End of Ecosystems: Nutrient Flow
Beginning of Environmental Crisis
Lecture 12
Principles of Ecology
College of Forestry, Guangxi University
Eben Goodale
Today and next Tuesday
1. Finish ecosystems
by talking about
nutrient flow.
2. Move to higher
levels: “applied and
large-scale ecology”
3. Introduce
environmental
challenges and
global challenges.
4. Talk about
conservation biology as
one response.
5. Talk about landscape
ecology and
management as
another response.
Today leave 45 minutes for writing.
Tuesday leave 1 hour for review for
Midterm.
Saturday May 16 final exam!
Moving up a Layer:
Definition of an Ecosystem
Ecosystem
Characteristics of the ecosystem
That we’ll talk about:
- Productivity
- Energy flow
- Nutrient flow
What is a nutrient?
C is
definition
of organic
molecule.
Remember
N and P
were limiting
nutrients of
NPP on land
and in sea.
What is a nutrient?
C:N ratio
measures nutrientrich, as carbon
usually structural.
Animals << plants
Nutrients are in the air
• Some nutrients like carbon (CO2), oxygen
(O2) can be fixed by living things from the
air.
• But other nutrients like nitrogen (N) can
not be: N2 is very plentiful but difficult to
get N out of. P not in atmosphere.
• Only certain kinds of bacteria able to fix N,
as we will see…
Nutrients are in the ground
• Mineral supplies.
• Rocks are called
“parent materials”…
• Nutrients slowly come
out of them due to
weathering (slow
breaking down of rock).
Nutrients are in the ground: soil
• Decomposition is
an important
process that makes
dead things like leaf
litter soluble
(available in water)
to living organisms.
• Strongly dependent
on temperature.
Nutrients are in the ground: soil
• Soils different in particle
size.
• Different soils are better
able to hold water and
nutrients.
• Leaching is the loss of
nutrients from soils
carried away by water.
Medium:
silt
Smallest:
clay
Largest: sand
Nutrients are in the ground: soil
• Soils develop over
successional time.
• The more
weathering,
decomposition the
better the soils.
• Poor soils in tropics
where decomposition
so quick, all nutrients
leach out.
Nutrients are moved within the
organism
• Most nutrients in
leaves.
• Chlorophyll
reabsorbed before leaf
dropping.
• 60-70% of N, 40-50%
of P saved this way.
Nutrient cycling
How nutrients are moved between
atmosphere, rocks, soils, water, living
organisms.
Rocks
Soil
Basics of nutrient cycling
• Reservoir or pool: we can define as a part of the
cycle (e.g. atmosphere, soil) in which a nutrient
stays for some time.
• Residence time: the average time a substance
spends within a reservoir.
• Flux:
movement
from one
pool to
another
The water cycle
Reservoir
Average
residence
time
Oceans
3,200 years
Glaciers
20 to 100 years
Seasonal snow cover
2 to 6 months
Soil moisture
1 to 2 months
Groundwater: shallow
100 to 200 years
Groundwater: deep
10,000 years
Lakes (see lake
retention time)
50 to 100 years
Rivers
2 to 6 months
Atmosphere
9 days
Cycle is fairly quick (except for ground water, deep
ocean circulation)
Phosphorus (P)
• Needed for DNA, ATP
• Little in atmosphere
(just dust, mostly from
human activities) so
most derived from
weathering of rocks.
• Most important/limiting
in aquatic ecosystems,
tropical terrestrial
habitats
Phosphorus Cycle: the numbers are 1012 g P or fluxes as 1012 g P per year
Amount in pool
in box.
Fluxes
are the small
numbers next
to arrows
Very little in atmosphere. Huge pool in marine sediments.
Marine sediments mined by humans. 4 times the amt of natural weathering.
Nitrogen
Note: a different kind of
bacteria, sends N back to
atmosphere…
• Nitrogen: used for
DNA, proteins
• Nitrogen fixation
done by some
free-living bacteria
and others
associated with
plants, especially
legumes.
In some agriculture, legumes
Added because of N fixing properties.
Nitrogen Cycle: the numbers are fluxes as 1012 g N per year
Orange shows
human
contribution
Human fix
N2 by HaberBosch process
(industrial way
to make fertilizer)
Carbon cycle
• Central “nutrient”:
– closely bound to
energy
– bound to N
– makes up
structure of most
organisms: 50%
of dry biomass
• Major carbon storage, or sinks:
– slow-decomposing compounds in soil
– bicarbonate in the ocean
– fossil fuels
– wood
Carbon Cycle: the numbers are storage as 1015 g C or fluxes as 1015 g C per year
Gaseous phase:
well-mixed.
Atmospheric
concentration 
350 ppm (preindustrial  250
ppm)
Aqueous
phase:
dissolves in
ocean water
(bicarbonate
HCO3).
Solid phase: residence
times of carbon in soil,
and in plants, from
weeks to centuries
Human influence on nutrient
cycle and its outcome
• As we move to talking about conservation
biology and global ecology, we will talk
more about how humans have altered
nutrient cycling, especially:
• N deposition (added to atmosphere by
industrial activity, then falls down).
• CO2 increase and global warming.
Manipulation and disturbance of ecosystems
One local scale human influence on ecosystems is that human activity
Like logging can influence what much leaching occurs, and thus
How much of the nutrients of an ecosystem are lost (flow out with water).
Famous studies have calculated nutrient cycles for a whole catchment area.
Ecosystem Modeling
Looking at ecosystems like a machine and see how human disturbance
Influences them.
Today and next Tuesday
1. Finish ecosystems
by talking about
nutrient flow.
2. Move to higher
levels: “applied and
large-scale ecology”
3. Introduce
environmental
challenges and
global challenges.
4. Talk about
conservation biology as
one response.
5. Talk about landscape
ecology and
management as
another response.
Today leave 45 minutes for writing.
Tuesday leave 1 hour for review for
Midterm.
Saturday May 16 final exam!
Moving up to the top!
Landscape
Describes how
Different ecosystems
Are put together in space
We are also going to talk about
environmental problems the earth
faces at a global level.
th
6
Are we in the
major
extinction event?
Rates of extinction
are 100 to 1000
times what the
normal rate is
according to the
fossil record.
From Barnosky et al. 2011
Humans have been causing both
extinctions and introductions of animals
Introduced plants (to US)
# of species of birds
on Pacific island
(many were
flightless)
Introduced plants could be intentional or not.
In what ways are they non-intentional?
They can cause much destruction
The environmental crisis: man’s
impact on the globe
CO2
Climate
Change
Some changes we will discuss
•
•
•
•
•
•
•
•
Habitat loss
Species invasions
Overharvesting
Global climate change
Nitrogen deposition
Toxin accumulation
Ozone hole
Acid Rain
A happy ending?
Habitat Loss
2006
Worst right
now in tropics
(bad in boreal forests
too but less diversity)
2002
Habitat Loss
3 factors are here associated:
Habitat loss: less natural land
cover.
Habitat fragmentation: smaller,
more isolated pieces.
Habitat degradation: what
remains has been changed to
be poorer quality.
We will talk about fragmentation
next lecture when we talk
about landscapes.
Habitat loss: what does this mean
for biodiversity?
Large animals with the greatest
Space requirements most affected.
The hammerhead,
great white and thresher
sharks have each declined
more than 75% in last 15 years.
(Baum et al, Nature, 2003)
Last (2015) male white
rhinoceros being guarded
At the same time, we must
remember that of the world’s
5-10 million species are plants
and insects that are being lost
before they are even discovered.
Many species may already be “ghosts”
reduced to such low numbers that they will eventually go extinct.
Habitat loss: population driver
Habitat loss will be directly affected by population growth …
Population predicted to peak around 10 billion in 2100
Habitat loss: life-style drivers
Many developing
countries
like India increasing
their consumption
India has traditionally
been vegetarian.
but chicken consumption
doubled 2000 to 2014.
The Tata
Nano,
A $2000
car aimed
at India’s
middle class
Next issue: Species invasions
• As we move around
the globe,we move
organisms, too,
intentionally, and
nonintentionally.
• Species without their
natural predators and
pathogens can
reproduce in
remarkable ways
Brown rat snake
Zebra mussels
(a) Brown tree
snake, introduced to Guam
in cargo
(b) Introduced kudzu thriving in South Carolina
Some well known invaders…
economic damage can go into
billions of dollars
Next issue: overharvesting
http://www.montereybayaquarium.org/cr/seafoodwatch.aspx
Next issue: global warming
If left unchecked, at current rate 1200 ppm
By 2100 (source: NASA).
CO2rates
increasing and
CO2 closely
associated
with
temperature …
Although not
only
greenhouse gas
(methane, etc.)
Tracking man-made CO2
• Carbon in 3 forms: C12, C13 (1%) and C14
(1 X 10-12 %)
• Plants and fossil fuels high in C13, higher
than other sources of C (e.g., deep
oceans)
C12/C13
ratio changing
rapidly
Global warming: effects
Associated problems….
Sea level rising ~ 1.7 mm year
Extent of sea ice
in Artic … -10%
Per decade
From NOAA (www.ncdc.noaa.gov)
Global warming: predictions
Predictions:
Range of
estimates from
1.8 to 6.0ºC
increase by
2100, depending
on control of
emissions
levels, among
other factors.
From NOAA (www.ncdc.noaa.gov)
So many man-made source of C that solution to global warming will be complex!
Effects of global warming not
uniform
Increase in temperature expected to hurt agriculture in
developing, tropical regions.
Next issue: Nitrogen deposition
N fixation by humans now greater than natural fixation
Nitrogen deposition
Nitrogen deposition
1. N is a fertilizer so it increases plant biomass.
2. But unfortunately, it also decreases species
diversity, because only a few species are well
adapted to high N level.
A famous experiment
In England that has shown
species diversity to decrease
over 150 years.
Other toxins
Humans are producing thousands
of chemicals, many of which have
effects we do not fully understand.
These toxins are concentrated as
the higher the organism is in the
food web.
Some species are endocrine disruptors:
lower the natural fertility of wildlife.
Eggs cells develop
in frog testes
after exposure to the
common pesticide
atrazine
From Hayes et al. 2003
Some hopeful signs …
The ozone hole: a problem
addressed?
The ozone layer
is very important
for blocking UV
radiation
The largest ozone
hole was recorded
over Antartica in 2006
In the 1980’s,
Scientists
began to notice
bigger and bigger
holes in the ozone
layer.
It was shown that
some of the loss
of ozone was due to
CFCs, chemicals
used in refrigeration.
Some hopeful signs …
The ozone hole: a problem
addressed?
In 1987, the
Montreal Protocol
was signed, which
gradually phased
out CFCs.
Recently, the hole
in the ozone layer
has slowly begun to
decrease.
Some hopeful signs: acid rain
Today and next Tuesday
1. Finish ecosystems
by talking about
nutrient flow.
2. Move to higher
levels: “applied and
large-scale ecology”
3. Introduce
environmental
challenges and
global challenges.
4. Talk about
conservation biology as
one response.
5. Talk about landscape
ecology and
management as
another response.
Today leave 45 minutes for writing.
Tuesday leave 1 hour for review for
Midterm.
Saturday May 16 final exam!
Conservation Biology
• The scientific study of phenomena that
affect the maintenance, loss and
restoration of biodiversity (genes,
individuals, species, communities).
• Conservation to be successful needs to
combine biology with social sciences like
politics, economics and physchology.
Why conserve?
Economic reasons
Genes: Genetic variation is key to a species’ longterm viability and flexibility to change.
Species:
- Derived products
- Biophilia and ecotourism
- Product extraction from an environment that
conserves species.
Ecosystems:
There are also
spiritual and cultural
- Ecosystem services.
reasons to conserve
Benefits of Diversity:
Pharmacology
Gila monster produces
enzyme that binds to
insulin, used in new
diabetes drug
Fungal endocyte
that lives within
Pacific Yew: source
of Taxol.
Polymerase from
bacteria in hot springs
used for PCR and
revolutionized biotech
Biophilia = our natural interest in
biology. Can it pay the bills?
Eco-tourism
Tourism principle foreign exchange earner
for 83% of developing countries; tourism up
20% from 2002-2007
(Global Ecotourism Conference, 2007)
Problems:
- But in most countries, tourism
controlled by major (often international)
businesses.
-Have ecotourism promoters over-promised?
Balancing extraction with
biodiversity
Micro-industries
which can be performed
on buffer of conserved
forest.
Rattan gathering in Myanmar
Palm sugar tapping in Sri Lanka
Honey collecting in Bangladesh
Balancing extraction with
biodiversity
Plantation crops that
conserve *some* of the
biological diversity of
an area.
Shade coffee
Cardomum plantation
Ecosystem Services
• Ecosystem services include
–
–
–
–
–
Purification of air and water
Detoxification and decomposition of wastes
Cycling of nutrients
Moderation of weather extremes
And many others
• We get these services for free. Should we
charge for their removal?
• How do we place a value on such services?
Ecosystem Services
But is this realistic? Who pays?
Ecosystem Services
The NY watershed
example: Bought
land worth $1 billion;
saved ~ $6 billion in
new treatment plant.
Ecosystem Services
Debt for Nature
swaps and the
establishment of
Costa Rica’s park
system
But politically and economically: are these even trades,
and are governments “selling out” their people?
An example of what conservation biologists
do: What is wrong with small populations?
•
•
•
•
Loss of genetic variation
Inbreeding
Difficulty to find mates
Susceptibility to demographic fluctuations
The Extinction Vortex
A small population is prone to positivefeedback loops that draw the population
down an extinction vortex
Small
population
Inbreeding
Genetic
drift
Lower
reproduction
Higher
mortality
Reduction in
individual
fitness and
population
adaptability
Smaller
population
Loss of
genetic
variability
Stopping the Extinction Vortex:
Conservation Genetics
• The case of the Greater
Prairie Chicken.
• Florida Panther.
• The case of the Red Wolf:
after out-breeding is it still a
Red Wolf?
Detecting declining populations
and making recovery plans
• Stressing the external
environmental reasons
for decline rather then
reasons internal to the
population.
• Breeding bird surveys =
“citizen science”
• Red-cockated WP:
– Habitat destruction
(Southern pines)
– Habitat restoration (fire)
– Nest excavations
Ornithologists
gossip: the
story of the
Ivory-billed WP
Ex-situ conservation
Strategies of conservation
• Endangered species conservation
– Species by species approach
• Multi-species habitat planning
– Attempts to conserve large tracts with viable
populations of most species
– “No surprises”
Remember conservation is a political as well as a
biological science. Human welfare (economic, health, spiritual)
must be factored into every decision.
Ranking species for protection
National, International
protection for Species
Today and next Tuesday
1. Finish ecosystems
by talking about
nutrient flow.
2. Move to higher
levels: “applied and
large-scale ecology”
3. Introduce
environmental
challenges and
global challenges.
4. Talk about
conservation biology as
one response.
5. Talk about landscape
ecology and
management as
another response.
Today leave 45 minutes for writing.
Tuesday leave 1 hour for review for
Midterm.
Saturday May 16 final exam!
Landscape Ecology: an
Introduction
Landscape Ecology:
Applications for Conservation
Park Design
• Thinking about
fragmentation:
- Edge effects
- Linkages (corridors)
• Many small vs. large
• Priority conservation:
“hotspots”
“Y2Y”: Yellowstone to Yukon
Fragmentation
• Leads to small islands in
midst of disturbed area.
• Importance of matrix:
can animals move
between?
• Corridors
The Biological Dynamics of
Forest Fragments study in
Amazonia
Fragmentation: Edge Effects
• Importance of edge:
edge/area ratio goes
up as size goes down.
• Edge species include
carnivores / nest
predators.
• Forest interior species
most vulnerable
Park Design and Island
Biogeography
• Some ecologists have
argues that island
biogeography argues
for large reserves.
• Others argue for
several small reserves
• An ongoing debate
(SLOSS)
Single Large or Several Small?
Park Design and Island
Biogeography
While several small parks will in the beginning
have more species, the large parks retain
more species over time, as
predicted by island biogeography theory
Park Design and Island
Biogeography
Single large parks
hard to make (not many!),
so best solution may be
connected small parks…
connection of course
improving immigration.
Single Large or Several Small?
Y2Y: an idea
Inspired by migration
Conservation Priorities:
Biological Hotspots
What happens
when they
are?
What happens when these
hotspots are not in your country?
http://www.biodiversityhotspots.org/Pa
ges/default.aspx