Asked by Pman
Consider this claim: Changes in environmental conditions always result in new ecosystems and loss of biodiversity characterized by an increase in the number of some species, the evolution of new species, and the extinction of some species.
Use what you have learned from the lesson, as well as reliable and reputable resources, to evaluate this claim. Use at least three examples from the lesson and other sources to support the valid ideas in the claim and refute the invalid ones. Add a list of your resources at the end of your response. Then, draw a conclusion about the stability of ecosystems, how and what can affect the stability of ecosystems, and how changes in the environment may affect the types and number of living things in an ecosystem.
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Short answer: The claim is partly true but too absolute. Environmental changes often do alter ecosystems and can cause increases in some species and extinctions of others, but they do not always produce “new ecosystems,” and they do not always cause net losses of biodiversity or the evolution of new species. Whether change produces loss or gain, local or global effects, or speciation depends on the magnitude, rate, and scale of the change and on species’ biology and landscape context.
I’ll evaluate each part of the claim, give examples that support or refute it, and finish with a summary about ecosystem stability and how environmental change affects the number and types of organisms.
1) “Changes in environmental conditions always result in new ecosystems”
- Why this is too strong: “Always” is incorrect. Some changes produce short-term disturbances but the original ecosystem may recover (high resilience). Other changes shift community composition without creating a fundamentally different ecosystem. Whether a “new ecosystem” appears depends on how big, fast, and persistent the change is.
- Supporting example (change → new ecosystem over time): Krakatau / Surtsey island succession — after volcanic eruptions exposed bare rock, these islands were colonized and underwent primary succession, producing communities quite different from the pre-eruption situation. This shows how major disturbances can generate new ecosystem assembly over decades to centuries.
- Source example: Surtsey research / island colonization literature; classic island biogeography and primary succession studies.
- Refuting example (change but recovery to prior state): Many temperate forests recover after moderate disturbances (storms, fires) through secondary succession and return to a state similar to the pre-disturbance community. The intermediate-disturbance idea shows that not every disturbance produces a permanently “new” ecosystem.
- Source example: US Forest Service and ecological succession literature.
2) “Changes … always result in loss of biodiversity”
- Why this is too strong: Effects on biodiversity vary. Some disturbances reduce diversity (especially intense or novel changes), but some disturbances can increase local diversity (at least temporarily) by creating new habitats or by reducing dominance of a single species (the intermediate-disturbance hypothesis).
- Supporting example (biodiversity loss): Coral bleaching from ocean warming and acidification has caused large losses of coral species and the complex reef habitat they create, reducing overall reef biodiversity in many regions (e.g., repeated mass-bleaching events on the Great Barrier Reef).
- Source: IPCC assessments; Hughes et al., 2017 (mass bleaching).
- Counterexample (local increase or shift in diversity): In some disturbed systems, opportunistic or invasive species increase in number, and local species richness can rise temporarily. For example, after some types of disturbance or nutrient enrichment, fast-growing opportunists may increase abundance and local species counts can temporarily rise even while native specialists decline.
- Theory: Intermediate-disturbance hypothesis and studies showing transient increases in local diversity after moderate disturbances.
3) “Changes … characterized by an increase in the number of some species”
- True and well supported: Environmental change rarely affects all species equally. Some species benefit and increase in numbers (generalists, r-strategists, invasive species, range-expanding species), while others decline. This heterogeneity of responses is well documented.
- Examples:
- Zebra mussels in the North American Great Lakes: introduction of zebra mussels caused dramatic increases in mussel biomass and major shifts in benthic communities; some native species declined.
- Source: USGS, Great Lakes invasive species literature.
- Range-shifting species under climate warming: many temperate plants and animals have expanded poleward or uphill, increasing local abundance in newly favorable regions (e.g., some temperate insects and plants).
- Source: IPCC WG2 and species-range shift literature.
4) “Changes … characterized by the evolution of new species”
- Not generally true as an immediate or necessary outcome: Speciation is a long-term evolutionary process that requires reproductive isolation and many generations. Environmental change can create conditions that promote speciation (new niches, geographic isolation), but it does not reliably or quickly produce new species. In many cases, change leads to migration, local adaptation, or extinction rather than speciation.
- Example illustrating slowness/conditionality: The classic examples of rapid speciation (e.g., cichlid fishes in African lakes, Darwin’s finches) require specific circumstances and long periods. Most modern environmental changes (especially rapid human-driven changes) are too fast for new species to evolve before populations decline or go extinct.
- Source: evolutionary biology literature; reviews on rates of speciation vs. rates of environmental change.
5) “Changes … characterized by the extinction of some species”
- True in many cases: Environmental change (climate change, habitat destruction, pollution, introduced pathogens) has caused many extinctions, and continues to raise extinction risks. Extinctions can be local or global.
- Examples:
- Amphibian declines and extinctions from the chytrid fungus (Batrachochytrium dendrobatidis) combined with habitat loss and climate impacts: many species have declined or gone extinct.
- Source: Skerratt et al., 2007 (Science) and IUCN amphibian assessments.
- Coral reef species declines tied to mass bleaching and ocean warming (multiple reports).
- Historical extinctions tied to habitat change and human arrival (e.g., the dodo, passenger pigeon), demonstrating how environmental change (often human-caused) can cause extinctions.
Synthesis using at least three concrete examples (summary):
- Coral reefs (Great Barrier Reef and global reefs): warming and acidification have produced repeated mass-bleaching events that kill corals, reducing reef structural complexity and biodiversity. Some algae and opportunistic species increase, but many specialized reef species decline. This supports that environmental change can cause extinctions and increases of some species, and can produce fundamentally altered reef ecosystems (Hughes et al., IPCC).
- Yellowstone wolves: removal and reintroduction of a top predator changed community structure and ecosystem processes. Wolf reintroduction altered elk behavior and numbers, which affected vegetation and riparian systems and had cascading effects on other species. This shows that environmental or management changes can shift ecosystem structure without necessarily creating a completely new ecosystem; it can also restore prior conditions (National Park Service and ripple/beschta literature).
- Mount St. Helens / Surtsey / Krakatau primary succession: volcanic eruptions created bare substrates that have been colonized over decades, producing new assemblages and demonstrating that major changes can generate new ecosystems over time (USGS, island succession studies).
- Zebra mussels (Great Lakes): an invasive-species-driven environmental change increased the abundance of one species group and altered ecosystem function, showing that some species may flourish while others decline (USGS/invasive species studies).
- Amphibian chytrid declines: novel pathogens plus environmental stressors have led to extinctions and severe declines, showing that environmental change can directly drive loss of species (Skerratt et al. and IUCN).
Conclusions about ecosystem stability and effects of environmental change
- Stability is context-dependent. Two related but distinct concepts are important:
- Resistance: ability of an ecosystem to remain unchanged when disturbed.
- Resilience: ability to recover after disturbance.
- What affects stability and outcomes:
- Magnitude and rate of change: Slow, small changes allow migration or adaptation; rapid, large changes are more likely to cause extinctions and irreversible shifts.
- Type of change: Novel stressors (e.g., introduced pathogens, invasive species, anthropogenic climate change) can have particularly disruptive effects.
- Species traits: Generalists, fast reproducers, and good dispersers are more likely to increase; specialists and poor dispersers are most vulnerable.
- Connectivity and refugia: Landscapes with corridors, refuges, and intact habitat facilitate migration and recovery.
- Biodiversity and redundancy: Systems with higher functional redundancy (multiple species performing similar roles) can be more resilient.
- Human actions: Land-use, pollution, harvesting, and conservation measures strongly mediate outcomes.
- How changes affect types and number of living things:
- Some species increase, some decrease, and some go extinct; overall biodiversity may increase locally, decrease locally, or decrease globally depending on the balance of these changes.
- New species (speciation) are a possible long-term outcome, but not an immediate or guaranteed consequence of environmental change.
- Rapid anthropogenic change tends to favor generalists and invasives and threatens specialists and endemic species, often producing biotic homogenization (different places becoming more similar in species composition).
Practical implications
- Because outcomes are variable (not “always” the same), management should focus on: reducing the rate and scale of damaging changes (e.g., greenhouse gas mitigation, habitat protection), maintaining connectivity and refugia, and targeted conservation for vulnerable species and ecosystems.
- Monitoring is essential to detect when a system is crossing thresholds that make recovery unlikely.
Resources and further reading
- Hughes, T. P., et al. (2017). Global warming and recurrent mass bleaching of corals. Science. (summary and review articles on coral bleaching)
- IPCC (AR5/AR6) reports — sections on ecosystems, biodiversity, and climate impacts.
- USGS / National Oceanic and Atmospheric Administration (NOAA) — Great Lakes invasive species (zebra mussel) fact sheets.
- National Park Service — Yellowstone wolves and ecosystem effects.
- Skerratt, L. F., et al. (2007). Spread of chytrid fungus and amphibian declines. Science; IUCN Amphibian Specialist Group reports.
- USGS and research on Mount St. Helens ecological recovery; Surtsey Research Society webpages and island colonization literature.
- Connell, J. H. (1978). Diversity in tropical rain forests and coral reefs — intermediate disturbance hypothesis (classic theory).
- Reviews of species range shifts and climate change impacts: Parmesan, C. (2006) and IPCC WG2 ecosystem chapters.
If you’d like, I can:
- Provide direct links or PDFs to any of the cited papers or agency pages.
- Expand any example into a one-page case study with timeline, data, and references.
- Discuss specific ecosystems (your local region, a marine vs. terrestrial comparison) in more detail.
I’ll evaluate each part of the claim, give examples that support or refute it, and finish with a summary about ecosystem stability and how environmental change affects the number and types of organisms.
1) “Changes in environmental conditions always result in new ecosystems”
- Why this is too strong: “Always” is incorrect. Some changes produce short-term disturbances but the original ecosystem may recover (high resilience). Other changes shift community composition without creating a fundamentally different ecosystem. Whether a “new ecosystem” appears depends on how big, fast, and persistent the change is.
- Supporting example (change → new ecosystem over time): Krakatau / Surtsey island succession — after volcanic eruptions exposed bare rock, these islands were colonized and underwent primary succession, producing communities quite different from the pre-eruption situation. This shows how major disturbances can generate new ecosystem assembly over decades to centuries.
- Source example: Surtsey research / island colonization literature; classic island biogeography and primary succession studies.
- Refuting example (change but recovery to prior state): Many temperate forests recover after moderate disturbances (storms, fires) through secondary succession and return to a state similar to the pre-disturbance community. The intermediate-disturbance idea shows that not every disturbance produces a permanently “new” ecosystem.
- Source example: US Forest Service and ecological succession literature.
2) “Changes … always result in loss of biodiversity”
- Why this is too strong: Effects on biodiversity vary. Some disturbances reduce diversity (especially intense or novel changes), but some disturbances can increase local diversity (at least temporarily) by creating new habitats or by reducing dominance of a single species (the intermediate-disturbance hypothesis).
- Supporting example (biodiversity loss): Coral bleaching from ocean warming and acidification has caused large losses of coral species and the complex reef habitat they create, reducing overall reef biodiversity in many regions (e.g., repeated mass-bleaching events on the Great Barrier Reef).
- Source: IPCC assessments; Hughes et al., 2017 (mass bleaching).
- Counterexample (local increase or shift in diversity): In some disturbed systems, opportunistic or invasive species increase in number, and local species richness can rise temporarily. For example, after some types of disturbance or nutrient enrichment, fast-growing opportunists may increase abundance and local species counts can temporarily rise even while native specialists decline.
- Theory: Intermediate-disturbance hypothesis and studies showing transient increases in local diversity after moderate disturbances.
3) “Changes … characterized by an increase in the number of some species”
- True and well supported: Environmental change rarely affects all species equally. Some species benefit and increase in numbers (generalists, r-strategists, invasive species, range-expanding species), while others decline. This heterogeneity of responses is well documented.
- Examples:
- Zebra mussels in the North American Great Lakes: introduction of zebra mussels caused dramatic increases in mussel biomass and major shifts in benthic communities; some native species declined.
- Source: USGS, Great Lakes invasive species literature.
- Range-shifting species under climate warming: many temperate plants and animals have expanded poleward or uphill, increasing local abundance in newly favorable regions (e.g., some temperate insects and plants).
- Source: IPCC WG2 and species-range shift literature.
4) “Changes … characterized by the evolution of new species”
- Not generally true as an immediate or necessary outcome: Speciation is a long-term evolutionary process that requires reproductive isolation and many generations. Environmental change can create conditions that promote speciation (new niches, geographic isolation), but it does not reliably or quickly produce new species. In many cases, change leads to migration, local adaptation, or extinction rather than speciation.
- Example illustrating slowness/conditionality: The classic examples of rapid speciation (e.g., cichlid fishes in African lakes, Darwin’s finches) require specific circumstances and long periods. Most modern environmental changes (especially rapid human-driven changes) are too fast for new species to evolve before populations decline or go extinct.
- Source: evolutionary biology literature; reviews on rates of speciation vs. rates of environmental change.
5) “Changes … characterized by the extinction of some species”
- True in many cases: Environmental change (climate change, habitat destruction, pollution, introduced pathogens) has caused many extinctions, and continues to raise extinction risks. Extinctions can be local or global.
- Examples:
- Amphibian declines and extinctions from the chytrid fungus (Batrachochytrium dendrobatidis) combined with habitat loss and climate impacts: many species have declined or gone extinct.
- Source: Skerratt et al., 2007 (Science) and IUCN amphibian assessments.
- Coral reef species declines tied to mass bleaching and ocean warming (multiple reports).
- Historical extinctions tied to habitat change and human arrival (e.g., the dodo, passenger pigeon), demonstrating how environmental change (often human-caused) can cause extinctions.
Synthesis using at least three concrete examples (summary):
- Coral reefs (Great Barrier Reef and global reefs): warming and acidification have produced repeated mass-bleaching events that kill corals, reducing reef structural complexity and biodiversity. Some algae and opportunistic species increase, but many specialized reef species decline. This supports that environmental change can cause extinctions and increases of some species, and can produce fundamentally altered reef ecosystems (Hughes et al., IPCC).
- Yellowstone wolves: removal and reintroduction of a top predator changed community structure and ecosystem processes. Wolf reintroduction altered elk behavior and numbers, which affected vegetation and riparian systems and had cascading effects on other species. This shows that environmental or management changes can shift ecosystem structure without necessarily creating a completely new ecosystem; it can also restore prior conditions (National Park Service and ripple/beschta literature).
- Mount St. Helens / Surtsey / Krakatau primary succession: volcanic eruptions created bare substrates that have been colonized over decades, producing new assemblages and demonstrating that major changes can generate new ecosystems over time (USGS, island succession studies).
- Zebra mussels (Great Lakes): an invasive-species-driven environmental change increased the abundance of one species group and altered ecosystem function, showing that some species may flourish while others decline (USGS/invasive species studies).
- Amphibian chytrid declines: novel pathogens plus environmental stressors have led to extinctions and severe declines, showing that environmental change can directly drive loss of species (Skerratt et al. and IUCN).
Conclusions about ecosystem stability and effects of environmental change
- Stability is context-dependent. Two related but distinct concepts are important:
- Resistance: ability of an ecosystem to remain unchanged when disturbed.
- Resilience: ability to recover after disturbance.
- What affects stability and outcomes:
- Magnitude and rate of change: Slow, small changes allow migration or adaptation; rapid, large changes are more likely to cause extinctions and irreversible shifts.
- Type of change: Novel stressors (e.g., introduced pathogens, invasive species, anthropogenic climate change) can have particularly disruptive effects.
- Species traits: Generalists, fast reproducers, and good dispersers are more likely to increase; specialists and poor dispersers are most vulnerable.
- Connectivity and refugia: Landscapes with corridors, refuges, and intact habitat facilitate migration and recovery.
- Biodiversity and redundancy: Systems with higher functional redundancy (multiple species performing similar roles) can be more resilient.
- Human actions: Land-use, pollution, harvesting, and conservation measures strongly mediate outcomes.
- How changes affect types and number of living things:
- Some species increase, some decrease, and some go extinct; overall biodiversity may increase locally, decrease locally, or decrease globally depending on the balance of these changes.
- New species (speciation) are a possible long-term outcome, but not an immediate or guaranteed consequence of environmental change.
- Rapid anthropogenic change tends to favor generalists and invasives and threatens specialists and endemic species, often producing biotic homogenization (different places becoming more similar in species composition).
Practical implications
- Because outcomes are variable (not “always” the same), management should focus on: reducing the rate and scale of damaging changes (e.g., greenhouse gas mitigation, habitat protection), maintaining connectivity and refugia, and targeted conservation for vulnerable species and ecosystems.
- Monitoring is essential to detect when a system is crossing thresholds that make recovery unlikely.
Resources and further reading
- Hughes, T. P., et al. (2017). Global warming and recurrent mass bleaching of corals. Science. (summary and review articles on coral bleaching)
- IPCC (AR5/AR6) reports — sections on ecosystems, biodiversity, and climate impacts.
- USGS / National Oceanic and Atmospheric Administration (NOAA) — Great Lakes invasive species (zebra mussel) fact sheets.
- National Park Service — Yellowstone wolves and ecosystem effects.
- Skerratt, L. F., et al. (2007). Spread of chytrid fungus and amphibian declines. Science; IUCN Amphibian Specialist Group reports.
- USGS and research on Mount St. Helens ecological recovery; Surtsey Research Society webpages and island colonization literature.
- Connell, J. H. (1978). Diversity in tropical rain forests and coral reefs — intermediate disturbance hypothesis (classic theory).
- Reviews of species range shifts and climate change impacts: Parmesan, C. (2006) and IPCC WG2 ecosystem chapters.
If you’d like, I can:
- Provide direct links or PDFs to any of the cited papers or agency pages.
- Expand any example into a one-page case study with timeline, data, and references.
- Discuss specific ecosystems (your local region, a marine vs. terrestrial comparison) in more detail.
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