Environmental Science Mid-term Notes
The Base Cause of Environmental Degradation
My opinion (probably the same as most Environmental Scientists:
World population growth, consumption, far above what we can be replaced
Our Future: Cornucopians vs. Cassandras
Cornucopia: horn of plenty
– Human ingenuity will see us through our environmental problems via new
technologies and the such.
Cassandra: mythical princess of Troy who prophesized about dire future
– All is lost because of our impact on the environment.
• 1974: Paul Ehrlich and John Holdren
I P A T S
• Impact is largely POLLUTION, RESOURCE DEPLETION, or both.
Population = individuals need space and resources
Affluence = greater per capita resource use
Technology = increased exploitation of resources or ways of better dealing with our need
Sensitivity = how sensitive an area is to human pressure
The First Humans Oldest known homonid (human-like) fossils:
• The number of years it takes, given a specific rate of increase, for a number (such as
population to double.)
1979 China growth rate = 2.8% (popl’n at )me: 1B)
Current global growth rate = 1.2% (now: ~6.9B)
Current Canada growth rate (natural and net immigration together) = 0.9% (now: 33.5M)
• “The maximum population size of a species that a given environment can
• Limiting factors
• Births ≈ deaths
• Earth’s carrying capacity? Between 10 million and 33 billion.
Cultural Revolution/Paleolithic Period:
• Development of tools; stone, bone, wood
– (Note animal tool use – crows) Environmental Science Mid-term Notes
• Omnivorous diet
• Manipulation of fire
• Development of speech and communication
– Ethiopia: 2.6 My bp
– Tanzania: 1.75 My bp
• Little evidence of population at time.
• Start ~ 10-12,000 years bp
• Transition from nomadic hunter-gatherer to settled farmer (environmental
manipulation to meet needs)
– Reduction of area needed per person
– 500 X population density
– Excess of food production over minimum
– Whole population need not be in food production or acquisition
– Establishment of settlements
– Social structures – priests – accountants – salesmen
– “Fertile Crescent” – note soil salinization & collapse of society
• Easier to meet needs (food, safety, ease of raising children) = population increase
• Began mid-1700’s (Great Britain)
• Transition from rural, basic farming to manufacturing, urban society and massive
use of energy
• Improved sanitation and medicine
• Major advance in agriculture (powered machinery-driven) leads to
increases in food production
• Greater supply of energy, resources, labour
• Accumulation of wealth and market for manufactured goods
• We are in the middle of this one
• Developments in medicine and pharmaceuticals
• Improved sanitation
• Global communication
• Green Revolution (agriculture advances) Environmental Science Mid-term Notes
• People live longer, healthier lives
• Gap between rich and poor widened
Demography: The study of human population - Considerations:
• Population size
• Population density and distribution
• Age structure
• Sex ratios
• Birth, death, immigration, and emigration rates
^Shape a population’s environmental impact.
In the United Arab Emirates and Qatar, the ratio is closer to 200 to 100.
Such ratios are bound to lower population growth rates.
• It has occurred in Europe, U.S., Canada, Japan, and other nations over the past
• The transition could fail in cultures that
– Place greater value on childbirth
– Grant women fewer freedoms
Factors Affecting Population Growth
Education and the status of women (family planning), Poverty, Disease, (HIV/AIDS)
Difficult to find closed system
Open system: ex. Automobile inputs and outputs energy, matter
Closed system: inputs energy, outputs energy
Negative feedback loops: output from system becomes input to a system, moving system
in opposite direction (don’t let things change too much)
Ex. Rabbit and lynx population depleting and growing in a cycle
Positive feedback loops: output from system exacerbates the system response by moving
it further toward one extreme
Ex. Sea ice melting
Emergent properties: characteristics of a system not evident (perceivable) from its
components alone or individually
The rate (amount per time) if energy (joules) received at a surface called power
(Js ^-1). This is Watt (W) Environmental Science Mid-term Notes
Power per surface area is an Energy Flux measured in W m^-2
The rate of energy emitted by a substance is governed by the Stefan-Boltzmann
Solar constant: the rate at which isolation is received at the outer atmosphere of Earth
• Hydrologic Cycle (next class)
• Global Energy Balance (next class)
• Biogeochemical Cycles:
– Carbon Cycle
– Nitrogen Cycle
– Phosphorus Cycle
– Sulphur Cycle
– Mercury Cycle and lots of others
Ecosystem: All organisms and nonliving entities that occur and interact in a particular
area at the same time
– Includes abiotic and biotic components
– Energy flows and matter cycles among these components
– Generally, the smallest ecologically “self-sufficient” space
• BIG POINT: Energy enters, flows through, and exits this system, but matter is
cycled within it.
Conversion of Energy to Biomass in Ecosystems
• Biomass: organic material that makes up living organisms.
• Autotroph: an organism that produces complex organic compounds from
sunlight and inorganic molecules (i.e., plants and some bacteria).
• Gross Primary Production (GPP): Overall conversion of solar energy into
chemical energy by autotrophs.
• Respiration: metabolism.
• Net Primary Productivity (NPP): Energy remaining after respiration, that goes
toward accumulating biomass.
• Net Ecosystem Productivity (NEP): NPP minus heterotrophic respiration and
Key Chemical Equations:
Photosynthesis occurs in the presence of light and chlorophyll:
Respiration involves the use of accumulated carbon to produce needed energy (below is
the aerobic process): Environmental Science Mid-term Notes
NPP vs. NEP
• NEP = NPP – Ecosystem Respiration
• Ecosystem respiration includes both the respiration of carbon above the surface
and from soil.
Factors Affecting NEP:
• Nutrients (especially macronutrients like nitrogen and phosphorus) can be
limiting factors for productivity.
• Nitrogen usually limiting factor in marine systems, usually phosphorus in
Energy Produced = 2872 kJ per mol glucose
• Earth is a “closed” system. Open to energy, but matter “cycles” (is circulated)
within it over and over again (some VERY minor exceptions).
• Matter circulates between pools or reservoirs.
• The volume of material moving among reservoirs per unit time (a rate) is called a
• Fluxes are not necessarily stable (e.g., we have greatly affected the flux of C to
• Residence time (T ): Rverage amount of time a molecule or atom stays in a pool.
• Sources vs. Sinks.
• Lots of feedbacks in biogeochemical cycling.
Importance of Nitrogen
• 78% of atmosphere
• 6 most abundant element on earth
• Key ingredient in proteins and DNA
• Essential nutrient for plant growth
Key Processes in the N Cycle
• Nitrogen Fixation: combination of nitrogen gas (N ) with 2ydrogen to form
ammonia (NH ) an3 subsequently, the biologically available and soluble
ammonium ion (NH ). 4
• Two driving processes: lightning and nitrogen-fixing bacteria.
• Nitrification: Conversion of NH to N4 and then2NO by specializ3d bacteria.
Plants take up NO . -
• Denitrification: Conversion of NO back 3o N gas by s2ecialized bacterial Environmental Science Mid-term Notes
Human Alteration of N Cycle
• Doubling of nitrogen fixation. Due to Haber-Bosch process (fertilizer
production) and increased production of legumes (soybeans).
• Increased atmospheric N O 2greenhouse gas) and other NO (produxe smog).
Due to fossil fuel burning and animal waste decomposition.
• Depletion of micronutrients (Ca, K) from soils (N fertilizers make them more
mobile and they flush out).
• Acid rain.
• Eutrophication devastating to fisheries (especially coastal marine fisheries).
• Increased plant growth and carbon storage.
Eutrophication: The process of nutrient over-enrichment, blooms of algae, increased
production of organic matter, and ecosystem degradation
Importance of Phosphorus
• Key component of cell membranes, DNA, and ATP (energy).
• Often limiting nutrient for autotroph growth.
• Biogeochemical cycle is largely restricted to lithosphere and hydrosphere (NOT
• Cycle is largely driven by: