BIOL 4120: Principles of Ecology
Lecture 21: Human Ecology
Dafeng Hui
Room: Harned Hall 320
Phone: 963-5777
Email: dhui@tnstate.edu
What Controls Climate?
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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
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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 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)
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 increased
tremendously in 50 years
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
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 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
29.5 Plants respond to increased
atmospheric CO2
CO2 experiments
•Treatment levels: Ambient CO2, elevated CO2
•Facilities: growth chamber, Open-topchamber, FACE
Some results at leaf and plant levels
Ecosystem results
Growth chamber
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.
Open-top chamber
Rhinelander, deciduous forest
Duke, coniferous forest
Oak Ridge, deciduous forest
Nevada, desert shrub
CO2 effects on plants
Enhance photosynthesis
Produce fewer stomata on the leaf surface
Reduce 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
10
370 ul/l
9
570 ul/l
8
7
6
5
4
3
2
1
0
1999
2000
2001
2002
2003
2004
Plants respond to increased atmospheric CO2
CO2
fertilization
effect:
Enhanced
photosynthesi
s 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
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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
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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
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Direct effects
• Increased heat stress, asthma, and other
cardiovascular and respiratory ailments
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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
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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 & Snow
Heat from Sun Determines Ice Melt and Water Runoff
Change in Ocean Temperature Determines Ocean Circulation
Natural Climate Variability - Temperature
Earth Gradually
Cooled Over Time
(160o F to 58o F)
Billion Years
Alternating Warm
And
Cool Periods
Thousand Years
Natural Climate Events Can Not Completely Explain
Recent Global Warming
Increased Solar Activity and Decreased Volcanic Activity Can
Explain up to 40% of Climate Warming