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: dhui@tnstate.eduEmail: 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

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