S E C T I O N
16.4
Plant Technology and the Biosphere
E X P E C TAT I O N S
Appreciate that Earth’s human
population is supported by
agricultural technology.
Describe the energy and water
costs of intensive agriculture.
Evaluate the interactions
among society, plant
technology, and the
environment.
Figure 16.26 A very large
amount of energy is used by
giant combines to harvest crops
from the fields.
It is estimated that Earth’s natural resources could
have supported a maximum of 10 million humans
before the agricultural revolution. By 1750, our
planet was supporting 800 million humans —
many more than would have been possible without
agricultural technology. Abundant food has
provided many opportunities for growth and
development, but they have created an entirely
new lifestyle that has shaped human society in
many ways. They effects include:
A new vulnerability. People became more
vulnerable to bad weather. As well, investing
heavily in non-portable technology means people
can not easily abandon their fields and
permanent dwellings.
A new work ethic. In order to produce adequate
amounts of food, humans have had to work very
hard in certain seasons. In earlier agricultural
societies, there was little leisure time for most
individuals.
A new awareness of time. People have had to
become very time-conscious to maximize the
time for planting and harvesting.
A new definition of group. As large families
became both possible and practical, family
interests came to predominate over the welfare of
the group. Children became a valuable resource.
A new need for sanitation. Areas of permanent
settlement needed to develop sanitary systems for
disposing of waste products.
A new need for disease resistance. Large numbers
of people in close proximity to each other for
extended periods of time provided breeding
ground for disease. Epidemics became common.
Energy Cost of Modern
Food Production
For early hunter-gatherers, the energy costs of food
gathering were low: they obtained about 5–10 J of
energy for each joule of energy they spent gathering
food. Most members of the population took part in
food gathering. The earliest form of agriculture —
rotational cropping — yielded about 20 J of energy
for each joule of energy “spent”. This greater
efficiency freed some individuals to specialize
in other non-food collecting activities such as
tool-making.
Modern agricultural technology is far less
efficient: it yields only 0.1 J of food energy for
every joule of energy invested. In the developed
world, only 2% of the population actually work on
farms. Another 18% do the related work of food
processing, transportation, and marketing. The
remaining 80% of the population are free to do
other work. However, the energy required to
liberate 80% of the population is enormous.
Modern humans use far more energy per person
than any earlier society. Each new technology is
followed by a sharp surge in energy consumption.
Where does that energy come from? For early
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605
Figure 16.27 In the long term, family advantage was not always equal to good
public policy. Dividing properties into smaller and smaller parcels yielded farms
incapable of supporting all of the subsequent generations.
farmers it came from their own muscles; that is,
from their food, whose energy can be traced back to
the Sun. For modern farm operations, most of the
energy used comes from the burning of fossil fuels,
whose energy can also be traced back to the Sun.
However, the energy we are using now when we
burn petroleum fuels first reached the Earth
millions of years ago. We are withdrawing this
energy from ancient reserves that are not being
replenished.
The Water Cost
Unlike many of the world’s countries, Canada
contains extensive natural water resources. Modern
societies have numerous uses for fresh water, using
it for drinking, sanitation, and industry, as well as
for growing crops. In many of the sunniest parts of
North America, rainfall is inadequate for intensive
crop production, so water from rivers, lakes and
underground rivers called aquifers is used to
irrigate the land. For example, river water is
sometimes redirected and used for irrigation.
However, when the used water returns to the river
it contains a heavy concentration of mineral
compounds that it picked up from fertilizers in the
ground. About 40% of the water we use for
irrigation is taken from aquifers, often at a rate
many times faster than nature can replace it.
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MHR • Plants: Anatomy, Growth, and Functions
Table 16.5
Costs and benefits of some agricultural practices
Benefits
Costs
Fertilizers
Fertilizers can enhance
the quality and quantity of
produce while preventing
impoverishment of the
soil.
Fertilizers can be harmful
to other parts of the
biosphere.
Pesticides
Pesticides can reduce
crop loss and increase
yield.
Bioconcentration of
pesticides can cause
harm to entire food chains.
High-yield
hybrid seed
High-yield hybrid seed
can generate a profitable
crop.
Farm managers must buy
new high-yield hybrid
seed every year. They
cannot save some seeds
from the crop for use the
next season. Either the
seeds will not grow true,
or they will not grow
at all.
Gene transfer
Seed containing genes
transferred from other
species can generate
crops with a better yield
and special features.
Farmers must pay a
royalty to seed growers
for the seed containing
genes transferred from
other species.
New crop plant
varieties
New crop plant varieties
may have a longer shelf
life.
New crop varieties may
have a different flavour
or nutritional value than
previous varieties.
Practices
Groundwater pollution — from industry, from
farming, and from sewage disposal — is
contaminating many aquifers. From all this, you
can infer that a water crisis is possible. So far, the
cost of fresh water has remained low considering
its true value. This means that plant foods cost less
than perhaps they should. Another problem with
irrigation practices is that they may be
contaminating the soil itself. You will explore this
idea in the following Minilab.
The Impact of Plant Technologies
on the Biosphere
The hunter-gatherer societies that preceded the
agricultural revolution had a much smaller impact
on the biosphere than our present societies have.
They did not modify the environment to the extent
that is common today. The agricultural revolution
altered this pattern by applying technology and
increasing certain plant populations for human use.
This has affected our biosphere in several ways:
Loss of diversity. As agriculture displaced natural
ecosystems with plant monocultures, many wild
species (both plants and animals) have declined
or died out entirely.
Loss of forests. Forests have been cut down for
farmland, fuel, and development.
MINI
Contaminated soil and water. Many of the
earliest agricultural sites that depended on
irrigation no longer support agriculture because
mineral salts have migrated to the upper levels of
the soil as a result of irrigation. The main impacts
that agriculture has had on the biosphere are
summarized in Figure 16.28 on the next page.
Who Is Defending the Biosphere?
Some people worry that our interactions with the
global ecosystem have placed the entire biosphere
at risk. In fact, we see and hear so many negative
statistics about issues such as diminishing forests
and farmland, increasing pollution, and ozone
depletion that it can lead to despair and a
discouraging sense of hopelessness.
So, can you do anything to defend the biosphere?
The answer is yes — here are some suggestions.
Continue to educate yourself. You do not need an
advanced degree to stay informed about issues
relating to biology and technology.
What does media communicate? Are issues
chosen based on their “shock value”? Think
about whether these media companies are in
business to disseminate accurate information and
well-considered opinion, or whether they just
want to sell more advertising space or
commercial time.
LAB
Modelling Irrigation
To model the contaminating effect that irrigation can have
on agricultural soil, hang a strip of soaking wet filter paper
— representing healthy, irrigated soil — in a jar containing
dry crystals of a soluble, coloured mineral compound such
as hydrated copper sulfate. When the paper dries out,
irrigate it (wet it and hang it) again.
Analyze
1. Describe the appearance of the strip of filter paper
after several cycles of “irrigation”. If you “irrigated” the
paper 10 more times, what would you predict about
its appearance?
2. What does the hydrated copper sulfate represent in
your “soil”? Based on this information what can you
infer is happening to the mineral content of the upper
layers of soil in an irrigated field? Evaluate the mineral
content of the upper layers of soil after 10 irrigation
cycles. 100 cycles? 1000 cycles?
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607
Develop a healthy skepticism. Beware of easy
answers to your questions. Consider whether the
data you access so easily on the Internet are the
products of research or opinion. Try to find
information about the the author.
the ones discussed in this chapter, but science
cannot always give a definitive answer.
Take action. Decide what issue is most important
to you and pursue it. Write to politicians and
corporations expressing your opinion.
Recognize the limitations of science. Scientific
knowledge can help us solve problems such as
CONCEPT ORGANIZER
Agriculture and the Biosphere
Monoculture
Chapter 16, Section 16.3
Fertilizers
Chapter 16,
Section 16.3, 16.4
Ecosystem Degradation
Pesticides and Herbicides
Chapter 16,
Section 16.3, 16.4
Monocultures have drastically altered the natural landscape.
Forests and other vegetation have, over the last century, in
particular, been cleared and wetlands drained to provide
hectares of arable land for crops. Manufactured fertilizers
enhance soil fertility, but excess nutrients are carried away
by run-off and pollute water systems. Pesticides and
herbicides can enter food chains where they become
concentrated in consumers. Many agricultural practices
require the use of fossil fuels, which release hydrocarbons
into the atmosphere. Collectively, these factors can degrade
or completely destroy natural ecosystems.
Figure 16.28 Modern agricultural practices degrade natural ecosystems.
SECTION
1.
What societal factors drive the development of
new technologies?
2.
K/U List three ways that the development of
agricultural altered human societies.
K/U
3.
How can the storage of food consume energy?
What energy resources supply the energy that is
consumed?
4.
MC The impact of habitat loss on vulnerable and
endangered species is not always a direct result of
reducing the amount of food available. Many
previously natural habitats are being destroyed for the
purposes of agriculture. List two different ways, other
than loss of food, that the loss of habitat can affect
wild animals.
5.
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REVIEW
K/U
If the agricultural revolution had never reached
this country, how do you think you would you be
living today? Where would you likely be living?
MC
MHR • Plants: Anatomy, Growth, and Functions
6.
Does modern agriculture represent an “advance”
for humans? Does it represent an “advance” for the
biosphere? Explain your answer.
7.
MC The concept organizer shown in Figure 16.28
illustrates agricultural practices that can have a
negative impact on ecosystems. Select one of these
practices and suggest ways in which its impact on
the environment can be reduced.
MC
UNIT PROJECT PREP
This section has looked at the effects of modern
agricultural technologies on the biosphere. You will be
preparing an executive brief for your Unit 5 Project and
the purpose of this brief is to summarize information
about a plant-based industry. Think about the ways in
which the plant-based industry you are investigating will
influence the biosphere. Keep an ongoing file of your
thoughts so you can add this information to your brief.