Chapter 25- Global Ecology

Elements move

among geologic, atmospheric, oceanic, and biological pools at a global scalr

Global cycling of C, N, P, and S are

emphasized because of their biological importance and their roles in human alteration of the global environment

Pool or reservoir

amount of an element in a component of the biosphere

Flux

rate of movement of an element between pools

Example of pool and flux

Terrestrial plants are a pool of carbon; photosynthesis represents a flux

Carbon cycle

-C is critical for energy transfer and biomass

99% of global C is in sediments and rock, the most stable pool; fluxes occur on geological time scales

-of the biologically active C, soils contain twice as much C as plants

-the ocean takes up CO2 from the atmosphere, but most is transferred to deeper water ( as organic detritus and carbonate shells)

Carbon naturally fluxes between the

biosphere-atmosphere (photosynthesis and respiration)

biosphere- hydrosphere (river transport to the oceans)

hydrosphere— atmosphere (phytoplankton photosynthesis and respiration; solubility equilibrium)

Anthropogenic release of C to the atmosphere from:

-the terrestrial pool results from land use change, mostly deforestation (8%)

-the geologic (rock and sediment) pool, from extraction and burning fossil fuels (92%)

-most is released to the atmosphere as carbon dioxide, some as methane

Anthropogenic emissions of CO2

more than doubled from 1970 to 2011

CO2 concentrations in the atmosphere are

increasing faster than anytime in the past 400,000 yeara

Missing carbon

only about 45% of the CO2 released during bunring fossil fuels, deforestation, etc. is found in the atmosphere.

Terrestrial uptake

varies spatially and temporally

Terrestrial uptake strongly influenced by

-season

-drought/ppt patterns

-deforestation

Higher concentrations of CO2

may stimulate photosynthesis

High CO2 accelerates photosynthesis,

more than photorespiration, especially in C3 plants

Duke FACE

-in the first 8 year, elevated CO2 levels increased the overall NPP of the forest by 23%

Over the long-term, FACE

experiments generally reveal the increased photosynthetic rates is short lived

-plants acclimate to higher concentrations

-other factors begin to limit production (N or P)

The ocean absorbs 1/3 of anthropogenic CO2 through two mechanisms

-solubility equilibrium

-photosynthesis

Most anthropogenic C is stored in the deep ocean

1. photosynthesis

2. sinking

3. remineralization or burial

CaCO3 acts as ballast

Since preindustrial times, average ocean surface water pH has

-decreased .1 units, from 8.21 to 8.10

-Equates to a 30% increase in acidity

-at pH 8.1 90% bicarbonate, 9% carbonate, 1% CO2

-projected 50% decrease in carbonate by 2100

Increasing acidity will

dissolve carbonate shells and decrease the ability to synthesize new shells

On Australia’s Great Barrier Reef

calcium carbonate formation declined by 14% from 1990 to 2009

Anthropogenic emissions of CH4

have increased

Atmospheric CH4 levels are much

lower than CO2, but CH4 is a more effective greenhouse gas (25x more heat-ttrapping ability than CO2 per molecule)

Nitrogen cycle

-N is a constituent of enzymes and proteins and often limits primary productivity

-N and C cycles are tightly coupled through photosynthesis and decomposition

-the largest N pool (atmospheric N2) is not available to most organisms

-terrestrial N-fixers supply 12% of the annual biological N demand. the rest comes from decomposition

80% of N in human tissue

was fixed by the Haber-Bosch Process

Phosphours

-12th most abundant element in lithosphere

-majro limiting nutrient in aquatic systems (lakes, rivers)

• most P is not bioavailable

-Soils and sediments major P reservoir

-no gaseous phase

Inputs of phosphorus

Natural- rock weathering, and atmospheric deposition

anthropogenic: fertilizers , detergents

Essential component of:

-ATP

-DNA

-RNA

-phospholipids

-bone and teeth

Healthy leaf tissue contains

.2-.4% P

about one-tenth of N content

Adequate phosphorus enhances

photosynthesis, N fixation ,flowering, fruiting

Phosphate sources

-historically guano

-currently. phosphate rock/phosphorite

• 15-20% phosphate

• sedimentary rocks: limestones, mudstones, Apatite, Ca5(PO4)3(OH)

Phosphorous fertilizer use

most P quickly complexes with minerals in the soil. only 10-15% is taken up by plants in the year of application

Phosphate mining

-bone valley of FL

-clays rich in phosphate

-phosphatic dolomite

-multi-million dollar industry

-began 1880s

-also deposits in middle east and oceana

Earth is weathering due to

anthropogenic emissions of greenhouse gases

weather

current state of the atmosphere at any given time

climate

long term descripition of weather, averages ansd variation

climate change

refers to directional change in climate over a period of at least three decades

Greenhouse effect

warming of Earth by atmospheric absorption and re-readiation of infrared radiation emitted by Earth’s surface

Greenhouse gases

water vapor, CO2, CH4, and N2O

Earth’s energy balance

1. increased GHG: additional back radiation

2. Land cover change: decreased latent heat loss

3. pollution: change in cloud properties

Average global surface temperature

increase .97C between 1880 and 2011

Climate change, especially change in frequency of extreme events

will have profound effects on ecosystems

Extreme events are often critical

in determining species’ geographic ranges

What is the relationship between concentration and temperature?

concentraions of CO2 and CH4 in the atmosphere directly correlate with temperature

Associated with this warming, there has been

-widespread retreat of mountain glaciers

-thinning of the polar ice caps

-melting permafrost

-a 19cm rise in sea level since 1990

Precipitation trend

In the northern latitude has increased; subtropics and tropics are drier

The Intergovernmental Panel on Climate Change (IPCC)

concluded that the majority of the observed global warming is attributable to human activities

How can biological communities respond to climate change?

-geographic range shifts

-extinction

Due to the current rapid rate of climate change

some believe adaptive evolution will not be possible for many species

Organisms have already begun to respond to climate change

-earlier migrations in birds

-local extinction of amphibian and reptile populations

-earlier leaf-out of vegetation

-changes in geographic range

Anthropogenic emissions of sulfur and nitrogen cause

acid deposition, alter soil chemistry, and affect the health of ecosystems

Since the Industrial Revolution, air pollution has been associated

with urban industrial centers, power plants, and oil and gas refineries

Emissions of N and S have resulted in two related issues

Acid precipitation

N deposition

The mandatory installation of scrubbers on smoke stacks has

effectively reduced S emission.

Acid rain (pH 2-5)

leaches Aluminum into soils, which can interfere with water uptake in plants and kill forests

Nitric Oxides (NOx)

Natural sources and fossil fuel combustion

NOx is only pollutant that has not decreased since passage of clean air act

vechicles contribute 53% of anthropogenic NOx

contributes to photochemical smog NOx+ UV- O3

Anthropogenic emissions of reactive N (NO3- and NH4+)

has increased 3x since 1860

Reactive N can come back to Earth via

wet and dry deposition after having been transported long distances in the atmosphere

What pose risks to organisms?

losses of ozone in the stratosphere and increases in ozone in the troposphere

Minor gas in the atmosphere (<.000001%), but important to humans

-protection from UV in stratosphere

-pollutant in troposphere

Stratospheric ozone concentrations

decrease in spring in polar regions (polar stratospheric clouds of ice and HNO3, which provides a surface for Cl to catalyze O3 destruction)

ozone hole

phenomenon of low ozone concentrations

increased uvb radiation

Chlorofluorocarbons (CFCs)

are man-made compounds developed 1930s as refrigerants and propellants in spray cans

in the stratosphere CFCs-Cl

1 Cl atom can destroy 100,000 ozone molecules

Montreal Protocol (1989)

called to reduce and ban on CFCs and ozone- degrading chemicals

-150 countries signed

CFCs long-lived ( not expected to recover until 2040)