4.3: Carbon Cycling 4.4: Climate Change Chapter 4: Ecology 4.3: Carbon Cycling 4.4: Climate Change

Carbon! Organisms on planet Earth are carbon based All most every important compound in your body contains carbon: carbohydrates, lipids, proteins, nucleic acids….. Carbon is continuously cycled in an ecosystem

Carbon Cycle Show how carbon is recycled throughout the environment Show transformation of carbon from organic forms and inorganic forms Includes: Photosynthesis - removes carbon from atmosphere Cellular respiration Combustion - adds carbon to atmosphere Fossilization

Construct a diagram of the Carbon Cycle See page 226 Your diagram will have “pool” and flux” Pool: reserve of the element (i.e. atmosphere is an inorganic carbon pool.) Flux: transfer of the element from one pool to another, shown with arrows

The Carbon Cycle Carbon exists in many forms: Atmospheric gases (CO2 and methane) Dissolved CO2 in aquatic systems Organic carbon in living organisms Carbon deposits in the lithosphere as minerals (carbonates) or fossil fuels

Carbon fixation Autotrophs convert inorganic carbon ( CO2 from atmosphere) into organic carbon (carbohydrates, lipids, amino acids, nucleic acids) through photosynthesis or chemosynthesis This has an effect of reducing atmospheric CO2 concentration Although most autotrophs fix carbon by photosynthesis. A few are Chemoautotrophs and fix carbon by utilising the energy in the bonds of inorganic compounds such as hydrogen sulfide.

Carbon dioxide in solution CO2 is soluble in water. Some CO2 will remain in water as a dissolved gas, but most will combine with water to become carbonic acid (H2CO3). Carbonic acid can dissociate to form hydrogen and hydrogen carbonate ions (H+ and HCO3-) This explains how CO2 reduces the pH of water. CO2 + H2O → H2CO3 → H+ + HCO3–

Carbon dioxide in solution Both dissolved CO2 and hydrogen carbonate ions are absorbed by aquatic plants and other autotrophs that live in water.

In land plants with leaves, diffusion occurs through stomata CO2 from outside the leaf diffuses down the concentration gradient into the leaf CO2 moves through stomata pores in the leaves of land plants* atmosphere or water High CO2 Concentration gradient Low Photosynthesis uses CO2 keeping the concentration of CO2 inside the leaf low Inside the leaf atmosphere or water Transverse section of parsnip leaf (Pastinaca sativa) In land plants with leaves, diffusion occurs through stomata In aquatic plants, the entire surface of leaves and stems is permeable to CO2

Release of carbon dioxide from cellular respiration Organisms carry out respiration to release energy in the form of ATP. Carbon dioxide is a waste product of respiration. It diffuses out of cells and into surrounding atmosphere or water.

Carbon is also released into the environment when an organ dies and decomposes.

Carbon cycling… it’s not just carbon dioxide METHANE! (oxidized to water and CO2) Methanogenesis: Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and some diffuses into the atmosphere. Archaea are single-celled prokaryotic microorganisms that share some traits of bacteria and some of eukaryotes

Methanogenesis Archaeans produce methane from CO2 and hydrogen or acetate in these two chemical reactions: CO2 + 4H2 CH4 + 2H2O CH3COOH CH4 + CO2 (acetate)

Methanogenesis Methanogenic archaeans carry out methanogenesis in a variety of anaerobic environments: Wetlands (e.g. paddies, swamps, mangroves) where soil and peat deposits are waterlogged Digestive tracts of ruminant animals (grazing animals ie cows, sheep) Marine and freshwater sediments (e.g. mud in the beds of lakes) Landfill sites (in which organic matter has been buried) Methane is emitted from a range of natural and anthropogenic (relating to human activity) sources as a result of the anaerobic decomposition of organic matter, land use changes and fossil fuel related emissions

Methanogenesis Some of the methane produce by archaeans in these anaerobic environments diffuses into the atmosphere Methane produced from organic waste in anaerobic digesters is not allowed to escape and instead is burned as fuel

Oxidation of Methane Methane is oxidized into CO2 and H2O in the atmosphere It is estimated that, on average, methane persists in the atmosphere for 12 years, as it is naturally oxidized in the different regions of the atmosphere (troposphere and stratosphere), and can also be taken up in soils by bacteria.

Peat Formation Peat is partially decayed organic matter/ vegetation that forms as a result of anaerobic conditions in waterlogged soils. “Soil-like”, dark brown, acidic

Peat Formation Saprotrophic bacteria and fungi break down organic matter from plants in the soil. They require air pockets in the soil to supply O2. In environments where water is unable to drain from the soil, water fills the air pockets creating anaerobic conditions Most saprotrophs will die so organic matter will not be completely broken down. Large quantities of partially decomposed organic matter will accumulate and in some ecosystems become compressed to form peat.

Peat formation Peat is a highly effective carbon sink It is estimated that peatlands contain 180-455 billion tons of sequestered carbon and release 20-45 million tons of methane, annually Once dried peat burns easily and can be used as a fuel. Toppila Peat-Fired Power Plant in Oulu, Finland

Fossilization of Organic Matter: Coal, oil and Gas formation Partially decomposed organic matter from past geological eras was converted either into coal or into oil and gas that accumulate in coal or porous rocks.

Coal Formation Coal is formed when deposits of peat are buried under other sediments. The peat is compressed and heated over millions of years an eventually becomes coal. The cycle of sea-level changes that happened during the Carboniferous period caused coastal swamps to be buried, promoting the formation of coal.

Limestone formation Animals such as reef-building corals and mollusks have exoskeletons/shells that are composed of calcium carbonate. When the animals die, the soft body parts decompose, but the calcium carbonate remains form deposits on ocean floor which are buried and compressed and eventually form limestone rock. Imprints of the hard body parts remain in the rock as fossils. Limestone rock is a carbon sink. Huge amounts are locked up in limestone rock on Earth.

Combustion Reactions of hydrocarbons (such as fossil/biomass fuel) with heat and oxygen to release energy and produce CO2 and water Carbon dioxide is produced by the combustion of biomass and fossilized organic matter.

Environmental Monitoring It is important to obtain reliable data on the concentration of carbon dioxide and methane in the atmosphere Why? – may have an effect on climate change

Analyzing Changes in Atmospheric CO2 Average CO2 concentration has increased from ~315 ppm to ~380 ppm in a span of just over 40 years. Fluctuations within the year are due to seasons. When trees lose their leaves, they will not be able to remove CO2 from the environment

Relationship between greenhouse gases and the Enhanced Greenhouse Effect

The above graph show that global temperatures have been rising Shows a correlation between rise in carbon dioxide levels and temperature rise. But is this causation? Not a just a recent phenomenon; pattern has repeated itself several time throughout Earth’s history

Monitoring of CO2 Atmospheric monitoring stations Ice cores Mauna Loa Observatory in Hawaii has records for the longest period Ice cores

Ice samples taken from Antarctica contain small pockets of air, that can be analyzed for composition to determine past atmospheric CO2 concentrations and temperature Periods of higher carbon dioxide concentration repeatedly coincide with periods when the Earth was warmer

Vostock ice core (pictured) drilled at a Russian monitoring station in East Antarctica is an example of an ice core. A cylinder of ice was collected by drilling from to the bottom of the Antarctic ice sheet. The total length of the core was 2083 meters. The core shows annual layers, which can be used to date the air bubbles trapped in the ice. Analysis of the gas content of the bubbles gives both the concentration of carbon dioxide in the atmosphere and the air temperature (from oxygen isotopes) at the time ice was formed. http://commons.wikimedia.org/wiki/File:GISP2_1855m_ice_core_layers.png http://en.wikipedia.org/wiki/File:GISP2_team_photo_core37.jpeg

The Greenhouse Effect Of all the light energy that reaches the Earth from the Sun, ~30% is reflected back into space and ~70% will warm up the Earth’s surface and eventually radiate out as infra red radiation. The Greenhouse Effect is the concept that some of this infra red radiation will become trapped in the Earth’s atmosphere by (greenhouse) gases, thus warming the Earth

The trapping of this energy is essential to life on Earth – it makes Earth habitable planet with temperatures suitable for sustaining life. These naturally occurring greenhouse gases have been around for a long time, but with an increase in industry, population, and land development, there has been an increase in the burning of fossil fuels, the level of these greenhouse gases has been increasing

Greenhouse Gases Carbon Dioxide CO2 most important Water vapour greenhouse gases Methane CH4 smaller impact but Nitrogen oxides NOx still greenhouse gases All greenhouse gases together make less than 1% of the atmosphere

Long-wavelength emission from Earth The Earth absorbs short-wavelength energy from the sun and then re-emits it as much longer wavelengths. Greenhouse gases in the atmosphere absorb the long wavelengths of infra red light, keeping them in the Earth’s atmosphere longer. This causes a Global Warming We rely on this to keep our planet warm, but is it too warm?

How the Greenhouse effect works If the Earth had no atmosphere, and hence no greenhouse effect, the average surface temperature would be approx. -18oC. Approx. 25% of short-wavelength solar radiation is absorbed by the atmosphere (most of which is UV light absorbed by ozone). 1 2 4 Approx. 75% of solar radiation penetrates the atmosphere and reaches the Earth’s surface. Up to 85%* of re-emitted heat is captured by greenhouse gases in the atmosphere. 5 3 This energy is re-emitted, some heat passes back to the surface of the Earth, causing warming The surface of the Earth absorbs short-wave solar energy and re-emits at longer wavelengths (as heat). *This value, though variable, is known to be rising; very likely the result of human activities. http://www.sumanasinc.com/webcontent/animations/content/globalcarboncycle.html

Consequences of Global Warming on Arctic Ecosystems Melting of the Polar Ice Caps as the ice caps melt, they add fresh water to the ocean’s salt water  Thus, they alter the salinity. This can disrupt ecosystems This can alter ocean currents, which can alter wind currents, which can alter climate and result is drastic climate change  Increase the volume of water in the ocean This can cause severe flooding in coastal cities

Consequences of Global Warming on Arctic Ecosystems The white snow and ice in the Arctic reflect a lot of the Sun’s radiation. When the snow and ice melt (bc of global warming), the Arctic will warm up even faster (bc light will be absorbed rather than reflected) Melting of the permafrost in Siberia would release methane gas (a greenhouse gas) thus making the planet even warmer Positive Feedback!

Consequences of Global Warming on Arctic Ecosystems The warmed Arctic climate causes a change in the Arctic habitat, thus changing the migration and feeding patterns of various species Includes: polar bears, seas, caribou Native Americans who hunt these animals would find it difficult due to changing migration patterns Some villages have had to relocate because of swampy conditions created with the warming

Consequences of Global Warming on Arctic Ecosystems Effects on Polar Bears? High temperatures melt the snow in polar bear dens, shortening their hibernation periods. Lack of ice mass mean polar bears have to swim longer distances and expend more energy to reach prey or travel. Polar bears drowning???

Consequences of Global Warming on Arctic Ecosystems The plant species that live and prosper in the Arctic are adapted to the environment Milder climates mean that more species would be able to survive in the Arctic. This Increases biodiveristy which is usually a good thing, but it also increase increases competition for resources. Native species can become vulnerable and possibly at risk because of this competition

Threats to Coral Reefs Dissolved carbon dioxide increases acidity of oceans which breaks down calcium carbonate that makes up reefs.

Consequences of Global Warming on Arctic Ecosystems POSITIVES? More plant species means higher biodiversity More food for Arctic herbivores There are a lot of gas reserves in the Arctic that remain largely inaccessible. The melting of the ice would allow us to tap into this resource for oil and gas However, would that lead to positive feedback?

Climate Science “Controversy” Some claim human actions are not the main reason (or even any reason) for recent increases in carbon and global temperature. Some claim CO2 levels are increases but increase in temps haven’t been consistent.

Climate Science Controversy In science, we should always base our evaluations on reliable non biased evidence. Remember, not all sources on the internet are trustworthy. We need to be careful to distinguish between sites with objective assessments based on reliable, evidence opposed to others that show a bias. It is also important to investigate all aspects of the claim.

The truth is… Humans release large quantities of CO2 into the atmosphere with the combustion of fossil fuels. Carbon dioxide causes temperatures to rise. Global warming is continuing Perhaps not with equal increases each year. But, that’s because there a multiple factors that influence temperatures each year (volcanic activity, cycles in ocean currents…) not just greenhouse gases. So even if greenhouse gas emissions were not considered there would be fluctuations year by year.