IB Diploma Environmental Systems & Societies HL · Foundations of Environmental Systems and Societies
Mini-Lesson
Foundations of ESS
This mini-lesson builds the toolkit for the whole course: environmental value systems (how worldviews shape decisions), systems and models (storages, flows and their limits), energy and equilibria (the laws of thermodynamics, steady states and feedback) and sustainability (natural capital, ecological footprints, the Anthropocene and the UN SDGs).
Three key concepts of the 2024 guide:perspectives, systems and sustainability. Every topic in ESS returns to these three lenses.
Work through each screen, answer the questions as you go (some are wordy, some are calculations) and collect ⭐ stars. Press Start when you're ready.
Perspectives · environmental value systems
Environmental value systems (EVS)
An environmental value system (EVS) is a worldview that shapes how an individual or society appraises environmental issues. Like any system it has inputs (education, media, culture, religion, experience), a process (weighing and valuing) and outputs (decisions, laws, actions).
Ecocentric — nature-centred; minimal human interference, intrinsic value of nature, small-scale local solutions.
Anthropocentric — people-centred; humans sustainably manage the global system using taxes, regulation and population policy.
Technocentric — technology-centred; scientific innovation and free markets provide the solutions.
Perspectives are a spectrum. Deep ecologists sit at the far ecocentric end; cornucopians at the far technocentric end. An EVS can shift with new information.
Quick check
Placing a worldview
?A politician argues that new carbon-capture machines and market incentives will let the economy keep growing while fixing climate change. Which EVS does this best reflect?
Systems · storages and flows
Systems, storages and flows
A system is a set of interacting parts. We classify by what crosses the boundary:
Open system — exchanges both energy and matter (e.g. a natural ecosystem).
Closed system — exchanges energy but not matter (e.g. the Earth as a whole; a sealed terrarium).
Isolated system — exchanges neither. None exist in nature; a theoretical idea only.
Systems are described by storages (boxes, where matter or energy is held) and flows (arrows: inputs, outputs, internal transfers). A transfer moves matter/energy without changing its form; a transformation changes the form (photosynthesis turns light into chemical energy).
Systems · working with models
Models: strengths and limitations
A model is a simplified representation of reality used to understand and predict how a system behaves.
Strengths — simplify complex systems, let us test scenarios and predict outcomes, and communicate ideas clearly.
Limitations — rely on simplifying assumptions; accuracy depends on the quality of input data; small errors can amplify, so long-range predictions carry large uncertainty.
Systems diagrams are the models you will draw most: label every storage as a box and every flow as an arrow, and keep the boundary clear.
Quick check
Which kind of system?
?Sunlight and heat cross Earth’s atmosphere freely, but essentially no matter enters or leaves the planet. Earth is best modelled as which type of system?
Sort it
Sort the worldviews
Tap a statement, then tap the environmental value system it best fits.
🌱 Ecocentric
👥 Anthropocentric
⚙️ Technocentric
Systems · energy and equilibria
Energy, equilibria and thermodynamics
Two laws of thermodynamics govern every energy flow in the biosphere:
First law (conservation): energy is neither created nor destroyed, only transformed. Energy in = energy stored + energy out.
Second law (entropy): in every transformation some energy is degraded to low-grade heat, so entropy (disorder) rises. Living systems stay ordered only through a constant input of solar energy.
A system in steady-state equilibrium has continuous inputs and outputs but its storages stay roughly constant (change in storage = inputs − outputs ≈ 0). This differs from static equilibrium (no change at all).
Calculate
Your turn — change in storage
1A forest soil store gains 1200 tonnes of organic matter per year as leaf litter and loses 900 tonnes per year through decomposition. If these are the only flows, calculate the annual change in the soil carbon storage.
Feedback is information that returns to influence a system:
Negative feedback — counteracts change and restores balance (stabilising). As a predator population grows, prey decline, so predators later decline.
Positive feedback — amplifies change, driving the system further from its original state. Melting sea ice lowers albedo, so more sunlight is absorbed, causing more warming and more melting.
Past a tipping point, positive feedback can shift a system abruptly and irreversibly to a new state. Resilience is the ability to absorb disturbance and still return to equilibrium; more biodiversity and larger storages generally raise resilience.
Quick check
Feedback in action
?Warming melts Arctic permafrost, releasing methane, a greenhouse gas that causes further warming and more melting. What type of loop is this?
Quick check
The stabilising loop
?In a lake, as algae grow, they use up nitrates until the shortage of nitrates slows further algal growth. What type of feedback keeps the algal population in check?
Calculate
Your turn — energy efficiency
2A green plant receives 4000 kJ m⁻² of light energy in a day and fixes 40 kJ m⁻² of it as new biomass. Calculate the efficiency of this energy conversion.
%
Hint: efficiency = (useful energy out ÷ energy in) × 100 = (40 ÷ 4000) × 100.
Sustainability · capital and footprints
Sustainability, natural capital and footprints
Sustainability means using resources so they can be maintained for future generations — living off the interest, not the capital.
Natural capital — resources that yield a sustainable income (forests, fisheries, fertile soils, aquifers).
Natural income — the goods and services natural capital provides without depleting the stock.
Ecological footprint — the area of land and water needed to supply a population’s resources and absorb its waste; if it exceeds the biocapacity available, use is unsustainable.
Frameworks: the UN SDGs set 17 global targets to 2030; planetary boundaries define nine safe limits (climate, biosphere integrity, nutrient cycles and more), several already exceeded.
Quick check
Living sustainably
?A fishery lands 8000 tonnes a year while the fish can only replace 6000 tonnes a year. Why is this unsustainable in natural-capital terms?
Calculate
Your turn — ecological deficit
3A country has an ecological footprint of 4.0 global hectares per person and a biocapacity of 1.6 global hectares per person. Calculate the ecological deficit per person.
Tap a statement on the left, then its matching answer on the right.
Statement
Answer
Sustainability · a new epoch
The Anthropocene
The Anthropocene is the proposed geological epoch in which human activity is the dominant influence on climate, ecosystems and Earth systems. Evidence includes fossil-fuel carbon in the atmosphere, radioactive isotopes from nuclear tests, plastics and concrete in sediments, and a human-driven mass extinction.
Environmental indicators (atmospheric CO₂, global mean temperature, extinction rates, the ecological footprint) let us monitor how far human pressures have shifted Earth systems from their pre-industrial baseline.
Why it matters: recognising the Anthropocene frames sustainability as a whole-planet responsibility — the message that ties every ESS topic together.
Recap
The big ideas to know
Perspectives: ecocentric → anthropocentric → technocentric; an EVS has inputs, a process and outputs
Systems: open (energy + matter), closed (energy only), isolated (neither); storages and flows; transfer vs transformation
Thermodynamics: 1st law = energy conserved; 2nd law = entropy rises, energy degraded to heat