Unit B: Sustainable Ecosystems and Human Activity
Chapter 4: Ecosystems by Design
Key Question: Are human-designed environments
sustainable?
Key Concepts:
- Some ecosystems are designed, created, and
maintained by humans.
- Agricultural practices disrupt natural biogeochemical
cycles.
- It is important to keep Earth’s soil healthy.
- Pesticides are used to reduce crop losses due to insects,
weeds, and other pests.
- Urban ecosystems depend on natural ecosystems for
food and materials.
4.1: Engineering Ecosystems and Modern Agriculture
pg. 126
Key Concepts:
1. Some ecosystems are designed, created, and
maintained by humans.
2. Agricultural practices disrupt natural
biogeochemical cycles.
Comparing Natural and Engineered Ecosystems
Humans spend little time in natural ecosystems, where all
other organisms do. Humans can manipulate their
surroundings to suit their needs. Areas designed and
constructed by humans are known as engineered
ecosystems, and are artificial. (Lawns, gardens, sports
fields and farms)
Engineered ecosystems are different from natural
ecosystems. In a natural ecosystem, a human’s influence is
equal to all the other organisms found there. These
ecosystems have a greater diversity (variety) of organisms
living there. The ecosystem is kept in balance through
natural processes and relationships among the diverse
organisms.
In artificial ecosystems, there is very little diversity,
because features have been added and removed on purpose.
Humans must maintain these ecosystems or they would fail
on their own.
Modern Agriculture
The agricultural industry in Canada is a major contributor
to our survival. The food in which we eat come from all
over Canada, P.E.I. produces the potatoes we eat, while
British Columbia’s cranberries, and wheat from the Prairie
provinces.
Foods produced in Canada come from other parts of the
world, which gives us the varieties of nutritious foods.
Non-native animals and plants are now grown and raised
here.
Table1: Agricultural Products of Canada.
Farmlands as Engineered Ecosystems
Agro-ecosystem: is an agricultural ecosystem designed and
maintained by humans to meet the human need for food.
Engineered ecosystems are designed by humans to fulfill a
specific role or function. The most common engineered
ecosystem is the farm, which are designed to provide us
with food and other products.
Comparing Natural Ecosystems and Agro-ecosystems
Pest: any plant, animal, or other living organism that
causes illness or harm and is an annoyance to humans.
In natural ecosystems, the organisms interact, and maintain
the natural balance. Bees pollinate the flowers, rabbits eat
grass and their waste is used as soil fertilizer. In an Agroecosystem, there are a limited number of species interacting,
and the natural cycles no longer work. Plants are started in
a greenhouse, only one type of crop is grown in a field.
Bees and rabbits are no longer needed in the ecosystem.
Figure 4: a) A natural ecosystem maintains its own balance of biotic and abiotic b)
In an agro-ecosystem, humans work to maintain the balance.
Monocultures
Monocultures: agro-ecosystems (farms) consisting of
single crops in an area.
On farms, monoculture is the normal, only one type of crop
is grown in a given area.
Growing only one type of crop, allows the farmer to get the
highest crop yield, there is no competition from other
species. Crops can be harvested quickly and easily.
In a monoculture, a single disease can kill the entire crop,
causing the whole crop to collapse in a short time. These
crops also put a strain on the soil, nutrients are depleted,
and therefore, a large amount of fertilizer is required to
support the crop.
Check Your Learning:
Questions 1 – 7, pg. 129
Wrap Up:
- Humans change their surroundings to suit their needs.
- Engineered ecosystems have low biodiversity.
- Many engineered ecosystems are unsustainable because
they lack the natural cycle necessary to keep the ecosystem
in balance.
- The most common type of engineered ecosystem is an
agro-ecosystem.
- Modern farming often involves planting fields of only one
type of crop, known as monocultures.
- Most of the crop and livestock species in Canada are nonnative species.