BIOL 4120: Principles of Ecology Lecture 21: Human Ecology(Ch. 29, Global Climate Change) Dafeng Hui Room: Harned Hall 320 Phone: 963-5777 Email: firstname.lastname@example.org
What Controls Climate? • Solar radiation input from the Sun • Distribution of that energy input in the atmosphere, oceans and land
Relationship between Sun and Earth Major Impact on Solar Radiation • The pacemaker of the ice ages has been driven by regular changes in the Earth’s orbit and the tilt of its axis Approximate primary periods: Eccentricity 100,000 years Precession 23,000/18,000 years Tilt 41,000 years elliptical Hence a rich pattern of changing seasonality at different latitudes over time, which affects the growth and retreat of the great ice sheets (latest 20k to 18k BP). Diagram Courtesy of Windows to the Universe, http://www.windows.ucar.edu
29.1 Greenhouse gases and greenhouse effect Water Vapor – most important GH gas makes the planet habitable
29.2 Natural Climate Variability - Atmospheric CO2 Very High CO2 about 600 Million Years Ago (6000 ppm) CO2 was reduced about 400 MYA as Land Plants Used CO2 in Photosynthesis CO2 Has Fluctuated Through Time but has Remained stable for Thousands of Years Until Industrial Revolution (280 ppm)
Global Fossil Carbon Emissions Fossil fuel use has increased tremendously in 50 years
Annual input of CO2 to the atmosphere from burning of fossil fuels since 1860 US 24%, per capita 6 tons C
Issue of Time Scale CO2 Uptake and Release are not in Balance CO2 Taken Up Over Hundreds of Millions of Years by Plants And Stored in Soil as Fossil Fuel CO2 Released by Burning of Fossil Fuels Over Hundreds Of Years
Rising Atmospheric CO2 Charles David keeling
29.3 Tracking the fate of CO2 emissions Emissions From fossil fuel: 6.3Gt Land-use change:2.2Gt Sequestrations: Oceanic uptake: 2.4Gt Atmosph. accu.: 3.2Gt Terrestrial Ecos.: 0.7Gt Missing C: 2.2 Gt
Global Carbon Emissions by land use change Land use change (deforstration: clearing and burning of forest)
Carbon Sink: Convergence of Estimates for Continental U.S. from Land and Atmospheric Measurements(From Pacala et al. 2001, Science) Land estimates based on USDA inventories and carbon models PgC/yr
Carbon Stocks and Stock Changes Estimated from Forest Inventory Data Tree carbon per hectare by U.S. county
29.4 Absorption of CO2 by ocean is limited by slow movement of ocean Currents Given the volume, oceans have the potential to absorb most of the carbon that is being transferred to the atmosphere by fossil fuel combustion and land clearing This is not realized because the oceans do not act as a homogeneous sponge, absorbing CO2 equally into the entire volume of water
Two layers Thin warm layer 18oC Deep cold layer 3oC Ocean Water Currents are Determined by Salinity and Temperature Cold and High Saline Water Sinks and Warm Water Rises Rising and Sinking of Water Generates Ocean Currents Ocean Currents Have Huge Impacts on Temperature & Rainfall on Land This process occurs over hundreds of years Amount of CO2 absorbed by oceans in Short-term is limited
29.5 Plants respond to increased atmospheric CO2 • CO2 experiments • Treatment levels: Ambient CO2, elevated CO2 • Facilities: growth chamber, Open-top-chamber, FACE • Some results at leaf and plant levels • Ecosystem results
Growth chamber Potted plants can be grown in this growth chamber Greenhouses at a Mars Base: 2025+
EcoCELLs DRI, Reno, NV Air temperature and humidity, trace gas concentrations, and incoming air flow rate are strictly controlled as well as being accurately and precisely measured.
Aspen FACE, WI, deciduous forest Duke, coniferous forest Oak Ridge, deciduous forest Nevada, desert shrub
CO2 effects on plants • Enhance photosynthesis (CO2 fertilization effect) • Produce fewer stomata on the leaf surface • Reduce water use (stomata closure) and increase water use efficiency • Increase more biomass (NPP) in normal and dry year, but not in wet year (Owensby et al. grassland) • Initial increase in productivity, but primary productivity returned to original levels after 3 yrs exposure (Oechel et al. Arctic) • More carbon allocated to root than shoot
Poison ivy plants grow faster at elevated CO2 10 350 ul/l 9 550 ul/l 8 7 6 5 4 3 2 1 Mohan et al. 2006 PNAS 0 1999 2000 2001 2002 2003 2004
Plants respond to increased atmospheric CO2 BER (biomass enhancement ratio) Hendrik Poorter et al. Meta-data, 600 experimental studies
Ecosystem response to CO2 Luo et al. 2006 Ecology
29.6 Greenhouse gases are changing the global climate Methane CH4 and nitrous oxide N2O show similar trends as CO2 CH4 is much more effective at trapping heat than CO2
General circulation models General circulation models (GCMs): Computer models of Earth’s climate system Many GCMs, based on same basic physical descriptions of climate processes, but differ in spatial resolution and in how they describe certain features of Earth’s surface and atmosphere. Can be used to predict how increasing of greenhouse gases influence large scale patterns of climate change.
GCMs prediction of global temperature and precipitation change Changes are relative to average value for period from 1961 to 1990. Despite differences, all models predict increase in T and PPT. T will increase by 1.4 to 5.8oC by the year 2100.
Changes in annual temperature and precipitation for a double CO2 concentration Temperature and PPT changes are not evenly distributed over Earth’s surface For T, increase in all places For PPT, increase in east coastal areas, decrease in midwest region (<1). 1 means no change to current. Another issue is increased variability (extreme events).
Global temperature has increased dramatically during past 100 years IPCC, 2007.
29.7 Changes in climate will affect ecosystems at many levels Climate influences all aspects of ecosystem • Physiological and behavioral response of organisms (ch. 6-8) • Birth, death and growth of population (ch. 9-12) • Relative competitive abilities of species (ch.13) • Community structure (Ch. 16-18) • Biogeographical ecology (biome distribution, extinction, migration) (Ch. 23) • Productivity and nutrient cycling (Ch. 20,21)
Example of climate changes on relative abundance of three widely distributed tree species Distribution (biomass) of tree species as a function of mean annual temperature (T) and precipitation (P) Distribution and abundance will change as T and P change
Anantha Prasad and Louis Iverson, US Forest Service Used FIA data, tree species distribution model and GCM model (GFDL) predicted climate changes with double [CO2] Predicted distribution of 80 tree species in eastern US Here shows three species Red maple, Virginia pine, and White oak
Species richness declines in southeastern US under climate change conditions predicted by GFDL
Distribution of Eastern phoebe along current -4oC average minimum January T isotherm as well as predicted isotherm under a changed climate
David Currie (University of Ottawa) Use relationship between climate (mean Jan July T and PPT) and species richness Predict a northward shift in the regions of highest diversity, with species richness declining in the southern US while increasing in New England, the Pacific Northwest, and in the Rocky Mountains and the Sierra Nevada.
Passive warming (OTC) at International Tundra Experiment (ITEX) site at Atqasuk, Alaska
Multiple factor experiment (CO2, T, PPT, N) at Jasper Ridge Biological Reserve, CA