BIOL 4120: Principles of Ecology
Lecture 21: Human Ecology
(Ch. 29, Global Climate
Change)
Dafeng Hui
Room: Harned Hall 320
Phone: 963-5777
Email: dhui@tnstate.edu
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
elliptical
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 (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)
Human Industrialization Changes Climate
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)
PgC/yr
Land estimates
based on USDA
inventories and
carbon models
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-topchamber, 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.
Open-top chamber
FACE (Free air CO2 enrichment)
Aspen FACE, WI,
deciduous forest
Oak Ridge, deciduous forest
Duke, coniferous forest
Nevada, desert shrub
CO2 effects on plants





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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 at Duke Face ring.
Poison ivy plants grow faster at
elevated CO2
10
350 ul/l
9
550 ul/l
8
7
6
5
4
3
2
1
0
1999
2000
2001
2002
2003
2004
Mohan et
al. 2006
PNAS
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
Ecosystem responses to CO2
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
How to study greenhouse gases effects
on global climate change?
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.
What is a GCM?
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. 912)
 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.
Global warming research
Passive warming (OTC) at International Tundra Experiment (ITEX)
site at Atqasuk, Alaska
Warming and CO2 experiment in ORNL, TN
Global warming experiment at Norman, Oklahoma
Multiple factor experiment (CO2, T, PPT, N) at Jasper Ridge
Biological Reserve, CA
Global warming experiment in Inner Mongolia, China
Global warming experiments

Facility
•
•
•
•
Passive warming (open-top chamber)
Active warming (warm air)
Electronic heater
Buried heating cables

Changes in species composition (Shrub increases
in heated plots, grass decreases)
Decomposition proceeds faster under warmer
wetter conditions
Soil respiration increases 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
India: 1m 7.1 million people, 5.8
million ha of land loss. Mumbai,
economic impact is estimated to go
as high as US $48 billion.
29.10 Climate change
will affect agricultural
production
Complex:
CO2, area, and other factors
Crops will benefit from a rise
in CO2
Temperature will influence
the optimal growth range of
crops, and associated
economic and social costs.
a: “corn belt” shifts to north
b: shift of irrigated rice in
Japan
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: Adams et al. 1995)
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 diseases

Indirect effects
• Increased incidence of communicable disease

Insects, virus, bacteria as vector
• Increased mortality and injury due to
increased natural disasters

Floods, hurricanes, fires
• Changes in diet and nutrition due to change in
agricultural production.
More hot
days
(>35oC)
Nearly 15,000 people died in the European hot wave in 2003
Average annual excess weather-related
mortality for 1993, 2020, and 2050 (Kalkstan
and Green 1997
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) together as a single,
integrated system
Feedback from population, community,
ecosystem, regional scale (tropical forest,
Arctic)
Global network of study
Modeling is an important approach
To slow down CO2 increase
and
global warming,
we need
to act now!
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
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
Carbon balance in China (Piao et al. 2009, Nature)
PgC/yr
Each line represents
an experiment using
different tree species