Daisy World Theory
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Daisy World Theory

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climate homeostasis

climate homeostasis

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Daisy World Theory Daisy World Theory Presentation Transcript

  • Palaeoecology Bioenergy through time and space
  • Structure of the Biosphere genes individuals/colonies communities/ ecosystems provinces realms Gaia?? Inputs Timescale Radiation/mutagens weather climate/anthropogenic longterm climate, oceanic circulation plate tectonics solar output, style of tectonics Instant-years seasonal Decades - 100 yrs 2 Kyr - 1 Myr 300 Myr 109 yr ecologygeneticsbiogeography
  • Daisyworld - Gaia in theory!
  • Palaeoecology  Ecology: from Greek “oikeia” and “logos” = the study of housekeeping.  Palaeoecology can be seen as two things:  Ecology in the past - how past organisms lived  Evolution of ecology - how ecological systems have evolved
  • Example: a reef  Several levels of analysis possible:  What do the organisms in it do, and how do they interact?  How have those organisms evolved or been replaced through time?  How have the functional interactions themselves evolved through time?
  • Then…
  • …and now
  • What has changed? Atmospheric composition Landscape dynamics (vegetation) Weathering and runoff Human activity All biologically mediated!
  • What is ecology? Fundamentally, can be seen as the study of how energy is transferred from initial sources through to biomass and eventual burial or recycling
  • Ecosystem ecology: the study of natural systems from the standpoint of the flow of energy, nutrients and matter.  Organisms treated as “black boxes” and seldom studied directly.  Ecosystems may be modeled as linked compartments among which elements are cycled at various rates:  photosynthesis moves carbon from an inorganic compartment (air or water) to an organic compartment (plant)  respiration moves carbon from an organic compartment (organism) to an inorganic compartment (air or water) Overview
  • Overview Cycling of elements and energy flux:  chemical elements are reused repeatedly  energy flows through the system only once and some energy is lost in all coupled redox reactions. Energy transformations and element cycling are linked. Organisms play important roles in cycling of elements when they carry out chemical transformations: Most biological energy transformations are associated with biochemical oxidation and reduction of C, O, N and S
  • Assimilatory processes:  incorporate inorganic forms of elements into organic forms, requiring energy  example: photosynthesis (reduction of carbon) Dissimilatory processes:  transform organic forms of elements into inorganic forms, releasing energy  example: respiration (oxidation of carbon) Assimilatory and dissimilatory processes are often linked, one providing energy for the other Overview
  • Energy sources Sunlight - by far the most important (today) Chemosynthesis - important in some systems - more important in the past? Thermal - but (probably) too low grade to be of use to life
  • Energy availability Sunlight - in the PHOTIC zone Chemical energy - in the REDOX zone
  • Primary production NEW REGENERATED Food chain Terrestrial input Base of Photic Zone Export production upwelling Nutrient and organic matter cycling in the ocean Organic matter Nutrients
  • Carbon Cycle Carbon is the “currency” of the global biological energy budget. It is passed from the atmosphere to organisms by photosynthesis, and back by respiration.
  • Palaeoecology Energy transfer through organisms
  • Ricklefs Figure 7.3 Overview
  • The carbon cycle • (1) Biotic carbon exchange  Approximately 85 gigatons* (GT) of carbon enter into balanced assimilatory / dissimilatory transformations each year.  About 2,650 GT of global carbon is in organic matter (living organisms plus organic detritus and sediments).  Residence time for carbon in biological molecules = 2,650 GT / 85 GT / yr = 31 years *1 gigaton = 109 metric tons = 1 billion metric tons
  • The carbon cycle (2) Ocean-atmosphere exchange  Exchange of carbon across the atmosphere-ocean interface links carbon cycles of terrestrial and aquatic ecosystems.  Dissolved carbon in the oceans is 30,000 GT, nearly 50 times more than that of atmosphere (640 GT).  Net atmospheric flux (assimilation/dissimilation and exchange with oceans) is 119 GT/yr for mean atmospheric residence time (640 GT / 119 GT / yr) of about 5 years
  • The carbon cycle (3) Precipitation and sedimentation of carbonates Precipitation (and dissolution) of carbonates occurs in aquatic systems. Precipitation (as calcium and magnesium carbonates) leads to formation of limestone and dolomite rock. Turnover of these sediments is far slower than those associated with assimilation/dissimilation or ocean-atmosphere exchange. Carbonate sediments represent the single largest compartment of carbon on planet (18,000,000 GT).
  • The carbon cycle Precipitation of calcium and carbon CO2 dissolves in water to form carbonic acid, which dissociates into hydrogen, bicarbonate and carbonate ions: CO2 + H2O  H2CO3 H2CO3  H+ + HCO3 -  2H+ + CO3 2- Calcium ions combine with bicarbonate ions to form slightly insoluble calcium carbonate, which precipitates: Ca2+ + CO3 2-  CaCO3
  • The global energy budget Humans at present use about 13.5 Terawatts of energy = 13.5 x1012 Js-1  = 4.25 x 1020 Jy-1 What about the rest of the planet?
  • Planet energy cycle  Total radiant energy from sun hitting top of atmosphere:  Total hitting surface (51%) = 88 000 TW  From this, total of 104.9 x109 Gt of C are fixed by plants every year  = approx 130 TW fixed by plants, ie total energy fixed by plants a year = 4.1 x 10 21 Jy-1
  • Humans: important energy players! If say 10% of plant carbon is available for energy input into ecosystems, then human energy use is approximately equal to total carbon energy fixation per year! Human energy usage may triple in the next 50 years or so…
  • Earth as a living planet Earth Titan Venus Mars
  • Planetary atmospheres 90-97% Nitrogen 0-6% Argon 2-5 % Methane 0.2% Hydrogen 95% Carbon Dioxide 2.7% Nitrogen 1.6% Argon 1.3% Oxygen 77% Nitrogen 21% Oxygen 0.93% Argon ~ 1% water (varies) + methane etc 96% Carbon Dioxide 3.5% Nitrogen Atmospheric composition -180 C-55 C15 C457 CAverage surface temperature TitanMarsEarthVenus
  • Earth’s strange atmosphere Note the large amount of oxygen… …and the chemically unstable mix of gases (e.g. Oxygen plus Methane) Suggests thermodynamic disequilibrium
  • The oxygen cycle All the oxygen in the atmosphere is replaced every 2000 years. Thus, if photosynthesis stopped, all the oxygen in the atmosphere would disappear within about 2000 years.
  • Summary Life is a major player in shifting chemicals around the Earth - and the way in which it does it has changed through time. Earth is thus the living planet, first of all!