Energy Powers Ecosystems Sustainable Practices Ecologists and economists characterize practices that can be continued indefinitely as sustainable Ecological Footprint T he area of land required to sustainably provide all resources a population uses and assimilate all the waste it gener ID: 272449
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Slide1
Ecosystem EcologySlide2
Energy Powers EcosystemsSlide3
Sustainable Practices
Ecologists and economists characterize practices that can be continued indefinitely as
sustainable
.Slide4
Ecological Footprint
T
he
area of land required to sustainably provide all resources a population uses and assimilate all the waste it generates, given the prevailing current technology.Slide5
Energy Powers Ecosystems
All life requires energy—energy that is used to maintain tissues, grow, move, reproduce, and
keep
warm
.
Energy flows through ecosystems
Nutrients cycle within ecosystemsSlide6
What is an Ecosystem?
Ecosystem
– the community of organisms plus their physical environment.
How well a tree grows is affected by the organisms it interacts with and the physical environment it lives in.
Biotic
and
abiotic
factorsSlide7
Scale of Ecosystems
The spatial scale of an ecosystem varies widely:
The “lake” within a rain-filled pitcher plant
A New Hampshire forest
The whole EarthSlide8
Photosynthesis Powers Ecosystems
Energy arrives as sunlight.
Captured by
autotrophs
during the process of photosynthesis.
Primary productionSlide9
Other Autotrophs
Some autotrophs, primarily bacteria, can use the energy stored in methane or in inorganic chemicals like ferrous iron (Fe
2+
), manganese (Mn
2+
) and hydrogen sulfide (H
2
S) to power the synthesis of organic molecules through a process known
as
chemosynthesis
. Slide10
Primary Producers
Primary producers burn up half the energy they capture during photosynthesis.
Respiration
The rest is stored.Slide11
Primary Producers
Gross primary production
– the rate at which energy is captured by
photosynthesis.
Net primary production
– the difference between the rate at which energy is captured by photosynthesis and the rate at which energy is lost as heat.
GPP - Ra = NPPSlide12
Energy Moves up Food Chain
Producers are eaten by
herbivores
, or by
decomposers
after they die.
Energy is passed along to
predators
when they eat the herbivores.Slide13
Aquatic Ecosystems
Light is important for photosynthesis.
Light penetration is reduced with depth.
Photosynthesis is reduced as well.Slide14
Aquatic Ecosystems
The transition between these two regions occurs at the
compensation depth
—the point at which GPP = Re and NEP = 0
.
NEP = net ecosystem production
In
highly productive systems with dense populations of phytoplankton, light decreases quickly with depth, and the compensation depth is close to the surface.Slide15
What limits primary production in aquatic ecosystems?
In order to grow, phytoplankton must obtain sufficient quantities of nutrients from their environment, and primary production can be slowed if any required nutrient is in short supply.
N,P, Fe, SiSlide16
What limits primary production in
terrestrial ecosystems
?
Light and nutrients are important in terrestrial ecosystems, too.
Length of the growing season
N, P, KSlide17
What limits primary production in terrestrial ecosystems?
Most important
in limiting production in terrestrial ecosystems are temperature
and
precipitation.Slide18
What Happens to NPP
Much of a plants NPP gets eaten by herbivores.
Trophic levels
Primary producers
Herbivores
Primary carnivores
Secondary carnivoresSlide19
Secondary Production
Collectively, the biomass that accumulates in heterotrophs is called
secondary production
.
Primary production fuels secondary productions.
Other factors involved too.Slide20
Energy Transfers are Inefficient
Going from plant to animal appears to be very
inefficient
.Slide21
Food Quality Matters
The
quality of food, and not just its energy content, affects production efficiency
.
Clover is N fixer – lowers C:N ratio in plant, herbivore can build more proteins.Slide22
The Cost of Thermoregulation
Endotherms
have lower production efficiency than
ectotherms
, which suggests that an organism's thermal physiology affects how efficiently it is able to grow.
I
n
order to keep warm, endothermic organisms must devote more of the energy they assimilate to maintaining their energy budget than
ectotherms
, and consequently will have less energy available for growth.Slide23
Energy Availability Declines along Food Chains
As the diagram indicates, energy is lost at every step along the grazer food chain, which is why the
trophic efficiencies
of herbivores and carnivores are low. Slide24
Ecosystem EnergeticsSlide25
Detrital Food Chain
Plants that don’t get eaten eventually die and become
detritus
.
An ecosystem’s
secondary production
includes the growth and reproduction of decomposers as well as grazers.Slide26
Eltonian Pyramids
W
ithout
imports, substantially less energy flows through higher trophic levels than through primary producers.
Ecologists
often illustrate this pattern
with energy
pyramids.Slide27
Ecosystem ServicesSlide28
Our Growing Footprint
The collapse of the Atlantic cod fishery helps illustrate the enormous and increasing pressure people place on global ecosystems.
Demand
for goods and services provided by Earth's ecosystems is increasing rapidly as human populations increase in size and affluence. Slide29
Ecological Footprint
The
Ecological
Footprint
is the area of land required to sustainably provide all the resources a population uses and to assimilate all the wastes it generates, given the prevailing
technology.
It includes the area of biologically productive land and water required to meet demands for human infrastructure, timber and fuel woods, fishing, livestock, food, and fiber, and for assimilating carbon dioxide released during fossil fuel combustion.
http://footprintnetwork.org/en/index.php/GFN/page/calculators/Slide30
Our Growing Footprint
B
etween
1965 and 2007 humanity's Ecological Footprint grew from about 0.6 Earths to nearly 1.5 Earths.
In
other words, humanity's current annual demand is one-and-a-half-times that of Earth's annual productivity. Slide31
Our Growing Footprint
To make up the difference, people consume the
standing crop
rather than just what was produced in a given year.
This suggests that, as a whole, humanity is not living sustainably but instead is depleting the natural capital needed to support future generations.Slide32
Our Growing Footprint
The growing carbon footprint is the principal reason humanity's total Ecological Footprint has nearly doubled since 1961.
This
carbon footprint represents the area of forest land needed to assimilate the CO
2
people release into the atmosphere each year—primarily as a result of fossil fuel combustion and land use change—after accounting for CO
2
that is absorbed by the world's oceans.Slide33
Ecological Services
The Ecological Footprint makes it clear that we rely on ecosystems for a wide variety of goods and services, or
ecosystem services
, that directly or indirectly contribute to our welfare and without which our existence would be impossible.Slide34
Ecosystem Services
Supportive
fundamental
processes like primary
production, necessary
for producing all other ecosystem services.
Provisioning
D
irectly
consumed by people.
Regulating
benefits that result from the regulation of ecosystem processes including Earth's climate, water purification, and flood control.
Cultural
various nonmaterial cultural and recreational benefits people gain from ecosystems.Slide35
Ecosystem Services
To meet the demands of a
growing global
Ecological Footprint, people have
taken more
and more of a critical supporting service, net primary
production.
What we take is not available for other species or to support other ecosystem services.Slide36
Ecosystem Services
Clearly, people are critically dependent on ecosystem services like primary production for their welfare.
E
cosystem
services are often ignored in policy decisions.
As
a result of this oversight, ecosystems are increasingly stressed and their ability to sustainably provide critical services is compromised. Slide37
Service Valuation
Forest Preserve
Cropland Ecosystem
Restored CroplandSlide38
Tragedy of the Commons
Even when ecosystems are valued, they can be hard to protect.
The Atlantic cod fishery collapsed because harvest rates were higher than secondary production over a long time period.
The
overharvest was due in part to the fact that fish in the open ocean are a common resource and fishermen benefit by catching more fish.
Unfortunately
, with enough fishermen, rational individual choices to catch more led to overfishing and the potential demise of the entire fishery, a phenomenon often called
the tragedy of the
commons
.Slide39
The Tragedy of the Commons
Part 1:
http://youtu.be/KZDjPnzoge0
Part 2:
http://youtu.be/IVwk6VIxBXg
A managed commons, though it may have other defects, is not automatically subject to the tragic fate of the unmanaged commons. - Garrett
Hardin
http://youtu.be/fNhr2RNhw5w