Solar energy is renewable because it is constantly replenished by the sun, unlike fossil fuels which are finite and deplete over time. This basic concept is central to understanding sustainable energy sources.

Acid rain primarily results from the emission of sulfur dioxide and nitrogen oxides, which react with water vapor in the atmosphere to form acidic compounds. Recognizing these emissions is key for understanding air pollution issues.

The ozone layer, found within the stratosphere, absorbs and scatters the sun's harmful ultraviolet radiation. This protective function is critical for life on Earth.

Producers, such as plants and algae, use photosynthesis to convert sunlight into chemical energy. They form the base of the food web by providing energy for other organisms.

Nitrogen fixation is the process by which atmospheric nitrogen (N2) is transformed into ammonia (NH3), a form that plants can assimilate. This is a foundational concept in nutrient cycles.

Carbon dioxide is the primary greenhouse gas emitted through activities like burning fossil fuels and deforestation. Its accumulation in the atmosphere intensifies the greenhouse effect, leading to global warming.

Eutrophication leads to nutrient overload, which causes algal blooms that decrease oxygen levels in water bodies. The resulting hypoxia can create dead zones harmful to aquatic life.

Hydroelectric dams convert the gravitational potential energy of stored water into kinetic energy as water flows, which is then transformed into electrical energy via turbines. This sequence illustrates the practical application of energy conversion principles.

Habitat destruction, primarily through deforestation, urbanization, and agricultural expansion, is a leading driver of biodiversity loss. The reduction of natural habitats directly impacts species survival and ecosystem stability.

Treating wastewater removes contaminants before they reach natural water bodies, effectively reducing pollution. This approach is a key method for protecting aquatic ecosystems and human health.

Keystone species play a critical role in maintaining the balance and integrity of their ecosystems, even if their population numbers are low. Their presence or absence can trigger significant changes in ecosystem structure and function.

Sustainable forest management seeks to balance economic needs, such as timber production, with the conservation of biodiversity and ecosystem health. This practice ensures that forests continue to provide essential services over the long term.

Chlorofluorocarbons (CFCs) are chemicals that break down ozone molecules in the stratosphere, leading to a thinner ozone layer. Understanding the impact of CFCs is essential for recognizing human influence on atmospheric changes.

Externalities describe unintended side effects of economic activities that affect uninvolved third parties. Recognizing externalities helps in understanding why markets may fail to address environmental costs adequately.

Crop rotation and cover cropping protect the soil by reducing erosion and maintaining soil structure. These practices help retain nutrients and moisture, contributing to sustainable agriculture.

Positive feedback loops, such as the melting of ice reducing Earth's albedo, amplify initial warming, leading to further temperature increases. This self-reinforcing mechanism is central to many advanced climate models.

The precautionary principle underscores acting to prevent harm even when scientific certainty is lacking. It shifts the focus toward preventing damage rather than waiting for irrefutable evidence, thereby protecting public health and the environment.

Solar radiation management, particularly through techniques like stratospheric aerosol injection, aims to reflect sunlight away from Earth to cool the planet. This controversial approach is studied for its potential to offset some effects of climate change.

The concept of ecosystem services involves quantifying and valuing the benefits that natural ecosystems provide, such as water purification and carbon sequestration. This valuation can lead to better-informed policies that integrate environmental health with economic planning.

Ecosystems with greater biodiversity tend to be more resilient because the presence of multiple species performing similar functions helps maintain ecological balance after disturbances. This redundancy ensures that some species can compensate when others are lost.