or glaciation creates new habitats over geological time (EK ERT-2.G.2, ERT-2.G.4). These processes also drive migration and the formation of climate refugia (ERT-2.G.6). On the AP exam, expect questions that ask you to explain short- vs long-term impacts or connect a disruption to succession or species migration (Practice 1/5; Topic 2.5). For a focused review, check the Topic 2.5 study guide (https://library.fiveable.me/ap-environmental-science/unit-2/natural-disruptions-ecosystems/study-guide/QpHtIjQYZUMm1mTZghkU), the Unit 2 overview (https://library.fiveable.me/ap-environmental-science/unit-2), and practice questions (https://library.fiveable.me/practice/ap-environmental-science).