ESS Topic 2.3: Biogeochemical Cycles

What are biogeochemical cycles?

Closed systems that recycle nutrients from the environment to organisms and back, ensuring chemical elements are available to living organisms through transfers and transformations.

Outline how trees contribute to carbon absorption and storage

Trees and vegetation absorb CO₂ from the atmosphere during photosynthesis, converting it into organic compounds like glucose, which are then used to build plant tissues.

define and describe stores

where elements are held or stored for varying lengths of time

• located in reservoirs like the ocean, soil, atmosphere, or living organisms (e.g., carbon in fossil fuels, nitrogen in soil, phosphorus in sediments).

define and describe sinks and their role

Parts of a biogeochemical cycle with a net accumulation of elements, absorbing or storing more than they release

• e.g., forests absorbing more CO₂ than they release, oceans absorbing excess atmospheric CO₂

• regulating concentration of elements

• helps mitigate potential imbalances

define and describe a source and its role

Areas with a net release of elements into the environment, releasing more than they absorb or store

• e.g., fossil fuel combustion releasing stored carbon, agricultural activities releasing nitrogen from the soil

• availability of elements in different forms and locations

• can have both positive + negative impacts

list ways carbon can be stored organically

• Living organisms - within organic molecules

• crude oil and natural gas - stored as hydrocarbons and CO₂ released during combustion

• soil - dead organic matter

list ways carbon can be stored inorganically

• atmosphere - carbon dioxide (CO₂) as a GHG

• soils - carbonates (mineral form)

• oceans - dissolved CO₂, bicarbonate (HCO₃⁻), and carbonate ions (CO₃²⁻)

  • absorbs excess CO₂ from the atmosphere

define carbon sequestration

Process of capturing gaseous and atmospheric carbon dioxide and storing in a solid or liquid form to reduce GHG

explain the importance of carbon sequestration

• climate regulation - regulate the global climate by reducing atmospheric CO₂ levels ; mitigating climate change

• biodiversity + ecosystem health - support diverse plant and animal species ; ecological health/resilience

describe the process of fossil fuel formation

Over millions of years, dead plants and microorganisms accumulate in sediment layers, becoming buried and subjected to high pressure and temperature (organic matter burial), gradually transforming into fossil fuels (fossilization)

identify ways that carbon flows through an ecosystem [6]

• photosynthesis - absorb CO₂ from the atmosphere into organic compounds using the energy from sunlight and stored in plant biomass

• cellular respiration - breaks down organic compounds to produce energy

• defecation - consumed carbon is excreted and contributes to soil organic matter

• feeding - consumption transfers carbon into the consumer’s body, which is used for growth and energy

• sedimentation - deposited organic matter settles as sediment which transforms into coal/oil/gas deposits

• death + decomposition - decomposition process converts organic carbon back into inorganic forms, releasing CO₂ and other compounds into the soil and atmosphere

identify sources of human impact on carbon stores

Burning of crude oil/natural gas/coal releases large amounts of CO₂ into the atmosphere, rapidly depleting ancient carbon stores + increasing atmospheric CO₂ levels, contributing to global warming

describe ways that agricultural practices can act as a carbon source

• heavy tillage - removes nutrients, degrades soil structure + quality, increases soil erosion

• monocultures - deplete soil of the same nutrients repeatedly

• draining wetlands - released store CO2, reduces storage capacity, lack of extensive plant life and decaying organic matter

describe ways that agricultural practices can act as a carbon sink

• crop rotation - Plant different crops after each harvest = reduces nutrient depletion, increases healthy soil bacteria, reduces oxidation of organic material

• zero tillage - leave organic matter in the soil to decompose = returns nutrients to the soil

• cover cropping - planting cover crops (peas, beans, clover etc) to add nutrients + nitrogen and improve soil fertility

• composting - layering carbon and nitrogen rich materials for nutrients

describe the process of ocean acidification

CO₂ + H₂O = H₂CO3 carbonic acid

lowers pH of ocean water

• makes it harder for coral and mollusks to grow shells

• pushes species outside of their pH tolerance range

describe strategies to mitigate human impact on carbon systems [6]

• low carbon technologies

  • transitioning to renewable energy sources to lower GHG emissions + dependence on fossil fuels

• energy efficiency

  • energy efficient tech + practices in industry, transportation, buildings

  • minimize demand for fossil fuels

• fossil fuel reduction

  • reduce burning of fossil fuels

• deforestation reduction

  • promoting sustainable forest management

  • protects tree’s carbon sequestration ability

• carbon capture reforestation

  • planting trees on degraded/deforested lands

  • restores carbon stores and sequestration

• artificial carbon sequestration

  • capture CO₂ emissions from industrial sources and store them underground in geological formations

draw a carbon cycle