2023年12月25日发(作者：)
Unit 9 Which Way Will It Go?
Introduction
TEACHER: The topic for today’s class is land as a resource. Land, water, trees, oil . . . these are all
resources, and as future environmental scientists, you need to understand how to manage these
resources. As the world population increases, managing land resources will become a greater priority.
Land is a limited resource. Today I’m going to divide the lecture into two parts. First we’ll look at some
of the factors contributing to pressures on the land we have, and then I want to turn to some of the ways
people worldwide are trying to address land problems and meet the needs of future generations. Think
of it as first the bad news, then the good news.
Body: Part 1
Let me start by saying there is less good productive land now than there was even ten years ago. By
productive land I mean land that is fertile, that we can use to grow food and raise animals. Each year
more and more land becomes degraded. We are losing productive land. Worldwide, new dry areas are
developing and expanding. This is happening on every continent except Antarctica. I don’t mean
existing deserts like the Sahara are getting bigger. I’m talking about new dry areas, areas where land
has been declining in quality. You can see these areas in the map in your book. Why are these areas
forming and expanding? What do you think? Theresa?
STUDENT l: It’s the climate, isn’t it? The earth is getting, you know, hotter because of global warming.
So water gets evaporated and the land dries out.
TEACHER: OK. Marcel, do you agree?
STUDENT 2: Well, yeah. It has to be the weather. What else could it be?
Body: Part 2
TEACHER: Well, different reasons have been given. Some people contribute it to global warming or to
climate changes. They say nature simply produces dry regions, like the Sahara Desert, as well as wet
regions, like the Amazon Rain Forest . . . . Well, let’s think about this. Is it only the weather? Let’s see
if there are other factors contributing to this trend. Is nature, or the weather, really the problem?
According to a large group of scientists, the weather isn’t the main factor. Instead, they say, people are
the main factor. When they say people are the main problem, they mean people’s actions－how people
use and manage land. Poor land management, overpopulation, poor farming techniques, too many
animals, and so on, can all affect the land. Look at the chart in your book. As you can see, researchers
have identified several ways human activities contribute to the problem. The first is overgrazing by
farm animals. They say about 35 percent of the loss of productive land is due to overgrazing by farm
animals. The second is overcutting of trees, which leads to about 30 percent of the loss. And lastly, 28
percent of the loss of good land is from methods of farming. Overgrazing, overcutting, and farming
methods. Let’s look at these one at a time.
1
Body: Part 3
The first is overgrazing. Good topsoil is lost or damaged because of overgrazing by farm animals.
Overgrazing means the animals eat too many of the plants. There are several bad results of overgrazing.
First, there aren’t enough plants left to hold the soil in place. Then, the topsoil is eroded by wind and
rain; they carry it away. Second, as the animals walk around, the soil is compacted, and gets very hard.
If the soil is too hard, rainwater isn’t absorbed into the soil, and this causes the soil to stay dry and
warm. As the soil gets drier, even fewer plants can grow. This, in turn, causes the animals to walk
around more and more, in order to find enough food to eat. And, this causes the ground to get packed
down even more, and get even drier, and so on. So, you can see that overgrazing can create this cycle.
Body: Part 4
Second, overcutting of trees also contributes to the loss of good land. The main problem is too many
trees are cut and not replanted. For years we’ve heard about how this is happening on a large scale in
the Amazon Rain Forest in Brazil. Trees, like land, are a resource we depend on. They’re vital to the
whole environmental balance on earth. If trees are cut down and not replanted, there is nothing to hold
the good soil. Wind and water carry the good soil away and it erodes quickly, leaving land that is dry
and less productive. So, overcutting is another reason why land quality is declining.
Body: Part 5
Third, farming methods are another big factor. In some places, traditional methods that have been used
for hundreds of years no longer work well. Why do they no longer work well? Partly because the
population is increasing, and farmers aren’t equipped to meet these new demands, and partly because
the soil is getting worn out. More people need to be fed from less land. As a result, some farmers may
use too much fertilizer on the limited land they have, or not let the land rest from year to year, causing
it to become less fertile. Irrigation is a huge factor many of us don’t think about. Irrigation water often
has salt in it, and when the salt builds up in the soil, the soil can no longer be used for farming.
Currently, about one third of the irrigated land in the world has too much salt in it. Irrigation has taken
a heavy toll on good land.
Body: Part 6
So, basically, how people use the land seems to be a bigger factor in the decrease of productive land
than weather. Of course, weather extremes, like no rain or too much rain, can add to the problem.
However, the weather is not the main reason for the problem. Some of the extremes in the weather
caused by global warming can make the situation worse for people who live in these dry areas. But the
weather alone is not the main issue. The decline of productive land is a worldwide problem. Currently,
about one third of the world’s land area is considered unproductive because it is too dry and damaged.
2
Body: Part 7
OK, so that’s the bad news. Now let’s turn to the good news. What are countries doing to help preserve
land as a resource? As experts learn more about this worldwide problem, they have tried to find ways
to address it. Right now there are several organizations, the United Nations for one, that are working to
help people. They try to help countries or communities look at their specific problems and figure out
what possible changes they can make to protect their land. They talk to people about their farming
methods, their animals, and how they use trees and their resources. Then they suggest changes that
might alleviate some of their problems. Farmers might try to grow genetically engineered crops that
don’t hurt the soil as much, or plant new trees, or raise fewer animals, or build new irrigation systems
that leave less salt in the soil. They look for local solutions that will work best for that country. This
includes looking at what has been done traditionally and implementing modern farming methods in
ways that respect the local culture.
Conclusion
So, let’s review what we covered today. I mentioned that about one third of the available land
worldwide has become dry and less productive. The main reason for land degradation is people’s
actions, including overgrazing by animals, overcutting of trees, and farming methods. As scientists
learn more, we need to work to help countries make specific changes and for farmers to become better
equipped so that they can preserve the good land that is left.
Let me just add that if we look at the estimates of what the world population will be fifty years from
now－about 9 billion people－it helps us see that protecting the good land that’s left needs to be a high
priority.
I’ll stop there. We’ll continue with this next class. That’s all for this afternoon.
3
