How Human Activities Can Affect Sustainability

Section 7.3

Section 7.3 Topics

Nutrient Cycle Carbon Dioxide and Greenhouse gas Trophic Levels Water Pollution and Bioaccumulation

The four systems of the Earth: Geosphere (Lithosphere): is the solid part of

the earth, from the core to the surface

Hydrosphere: all the water found on our planet

Atmosphere: Air surrounding the Earth

Biosphere: the “life zone” of the Earth, includes all living organism.

Cycling of Matter in Ecological Systems

All nutrients flow from nonliving (abiotic) to living (biotic) and back to nonliving (abiotic) in what is called a biogeochemical cycle (cycle of matter).

What Type of Matter is cycled through ecosystems.

Matter such as carbon, nitrogen, phosphorous, sulfur, oxygen and water must continuously be cycled through ecosystem

No new matter is ever added to the planet and these types of matter are essential to life.

Earth is considered a closed system.

Sustaining Life on Earth…One way flow of high quality energy

The cycling of matter (the earth is a closed system)

Biosphere

Carboncycle

Phosphoruscycle

Nitrogencycle

Watercycle

Oxygencycle

Heat in the environment

Heat Heat Heat

Nutrient Cycles A nutrient cycle (or ecological recycling)

is the movement and exchange of organic and inorganic matter back into the production of living matter.

Nutrient Cycles Human activities are affecting the balance

of nutrients in ecosystems. There can be an increase or reduction in

the amount of nutrients available and this may upset the balance among biotic and abiotic factors.

This can compromise the sustainability of the ecosystem.

Example of Human Activities Affecting the Nutrient Cycles

Nitrogen is used in fertilizers to enhance the growth of plants.

Often not all of the nitrogen is absorbed by plants and the excess is carried into aquatic ecosystems in the run off from rainfall.

An increase in nitrogen in the water may cause an overgrowth of algae known as an algal bloom.

Example of Human Activities Affecting the Nutrient Cycles

Phosphorous is also used in commercial fertilizers. If excess phosphorous ends up in lakes it has the same effect as nitrogen, eutrophication of the lake.

Eutrophication A process in

which nutrient levels in aquatic ecosystems increase, leading to an increase in the populations of primary producers.

6 steps in eutrophication.

1. Fertilizer runs off from farmland into water.

2. Algae bloom occurs.

3. Submerged plants die due to reduced light.

4. Algae and the other plants die.

5. Bacteria use oxygen during decomposition.

6. Oxygen levels in the water drop too low for fish to survive.

Eutrophication

Greenhouse Gases

Atmospheric gases that prevent heat from leaving the atmosphere, thus increasing the temperature of the atmosphere.

Greenhouse Gases Greenhouse gases being trapped in our

atmosphere include water vapour, carbon dioxide and methane.

Fossil Fuels

Coal, Oil and Gas are fossil fuels. They are called fossil fuels because they have been formed from the fossilized remains of prehistoric plants and animals. They provide around:

66% of the world's electrical power95% of the world's total energy demands

How are fossil fuels formed?

Fossil fuels were formed millions of years ago. Remains of plants and animals that settled in

places where a lack of oxygen prevented them from decomposing.

Millions of years later the effects of pressure and heat turned the materials into what we now know as fossil fuels such as coal, petroleum and natural gas.

Industrial Revolution

The industrial revolution identifies a time in human history when humans began burning fossil fuels as a source of energy.

Affects of the Industrial Revolution

Burning fossil fuels as a source of energy released large amounts of carbon dioxide

This revolution marked the beginning of what is still massive amounts of carbon dioxide collecting in the atmosphere.

This collection of greenhouse gases is the reason that there has been an increase in the Earth’s surface temperature.

Greenhouse Effect The warming of

Earth as a result of greenhouse gases, which trap some of the energy that would otherwise leave Earth.

What Steps are Being Taken to Reduce Carbon Dioxide Emissions.

1. Kyoto Protocol: an agreement signed by over 180 countries to reduce emissions.

2. Protection of forests: Ontario and Quebec have protected roughly 50% of their boreal forests.

3. Recycling: Nova Scotia has been leading the way in recycling by banning the disposal of many substances such as plastic beverage containers since 1996.

Biomass

The total mass of living organisms in a defined group or area.

Trophic Level

A category of organisms that is defined by how the organism obtains energy.

Trophic Efficiency A measure of

the amount of energy transferred from one trophic level to the next higher trophic level.

Why are trophic efficiencies usually quite inefficient?

Trophic efficiencies are inefficient because only 10% of energy is passed from one trophic level to the next.

This is due to the fact that most organisms use the majority of the biomass they consume for life functions and production of waste. Organisms also lose energy as heat.

Bioaccumulation A process in which materials, especially

toxins, are ingested by an organism at a rate greater than they are eliminated.

What is biomagnification?

Biomagnification is the increase in the concentration of toxins in the body tissues of organisms as it moves from one trophic level to the next.

In other words, the top consumer in a food chain will have a much higher level of a toxin in their tissues than a primary consumer.

DDT and PCB’s

DDT is an agricultural insecticide. When used in the environment it entered the

water systems through run-off. It was absorbed by the Algae and was passed to other organisms (by ingestion up the food chain). Causing reproductive issues in some fish-eating birds

DDT and PCB’s

PCB’s are a compound previously used by industries and could be found in plastics, paints, rubber compounds and many other applications. It entered the water, air and soil when being used or

disposed of and consumers in those systems were effected.

Both of these substances are toxic to organisms and have subsequently been banned in North America.

Terrestrial and Aquatic ecosystems on the

Earth are connected. We must begin to understand that all

ecosystems are connected. Chemicals we use on land can reach aquatic ecosystems and have widespread effects.