Earth’s Environmental Systems
Our planet’s environment consists of complex
networks of interlinked systems.
Earth uses cycles that shape the landscapes around
us and guide the flow of key chemical elements and
compounds that support life and regulate climate.
Systems show several defining properties
System is a network of relationships among parts,
elements, or components that interact with and
influence one another through the exchange of
energy, matter, or information.
Open Systems are systems that receive input of both
energy and matter and produce outputs of both
Closed Systems receive inputs and produce outputs
of energy, but not matter.
o in nature, no system is perfectly closed
Energy inputs to the earth’s environmental systems
o Solar radiation
o Heat released by geothermal（地热） activity
o Organismal metabolism（生物体的新陈代谢） o Human activities (eg. Fossil fuel combustion)
Information energy can come in the form of sensory
o visual signs
o Olfactory (chemical) si嗅觉s
o Magnetic signs 磁迹象
o Thermal signs热的迹象
Inputs of matter occur when chemicals or physical
material moves among systems
o Eg. Seeds being dispered long distances
o Migratory animals迁徙动物 deposit waste far
from where they consumed food
Eg. Gulf of St. Lawrence receives inputs from the St.
Lawrence, fishers harvest some of the systems
output: matter and energy in the form of fish and
o Output becomes input to the human economic
system and to the digestive syste消化系统 of
the people who consumer seafood from the St.
Sometimes a system’s output can serve as input to
that same system o This is a circular process known as feedback
Can be positive or negative
In a negative feedback loop output
that results from a system moving in
one direction acts as input that moves
the system in the other direction,
o Input and output essentially
neutralize each other
o EG. Thermostat working to
stabilize rooms temperature
o EG. Our bodies, when we get too
hot, our sweat glands pumpe out
moisture that evaporates to cool
Most systems in nature
involve negative feedback
Positive feedback loops have the
opposite effect, rather than stabilizing
a system, they drive it further toward
one extreme or another. o eg. Populations growth, the more
people who are born, the more
there are to give birth to further
people, increased output leads to
increased input, leading to further
o Positive feedback loops are rare in
nature, common in natural systems
altered by human impact.
System is constantly active as input and outputs
When processes within a system move in opposite
directions at equivalent rates so that their effects
balance out is called dynamic equilibrium动态平衡
o Dynamic because even though the state is
balance, it is ever-changing
o Homeostasis 动态平衡 is the tendency of a system
to maintain constant or stable internal
Homeostatic systems are often said to be in
a stable or steady state
Earth is a homeostatic system o Resistance refers to the strength of a systems
tendency to remain constant
o Resilience 弹性 is a measure of how readily the
system will return to its original state once it’s
It is difficult to understand systems fully by focusing
on their individual components because systems can
show emergent properties
o Characteristics not evident in the components
o It is like saying “the whole is more than the sum
of its parts”
If you had a tree in its components parts
(leaves, branches) you wouldn’t be able to
predict the whole tree’s emergent
properties, which include the role the tree
plays as a habitat for birds etc. You could
analyze the trees chloroplast叶绿体 but still
be unable to understand the tree as habitat.
Systems have well defined boundaries
o Computer desktop example
In summary, systems may exchange energy, matter,
and info with other systems which may contain or be contained within other systems, where we draw
boundaries may depend on the spatial or temporal
scale at which we choose to focus.
Understanding a complex system requires considering
The great lakes, st. Lawrence river & atlantic ocean
are systems that interact with one another
o Waterways carry with them millions of tons of
sediment, hundreds of species of plants and
animals & numerous pollutants
o Must consider Great Lakes – St. Lawrence river
watershed as a system if an environmental
scientist is interested in runoff and the flow of
water, sediments or pollutants
Environmental systems may be perceived in various
The Lithosphere 岩石圈 is the rock and sediment
beneath our feet, in the planet’s most upper layers
The atmosphere is composed of the air surrounding
our planet The hydrosphere encompasses all water – salt, or
fresh, liquid, ice or vapour in surface bodies
underground or in the atmosphere
The biosphere consists of all the planet’s living
organisms and the abiotic(nonliving) portions in
which they interact.
All of the 4 boundaries above overlap重叠 , making it
o Bird could consume a worm (organism) by
removing it from the lithosphere(soil), all this
made possible because rain (from the
hydrosphere) recently wet the ground. The bird
then might fly through the air (atmosphere) to a
tree (organism) in the process respiring
(combining oxygen from the atmosphere with
glucose from the organism, and adding water to
the hydrosphere and carbon dioxide and heat to
the atmosphere). The bird might than defecate,
adding nutrients to the lithosphere below.
Geologic Systems 地质系统 : How Earth Works
The rock cycle is a fundamental environmental system Rocks change over time
Rocks and the minerals (naturally occurring,
inorganic crystalline solids) that compose them are
heated, melted, cooled, broken down, and
reassembled in a very slow process called the rock
The rock type in a given region helps determine soil
Igneous rock 火成岩
At high enough temperatures, rock will enter a
molten liquid state called magma
If magma is released in a volcanic eruption it may
flow or spatter across the earth’s surface as lava.
Rock that forms when magma cools is called igneous
o This rock comes in several different types
because magma can solidify in different ways.
o Magma that cools slowly and solidifies while it is
still well below earths surface is known as
intrusive or plutonic roc侵入岩或火成岩
Granite 花岗岩 is the best known type of
intrusive rock. A slow cooling process allows minerals
of different types to grow into the
larger crystals that give granite its
o When magma is ejected from a volcano is cools
very quickly so minerals have little time to grow
into coarser crystals
This kind of rock is called extrusive or
volcanic rock,喷出岩或火山岩 most common
representative is basal玄武岩 .
All rock weathers away with time
Particles of rock blown by wind or washed away by
water come to rest downward from their sources
o The eroded remains of rocks usually are
deposited slowly, but floods can speed up the
Sedimentary Rock is formed when minerals seep
through sediment layers and act as a kind of glue, called cement, which crystallizes and binds the
sediment particles together.
Lithification is the formation of rock through these
processes of compaction, cementation and
There are several types of sedimentary rock and are
classified by the way they form and the size and
composition of the particles they contain.
o Limestone & Rock salt form by chemical needs
when rocks dissolve and their components
recrystallize to form new rocks.
o The second type of sedimentary rock forms
when layers of sediment compress and become
physically cemented to one another.
Metamorphic Rock 变质岩
When great heat or pressure is exterted on rock, the
rock may change its form, becoming metamorphic
o Temperatures are lower than rock’s melting
point but high enough to reshape the crystals
within the rock.
o Common types include Marble 大理石
Formed when limestone is heated and
pressurized, strengthening its
FORMED WHEN SHALE IS HEATED AND
A more coarsely layered metamorphic rock called
GNEISS, makes up the Canadian Shield, which forms
the core of the North American continent.
Plate Tectonics shape Earth’s Geography
Plate tectonics is a process that underlies
earthquakes and volcanoes and that determines the
geography of earth’s surface
o Earths surface consists of a lightweight thin
crust of rock floating atop a malleable mantle,
which in turn surrounds a molten heavy core
made mostly of iron.
Earths internal heat drives convection currents that
flow in loops in the mantle, pushing the mantles soft
rock cyclically upward (as it warms) and downward
(as it cools) like a gigantic conveyor belt. o As the mantle material moves, it drags large
plates of crust along its surface edge
Earths surface has 15 major tectonic plates
o Including some combination of ocean and
o Plates move at 2-15 cm per year, changing
evolution throughout our planet’s history.
At divergent plate boundaries, magma surging
upward to the surface divides plates and pushing
them apart creating new crust as it cools and
When two plates meet, they form a transform plate
boundary 转换板块 and creating friction that
spawns earth-quakes along strike-slip faults
When two plates collide at convergent plate
boundaries , either of two consequences may result
o 1. One plate of crust may slide beneath another
in a process called subduction. Subducted crust
is heated as it dives into the mantle, and may
send up magma that erupts through the surface
in volcanoes. o When densor ocean crust slides beneath lighter
continental crust, volcanic mountain ranges are
formed that parallel coastlines.
o Deep trenches can be created.
o Some areas are in a marine protected area that
lies a top of an active subduction zone.
An ecosystem consists of all organisms and nonliving
entities that occur and interact in a particular area at
the same time.
Ecosystems are systems of interacting living and
Ecosystems are systems that receive inputs of
energy, process and transform that energy while
cycling matter internally, and produce a variety of
outputs (such as heat, water flow, and animal waste
Matter is recycled within ecosystems, because when
organisms die and decay their nutrients remain in
Energy is converted to biomass 生物量 Energy flow in most ecosystems begins with
radiation from the Sun.
The process of green plants using photosynthes光合
作用 to capture the sun’s energy and produce food is
a the process of biomass , organic material of which
living organisms are formed.
As autotrophs自养生物 convert solar energy to the
energy of chemical bonds they perform primary
o Gross primary production is the assimilation of
energy by autotrophs.
o The energy that remains after respirati呼吸 ,
which is used to generate biomass, ecologists
call net primary production
Net primary production = Gross Primary
Production Minus Respiration
Measured by the energy or the organic
matter stored by plants after they have
metabolized enough for their own
o The total biomass that heterotroph异养生物
generate by consuming autotrophs is termed
secondary production Productivity is the rate at which plants convert
energy to biomass
o Ecosystems in which plants convert solar energy
to biomass rapidly are said to have high net
Algal beds, tropical forests, wetlands, coral
reefs are all examples of the highest net
Lowest net p.p include deserts, tundra,
o Increases with temperature and
In aquatic ecosystems, 水生生态
系统 increases with light and
availability of nutrients
Nutrients can limit productivity
Nutrients are elements and compounds that
organisms consume and require for survival.
o Elements & compounds in large amounts are
eg. Nitrogen, Carbon, Phosphorus 磷 o Nutrients needed in small amounts are
Lack of nutrients can limit production.
The availability of nitrogen or phosphorus frequently
is a limiting factor for plant or algal frowth
o Did experiments manipulating entire lakes to
see the effects of phosphorus on freshwater
The number of hypoxic zones is about 200 and
o Most resulting from rising nutrient pollutant
from farms, cities and industries.
Ecosystems are integrated spatially
Ecosystem can be as small as a puddle of water or as
large as a bay,a lake or forest.
Scientists even view the entire biosphere as a single
Areas in which ecosystems meet may consist of
transitional zones called ecotones,交错群落in
which elements of both ecosystems meet.
Landscape ecologists study geographic areas with
Landscape ecology , scientists study how landscape
structure affects the abundance, distribution, and
interaction of organisms.