Human Impact on Ecosystems

Chapter 16

16.1 Human Population Growth and Natural Resources

A. Earth’s human population continues to grow.

1. Earth’s carrying capacityHow many people can Earth support??Recall that carrying capacity is the maximum

population size an environment can constantly support.

Thomas Malthus wrote an essay in the 1700s claiming the human population was growing faster than Earth’s resources could support.

In Malthus’s lifetime the human population was around 1 billion.

Today the human population is more than 6 billion.

It took all of human history to reach 1 billion, a little over a 100 years to reach 2 billion, only 30 years to reach 3 billion, an d 15 years to reach 4 billion

What is the limit?

2. Technology and human population

Recall that carrying capacity can change as a result of the environment.

Humans have modified their environment through agriculture, transportation, medical advances and sanitation.

The carrying capacity of Earth has increased.

B. Pressures on Earth’s Natural Resources

There are two types of natural resources:1. Nonrenewable- resources are used

up faster than they can form (example- oil and coal)

1. Renewable- resources that cannot be used up. These resources renew themselves over time

(example solar and wind energy)

Nonrenewable ResourcesTwo resources, oil and coal currently

support the majority of our countries energy use.

It takes MILLIONS of years for the natural process of transforming dead organic matter into the concentrated carbon substance we use today

In 2006, the human population was using oil at a rate of 77 million barrels per day!!

Renewable ResourcesRenewable resources can

become nonrenewable if they are not used carefully..

A good example is drinking water. Because of pollution and overuse, our fresh water supplies are threatened.

Groundwater is also being extracted from aquifers faster than it is being replaced

The United States uses more resources and produces more waste than any other country on Earth.

Each year, The U.S. generates about 230 million tons of garbage. (4.2 pounds per day, per person- or almost a ton a year per person!)

C. Managing Earth's Resources

• Management of Earth's resources affect both current and future generations….

1. Ecological FootprintThe amount of land necessary to produce and

maintain enough food and water, shelter, energy and waste is known as an ecological footprint

The size of an ecological footprint depends on:

1. The amount and efficiency of resource use

2. The amount and toxicity of waste produced

16.2 Air Quality

Fossil fuels• Fossil fuels are important part of our

world

• Ancient organisms absorbed the sun’s energy and stored this energy in their biomass

• Today, humans burn these fuels in the form of gas and oil

• This in turn pollutes our atmosphere

A. Pollutants Accumulate

• Each year humans add synthetic chemicals and materials to the Earth

• Many of these can not be integrated into normal ecosystem functions

• Pollution describes any desirable factor, or pollutant, that is added to the air, water or soil

• Pollution can take the form of microscopic air particles or waste products from factories and sewers, or household chemicals that are pored down the sink!

• The harmful effects from pollution can be immediate or delayed, and they may ADD UP over time

Smog and Ozone• Most common• Comes from burning fossil fuels• Smog is a type of air pollution that comes

from the interaction of sunlight and pollutants produced from fossil fuel emissions

• Components of smog include particulates (microscopic bits of dust, metal, and unburned fuel) and ground level ozone

Acid Rain

• Burning fossil fuel creates nitrogen oxides and sulfur oxides which in turn create acid rain (pH > 7)

• Acid rain in turn decreases the pH of lakes and streams and threatens our water supply and species habitat

• Acid rain can also cause growth rate to decline and cause trees to become more at risk for disease

B. Air Pollution and Biosphere

• Our atmosphere naturally includes molecules of CO2 that help keep the biosphere at a temperature to support life

• The levels of CO2 naturally rise and fall.

• Higher levels of CO2 are typically in warmer periods, lower levels are associated with cooler climates

1. Greenhouse effect

Global Warming• Over the past 100 years the average temperatures

have risen 0.6 °C ( 1.2 °F)• Increased levels of greenhouse gases have

caused this change (CO2, water vapor and methane)

• Ecological disasters such as increased flooding, stronger tropical storms, and loss of biodiversity are a few threats that may be caused by global warming

• Polar ice caps are melting• By 2100 scientists estimate temps to increase 2.2 – 10 °F

16.3 Water Pollution

A. Effects on Ecosystems

• Pollution has a major impact on water ecosystems• Raw sewage, trash, chemical pollutants etc. end up

in our rivers, aquifers all over the word • One way scientists determine the health of an

ecosystem is through indicator species (bioindicator)

• Indicator species provide a sign of the quality of an ecosystem’s environmental condition.

• Frogs and tadpoles are often used because their skin can be permeated by water- thus extra arms and legs can indicate direct contact with pollution

B. Biomagnification

• Occurs when fat soluble pollutants move from one organism to another up the food chain accumulating in higher concentrations in the bodies of predators

• Measured in ppb

• Pesticides are a good example