IB ESS exam format from 2026: Paper 1 case study, Paper 2 and the HL lenses

From May 2026, IB ESS is examined at both SL and HL with two papers plus the internal assessment. Paper 1 is an unseen case study: a set of data in different formats about one specific place or issue you have not seen before, with every question compulsory (SL 1 hour, 35 marks, 25%; HL 2 hours, 70 marks, 30%). Paper 2 is worth 50% at both levels and combines short-answer and data questions with structured essays (SL 2 hours, 60 marks; HL 2 hours 30 minutes, 80 marks). Here is what each paper contains, how to work through the case study, and how to spend your minutes.

What does the ESS exam look like in 2026?

Three more details. There is no pre-release: nothing about the case study is published before the exam. A calculator is required for both papers and graphic display calculators are allowed (the guide states this in the SL section; nothing suggests HL differs). And the ESS guide does not mention a data booklet, so learn the formulas you use, such as NPP = GPP − R, Simpson's index and the Lincoln index; ask your teacher if you are unsure what will be supplied.

What changed from the old SL-only course?

• HL now exists. The old course (last examined in 2025) was SL only. HL adds content, a longer Paper 1, a second essay and three "lenses": environmental law, environmental economics and environmental ethics.
• SL weightings are unchanged. Paper 1 was 1 h and 25%, Paper 2 was 2 h and 50%, the IA was 25%, as now. HL shifts weight towards Paper 1 (30%) and away from the IA (20%).
• Paper 1 is still a case study, but unseen. The old Paper 1 also used a case study with a resource booklet supplied in the exam. The new one gives you a range of data in different formats on one case, and nothing is released beforehand.
• The course is built on three concepts: perspectives, systems and sustainability. They run through all eight topics, from Foundation to Human populations and urban systems.
• The IA gained a Strategy criterion, where you analyse a real environmental strategy and the tensions between perspectives it creates. More in the ESS IA guide.

How do you handle the unseen case study in Paper 1?

Paper 1 tests analysis and evaluation of data you have never seen. You cannot revise the case, but you can practise a routine that works on any case.

1. Get the big picture first. Spend the first few minutes skimming the whole case: where it is, what the system is (a lake catchment, a city, a fishery), who the stakeholders are and what is changing. Write one line at the top: "Coastal lagoon, mangrove loss, shrimp farming vs fishers vs tourism."
2. Annotate every figure before answering anything. For each graph, map or table, note the units, the time period, the scale (watch for logarithmic axes and axes that do not start at zero) and the source. Circle the biggest change.
3. Read the question, then go back for data. Each question usually points to particular figures. Use those, and quote numbers with units: "fell from 1,250 ha to 800 ha (−36%) between 1990 and 2020".
4. Link to a named syllabus concept. The data are the evidence; the marks come from explaining them with ESS ideas (see the table below).
5. For evaluate and to-what-extent questions, use more than one source. Cases are built so that one figure supports a claim and another complicates it. Find both.

Reading the case material eats into the paper, so build it into your plan: on SL Paper 1, roughly 8–10 minutes to read and annotate leaves about 50 minutes for 35 marks. Take the same proportion on HL.

How are Paper 2 short answers and essays marked?

Section A (40 marks at both levels)

Short-answer and data-based questions across the syllabus. Mark scheme points are specific, so precision beats length: a 2-mark "outline" wants two distinct, correct points, not one point written twice. Calculations need working and units. If a question gives data, use it; an answer that ignores the figure rarely reaches full marks.

Section B (structured essays, 20 marks each)

Each essay is split into parts. The earlier parts are marked against a mark scheme, so they reward specific, correct content. The final part of each essay, worth 9 of the 20 marks, is marked with markbands (levels 1–3, 4–6 and 7–9), so it rewards the quality of the whole argument rather than a checklist. For that final part:

• Spend two or three minutes planning: your judgement, two or three arguments for, one or two against, and the example for each.
• Define the key terms in the question in a sentence each.
• Use named examples with specifics: a place, a date, a number. "The Aral Sea shrank after its feeder rivers were diverted for cotton irrigation from the 1960s" beats "a lake dried up".
• Bring in perspectives. Show how a technocentric and an ecocentric stakeholder would judge the same strategy differently.
• End with a judgement that answers the question, including how far and under what conditions.

The habit of writing to the mark scheme is covered in how IB mark schemes work.

What do the HL lenses add?

HL students study three lenses (17 hours in total) and must apply them, as well as the extra HL content. The guide tags lens material throughout the syllabus, so lens thinking can be relevant to any topic, not only a separate section. For each topic, prepare one example per lens:

The strongest HL answers use lenses together: a carbon tax is an economic tool, set by law, and judged fair or unfair through an ethical lens (who pays, and who bears the harm).

Which command terms matter most in ESS?

ESS uses most of the familiar science command terms, plus several you won't meet in Biology: apply, interpret, examine, demonstrate, derive and to what extent. What each one wants, in short:

The full list, with how each term is marked, is in IB command terms explained. Quote the IB's own definitions from your subject guide if you need them word for word.

How much time do you have per mark?

Use these as checkpoints rather than a strict clock: if a 3-mark question has taken eight minutes, write what you have and move on. More on pacing in time management in IB exams.

What should you revise first?

1. Topic 1, Foundation. Systems, perspectives and sustainability appear in every other topic and every paper. If you can draw a systems diagram with storages, flows and feedback for any issue, you can answer questions on cases you have never seen.
2. Data skills. Describing trends with numbers, percentage change, rates, reading log scales, telling correlation from cause. This is the whole of Paper 1 and much of Paper 2 Section A.
3. The calculations ESS uses: productivity (GPP, NPP, secondary productivity), efficiency of energy transfer, Simpson's index, the Lincoln index, population growth and doubling time.
4. A bank of specific case studies. For each topic, one or two examples with a place, a date and at least one number.
5. HL only: one example per lens per topic, as in the table above.

Then practise under timed conditions. Old ESS papers are useful for data handling and the case-study style, though they were written for the old syllabus; where to find past papers explains how to get them legally. Before you start, read the common ESS mistakes so you do not practise the wrong habits.