Summary
Highlights
Stratospheric ozone (O3) is crucial for absorbing dangerous high-energy UV radiation from the sun, protecting us from sunburn, skin cancer, and eye damage. Ozone is formed when UV radiation splits O2 molecules into single oxygen atoms, which then react with other O2 molecules to form O3.
Ozone depletion, discovered in 1985 as a 'hole' over the Antarctic, is caused by human-made chemicals, primarily chlorofluorocarbons (CFCs). UV radiation causes CFCs to decompose, releasing chlorine, which then reacts with and breaks down ozone molecules. The Montreal Protocol was established to phase out CFCs.
The greenhouse effect is a naturally occurring process that keeps Earth warm and hospitable. Greenhouse gases (GHGs) in the atmosphere trap infrared heat. However, an excess of GHGs, largely from anthropogenic (human-caused) fossil fuel combustion, intensifies this heat trapping, leading to a warming trend. The Kyoto Protocol aims to reduce GHGs globally.
Important greenhouse gases include water vapor, carbon dioxide (CO2), methane, nitrous oxide (N2O), and CFCs. Their warming potential and atmospheric lifespan determine their impact. Methane, N2O, and CFCs have a significantly higher warming potential than CO2, though CO2 is abundant. Water vapor, while a GHG, has a relatively short atmospheric lifespan due to the water cycle.
Global warming is characterized by increasing atmospheric CO2 levels and rising global temperatures, strongly correlated with human fossil fuel use and deforestation. Positive feedback loops, particularly in northern latitudes, accelerate warming. Examples include thawing permafrost releasing methane and melting ice (high albedo) exposing darker ocean water (low albedo), leading to more heat absorption.
Climate change leads to habitat loss (e.g., polar ice for polar bears), species migration, spread of diseases, soil productivity changes, shifting ocean/wind currents, rising sea levels due to ice melt and thermal expansion of the ocean, and ocean acidification.
Ocean warming causes metabolic and reproductive changes in marine species and coral bleaching. Ocean acidification occurs as the ocean absorbs excess atmospheric CO2, forming carbonic acid. This acid reduces the availability of carbonate, essential for shelled organisms to build their shells, threatening marine ecosystems.
Biodiversity loss is largely driven by human actions. The HIPPC-O acronym outlines major factors: Habitat destruction, Invasive species, Population growth (human), Pollution, Climate Change, and Over-exploitation. These factors often lead to species becoming threatened or endangered.
Efforts to protect biodiversity include strong legislation like the Endangered Species Act, international agreements such as CITES, criminalizing poaching, habitat protection, installing habitat corridors, reintroduction programs (e.g., gray wolves), sustainable land use monitoring, breeding programs, ecosystem restoration, and reducing non-native/invasive species.