Global challenges: human population growth and its environmental pressures, the concept of sustainability and sustainable development, carrying capacity, and the use of the ecological footprint to measure human demand.

What this dot point is asking

The SQA wants you to explain the global challenges that make sustainability necessary: human population growth and the environmental pressures it creates, the meaning of sustainability and sustainable development, carrying capacity, and how the ecological footprint measures human demand on the planet. This is the framing topic for the whole Sustainability area.

Human population growth

The global human population has risen steeply, from around one billion in 1800 to eight billion today, driven by better food supply, medicine and sanitation lowering death rates. This growth, combined with rising consumption per person, increases the demand for food, water, energy and raw materials and increases waste and pollution.

Sustainability and sustainable development

Sustainable development tries to balance three pillars: the environment, the economy and society. A choice is sustainable only if it keeps resource use within the rate of replacement and keeps waste within the environment's ability to absorb it, so that future generations are not left worse off.

Carrying capacity

When a population exceeds the carrying capacity of its environment, resources are used faster than they can be replaced and the population cannot be sustained, leading to a decline. The idea applies to wildlife and, with human technology and trade complicating it, to the human use of the whole planet.

The ecological footprint

The ecological footprint is a way of measuring how much of the planet human activity uses.

• It measures the area of productive land and sea needed to supply the resources a population uses and to absorb its waste (including carbon dioxide), usually in global hectares per person.
• Biocapacity is the productive area actually available to provide those resources and absorb that waste.
• When the footprint exceeds biocapacity, humanity is in overshoot: using resources faster than they regenerate and accumulating waste faster than it can be absorbed, which is unsustainable.

The footprint lets us compare the impact of different countries and lifestyles and judge whether humanity's total demand is within the planet's means.

Examples in context

Example 1. Earth Overshoot Day. Each year, campaigners calculate the date by which humanity has used as much from nature as the planet can renew in the whole year; it has been arriving earlier over recent decades, around late summer. It makes the abstract idea of overshoot concrete: for the rest of the year we draw down natural capital.

Example 2. Contrasting national footprints. High-income, high-consumption countries typically have footprints several times the global average biocapacity per person, while many lower-income countries live within it. Comparing footprints shows that lifestyle and consumption, not just population numbers, drive the pressure on the planet.

Try this

Q1. State the standard definition of sustainable development. [1 mark]

• Cue. Development that meets present needs without compromising the ability of future generations to meet their own needs.

Q2. Explain what it means for humanity's ecological footprint to exceed the Earth's biocapacity. [2 marks]

• Cue. We use resources faster than they regenerate and produce waste faster than it is absorbed (overshoot), which is unsustainable.