Hardest IB ESS Questions (And Answers)
Written by: Alistair Marjot
Reviewed by: Jacque Cartwright
Published
Contents
If you're taking IB Environmental Systems and Societies, you've probably noticed that some exam questions are trickier than others. The 9-mark essay questions in Paper 2 can feel particularly challenging. They require you to think critically, balance multiple perspectives, and present well-supported arguments.
This article focuses on the hardest 9-mark questions from each ESS topic. We'll show you exactly what examiners are looking for, how to structure your answers, and what earns those top marks.
This is your strategic guide to tackling the toughest questions with confidence.
These aren't just random difficult questions. We've carefully selected one challenging 9-mark question from each of the eight ESS topics, based on past paper analysis and what consistently trips students up in exams.
Key takeaways
9-mark questions appear in Paper 2 Section B and test your ability to evaluate, discuss, and analyse ESS concepts
Top answers (7-9 marks) need balanced arguments, precise terminology, well-explained case studies, and clear conclusions
Each question requires you to demonstrate both breadth of knowledge and depth of analysis
Case studies and real-world examples are crucial for reaching the highest mark band
Time management is key: spend about 15 minutes per 9-mark question
Essay writing and the ability to argue from different perspectives are what set ESS apart from other IB Group 4 Sciences. We’ve gone into more detail about this in our article answering the question: Is IB Environmental Systems & Societies Hard?
What are the IB ESS 9-mark 'essay' questions?
The 9-mark questions are the longest written responses you'll tackle in IB ESS. They're designed to test your ability to construct coherent arguments, evaluate different perspectives, and demonstrate a deep understanding of environmental systems.
Where the IB ESS 9-mark questions appear (Paper 2)
These questions appear in Section B of Paper 2. This section contains structured essay questions split into three parts: typically a 4-mark question, a 7-mark question, and a 9-mark question.
How many IB ESS 9-mark questions need to be answered (SL vs HL)
The number of essays you need to tackle depends on your level:
Standard Level (SL): You answer one complete essay from a choice of two. This means you'll write one 9-mark response.
Higher Level (HL): You answer two complete essays from a choice of three. This means you'll write two 9-mark responses.
Choose your essays wisely. Pick topics you feel confident about and where you can recall strong case studies.
What are the markbands for IB ESS 9-mark questions?
Examiners use three markbands to grade your 9-mark responses. Understanding these helps you aim for the top marks.
Marks 1-3 (Low band):
Minimal knowledge of ESS concepts
Facts poorly linked to the question
Missing or weak examples
Just lists facts without analysis
Vague conclusions with no evidence
Marks 4-6 (Middle band):
Sound knowledge of ESS issues
Good use of ESS terminology
Some relevant examples, but limited explanation
Clear analysis showing some balance
Conclusions supported by limited evidence
Marks 7-9 (Top band):
Substantial, detailed knowledge
Consistently precise use of ESS terminology
Well-explained, relevant examples showing originality
Thorough, well-balanced, insightful analysis
Strong conclusions backed by evidence and critical reflection
The jump from middle to top band happens when you add depth, balance, and critical thinking to your answer.
What are the command terms for IB ESS 9-mark questions?
Understanding the following three command terms used for the 9-mark questions is essential for structuring your response:
Evaluate:
Make an assessment by weighing up the strengths and limitations
Discuss:
Offer a thoughtful and balanced review that includes a range of arguments, factors or hypotheses. Opinions or conclusions should be presented clearly and supported by appropriate evidence.
To what extent:
Consider the merits or otherwise of an argument or concept. Opinions and conclusions should be presented clearly and supported with appropriate evidence and sound argument.
How to answer IB ESS 9-mark questions
Here's a step-by-step approach that works:
1. Decide your position
Read the question carefully and figure out where you stand. Do you agree or disagree? To what extent (by how much do you agree or disagree)? Having a clear position helps structure your argument.
2. Justify with logic
Explain the reasoning behind your claims. Show how your points directly relate to the question. Don't just state facts—explain why they are relevant.
3. Support with evidence
Use real-life examples and case studies to back up your arguments. Specific examples are far more convincing than vague statements.
You can structure individual paragraphs using PEEL (Point, Evidence, Explanation, Link). This keeps your writing focused and analytical.
4. Include counterarguments
A balanced answer is essential for top marks. Present opposing viewpoints and evaluate them fairly.
5. Write a strong conclusion
Sum up your arguments and restate your position. Include your key examples as justification. Clearly state whether you agree or disagree, and to what extent.
Hardest IB ESS 9-mark questions by topic
Topic 1: Foundation
Question: Evaluate the use of models for predicting future global warming.
Why this question is tricky:
Students often struggle with this type of question because it is tempting to focus too heavily on one side of the argument. Students either praise climate models without acknowledging their limitations or criticise them without recognising their value. The command word ‘evaluate’ means you must weigh up both sides fairly.
What the question is really asking:
You need to explain what climate models are and discuss their usefulness in predicting climate change but also acknowledge their limitations and uncertainties.
Key points for a top-band answer:
Intro points:
Define models as simplified representations of natural systems that enable predictions based on historical data
Climate models are used by scientists and the IPCC to predict future climate change
Strengths of climate models:
Help scientists understand complex environmental relationships
Identify vulnerable regions (e.g., poles warming faster than tropics)
Provide scenarios for policy decisions based on extensive historical data
Allow visualisation of projected effects like global temperature changes
Limitations of climate models:
Predictions can be inaccurate because detailed data has only been collected relatively recently
Models assume climate factors will behave as they have in the past, which may not be true
Different models produce conflicting results, creating uncertainty
Politicians can exploit model variations to support their own agendas
Common pitfalls:
Being too one-sided (only strengths or only limitations)
Not explaining the significance of limitations
Failing to mention specific organisations like the IPCC
Not concluding with a clear evaluative judgment
Other hard question areas in Topic 1: Foundation
Within Topic 1, watch out for these tricky areas:
Systems thinking: explaining feedback loops in environmental systems and distinguishing between positive and negative feedback
Sustainability and different worldviews: comparing ecocentric, anthropocentric, and technocentric perspectives
Resilience and tipping points: explaining how systems respond to disturbance and when they might collapse
Topic 2: Ecology
Question: Discuss the role of carrying capacity in determining population size in humans and other species.
Why this question is tricky:
This question is challenging because it requires you to compare human populations with other species—something many students struggle to do effectively. It's easy to discuss humans and other species separately, but the real skill is in making comparisons and explaining why humans often behave differently. Students also tend to forget that carrying capacity isn't just an abstract concept—it has real consequences when populations overshoot it.
What the question is really asking:
You need to explain what carrying capacity is and then explore how it affects both human and non-human populations differently. The command term 'discuss' means exploring different aspects and perspectives. Show why human populations often behave differently from other species.
Key points for a top-band answer:
Intro points:
Define carrying capacity: the maximum sustainable population size that an environment can support
Note that it affects all species but often operates differently for humans
How carrying capacity affects most species:
Most species fluctuate around their carrying capacity following an S-curve (sigmoid growth)
When populations overshoot carrying capacity, they typically crash
Species cannot easily switch resources when they become limiting
How carrying capacity affects human populations differently:
Human population growth often follows a J-curve (opens in a new tab) (exponential growth)
Humans can switch resources when they become limiting
Technology enhances resource efficiency and human adaptability
Humans can consciously control population growth through family planning
However, exceeding carrying capacity still leads to consequences: decreased fertility, increased mortality, migration, famines, water shortages
Key comparison:
Determining human carrying capacity is complex because technology keeps changing what's possible
Some scientists worry human populations may face a crash similar to other species that follow J-curve growth
What examiners want to see:
Top answers draw explicit comparisons between human and non-human populations rather than discussing them separately. Use terminology like 'density-dependent factors', 'overshoot', 'S-curve', and 'J-curve' accurately.
Common pitfalls:
Discussing humans and other species in isolation without comparing them
Not explaining why humans behave differently (technology, resource switching)
Forgetting to mention consequences of exceeding carrying capacity
Not addressing whether humans might eventually face a population crash
Other hard question areas in Topic 2: Ecology
Within Topic 2, watch out for these tricky areas:
Succession and climax communities: distinguishing between primary and secondary succession
Biomass and productivity calculations: converting between different units and explaining energy losses between trophic levels
Pyramids of energy vs biomass: explaining why pyramids of energy are always upright but biomass pyramids can be inverted
Topic 3: Biodiversity and Conservation
Question: Evaluate the usefulness of calculating diversity indices for understanding the nature of biological communities and the conservation of biodiversity.
Why this question is tricky:
Diversity indices seem purely mathematical, but this question asks you to discuss their real-world application and limitations. Students often struggle to explain why indices matter for conservation—what's the point of calculating a number? The challenge is connecting the math to practical conservation decisions and also recognising what the indices can't tell you.
What the question is really asking:
You need to explain what diversity indices are and what they measure, then evaluate how useful they are as tools for conservation. 'Evaluate' means weighing up their practical benefits against their limitations.
Key points for a top-band answer:
Intro points:
Define diversity indices: mathematical measures used to quantify species richness and evenness in communities
Mention Simpson's Diversity Index as a key example
State your position on their overall usefulness
Usefulness of diversity indices:
Help identify areas of high biodiversity that should be prioritised for conservation (higher values indicate more diverse communities)
Track biodiversity changes over time through long-term monitoring
Changes in diversity indices can indicate disturbances like pollution or habitat destruction
Provide early warning signals for ecosystem health problems
Quantify impacts of human activities, providing concrete data for mitigation strategies
Limitations of diversity indices:
Sensitive to sample size—results can be skewed in smaller samples
Potentially biased towards common species—might not adequately capture rare or endemic species
Difficult to distinguish between natural fluctuations and human-caused disturbances
Provide a number but don't explain why diversity is changing
What examiners want to see:
Examiners want to see that you understand diversity indices are tools, not perfect answers. Top responses acknowledge that a single number can't capture all aspects of biodiversity.
Other hard question areas in Topic 3: Biodiversity and Conservation
Within Topic 3, watch out for these tricky areas:
IUCN Red List categories: understanding the criteria for classifying species as endangered, vulnerable, or critically endangered
In-situ vs ex-situ conservation: evaluating the effectiveness and limitations of each approach with specific examples
Edge effects and habitat fragmentation: explaining how breaking up habitats affects biodiversity beyond just area loss
Convention on Biological Diversity: discussing international agreements and their effectiveness in protecting biodiversity
Topic 4: Water
Question: Discuss the following statement: 'Water scarcity problems are best addressed through technological developments, rather than through changing human behaviour.'
Why this question is tricky:
This question forces you to compare two fundamentally different approaches to solving water scarcity. Many students lean too heavily toward one side without properly evaluating both. There's also a temptation to write about water scarcity in general rather than focusing specifically on how technology and behaviour change compare as solutions. The real challenge is recognising that context matters—what works in Singapore might not work in rural Ethiopia.
What the question is really asking:
You need to explore whether technology or behaviour changes are more effective at solving water shortages. 'Discuss' means examining multiple perspectives. You should consider contexts where each approach works best.
Key points for a top-band answer:
Intro points:
Define water scarcity: insufficient water availability to meet demands
Distinguish between physical scarcity (not enough water) and economic scarcity (lack of infrastructure)
It's likely that both approaches are needed, but in different contexts
Technological solutions:
Benefits: Desalination increases freshwater supply in coastal areas; grey-water recycling reduces demand; technology enhances water availability for agriculture and domestic use
Drawbacks: High energy costs (especially desalination); expensive infrastructure inaccessible for many developing regions; doesn't address underlying overconsumption issues
Behavioural changes:
Benefits: Reducing water consumption addresses the root cause; efficient water use practices are low-cost; education programmes can create lasting cultural shifts; more sustainable long-term
Challenges: Difficult to change established habits; requires widespread public buy-in; may face resistance from industries
What examiners want to see:
Top answers recognise that this isn't an either/or question. Show geographical awareness—what works in wealthy coastal nations differs from what works in rural agricultural communities. Include discussion of socio-cultural factors affecting water use.
Common pitfalls:
Arguing only for technology or only for behaviour without balance
Not considering economic and geographical contexts
Failing to mention the role of policy and legislation
Not providing specific examples of technologies or behavioural interventions
Other hard question areas in Topic 4: Water
Within Topic 4, watch out for these tricky areas:
Eutrophication processes: detailing the step-by-step mechanism of how nutrient pollution leads to dead zones
Topic 5: Land
Question: Evaluate strategies for achieving sustainable food production in tropical areas.
Why this question is tricky:
This question is difficult because tropical agriculture involves complex ecological and socioeconomic factors that students often oversimplify. It's tempting to just list strategies (agroforestry, crop rotation, etc.) without properly evaluating their effectiveness or the real-world barriers to implementation.
What the question is really asking:
You need to explain what sustainable food production means in the context of tropical areas, present various strategies, and evaluate how effective they are in practice. 'Evaluate' requires weighing up successes and limitations.
Key points for a top-band answer:
Intro points:
Define sustainable food production: meeting current food needs without compromising future productivity
State that multiple strategies exist, each with trade-offs
Traditional approaches:
Agroforestry: Integrates trees with crops; trees fix nitrogen, prevent erosion, offer additional income. Example: cocoa under shade trees in West Africa
Crop rotation and intercropping: Maintains soil fertility; growing legumes replenishes nitrogen naturally; reduces pest spread
Conservation agriculture: No-till farming protects soil structure; reduces labour and fuel costs
Modern approaches:
Precision agriculture: Uses sensors to optimise fertiliser and water use; reduces waste but expensive for smallholders
Improved crop varieties: Enhanced pest resistance or drought tolerance; can increase yields but may require purchased seeds
Barriers to implementation:
Small-scale farmers often lack resources for new technology or training
Market pressures favour monoculture cash crops over diversified systems
Land tenure insecurity discourages long-term sustainable practices
Lack of government support or appropriate policies
Common pitfalls:
Simply listing strategies without evaluating their effectiveness
Ignoring economic and social barriers to implementation
Not explaining why tropical areas have specific challenges
Other hard question areas in Topic 5: Land
Within Topic 5, watch out for these tricky areas:
Soil profiles and horizons: explaining the formation and characteristics of different soil layers
Desertification processes: detailing the causes and consequences of land degradation in arid regions
Topic 6: Atmosphere and Climate Change
Question: There has been significant debate surrounding the causes of climate change. Discuss contrasting viewpoints on this issue.
Why this question is tricky:
You need to present viewpoints you may disagree with fairly and accurately—that's harder than it sounds. The real skill is presenting different perspectives fairly whilst still showing which you think is better supported.
What the question is really asking:
You need to present the scientific consensus on human-caused climate change alongside contrasting viewpoints that question or deny this consensus. 'Discuss' means exploring different perspectives fairly, even if one is overwhelmingly supported by evidence.
Key points for a top-band answer:
Intro points:
Acknowledge that climate change's causes have been debated
Note that scientific consensus strongly supports human causes
Scientific consensus: human-induced climate change:
IPCC reports show strong correlation between human activities and increased CO₂ and other greenhouse gases
Observable data shows warming trend correlating with industrialisation
Multiple independent data sources consistently show warming
Climate models successfully predicted warming trends we now observe
Contrasting viewpoints:
Climate and CO₂ levels have changed significantly in Earth's geological past, before human influence
Some argue current levels are moderate compared to geological history
Suggestion that observed warming could be a natural, short-term fluctuation
Critics argue complexity of climate models introduces uncertainty
Other hard question areas in Topic 6: Atmosphere and Climate Change
Within Topic 6, watch out for these tricky areas:
Stratospheric ozone depletion: distinguishing between ozone layer damage and climate change
Mitigation vs adaptation strategies: comparing different approaches to climate change
Topic 7: Natural Resources
Question: To what extent can different energy sources support a sustainable energy future?
Why this question is tricky:
Students often present renewables as perfect solutions, while ignoring their limitations. The phrase 'to what extent' demands a clear judgement about how much each energy source contributes to sustainability.
What the question is really asking:
You need to assess whether renewable and non-renewable energy sources can collectively support long-term sustainability.
Key points for a top-band answer:
Intro points:
Define sustainable energy: meets current needs without compromising future generations' ability to meet theirs
State that renewables are essential for long-term sustainability, though challenges exist
Renewable energy sources:
Solar, wind, hydropower, and others are renewable within human timescales
Low or zero greenhouse gas emissions—supports climate goals
Often locally available, enhancing energy security
Limitations: Intermit supply requires energy storage; high initial costs; land use requirements
Non-renewable energy sources:
Fossil fuels (coal, oil, gas) are finite—not sustainable long-term
Release CO₂, contributing to climate change
Nuclear has low emissions but produces radioactive waste and has high decommissioning costs
Both still provide majority of global energy due to established infrastructure
What examiners want to see:
Top answers evaluate multiple energy sources, not just one or two. Show awareness that sustainability isn't just environmental—it includes economic viability and social acceptance.
Common pitfalls:
Treating renewables as having zero environmental impact
Not explaining what 'sustainable' means in the context of energy
Failing to mention storage technology as essential for renewables
Other hard question areas in Topic 7: Natural Resources
Within Topic 7, watch out for these tricky areas:
Factors influencing energy choices
Topic 8: Human Populations and Urban Systems
Question: To what extent can ecological urban planning contribute to the sustainability of cities?
Why this question is tricky:
This question is challenging because 'ecological urban planning' is a broad concept that students often understand vaguely. It's easy to list green initiatives (parks, solar panels, recycling) without properly evaluating their contribution to overall sustainability. The real challenge is assessing the extent to which these strategies actually make cities sustainable—recognising both their potential and their limitations.
What the question is really asking:
You need to explain what ecological urban planning is and discuss how it contributes to urban sustainability but also acknowledge its limitations. 'To what extent' requires you to reach a clear judgement about how much ecological planning can actually achieve.
Key points for a top-band answer:
Intro points:
Define ecological urban planning: treating cities as ecosystems, considering both biotic and abiotic factors in design
Benefits of ecological urban planning:
Environmental sustainability:
Green infrastructure (parks, green roofs, wetlands) improves air quality, regulates climate, supports biodiversity
Renewable energy integration (solar panels, bio-digesters) reduces fossil fuel dependence
Waste recycling and rainwater harvesting conserve resources and reduces pollution
Urban farming reduces food transport emissions
Social and economic benefits:
Improves human well-being through green spaces, clean air, access to fresh food
Increases resilience to climate change (flood-resistant buildings, permeable pavements)
Can create jobs in green industries
Limitations of ecological urban planning:
High initial costs of green infrastructure and biophilic buildings
Requires long-term planning and political will
May not address all sustainability challenges (e.g., traffic congestion, social inequality)
Green gentrification can displace lower-income residents
Benefits often concentrated in wealthier neighbourhoods
What examiners want to see:
Top answers recognise that ecological planning is valuable but not a complete solution. Show awareness that sustainability involves environmental, social, and economic aspects. Use specific terms such as 'green infrastructure', 'biophilic design', and 'urban heat island effect'.
Common pitfalls:
Just listing green initiatives without evaluating their effectiveness
Not considering economic and social limitations
Failing to mention that benefits may not be equitably distributed
Other hard question areas in Topic 8: Human Populations and Urban Systems
Within Topic 8, watch out for these tricky areas:
Demographic transition model: explaining the stages and factors driving changes in birth and death rates
Urban sprawl vs compact cities: assessing the sustainability implications of different urban development patterns
Exam Strategy for Tough IB ESS Questions
Now that you've seen the hardest questions from each topic, let's talk strategy for tackling any difficult 9-mark question.
Breaking down long-answer questions
When you first read a 9-mark question, take a moment to:
Identify the command term (evaluate, discuss, to what extent)
Underline key concepts in the question
Think of two or three main points you can develop in depth
Recall relevant case studies before you start writing
Don't try to include everything you know. Depth matters more than breadth. It's better to fully develop two or three strong points throughout your answer than to skim over five weak ones.
Using case studies effectively
Case studies are what separate good answers from great ones. Here's how to use them well:
Be specific: Don't just say 'in Africa'—say 'cocoa production in Ghana'. Don't say 'renewable energy works'—say 'Iceland generates 100% of electricity from geothermal and hydropower.'
Explain, don't just name: Saying 'Singapore uses NEWater' doesn't earn many marks. Explaining 'Singapore recycles wastewater through advanced purification to produce NEWater, which now meets 40% of the nation's water demand' shows understanding.
Build a bank of case studies: As you progress through the course, collect 2-3 solid examples for each topic that you can adapt to different questions. Your teacher can help you with this.
Show range: If possible, include examples from different geographical regions or scales (local, national, global).
Time management
You have approximately 15 minutes per 9-mark question (accounting for time spent on the 4-mark and 7-mark parts of each essay).
Here's a rough breakdown:
2 minutes: Read the question, plan your response, recall case studies
10-11 minutes: Write your answer (introduction, 2-3 developed points, conclusion)
2 minutes: Quickly review what you've written
If you're running out of time, prioritise writing a solid conclusion. An answer without a conclusion struggles to access the top mark band.
For HL students: Using the three lenses
HL students need to apply the three HL lenses—Environmental Law, Environmental Ethics, and Environmental Economics—when analysing complex ESS issues in 9-mark questions.
Environmental Law:
Consider international agreements, national legislation, and regulatory frameworks. How do laws shape environmental outcomes? Are they effective? What are the challenges in implementation and enforcement?
Aspects covered by environmental law
Environmental Ethics:
Explore different value systems and moral perspectives. Consider ecocentric (nature-centred), anthropocentric (human-centred), and technocentric (technology-focused) viewpoints. Who benefits? Who is harmed? What about future generations or non-human species?
Environmental Economics:
Analyse costs, benefits, economic incentives, and market mechanisms. Consider whether economic growth can be decoupled from environmental degradation.
You won't necessarily apply all three lenses to every question, but showing awareness of these perspectives strengthens your analysis.
For example, when discussing energy sources, you might consider carbon taxes (economics), renewable energy targets (law), and whether we have obligations to future generations (ethics).
Head over to our article on how to pass IB ESS for more study tips and exam strategies.
Frequently Asked Questions
What are the hardest topics in IB ESS?
The 'hardest' topics vary by student, but many actually find Topic 1 (Foundation) conceptually challenging because it deals with abstract systems thinking.
How do examiners mark ESS questions?
Examiners use the markbands we discussed earlier. They're not looking for one 'correct' answer—they want to see:
Clear knowledge and understanding of ESS concepts
Appropriate use of terminology
Balanced analysis showing multiple perspectives
Well-explained, relevant examples
Clear, well-supported conclusions
Remember — 7-9 marks = excellent knowledge, strong examples, thorough balanced analysis, clear conclusions
How can I improve my ESS exam technique?
Practise past paper questions regularly. You can't learn essay technique by just reading—you need to write. Start by outlining answers, then progress to writing full responses under timed conditions.
Build your case study bank. Collect specific examples as you go through each topic. Write them down with key details so you can recall them under exam pressure.
Get feedback. Ask your teacher to mark practice 9-mark answers and explain where you can improve.
For more in-depth revision advice, check out our detailed guide on how to revise for IB ESS.
Final Thoughts
Tackling the hardest IB ESS questions isn't about memorising perfect answers—it's about developing the skills to think critically, argue effectively, and apply your knowledge to complex environmental issues.
The questions in this article represent some of the most challenging you'll face. Master these, and you'll be well-prepared for anything Paper 2 throws at you.
Now it's time to practise. Choose a 9-marker from our selection of hard-level IB ESS exam questions, spend 15 minutes writing your answer, then check out the model answer and marking guidance we’ve provided. That's how you'll build the skills to excel.
For more support with IB ESS revision and exam preparation, explore the full range of IB ESS resources available at Save My Exams. You've got this!
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