🌿Intro to Environmental Science Unit 2 – Earth Systems & Biogeochemical Cycles
Earth systems and biogeochemical cycles form the foundation of our planet's ecological balance. These interconnected processes involve the movement of matter between the atmosphere, hydrosphere, geosphere, and biosphere, shaping the environment we live in.
Understanding these cycles is crucial for addressing environmental challenges. Human activities have significantly altered natural cycles, leading to issues like climate change and ecosystem degradation. Studying these systems helps us develop sustainable practices to maintain Earth's delicate balance.
Earth systems encompass the complex interactions and processes between the planet's major components (atmosphere, hydrosphere, geosphere, and biosphere)
Biogeochemical cycles describe the movement and exchange of matter (such as water, carbon, nitrogen, and phosphorus) between living organisms and the environment
Consist of reservoirs (places where matter is stored) and fluxes (processes that move matter between reservoirs)
Feedback loops can amplify (positive feedback) or dampen (negative feedback) changes within Earth systems
Tipping points represent thresholds beyond which a system shifts abruptly and often irreversibly into a new state
Anthropogenic activities, such as fossil fuel combustion and land-use changes, significantly influence Earth systems and biogeochemical cycles
Sustainability involves managing human impacts to maintain the stability and resilience of Earth systems for future generations
Earth's Major Systems
The atmosphere is the gaseous envelope surrounding the Earth, consisting primarily of nitrogen (78%) and oxygen (21%)
Plays a crucial role in regulating the Earth's temperature through the greenhouse effect
Influences weather patterns and the distribution of heat and moisture across the planet
The hydrosphere encompasses all water on Earth, including oceans, lakes, rivers, groundwater, and water vapor in the atmosphere
Covers approximately 71% of the Earth's surface and is essential for life
Participates in various biogeochemical cycles and influences climate through heat storage and transport
The geosphere comprises the solid Earth, including the crust, mantle, and core
Provides the foundation for life and shapes the Earth's surface through processes like plate tectonics and weathering
Stores and releases nutrients and minerals that are essential for biological processes
The biosphere consists of all living organisms on Earth and the environments in which they live
Includes ecosystems ranging from tropical rainforests to deep-sea hydrothermal vents
Plays a critical role in biogeochemical cycles by assimilating, transforming, and recycling matter
Biogeochemical Cycles Overview
Biogeochemical cycles involve the transfer of matter between the Earth's major systems (atmosphere, hydrosphere, geosphere, and biosphere)
The water cycle (hydrologic cycle) describes the continuous movement of water through processes like evaporation, transpiration, precipitation, and infiltration
Drives weather patterns and shapes the Earth's surface through erosion and deposition
The carbon cycle encompasses the exchange of carbon between the atmosphere, oceans, land, and living organisms
Plays a crucial role in regulating the Earth's climate and supporting life
The nitrogen cycle involves the transformation of nitrogen between various chemical forms (such as nitrogen gas, ammonium, and nitrate) by biological and physical processes
Essential for the growth and reproduction of living organisms
The phosphorus cycle describes the movement of phosphorus through the environment, primarily through weathering, biological uptake, and sedimentation
Phosphorus is a limiting nutrient in many ecosystems and is essential for the formation of DNA, RNA, and ATP
Other important biogeochemical cycles include the sulfur cycle, which involves the transformation of sulfur compounds, and the oxygen cycle, which is closely linked to photosynthesis and respiration
Carbon Cycle
The carbon cycle involves the exchange of carbon between the atmosphere, oceans, land, and living organisms
Atmospheric carbon dioxide (CO2) is absorbed by plants through photosynthesis and converted into organic compounds
Some of this carbon is released back into the atmosphere through respiration by plants and animals
Carbon is stored in various reservoirs, including the atmosphere (as CO2), oceans (dissolved CO2 and carbonate sediments), land (soil and vegetation), and fossil fuels (coal, oil, and natural gas)
The burning of fossil fuels and land-use changes (deforestation) have significantly increased atmospheric CO2 levels, leading to climate change
The oceans absorb a substantial amount of atmospheric CO2, acting as a carbon sink
However, increased CO2 absorption leads to ocean acidification, which can have detrimental effects on marine ecosystems (coral reefs)
The carbon cycle is closely linked to the global climate system, as CO2 is a potent greenhouse gas that traps heat in the atmosphere
Nitrogen Cycle
The nitrogen cycle involves the transformation of nitrogen between various chemical forms, primarily through biological processes
Nitrogen gas (N2) makes up 78% of the Earth's atmosphere but is unavailable to most organisms
Nitrogen fixation converts atmospheric N2 into biologically available forms (ammonia, NH3) through lightning, industrial processes (Haber-Bosch), and nitrogen-fixing bacteria (root nodules of legumes)
Nitrification is the process by which ammonia is converted to nitrite (NO2-) and then to nitrate (NO3-) by bacteria in the soil
Plants absorb nitrate and incorporate it into organic compounds (amino acids, proteins)
Denitrification is the process by which nitrate is converted back into atmospheric N2 by bacteria in anaerobic conditions (waterlogged soils)
Human activities, such as the use of nitrogen fertilizers and the burning of fossil fuels, have significantly altered the nitrogen cycle
Excess nitrogen can lead to environmental problems like eutrophication (algal blooms) in aquatic ecosystems and groundwater contamination
Phosphorus Cycle
The phosphorus cycle describes the movement of phosphorus through the environment, primarily through weathering, biological uptake, and sedimentation
Phosphorus is a limiting nutrient in many ecosystems and is essential for the formation of DNA, RNA, and ATP
The main reservoir of phosphorus is sedimentary rocks, which release phosphorus through weathering and erosion
Dissolved phosphorus is taken up by plants and incorporated into organic compounds
Unlike the carbon and nitrogen cycles, the phosphorus cycle does not have a significant atmospheric component
Phosphorus is returned to the environment through the decomposition of organic matter and the excretion of waste products by animals
Human activities, such as the use of phosphate fertilizers and the discharge of wastewater, have altered the natural balance of the phosphorus cycle
Excess phosphorus can lead to eutrophication in aquatic ecosystems, causing algal blooms and oxygen depletion (dead zones)
The limited availability of phosphorus and its importance for agriculture has raised concerns about the future sustainability of phosphorus resources (peak phosphorus)
Human Impacts on Earth Systems
Anthropogenic activities have significantly altered Earth systems and biogeochemical cycles, often with unintended consequences
The burning of fossil fuels and deforestation have increased atmospheric CO2 levels, leading to climate change and ocean acidification
Climate change impacts include rising sea levels, more frequent and intense extreme weather events (hurricanes, droughts), and shifts in species distributions
Land-use changes, such as urbanization and agricultural expansion, have led to habitat loss and fragmentation, contributing to the ongoing biodiversity crisis (sixth mass extinction)
The widespread use of nitrogen and phosphorus fertilizers has disrupted nutrient cycles, causing eutrophication and dead zones in aquatic ecosystems
The release of pollutants, such as plastics, pesticides, and heavy metals, has contaminated air, water, and soil, with detrimental effects on human health and ecosystems
The overexploitation of natural resources (overfishing, deforestation) has led to the degradation and collapse of ecosystems, threatening the livelihoods of communities that depend on them
Addressing these challenges requires a transition towards sustainable practices, such as renewable energy, sustainable agriculture, and ecosystem-based management
Practical Applications and Case Studies
The Chesapeake Bay, the largest estuary in the United States, has suffered from nutrient pollution (nitrogen and phosphorus) due to agricultural runoff and urban development
Efforts to restore the bay include implementing best management practices (cover crops, riparian buffers) and setting nutrient reduction targets (Total Maximum Daily Load)
The Amazon rainforest, the largest tropical rainforest in the world, plays a crucial role in the global carbon cycle by absorbing CO2 and regulating regional climate
Deforestation and land-use changes have reduced the Amazon's carbon storage capacity and biodiversity, with implications for global climate change
The Sahel region of Africa has experienced desertification and land degradation due to a combination of climate change, overgrazing, and unsustainable agricultural practices
Initiatives to combat desertification include planting trees (Great Green Wall), promoting sustainable land management, and supporting local communities
The Arctic region is experiencing rapid warming and sea ice loss due to climate change, with consequences for local communities, wildlife (polar bears), and global climate patterns
Efforts to mitigate and adapt to these changes include reducing greenhouse gas emissions, supporting Indigenous knowledge and practices, and enhancing international cooperation (Arctic Council)
The Gulf of Mexico has been affected by nutrient pollution from the Mississippi River, leading to the formation of a large dead zone (hypoxic area) each summer
Strategies to address this issue include implementing nutrient reduction strategies in the Mississippi River Basin (precision agriculture, wetland restoration) and improving wastewater treatment
The Great Barrier Reef, the world's largest coral reef system, is under threat from climate change, ocean acidification, and water quality issues (agricultural runoff)
Conservation efforts include improving water quality, reducing greenhouse gas emissions, and supporting research and monitoring programs