biol 4120: principles of ecology lecture 21: human ecology dafeng hui room: harned hall 320 phone:...
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BIOL 4120: Principles of EcologyBIOL 4120: Principles of Ecology
Lecture 21: Human Ecology Lecture 21: Human Ecology
Dafeng HuiDafeng Hui
Room: Harned Hall 320Room: Harned Hall 320
Phone: 963-5777Phone: 963-5777
Email: [email protected]: [email protected]
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
Hence a rich pattern of changing seasonality at different latitudes over time, which affects the growth and retreat of the great ice sheets.
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 about600 Million Years Ago(6000 ppm)
CO2 was reducedabout 400 MYA as LandPlants Used CO2 in Photosynthesis
CO2 Has FluctuatedThrough Time but hasRemained stable forThousands of YearsUntil Industrial Revolution (280 ppm)
Human Industrialization Changes Climate
Global Fossil Carbon Emissions
Land use changes such as deforestation reduce CO2
uptake and increase CO2 loss
Fossil fuel use has increasedtremendously in 50 years
Issue of Time ScaleCO2 Uptake and Release are not in Balance
CO2 Taken Up Over Hundreds of Millions of Years by PlantsAnd Stored in Soil as Fossil Fuel
CO2 Released by Burning ofFossil Fuels Over Hundreds
Of Years
Rising Atmospheric CO2
Annual input of CO2 to the atmosphere from burning of fossil fuels since 1860
US 24%, per capita 6 tons C
Land use change (deforstration: clearing and burning of forest)
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
29.4 Global Climate – Impact of Ocean Currents
Ocean Water Currents are Determined by Salinity and TemperatureCold and High Saline Water Sinks and Warm Water RisesRising and Sinking of Water Generates Ocean Currents
Ocean Currents Have Huge Impacts on Temperature & Rainfall on Land
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
EcoCELLs
Air temperature and humidity, trace gas concentrations, and incoming air flow rate are strictly controlled as well as being accurately and precisely measured.
DRI, Reno, NV
Open-top chamber
Rhinelander, deciduous forest Duke, coniferous forest
Oak Ridge, deciduous forest Nevada, desert shrub
CO2 effects on plants
Enhance photosynthesisProduce fewer stomata on the leaf surfaceReduce water use (stomata closure)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)
Down-regulation: photosynthesis measured at high CO2 growth condition similar to that measured at lower CO2 concentration. – mostly observed in pot experiments, less in field studies
More carbon allocated to root than shoot
Poison ivy at Duke Face ring.
Poison ivy plants grow faster at elevated CO2
1999 2000 2001 2002 2003 20040
1
2
3
4
5
6
7
8
9
10370 ul/l
570 ul/l
Plants respond to increased atmospheric CO2
CO2 fertilization effect:
Enhanced photosynthesis at high CO2.
BER (biomass enhancement ratio)
Meta-data, 600 experimental studies
Each line represents an experiment using different tree species
Ecosystem response to CO2
Luo et al. 2006 Ecology
Ecosystem responses to CO2
Historic trends in greenhouse gas emissions
Methane CH4 and nitrous oxide N2O show similar trends as CO2
29.6 Greenhouse gases are changing the global climate
How to study greenhouse gases effects on global climate change?
General circulation models
General circulation models (GCMs):Computer models of Earth’s climate system
Can be used to predict how increasing of greenhouse gases influence large scale patterns of climate change.
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.
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 2001.
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).
29.7 Changes in climate will affect ecosystems at many levels
Climate influences all aspects of ecosystem Physiological and behavioral response of
organisms Birth, death and growth of population Relative competitive abilities of species Community structure Productivity and nutrient cycling
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 and GCM model (GFDL) predicted climate changes
Predicted distribution of 80 tree species in eastern US
Here shows three species
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)
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.
Global warming experiments Electric heater Passive warming (open-top chamber) Buried heating cables
Shrub increased in heated plots (grass decreased)
Decomposition proceeds faster under warmer wetter conditions
Soil respiration increased under global warming more CO2 will released back to atmosphere
29.8 Changing climate will shift the global distribution of ecosystems
Model prediction of distribution of ecosystems changes in the tropical zone
A: current
B: predicted
29.9 Global warming would raise sea level and affect coast environments
During last glacial maximum (~18,000 years ago), sea level was 100 m lower than today.
Sea level has risen at a rate of 1.8 mm per year
Large portion of human population lives in coastal areas
13 of world 20 largest cities are located on coasts.
Bangladesh, 120 million inhabitants
1 m by 2050, 2m by 2100
China east coast, 0.5m influence 30 million people
29.10 Climate change will affect agricultural production
Complex:
CO2, area, and other factors
Changes in regional crop production by year 2060 for US under a climate change as predicted by GCM (assuming 3oC increase in T, 7% increase in PPT, 530 ppm)
Reduce production of cereal crops by up to 5%.
29.11 Climate change will both directly and indirectly affect human health
Direct effects• Increased heat stress, asthma, and other
cardiovascular and respiratory ailments
Indirect effects• Increased incidence of communicable disease• Increased mortality and injury due to increased
natural disasters• Changes in diet and nutrition
Average annual excess weather-related mortality for 1993, 2020, and 2050
29.12 Understanding global change requires the study of ecology at a
global scale Global scale question, require global
scale study Link atmosphere, hydrosphere,
biosphere and lithosphere (soil) Feedback from population,
community, ecosystem, regional scale (tropical forest, Arctic)
Global network of study Modeling is an important approach
The end
Climate Interactions – Water Cycle
Heat from Sun Increases Rainfall & SnowHeat from Sun Determines Ice Melt and Water Runoff
Change in Ocean Temperature Determines Ocean Circulation
Natural Climate Variability - Temperature
Billion Years
Thousand Years
Alternating WarmAnd
Cool Periods
Earth GraduallyCooled Over Time(160o F to 58o F)
Natural Climate Events Can Not Completely ExplainRecent Global Warming
Increased Solar Activity and Decreased Volcanic Activity CanExplain up to 40% of Climate Warming