Question 1
Distinguish between direct and indirect human threats to biodiversity, giving one example of each.
[4]
Question 2
A marine mammal has an estimated population of 900 individuals. Its population has declined by 64% over three generations, it breeds once every four years, and it occupies a small coastal range affected by gillnet fishing.
Identify four types of information used by the IUCN that are included in this description.
[4]
Question 3
A forest landscape was surveyed before and after construction of a road and expansion of farmland. Figure 1 shows the changes in habitat distribution. Figure 2 summarizes measurements derived from the surveys.
Landscape measurements from surveys in Year 1 and Year 12.
| Landscape measurement | Year 1 | Year 12 |
|---|---|---|
| Total native-forest area / ha | 520 | 310 |
| Connected core habitat / ha | 480 | 180 |
| Separate forest patches | 1 | 6 |
Calculate the percentage decrease in connected core habitat area between Year 1 and Year 12.
[1]
Describe two changes indicating that habitat fragmentation occurred.
[2]
Explain how the changes shown could reduce the genetic diversity of a forest animal population.
[3]
Question 4
Students investigate the effect of trampling on plant diversity beside a recreational footpath. Their proposed sampling plan is shown in Figure 1.
Identify the independent variable in this investigation.
[1]
Outline three features of the sampling plan that increase the validity or reliability of the investigation.
[3]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 5
The brown tree snake was accidentally transported to Guam in cargo. It encountered abundant prey and few predators, and several native forest-bird populations subsequently declined.
Explain how the introduction of the brown tree snake reduced local biodiversity on Guam.
[4]
Question 6
Outline one way a government may use IUCN Red List information and one limitation affecting its decision.
[2]
Outline one way an environmental NGO may use the same information and one limitation affecting its decision.
[2]
Question 7
The Bale Mountains contain threatened, geographically restricted species including the Ethiopian wolf and mountain nyala. Their high-altitude habitats also regulate water supplies to surrounding river basins.
Distinguish between identifying a site as a key biodiversity area and legally protecting the site.
[2]
Outline two reasons why the Bale Mountains may qualify as an international conservation priority.
[2]
Question 8
A new recreational trail was opened through Belora Forest in 2021. Ecologists investigated plant diversity along four transects laid perpendicular to the trail. Identical quadrats were sampled during the same month in 2023.
Plant diversity, ground cover and soil conditions at increasing distances from the recreational trail; each value is a mean from four quadrats.
| Distance from trail / m | Mean species richness / species per quadrat | Mean Simpson's diversity index | Mean soil penetration resistance / MPa | Mean bare ground / % |
|---|---|---|---|---|
| 0 | 5 | 0.42 | 3.8 | 62 |
| 10 | 8 | 0.58 | 3.1 | 43 |
| 30 | 12 | 0.73 | 2.4 | 24 |
| 60 | 16 | 0.84 | 1.8 | 11 |
| 100 | 17 | 0.86 | 1.7 | 9 |
Calculate the percentage increase in mean plant species richness between 0 m and 60 m from the trail.
[2]
Describe the relationship between distance from the trail and plant diversity.
[2]
Explain how recreational use of the trail may have produced the pattern in plant diversity.
[3]
Distinguish between the direct and indirect human threats to biodiversity represented by this case study.
[3]
Evaluate the conclusion that recreational use of the trail caused the observed change in plant diversity.
[4]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 9
Students investigated plant diversity along a transect perpendicular to a heavily used footpath. At each distance they combined the abundance recorded in five quadrats. The results are shown in Table 1.
Table 1. Combined plant abundance from five quadrats at increasing distances from a footpath.
| Plant species / measurement | 0 m | 10 m | 20 m | 40 m |
|---|---|---|---|---|
| Species A | 12 | 10 | 7 | 5 |
| Species B | 4 | 4 | 4 | 4 |
| Species C | 2 | 2 | 3 | 4 |
| Species D | 1 | 2 | 3 | 4 |
| Species E | 1 | 2 | 3 | 3 |
| Total abundance | 20 | 20 | 20 | 20 |
| Mean soil compaction / MPa | 3.8 | 3.1 | 2.4 | 1.6 |
Simpson's diversity index was calculated using:
where is the abundance of each species and is the total abundance of all species.
Calculate Simpson's diversity index for the plants sampled at 0 m from the footpath.
[2]
Compare plant diversity at 0 m and 40 m from the footpath.
[1]
Suggest two reasons why the data do not demonstrate that trampling caused the observed difference in diversity, and one improvement that would strengthen the investigation.
[3]
Question 10
An alien shore crab was first recorded in Port Azul in 2012 after arriving in ballast water. The crab feeds on native snails and competes with them for shelter. A trapping programme began at the end of 2022.
Identify the period that most clearly represents the lag phase of the crab invasion.
[1]
Calculate the percentage decrease in mean crab abundance between 2022 and 2024.
[2]
Explain how the data support the conclusion that the crab is invasive, and assess the short-term effectiveness of trapping.
[3]
Question 11
A conservation agency is reviewing assessments for three mammal species. Figure 1 summarizes the available evidence. Species C is currently classified as data deficient (DD).
Figure 1. Summary of available evidence for three mammal species.
| Evidence | Species A | Species B | Species C |
|---|---|---|---|
| Estimated population 10 years ago / individuals | 6400 | 310 | Unknown |
| Current estimated population / individuals | 2200 | 190 | Unknown |
| Range or survey coverage / km^2 or % | ; fragmented | Only of potential range surveyed | |
| Breeding potential / offspring per adult female per year | One offspring per adult female per year | One offspring per adult female every 3 years | Unknown |
| Known threat(s) | Habitat clearance | Accidental capture in fishing gear | Mining and road construction |
| Current assessment category | Not stated | Not stated | DD |
| Evidence note | All values are estimates | All values are estimates | DD: available evidence is inadequate to assign extinction risk |
Calculate the percentage decline in the estimated population of species A.
[2]
Identify two characteristics that make species B vulnerable to extinction.
[2]
Explain why the data deficient classification of species C should not be interpreted as evidence that it is at low risk of extinction.
[2]
Question 12
Commercial whaling reduced many humpback whale populations to very low levels. International restrictions on commercial whaling and national protection were subsequently introduced.
Explain two ecological and two societal consequences of the recovery of humpback whale populations.
[4]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 13
Pacific bluefin tuna migrate across national jurisdictions and the high seas. Fishing fleets compete for the same stock, and juveniles are often caught before reaching reproductive age.
Explain how this fishery may demonstrate the tragedy of the commons.
[4]
Question 14
Explain why habitat destruction in tropical biodiversity hotspots may produce especially large global biodiversity losses and why conserving these areas can be challenging.
[4]
Question 15
Figure 3 compares patch-mosaic burning with a landscape where fire has been excluded for a long period.
Explain two ways patch-mosaic burning may support biodiversity.
[2]
Outline two challenges to the continuation of this traditional indigenous land-management practice.
[2]
Question 16
Red lionfish were first recorded near the Caribbean island of Santa Isela in 2008, probably after releases from aquariums elsewhere in the region. Lionfish consume small reef fish and have few predators in the invaded ecosystem. Divers began removing lionfish from selected reefs in 2017.
Figure 2(c). Mean values (± SE) for six removal reefs and six unmanaged reefs surveyed in 2023. Reefs had similar depth and coral cover before the removal programme.
| Measure | Removal reefs () | Unmanaged reefs () |
|---|---|---|
| Lionfish density [individuals ha] | ||
| Native juvenile biomass [kg ha] | ||
| Native reef-fish richness [species] |
Identify two human-mediated stages by which lionfish reached and spread within the new ecosystem.
[2]
Calculate the percentage reduction in mean lionfish density on removal reefs compared with unmanaged reefs in 2023.
[2]
Describe the change in lionfish density between 2008 and 2023.
[2]
Explain two mechanisms by which lionfish may reduce native reef-fish biodiversity.
[4]
Evaluate the effectiveness of diver removal as a strategy for reducing the impact of lionfish around Santa Isela.
[5]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 17
The Iberian lynx is a specialist predator whose principal prey is the European rabbit. Habitat loss, declining rabbit populations and road mortality caused a severe decline. Conservation measures included habitat restoration, captive breeding and release, wildlife crossings, supplementary rabbit management and monitoring.
Calculate the factor by which the estimated Iberian lynx population increased between 2002 and 2023.
[2]
Identify two criteria, other than number of individuals, that support continued assessment of the lynx's extinction risk.
[2]
Explain how habitat corridors and wildlife crossings may contribute to recovery of the lynx population.
[3]
Explain why changing the global conservation category may influence conservation priorities.
[3]
Evaluate the claim that the conservation programme has secured the long-term future of the Iberian lynx.
[4]
Question 18
Three national fleets harvest the same migratory fish stock in the Pelagos Sea. No fleet owns the stock, and fishing occurs both within national waters and on the high seas. Figure 1 shows changes in spawning biomass, total catch and fishing capacity.
Pelagos Sea fishery indicators during a period of voluntary catch limits.
| Year | Spawning biomass / 1000 t | Sustainable minimum / 1000 t | North catch / 1000 t | Central catch / 1000 t | South catch / 1000 t | Total catch / 1000 t | Vessel capacity |
|---|---|---|---|---|---|---|---|
| 2005 | 800 | 400 | 32 | 31 | 32 | 95 | 320 |
| 2010 | 620 | 400 | 44 | 43 | 43 | 130 | 410 |
| 2015 | 390 | 400 | 59 | 58 | 58 | 175 | 560 |
| 2020 | 250 | 400 | 49 | 48 | 48 | 145 | 610 |
| 2025 | 210 | 400 | 40 | 40 | 40 | 120 | 640 |
Calculate the percentage decrease in spawning biomass between 2005 and 2025.
[2]
Describe the relationship between fishing activity and spawning biomass shown in the figure.
[2]
Explain how the trends illustrate the tragedy of the commons and suggest one management response likely to improve sustainability.
[3]
Question 19
Indigenous rangers used patch-mosaic burning in a semi-arid landscape. Researchers compared an area managed with frequent small, cool burns with a nearby area where traditional burning had ceased 15 years earlier.
Figure 2. Ten-year comparison of landscapes and ranger programme conditions.
| Measure | Managed landscape | Unmanaged landscape |
|---|---|---|
| Mean area per unplanned wildfire / ha | 85 | 620 |
| Maximum unplanned wildfire / ha | 310 | 2800 |
| Native small-mammal species recorded | 11 | 7 |
| Invasive-grass cover / % | 14 | 36 |
| Vegetation-age classes present | 4 | 2 |
| Fire pattern and refuges | Frequent small, cool burns; discontinuous refuges retained | Large, intense fire crossed much of the landscape |
| Ranger programme employment | 24 community members | — |
| Funding approval | One year at a time | — |
| Safe burning season | Shortened by hotter, drier weather | — |
Calculate how many times larger the mean unplanned wildfire was in the unmanaged landscape than in the managed landscape.
[2]
Describe two differences in biodiversity-related conditions between the landscapes.
[2]
Explain why this traditional land-management practice may be sustainable and why its continuation is not guaranteed.
[3]
Question 20
Figure 2 shows land-use pressures and a proposed zoning strategy in a wetland key biodiversity area.
Outline one conflict between exploitation and biodiversity conservation shown in Figure 2.
[2]
Outline how one feature of the proposed zoning strategy could support sustainable development.
[2]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 21
A government proposes a protected forest to conserve endemic species and a regional watershed. An indigenous community living in the forest may lose access to food, medicine and culturally important sites. Most tourism income would initially be received by businesses outside the area.
Outline four environmental-justice considerations that should inform the conservation decision.
[4]
Question 22
Pacific bluefin tuna migrate through national waters and the high seas. Fishing fleets from several jurisdictions harvest the same stock. In 2015, participating authorities introduced catch allocations, minimum-size rules and electronic monitoring.
Pacific bluefin tuna catch and spawning biomass, 2000–2023.
| Year | Annual catch / thousand tonnes | Spawning biomass index / % of unfished level | Coordinated management |
|---|---|---|---|
| 2000 | 29 | 18 | No |
| 2005 | 36 | 11 | No |
| 2010 | 42 | 6 | No |
| 2015 | 34 | 7 | Introduced |
| 2020 | 25 | 13 | Yes |
| 2023 | 21 | 19 | Yes |
Age composition of Pacific bluefin tuna catch and selected management indicators.
| Indicator | 2010 | 2015 | 2023 | Change, 2015–23 |
|---|---|---|---|---|
| Juveniles in catch | — | — | ||
| Young adults in catch | — | — | ||
| Mature adults in catch | — | — | ||
| Reported catch coverage | — | percentage points | ||
| Market price | — | — | — | |
| Jurisdictions exceeding allocations | — | — | 2 | — |
Calculate the percentage change in the spawning biomass index between 2010 and 2023.
[2]
Describe the relationship between annual catch and spawning biomass from 2000 to 2023.
[2]
Explain how harvesting a high proportion of juvenile tuna can affect the stock.
[3]
Analyse how this fishery illustrates the tragedy of the commons.
[3]
Evaluate the effectiveness of the coordinated management measures in improving the sustainability of the tuna fishery.
[5]
Question 23
The Serra Clara landscape lies within Brazil's Atlantic Forest biodiversity hotspot. Agricultural expansion, road construction and urban growth have replaced and fragmented much of its native forest. A conservation proposal would restore corridors between the largest remnants while permitting farming in surrounding zones.
Calculate the percentage decrease in native forest cover between 1990 and 2024.
[2]
Using the data, identify the vertebrate group that should receive the highest priority if the criterion is the number of threatened endemic species. Justify your answer.
[2]
Explain why habitat fragmentation may increase extinction risk for endemic amphibians in Serra Clara.
[3]
Analyse how the evidence supports prioritizing Serra Clara for biodiversity conservation.
[4]
Evaluate the proposal to restore forest corridors while permitting farming in surrounding zones.
[5]
Question 24
Martu land managers in Australia's Western Desert use small, carefully timed fires to create a patch mosaic of vegetation at different stages of recovery. A ranger programme compared an area under regular Martu burning with a nearby area where customary burning had declined.
Fire-regime and biodiversity indicators for Martu-managed and comparison areas, 2014–2023.
| Indicator | Martu-managed area | Comparison area |
|---|---|---|
| Mean area burned per fire / ha | 18 | 460 |
| High-severity wildfire / % of area | 6 | 29 |
| Vegetation-age classes / 100 km^2 | 4.0 | 2.3 |
| Mean reptile richness / species per plot | 17 | 12 |
Fire-management challenges and supporting conditions, 2014–2023.
| Indicator | 2014 | 2016 | 2018 | 2020 | 2023 | Reported context |
|---|---|---|---|---|---|---|
| Ranger-supported burning trips / year | 84 | 78 | 61 | 49 | 43 | Distant wage employment can reduce local participation and weaken knowledge transfer. |
| Days above safe prescribed-burning threshold / year | 21 | 27 | 35 | 43 | 51 | Invasive-grass cover is increasing, creating more continuous fuel. |
| Land access and funding | Not quantified | Not quantified | Not quantified | Not quantified | Not quantified | Some traditional lands have restricted access; government grants are short term. |
Calculate how many times greater the mean area burned per fire was in the comparison area than in the Martu-managed area.
[2]
Describe two differences between the fire regimes in the two areas.
[2]
Explain how patch-mosaic burning may maintain biodiversity.
[3]
Analyse how internal and external pressures threaten the continuation of this land-management practice.
[3]
Evaluate the claim that expanding paid indigenous ranger programmes is the most sustainable strategy for managing this landscape.
[5]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 25
The fictional Serranía Verde region is a tropical biodiversity hotspot containing the Alto Nube key biodiversity area (KBA). The regional government is considering two development plans.
Comparison of current conditions and two development plans for the Alto Nube KBA.
| Scenario | Connected KBA habitat / km^2 | Agricultural income / million currency units | Direct local jobs | Main measures |
|---|---|---|---|---|
| Current conditions | 82 | 18 | 2100 | Existing conditions |
| Plan X | 46 | 34 | 3600 | Plantation expansion; road through corridor |
| Plan Y | 74 | 28 | 3300 | No core clearance; road rerouted; agroforestry and community buffer zones |
Using the figures, identify two reasons why Serranía Verde is a high international conservation priority.
[2]
Calculate the percentage of the current connected KBA habitat that would remain under Plan X.
[2]
Analyse whether Plan Y provides a more sustainable response to the conflict between exploitation and conservation than Plan X.
[4]
Question 26
The government of Lantala proposed creating a protected forest to conserve an endemic primate and a watershed. Two management options were presented to stakeholders.
Comparison of proposed protected-forest management options in Lantala.
| Indicator | Option A | Residents relocated / people |
|---|---|---|
| Management approach | Strict exclusion with state patrols | Community tenure recognized; joint patrols |
| Residents relocated [people] | 1400 | 80 |
| Community seats on governing board | 0 of 12 | 5 of 12 |
| Local share of tourism revenue [%] | 5 | 35 |
| Community tenure | Not recognized | Recognized |
| Cultural sites and local ecological knowledge | Not recognized | Recognized in management |
| Core breeding habitat | Strictly protected | Closed to extraction |
| Harvesting outside core habitat | Not permitted | Regulated harvesting |
| Protected forest area [km] | 600 | 540 |
| Current endemic primate population [individuals] | 460 | 460 |
| Projected primate population after 10 years [individuals] | 720 | 680 |
Using the figures, identify two environmental-justice concerns associated with Option A.
[2]
Compare the projected conservation outcomes of Options A and B.
[2]
Analyse which option is more likely to achieve both biodiversity conservation and environmental justice.
[4]
Question 27
Distinguish between habitat loss, habitat fragmentation and habitat degradation.
[4]
Explain how climate change, habitat fragmentation and an invasive alien species may interact to cause a greater decline in a native population than any one pressure acting alone.
[7]
Using named examples, evaluate the claim that preventing the introduction of invasive alien species is more effective than controlling them after establishment.
[9]
Question 28
Outline four types of evidence used by the IUCN to assess a species' conservation status.
[4]
Explain how publication of a species' conservation status may influence the actions of governments, non-governmental organizations and individual citizens.
[7]
Using named species, to what extent should IUCN conservation status determine conservation priorities?
[9]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 29
The Bale Highlands Key Biodiversity Area contains Afroalpine habitat used by the endangered Ethiopian wolf and supplies water to surrounding communities. Expansion of crops and livestock grazing, habitat fragmentation and disease transmission from domestic dogs threaten the area. Managers are considering a zoned conservation plan.
Stakeholder support and provisions of the proposed Bale Highlands zoning plan.
| Indicator | Group or provision | Value |
|---|---|---|
| Support for zoning plan | Pastoral households | 46% |
| Support for zoning plan | Crop farmers | 38% |
| Support for zoning plan | Tourism workers | 81% |
| Support for zoning plan | Downstream water users | 88% |
| Support for zoning plan | Conservation scientists | 93% |
| Core zone | Cultivation | Not permitted |
| Buffer zone | Livestock grazing | Seasonal permits |
| Disease control | Domestic dogs | Vaccination |
| Compensation | Households surrendering core fields | 2 years' average net income |
| Management board | Community representatives | 4 of 12 seats |
| Tourism revenue | Nearby households reached | 9% |
Calculate the percentage by which the livestock number index increased between 2005 and 2023.
[2]
Outline two reasons why the Bale Highlands qualify as an international conservation priority.
[2]
Explain how increasing livestock pressure may contribute to the decline in Ethiopian wolf abundance.
[3]
Analyse the conflict between exploitation, sustainable development and conservation in the proposed zones.
[4]
Evaluate whether the proposed zoning plan is likely to provide a durable resolution to the conflict.
[5]
Question 30
A government proposes expanding a protected forest in the Nembasa Highlands. The forest contains endemic species and supplies water to downstream towns. The Aruwe community claims customary tenure and depends on the forest for grazing, medicinal plants and cultural sites. Two management pilots operated from 2018 to 2024.
Figure 8(b): outcomes in comparable management sectors, 2018–2024. Both sectors had an area of 500 km and 240 monitoring visits yr throughout.
| Sector | Management pilot | Forest cover (2018) / % | Forest cover (2020) / % | Forest cover (2022) / % | Forest cover (2024) / % | Illegal clearing (2018) / incidents | Illegal clearing (2020) / incidents | Illegal clearing (2022) / incidents | Illegal clearing (2024) / incidents |
|---|---|---|---|---|---|---|---|---|---|
| Sector G | Government patrols; residents excluded | 72 | 73 | 74 | 75 | 31 | 27 | 25 | 22 |
| Sector C | Community monitoring; regulated access | 70 | 72 | 75 | 78 | 29 | 20 | 12 | 7 |
Stakeholder support, representation, benefit distribution and access arrangements for the proposed expansion.
| Indicator | Group / sector | Recorded value or arrangement |
|---|---|---|
| Support for expansion | Aruwe households | |
| Support for expansion | Government staff | |
| Support for expansion | Tourism businesses | |
| Support for expansion | Downstream residents | |
| Support for expansion | NGO respondents | |
| Planning committee seats | Aruwe representatives | 2 of 15 seats |
| Tourism income | Companies outside the region | |
| Tourism income | Aruwe households | |
| Relocation | Sector G | 64 households; no negotiated compensation |
| Customary forest access | Sector C | Medicinal plants and seasonal grazing under agreed limits |
Calculate the percentage decrease in recorded illegal clearing incidents in Sector C between 2018 and 2024.
[2]
Compare the ecological outcomes of the two management sectors.
[3]
Analyse the proposed expansion using the three dimensions of environmental justice.
[4]
Suggest two reasons why a more just conservation process may also improve biodiversity outcomes.
[2]
To what extent should the protected forest be expanded in its proposed form?
[5]
Question 31
Explain how unrestricted access to a shared natural resource may result in a tragedy of the commons.
[4]
Explain how nutrient contamination within a large river basin may cause biodiversity loss and illustrate the tragedy of the commons.
[7]
Using named examples, evaluate strategies for preventing biodiversity loss caused by the tragedy of the commons.
[9]
Question 32
Distinguish between a biodiversity hotspot and a key biodiversity area.
[4]
Analyse the conflict between exploitation, sustainable development and conservation in the Lake Alaotra key biodiversity area.
[7]
Using named examples, to what extent should global conservation funding be concentrated in biodiversity hotspots and key biodiversity areas?
[9]
Build a Practice Exam — ESS HL
Test your knowledge with a custom paper containing questions from selected topics.
Question 33
The Ifugao muyong system in the Philippines includes communally regulated or family-managed forest patches above irrigated rice terraces. Selective harvesting, assisted regeneration and protection of water sources maintain forest structure and water supply.
Outline four characteristics that may make a traditional indigenous land-management practice sustainable.
[4]
Explain how the muyong system may support biodiversity and how social or environmental change may threaten its continuation.
[7]
Using named examples, evaluate the claim that governmental support is the most important factor in maintaining sustainable traditional indigenous land management.
[9]
Question 34
Explain the three dimensions of environmental justice that should be considered in biodiversity conservation.
[4]
Analyse how an unjust conservation process may undermine both human well-being and long-term biodiversity protection, with reference to the Sengwer people and Kenya's Embobut Forest.
[7]
Using named examples, to what extent is community-led conservation more effective than strict exclusion in preventing biodiversity loss?
[9]
The Ultimate All-in-One
IB Platform
All content on this website has been developed independently from and is not endorsed by the International Baccalaureate Organization. International Baccalaureate and IB are registered trademarks owned by the International Baccalaureate Organization.