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UW ATMS 211 - Lecture Notes

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Lecture 35Today: Biology impacts of global warming(we’ll skip p.335-336 textbookon ‘economic discounting’)Tomorrow: Policy solutions.Thursday: Any questions?North. Hem. Latitudinal EffectTemperature increasesare expected to beabout 2 times greater in polarregionsMore responsive than tropicsbecause of• ice-albedo feedback• more land-masse.g. global mean increases +2.5 C mid-latitude increases 3-3.5 CMidlatitude Seasonal Change2 x CO2 means:Future Aprils like modern MaysFuture Novembers like modern Octobersi.e. two extra months of summer.short winterSeasons50-100 yearsin the futureSpring Earlier, Fall LaterOBSERVATIONS:Mediterranean deciduous plants now leaf 16 days earlierand fall 13 days later than 50 years agoEurope and North America, biological spring is 1-2 weeksearlier than 100 years agoGrowing season is 18 days longer in Eurasia, 12 days longerin N. America over past 20 yearsEffects on BiologyCan divide climate change impacts into:1. Marine environments2. Terrestrial ecosystemsMarine Biology & Global WarmingWe have already discussed sea-level rise. A potential long-term (22nd century?) catastrophe is a shut-down of thethermohaline circulation due to freshwater input in the N. Atlanticfrom precipitation and icesheet disintegration. (see p.332, Kump) Qu.) Suppose CO2 is increased? What happens to the pH of the ocean?Answer) CO2 dissolves to form carbonic acid. So we should expectthe ocean to become a bit more acidic.With “business as usual” emissions, pH decreases by 0.35 units by 2100.Qu.) How does acid affect organisms that make CaCO3 shells?It will decrease the ability of the organisms to make their shells.This is exacerbated by an increase in surface water temperature.Coral ReefsFig 18-5Colonies of animals that contain symbiotic algae and deposit CaCO3-habitat for 25% of marine species, protect shorelines, provide fisheries-contain ~4000 species of fishCoral Reefs under pressureRange of temperature for growth is narrow: 21 to 29°CAlgae give color to the naturally transparent coral animalsand provide them with food. In return…Corals protect the algae and provide algae with CO2 and ammonia 1. More CO2-rich waters prevent secretion of CaCO3 skeleton2. Warmer water stress the corals and they expel the algae- coral bleachingRESPONSE TO WARMING:Since 1980s: Coral bleaching outbreaks are more common1991-2: Mt. Pinatubo cool years saw a decline of coral bleaching1997-98, El Niño ocean temperatures wiped out 16% of the world's reefsToday: 30% of coral reefs damaged from warming (and pollution)2030: 60% prediced loss (Hughes et al. (2003) Science, 301, 930-933)Coral bleaching in the Red SeaBefore AfterNorth Sea cod: year-class (millions of 1-yr-old fish)empirically decreases with watertemperature.(O’Brien et al (2000) Nature 409, 142)Over-fishing + global warming arecausing collapse of this fish stock.Sockeye salmon: with 2 x CO2temperatures, Pacific marinehabitat shrinks to the BeringSea (Welch et al. (1998) Can. J.Fisheries Aquatic Sciences, 55, 937-948.)(thermal regime restricted by T-dependent metabolic rate vs. foodintake)FishMarine diseaseExample:25 years of increasing temperatrure on E. Coast of US:Increased spread of Dermo (parasite) and MSX (bacteria) diseasesin oysters by decreasing parasite mortality in winter1980s: MSX & Dermo spread throughout Cheasapeake Bay1990s: Dermo spread to Maine1998 (hot year): MSX spread to New York2000-2100: ???Terrestrial ecosystemsC3 photosynthesizers: cyanobacteria and most plantsC4 plants: (CO2-concentrating): corn, sugarcane, tropical grassesC3 and C4 are different types of photosynthetic metabolism.C4 plants evolved 7-8 m.y. ago and are insensitive to CO2 levelsbecause they can concentrate CO2 within inner cells in their leaves.Result: C3 weeds could do well,whereas C4 corn will do poorly in high CO2.actually grassesTreesHigh water capacity soil (clay)Low water capacity soil (sand)All species do poorly after 2050due to dry soil.ficonclusion: speciesdistribution is highly likelyto change in all scenarios.Move from cold-adaptedAspen/Spruce to Maple/BirchFig 16-11: Minnesota trees.Can trees keep pace with climate? No.500 km migration is needed from 2000-2100 for treesThis is about 25 times faster than the latitude shiftof forest ecosystems from the last glacialand considered too fast by tree botanists.(Roberts (1988) Is there life after climate change? Science, 242, 1010-1012)Another problem is break-up of forests by other human activity.Conclusion: Warming is likely to eliminate sedentary species.Extinction ratesThe modern (human-induced) extinction rate isabout 3000 times faster than the natural rate of species loss.This is mainly caused by tropical forest deforestation.Tropical forests contain ~50% of world’s animal/plant species.Global extinction rate: made worse by global warming. (Floods,droughts).Why care? Practical reasons: Medicinal use of plantse.g. rosy periwinkle, used against Hodgkins disease & child leukemiae.g. 1987: discovered that the Calophyllum tree of Borneo preventsHIV replication, but the tree has been eliminated by deforestationCurrently 42m people are infected with AIDS (www.unaids.org).Aesthetic reasons: nature is beautiful; loss of animals and plantsdiminishes our natural heritage and


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UW ATMS 211 - Lecture Notes

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