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Impact of Humans on the Biosphere


Impact of Humans on the Biosphere

Slide 1 – Introduction
Now that we have had an introduction to Ecology, let’s look at the impact humans have
had on the biosphere. We will focus our attention on agriculture and climate change.
This issue has arisen from human populations not using resources wisely.

After reviewing this lecture you should be able to:
•Describe unsustainable and sustainable agricultural practices.
•Discuss the concept of bioaccumulation.
•Describe the carbon cycle, including the sources of carbon and how the carbon
can be used.
•Discuss how humans are interfering with the carbon cycle and how these
activities might affect our climate.
•Explain the causes of climate change and list the problems that are developing
as climate change continues.
•List and explain several actions that can be taken by students, citizens, and
government agencies to help prevent the problems of climate change.

Slide 2 – Agriculture practices
Since the end of World War II, agriculture has changed radically. The advent of new
technologies, mechanization, and increased use of chemicals permitted a substantial
increase in the production of food and fiber. In addition government policies were put in
place that favored maximizing production. With these changes, farmers had reduced
labor demands, and thus fewer of them were needed to provide food and fiber to the
nation. Family farms transitioned into factory farms.

Many of the changes that agriculture has seen can be viewed as positive. However, there
are also environmental, financial, and social costs associated with these changes. Some
of these costs include: the decrease in diversity of natural food webs; topsoil erosion,
groundwater contamination; increased cost of production; and the degradation of
economic and social conditions in rural communities.

Slide 3 – Impacts of Agricultural Practices
Previous agricultural practices have diminished the diversity in natural food webs. This
is known as ecosystem simplification. Instead of having a robust and diverse food web
agricultural practices focused on growing food crops with very little diversity in order to
feed large masses of people, with the least amount of economical and labor input.

The potato famine of Ireland in the 1800s is an example of this. The potato was
introduce to Ireland in the late 16th century and became a food stable. In 1845 potato
blight, a fungus, began destroying crops and did so for five years. Due to the fact that
only a few varieties of potatoes were being grown and that those varieties were
susceptible to potato blight, 1 million people died of starvation and disease, while many
more emigrated to the United States.

Impact of Humans on the Biosphere

Slide 4 – Unsustainable farming methods
Although agriculture is the way in which we get our food, there are both good and bad
ways tackling the task of feeding the earth’s population. Unsustainable agriculture
practices do not help preserve the natural resources of the planet. Although these
practices do provide much needed food, they create additional problems for future
generations. Unsustainable agriculture methods include: monoculture, intensive
irrigation, over-sue of synthetic fertilizers, and over-use of pesticides.

Slide 5 – Unsustainable Farming Methods
Monoculture is the practice of planting multiple fields with a single crop. This practice
depletes the soil of nutrients. Since fields are left barren for a part of the year, erosion
readily occurs by wind and heavy rain. In addition, this type of farming leaves the crops
more susceptible to insect pests and crop disease

Intensive irrigation
Irrigation is the artificial provision of water to support agriculture. Intensive irrigation
depletes natural aquifers of water causing wells to run dry.

Slide 6 – Unsustainable Farming Methods
Over-use of synthetic fertilizers
Fertilizers are substances that promote plant growth by supplying essential nutrients to
the plant. Over use of synthetic fertilizers pollutes aquatic ecosystems when the over
applied substance runs into streams and rivers after it rains.

Over-use of pesticides
Pesticides are artificial chemicals used to kill insects (insecticides), plants (herbicides), or
fungi (fungicides). The over use of pesticides kills unintended organisms that are often
helpful to the ecosystem. In addition, the toxins from the pesticides can get into the food
chain and cause health problems for humans and other animals.

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