Earth as a system
Earth works as one interconnected Earth system of four main spheres:
| Sphere | What it includes |
|---|---|
| Geosphere | Rocks, minerals, soil, Earth’s interior |
| Hydrosphere | Oceans, lakes, rivers, groundwater, ice (the ice part is sometimes called the cryosphere) |
| Atmosphere | The layer of gases surrounding Earth |
| Biosphere | All living things |
Some scientists add the anthroposphere: human-made systems such as cities, farms and industries.
Interactions
A single event can ripple through all the spheres. For example, a volcanic eruption (geosphere) releases ash and gases into the atmosphere, which can cool the climate, change rainfall (hydrosphere) and affect crops and forests (biosphere). The 1815 eruption of Mount Tambora led to 1816’s "Year Without a Summer," with crop failures across North America and Europe.
Matter cycles between spheres (carbon, water, nitrogen, rock cycles) while energy flows through them, from the Sun and from Earth’s interior.
Natural resources
| Type | Definition | Examples |
|---|---|---|
| Renewable resource | Replaced naturally within a human lifetime, if not overused | Sunlight, wind, flowing water, forests, fish, fresh water |
| Non-renewable resource | Forms over millions of years; supply is finite | Coal, oil, natural gas, uranium, metal ores |
Some "renewable" resources can be overused faster than they recover. The collapse of the northern cod fishery off Newfoundland in the early 1990s ended a centuries-old industry and cost tens of thousands of jobs.
Canada’s resources
Canada has abundant resources: it’s among the world’s top producers of oil, natural gas, uranium, potash, aluminum, nickel and wood products, and it holds about 20% of the world’s fresh water (though only about 7% is renewable flow). Hydroelectricity provides about 60% of Canada’s electricity.
Energy resources compared
| Source | Advantages | Disadvantages |
|---|---|---|
| Fossil fuels | Reliable, energy-dense, existing infrastructure | CO₂ emissions, air pollution, finite |
| Nuclear | Very low emissions, reliable | Long-lived waste, high cost, accident risk |
| Hydroelectric | Low emissions, reliable, can store energy | Floods land, affects fish and communities |
| Wind | No fuel cost, low emissions | Variable output, land use, wildlife concerns |
| Solar | Abundant, rapidly falling cost | Variable output; needs storage |
| Geothermal | Constant, low emissions | Limited to certain locations |
| Biomass | Uses waste; renewable if managed | Land use; some emissions |
Ecosystem services
Healthy ecosystems provide ecosystem services worth trillions of dollars a year:
- Provisioning: food, fresh water, timber, medicines
- Regulating: climate regulation, flood control, water purification, pollination
- Supporting: soil formation, nutrient cycling
- Cultural: recreation, spiritual value, inspiration
Wetlands, for example, filter pollutants and absorb floodwaters. Bees and other pollinators are essential for about three-quarters of the world’s leading food crops.
Human impacts
| Impact | Earth system affected | Example |
|---|---|---|
| Climate change | Atmosphere, hydrosphere, biosphere | Rising temperatures and sea levels |
| Habitat loss | Biosphere | Wetland drainage, deforestation |
| Pollution | All | Plastic in oceans, smog, fertilizer runoff |
| Resource depletion | Geosphere, hydrosphere | Groundwater overuse, overfishing |
| Biodiversity loss | Biosphere | About 1 million species at risk of extinction (IPBES, 2019) |
Ecological footprint
An ecological footprint measures how much land and water are needed to support a person’s lifestyle. Humanity currently uses resources as if we had about 1.7 Earths. Canada’s per-person footprint is among the highest in the world.
Sustainability
Sustainability means meeting the needs of the present without compromising future generations’ ability to meet their own needs (the Brundtland Report, 1987).
Many Indigenous peoples have long practised a similar principle, often called Seventh Generation thinking: considering how decisions will affect people seven generations into the future.
Strategies
| Strategy | Examples |
|---|---|
| Reduce, reuse, recycle | Repairing electronics; composting |
| Circular economy | Products designed to be reused, repaired or recycled instead of thrown away |
| Renewable energy transition | Solar, wind, heat pumps, electric vehicles |
| Sustainable agriculture | Crop rotation, reduced tillage, integrated pest management |
| Conservation and protected areas | Canada’s goal to protect 30% of its land and oceans by 2030 |
| Sustainable fisheries and forestry | Catch limits, replanting, certification |
| Water conservation | Efficient fixtures, fixing leaks, protecting watersheds |
The United Nations’ 17 Sustainable Development Goals (2015) provide a global framework, including clean water, affordable clean energy, climate action and life on land and below water.
Common mistakes
- Thinking renewable means unlimited. Forests and fish can be overused.
- Thinking one sphere can change without affecting others.
- Thinking sustainability is only about the environment. It also includes social and economic well-being.
Try it yourself
- Choose an event (a wildfire, a dam, a new mine). Draw a diagram showing how it affects each of Earth’s four spheres.
- Calculate your ecological footprint with an online calculator and identify your largest category.
- Research where your community’s electricity comes from. List its advantages and disadvantages.
- Design a plan to make your school more sustainable, with three measurable goals.
Quick recap
- Earth’s geosphere, hydrosphere, atmosphere and biosphere interact as one system.
- Renewable resources can be replenished; non-renewable ones can’t on human timescales.
- Ecosystems provide essential services like clean water and pollination.
- Human activities strain Earth’s systems; our footprint exceeds what Earth can renew.
- Sustainability balances present needs with those of future generations.