BIOL 4120: Principles of EcologyBIOL 4120: Principles of Ecology

Lecture 21: Human Ecology Lecture 21: Human Ecology(Ch. 29, Global Climate (Ch. 29, Global Climate

Change)Change)

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 (latest 20k to 18k BP).

Diagram Courtesy of Windows to the Universe, http://www.windows.ucar.edu

elliptical

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

Fossil fuel use has increasedtremendously 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 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

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

Land use change (deforstration: clearing and burning of forest)

Global Carbon Emissions by land use change

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

Tree carbon per hectare by U.S. county

Carbon Stocks and Stock Changes Estimated from Forest Inventory Data

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

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 LandThis process occurs over hundreds of years

Amount of CO2 absorbed by oceans in Short-term is limited

Two layers

Thin warm layer 18oC

Deep cold layer 3oC

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+Greenhouses at a Mars Base: 2025+

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

FACE (Free air CO2 enrichment)

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 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

10350 ul/l

550 ul/l

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).

IPCC, 2007.Global temperature has increased dramatically during past 100 years

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.

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.

Nearly 15,000 people died in the European hot wave in 2003

More hot days (>35oC)

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 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 & 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

Natural Climate Events Can Not Completely ExplainRecent Global Warming

Increased Solar Activity and Decreased Volcanic Activity CanExplain 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