Systems and System Diagrams

IB DP ESS — Topic 1: Foundations | SL & HL | Paper 1 & Paper 2A

🎯 Learning Intentions By the end of this note, you will be able to:

• Define a system, and distinguish between open, closed, and isolated systems using IB ESS terminology.

• Identify storages (stocks), flows (fluxes), inputs, and outputs within a named environmental system.

• Explain how positive and negative feedback mechanisms regulate or destabilise environmental systems, with reference to named real-world examples.

• Describe the concept of steady state and dynamic equilibrium in environmental systems, and the conditions under which these can be disrupted.

• Construct a systems diagram for a named environmental system, correctly labelling storages, flows, inputs, outputs, and feedback loops.

• Analyse the behaviour of environmental systems using relevant ESS analysis parameters: scale, uncertainty, sustainability, and multiple perspectives.

• Evaluate the strengths and limitations of systems thinking as a framework for understanding complex environmental problems.

Real-World Context & Relevance

In September 2023, the European Space Agency confirmed that Arctic sea ice extent had reached its lowest recorded summer minimum — approximately 4.23 million km², roughly 1 million km² below the long-term average. Scientists were not simply alarmed by the number itself, but by what it implied about a self-reinforcing process already underway. As white ice melts, it exposes darker ocean water, which absorbs more solar radiation, which warms the ocean further, which melts more ice. A change in one part of the system was amplifying itself — a behaviour that cannot be understood by looking at ice or ocean temperature in isolation.

This is precisely why ESS begins with systems thinking. The Arctic ice example, the collapse of the Grand Banks cod fishery in 1992, the spread of algal blooms in the Baltic Sea, the recovery of wolf populations in Yellowstone after reintroduction in 1995 — none of these phenomena can be fully explained by examining a single variable. They are emergent properties of interconnected systems, where storages, flows, and feedbacks interact across multiple scales. Learning to read, draw, and interpret systems diagrams is the foundational skill that makes all subsequent ESS analysis possible.

🌍 Why This Matters Environmental decision-making — from fisheries management to climate policy to urban water planning — depends on understanding how systems behave, how they respond to disturbance, and when they might cross a threshold into a new, potentially irreversible state. Systems thinking is not an abstract academic exercise; it is the conceptual toolkit that distinguishes informed environmental management from guesswork.

Core Concepts & Definitions

Before we can analyse any environmental problem — whether it is soil degradation in the Sahel, nitrogen loading in the Chesapeake Bay, or deforestation in Borneo — we need a shared language for describing how the world is organised. That language is systems thinking. The central claim is simple but profound: the natural world, and human society within it, is not a collection of isolated objects but a web of interacting components whose behaviour can only be understood in relation to one another.

📖 Key Definition — System A system is a set of interrelated components that form a unified whole, operating within a defined boundary. Systems are characterised by storages (stocks), flows (fluxes), inputs, outputs, and feedback mechanisms that regulate or alter system behaviour over time.

The concept of a system boundary is crucial. It defines what is inside the system (the components we are studying) and what is outside (the surroundings). In practice, this boundary is often chosen by the analyst — a lake ecosystem, a national economy, or the entire Earth's climate system can all be treated as systems, depending on the question being asked. The choice of boundary affects what counts as an input or output, and therefore shapes the entire analysis.

Dos and Don'ts — Defining a System