Download Plant Ecology

Plant Ecology - Chapter 21
Global Change: Humans & Plants
Acid Deposition
Automobiles as a Source
NO from cars
Widespread Secondary Air Pollution: Aci
Deposition
Wet deposition
Dry deposition
Acid Deposition in the U.S.
Acid Deposition, Plants, and Soil
Acid Deposition, Plants, and Soil
Lowers soil pH
Affects mineral
solubility
Leach out positively
charged ions (K,
Mg, Ca) from clay
particles
Easily flushed away
Acid Deposition, Plants, and Soil
Increases concentration
of potentially toxic
minerals
E.g., aluminum
Damages xylem reduces ability to take in
water, nutrients - die
from lack of moisture,
nutrients
Acid Deposition, Plants, and Soil
Direct damage to
forest tree foliage
Erodes protective
waxes from leaves,
needles
Leaches nutrients
from leaves
Acid Deposition, Plants, and Soil
Has resulted in loss
of large stands of
trees in many
different regions
around world
Canada, New
England, Smoky
Mountains
Acid Deposition, Plants, and Soil
Acid Deposition, Plants, and Soil
Nearly 70% of
forests in Czech
Republic have been
destroyed
Trees in nearly half
of Germany’s Black
Forest have been
impacted
Acid Deposition, Plants, and Soil
Switzerland has lost
10% of its forests
Increased chance of
avalanches
Acid Deposition, Plants, and Soil
Large portions of
forests in Norway
have been lost,
especially in
southern regions
Acid Deposition, Plants, and Soil
Correlation between
dying forests and
thriving ground layer
of mosses
Acid Deposition, Plants, and Soil
Mosses are acidloving
Thick layer holds do
much moisture that
surface soils
become saturated
Feeder roots, tree
die from lack of
oxygen (drown)
Acid Deposition, Plants, and Soil
Mosses also may kill
mycorrhizal fungi
Reduce uptake of
nutrients
Acid Deposition, Plants, and Soil
Dense layer of
mosses may further
acidify water
passing through
them into soil
Dissolve more toxic
trace metals, leach
more soil nutrients
Acid Deposition, Plants, and Soil
Even if trees
somehow manage
to survive all these
problems, their
growth is reduced
substantially
Acid Deposition, Plants, and Soil
Acid Deposition, Plants, and Soil
Varying effects on
crop productivity, but
wide distribution
Acid Deposition, Plants, and Soil
Some evidence for
direct damage
Potatoes in Canada
- damage to foliage,
potential uptake of
toxins
Acid Deposition, Plants, and Soil
Coffee plants have
shown damage to
foliage in some
areas
Acid Deposition, Plants, and Soil
Although much
evidence points
toward harmful
effects from acid
rain, some studies
show the opposite
Acid Deposition, Plants, and Soil
Helpful to crops
where soil nutrients
may be very low nitrogen-limited
Acidification may
release nutrients,
allow for greater
uptake
Acid Deposition, Plants, and Soil
Some evidence
where crops show
now effect of acid
deposition, either
negative or positive
Balance each other
out
Acid Deposition and Aquatic Systems
 Fish declines
 Undesirable
species
 Aluminum
toxicity
 Acid shock
Global Carbon Cycle
Human effects: fossil fuel combustion,
cutting and burning of trees
Global Carbon Cycle
Global Carbon Cycle
Increasing
atmospheric CO2
has brought about a
rise in global
temperature
Greenhouse Effect
CO2 acts like glass
in a global
greenhouse
Slows escape of
infrared radiation
from earth’s surface
Greenhouse Effect
Many other gases are
far more effective at
trapping heat
Methane, CFCs, nitrous
oxide (N2O)
20-270 X as effective
CO2 responsible for 2/3
of increase in
greenhouse effect
Greenhouse Effect
CO2 concentrations
increased 21.5% from
1870-1990
Increasing consumption
of fossil fuels,
deforestation
Doubling of CO2
concentrations may
occur with continued
fossil fuel use over 50100 years
Greenhouse Effect
CO2 doubling may
increase average global
temperature by 2-5°C
Global temps have
increased 0.8°C over
last century, 0.6° of
that in last 30 years
Major Climate Changes
Worldwide change
in patterns of
precipitation,
storms, winds,
ocean currents
Each 1°C increase
pushes climatic
zones 90 mi N in N.
hemisphere
Major Climate Changes
Variable effects
worldwide, but greatest
changes between 40
and 70°N, in N. Amer.
and Eurasia
Caused by both warmer
temps and increased
CO2 (greater forest
productivity)
Major Climate Changes
Polar ice sheets and
glaciers have been
melting, and changes
would escalate
Major Climate Changes
Sea levels would rise
due to melting ice,
expansion of warming
water
4°C increase would
cause 0.5-1.5 m rise
worldwide
Flood coastal wetlands,
low-lying cities,
agricultural lands
Major Climate Changes
Frequency, intensity of
weather extremes
would increase
Heat waves, drought,
hurricanes
Major Climate Changes
Speed up decay of
organic matter
Further increase CO2
concentrations in
atmosphere
Major Climate Changes
Warmer climates
spreading northward
would bring insectborne diseases, more
pests into areas
currently protected by
cold temperatures
Major Climate Changes
Growth rates of many
tree species would be
lowered
Ranges would have to
shift northward
At rate up to 10 X
greater than they’ve
ever done in the past
Birch, sugar maple
Major Climate Changes
Stress from pests,
disease
microorganisms would
increase
Adapt faster than tress
to changing
environments
Major Climate Changes
More frequent fires
Forest and grassland
Increased disturbance:
decreased diversity?
Declining Global Biodiversity
300,000 plant species
have been described
and named
1.5 million species of all
kinds
At least 5-10 million
living species not
described
What’s out there?
Declining Global Biodiversity
Many large species
may be at risk of
extinction
But so may many
unknown or little known
forms (like mycorrhizae)
Also may lose genetic
diversity as some
populations disappear,
losing unique genes
Declining Global Biodiversity
Many current threats
to global diversity
Changes in land use
is greatest
Destruction,
degradation,
fragmentation
Habitat Loss
Outright loss of habitat
Varying degree of
disturbance elimination of important
species, soil damage,
overgrazing, altered
disturbance regime
Biodiversity Hotspots
Biodiversity Hotspots
25 areas - 1.4% of earth’s land surface
Contain half of world’s known plant species
Regions have lost 88% of original vegetation cover
Biodiversity Hotspots
20 are tropical forests or Mediterranean climates
9 are oceanic islands/archipelagos
Long-term isolation - evolution of endemic species
Biodiversity Hotspots
800 species most at risk in 600 locations
Many are areas within biodiversity hotspots
Less than half have any legal protection
Biodiversity Hotspots
Example: Madagascar tropical forests
10,000 plant species, 80% endemic
Rate of loss among highest in world - <10 of forests
remain
Deforestation
Losses have been accelerating rapidly in the Amazon
Rate of loss increased >80% in 1990s
Deforestation
Brazil: 17-year period
Deforestation
Similar rates of loss
in tropical Africa,
southeast Asia
Will disappear in
100 years at present
rate
Forest Fragmentation
Even more dramatic
increase in
fragmentation increased edges
Potential increase in
herbivory, disease,
invasives,
decline/extinction of
interior species
Threats to Other Communities
Biodiversity losses
occur in
communities with
much lower
diversities than
tropical forests
Not always the rare
species that are
affected
Threats to Other Communities
American chestnut
was once most
common and heavily
used timber species
in eastern U.S.
Disappeared
because of invasive
pathogen
Threats to Other Communities
Logging for teak,
rosewood
Formerly some of
most common
species - now
becoming rare (high
value)
Threats to Other Communities
Brazil nuts are
example of classic
sustainable use of
intact rain forest
Most important food
crop collected
entirely from wild
trees
Threats to Other Communities
Harvesting often
done by native
peoples
“Save the rainforest.
Eat Brazil nuts”
Threats to Other Communities
Brazil nut trees are
dwindling, populations
declining
So much harvest that
few or no young trees
have developed - no
seeds
Harvest at present
levels will lead to
extinction
Threats to Other Communities
Even low-diversity
ecosystems are not
exempt from problems
Many cacti face
extinction from amateur
collectors
Illegal in many areas,
but command high
prices with risk of
minimal fines
Threats to Other Communities
Many orchids are
facing the same fate
as cacti
High prices on black
market can lead to
intense depredation
from collectors
Threats to Other Communities
Overgrazing by
livestock can
destroy fragile
grasslands,
shrublands
Many Arizona
grasslands
destroyed by
grazing
Desertification
Threats to Other Communities
Overgrazing or
overbrowsing has
similar effects in
other habitats
Low predator
numbers, forest
fragmentation,
suburban protection
have increased deer
populations
Threats to Other Communities
Overbrowsing
has had dramatic
effects on forest
regeneration
Kills tree saplings
Threats to Other Communities
Deer have been
implicated in the
decline of several
species of spring
wildflowers
Trillium in PA
So have non-native
earthworms
The Human Impact
Land use changes
related to changes
in human population
size, but also
economic and
political forces
Concerns in both
developed,
developing nations
The Human Impact
In developing
nations, habitat loss
closely tied to
growing populations
Expansion into new
areas
The Human Impact
In developing
nations, populations
not growing
Suburbanization and
vacation homes are
fragmenting habitats