Baseline Studies in IB ESS: Design and Comparison Sites

27 Jul Baseline Studies in IB ESS: Design and Comparison Sites

A baseline study records conditions used as a reference for comparing later observations. It can help investigate an environmental intervention, but a before-and-after comparison alone does not prove that the intervention caused the change.

When is a baseline useful?

If you want to investigate change over time, establish what you can measure consistently before and after the intervention. Depending on the question, a comparison site, repeated observations or reliable historical records may also help. Not every ESS IA needs a separate pre-intervention baseline study.

Choose indicators and methods

Match indicators to the question: for example, vegetation cover, dissolved oxygen or energy consumption. Explain the sampling design, measurement technique and data-selection decisions. Check equipment, permissions and relevant safety or ethical considerations with your teacher.

Choose sampling effort according to variability, available resources and the conclusion you want to support. There is no universal requirement for five to ten replicates per zone or two baseline visits. A short pilot can help identify problems before the full investigation.

Plan a comparable before-and-after record

Create a recording table before collecting data. Include the date, site, indicator, unit, method and relevant conditions. Keep the same definitions and measurement procedure across visits. Note any unavoidable changes so you can explain how they affect the comparison.

Use a comparison site to strengthen interpretation

If vegetation cover changes beside a modified path, also observe a similar area where the path has not changed. Compare the change at each site over the same period. A difference between those changes can strengthen the interpretation, but different shading, trampling or maintenance can still confound it. Several quadrats within one site improve information about that site; they do not create several independently treated sites.

Interpret comparisons cautiously

Consider season, weather, sampling differences and other changes that could affect the results. Select graphs and statistical methods that suit the data and their assumptions. If your design does not isolate the cause, explain this limitation.

Use the current IA criteria

The current IA has six criteria: research question and inquiry, strategy, method, treatment of data, analysis and conclusion, and evaluation. A baseline is part of the evidence or method where relevant, rather than a separate criterion. Keep essential evidence and reasoning in the report; do not rely on an appendix to supply material needed for assessment.

Original planning exercise: Design a comparison of vegetation cover before and after a school-path change. Identify a possible comparison area and factors that might complicate interpretation. This is a suggested exercise with no invented results or marks.

Practise with individual ESS support

In Marija’s online IB ESS SL and HL lessons, you can work on concepts, data interpretation and clear explanations. Request a free 20-minute trial lesson to discuss your priorities. For IA work, the investigation and submitted writing remain your own.

Official reference: IB ESS guide, first assessment 2026. Updated 19 October 2026.