Environmental Science
Environmental science studies interactions between humans and the natural world — understanding problems and developing solutions.
Biogeochemical Cycles
Matter cycles through ecosystems. Key cycles:
Carbon cycle: photosynthesis absorbs CO₂; respiration/combustion release it.
Nitrogen cycle: bacteria convert atmospheric N₂ into usable forms.
Water cycle: evaporation → condensation → precipitation → runoff.
Climate Change
Enhanced greenhouse effect from burning fossil fuels (CO₂, CH₄) traps more heat. Consequences: rising temperatures, melting ice, sea level rise, extreme weather events, shifting ecosystems.
Biodiversity
Biodiversity = variety of life. More diverse ecosystems are more stable and resilient. Threats: habitat destruction, invasive species, pollution, climate change, overexploitation (the 5 main drivers of biodiversity loss).
Pollution Types
- Air pollution: NOx, SOx, particulates (smog, acid rain)
- Water pollution: agricultural runoff, plastics, sewage
- Soil pollution: pesticides, heavy metals
- Noise/light pollution: disrupt ecosystems and human health
Sustainability
Using resources to meet today's needs without compromising future generations' ability to meet theirs (Brundtland Commission, 1987). Key strategies: renewable energy, recycling, conservation, sustainable agriculture.
Following the Carbon Cycle
Carbon constantly moves between the air, living things, oceans, and rock. The cycle is not new — what changed is the speed at which humans move carbon out of long-term storage.
The natural cycle
- Plants pull CO₂ from the air during photosynthesis and build it into tissue.
- Animals eat plants, and respiration returns some carbon to the atmosphere.
- Dead organisms decompose, releasing more.
- Some carbon is buried and, over millions of years, becomes coal, oil, and gas.
Burning fossil fuels releases carbon that took millions of years to store, in a matter of decades. That mismatch in timescale is the core of the climate problem.
How the Greenhouse Effect Works
The greenhouse effect itself is not a problem — without it Earth would average about −18°C and be uninhabitable. The concern is its intensification.
- Sunlight passes through the atmosphere and warms Earth's surface.
- The surface radiates that energy back as infrared heat.
- Greenhouse gases absorb some of that outgoing heat and re-radiate it, including back downward.
- More greenhouse gas means more heat retained, so the average temperature rises.
Renewable and Non-Renewable Resources
- Non-renewable: coal, oil, natural gas, and mined minerals. They form far slower than we consume them.
- Renewable: solar, wind, hydro, and geothermal, which replenish continuously.
- Conditionally renewable: forests, fisheries, and soil renew only if harvested slower than they regrow. Overuse turns them into non-renewable resources in practice.
Ecological Footprint
Measuring impact
An ecological footprint estimates how much land and water it takes to supply what a person consumes and absorb the waste they produce. It makes an abstract idea concrete: if everyone lived like the average resident of a high-consumption country, humanity would need several Earths.
The largest components for most individuals are transport, diet, and home energy — which is why those three dominate the advice on reducing impact.
Common Misconceptions
- Weather and climate are different. A cold week says nothing about climate, which is measured in decades of averages.
- The ozone hole and climate change are separate problems with separate causes, though both involve atmospheric gases.
- Recycling is the least effective of the three Rs. Reducing consumption and reusing come first for a reason.
- "Biodegradable" does not mean it breaks down anywhere. Many such products need industrial composting conditions.
Summary
- Matter cycles through ecosystems; energy flows through and is lost as heat.
- The greenhouse effect is natural, but added greenhouse gases intensify it.
- Feedback loops can accelerate warming beyond the initial cause.
- Biodiversity makes ecosystems more stable and resilient to disturbance.
- Sustainability means meeting present needs without foreclosing future ones.
FAQ
What is the difference between weather and climate? Weather = short-term atmospheric conditions. Climate = long-term patterns over 30+ years.
What is the difference between weather and climate? Weather is atmospheric conditions right now; climate is the pattern of weather averaged over 30 years or more.
Why is biodiversity worth protecting? Diverse ecosystems recover from disturbance better, and species provide services humans depend on — pollination, water filtration, and the origins of many medicines.
What is an invasive species? An organism introduced outside its native range that spreads and harms the local ecosystem, usually because its natural predators are absent.
Does individual action matter if industry emits more? Both matter, and they are connected. Individual choices are small alone but shape demand, and policy change is what scales them up.
Quick Quiz
Test what you just learned. Choose the best answer for each question.