Hi. It’s Mr. Andersen and this is environmental science video 16. It is on agriculture. This
is a picture of wheat. We grind it to make flour and then make things like bread. And
we have been doing so for thousands of years. This sickle is over 5000 years old and was
used to harvest wheat. We still harvest wheat today in a similar fashion but now on an industrial
scale. What is the function of agriculture? It is to provide for our human nutritional
requirements. If you do not get enough calories in your diet we call that undernourishment.
And it is less of a problem. We generally can make enough food but it is not always
in the right place at the right time. And things like war can disrupt that flow. A bigger
problem is malnutrition. It is when you are not getting the proper nutrients. You are
not getting the right proteins, vitamins, minerals in your diet. A growing problem is
actually over nutrition where we eat too much and can lead to things like obesity. Agriculture
provides for these needs and it has been doing so for thousands of years. Now what happened
with industrialization is as we had exponential growth in the population we had to feed that
population. And therefore we had the green revolution where we have industrial agriculture
today. There are five characteristics of that. The first one is mono cropping, when you plant
just one crop type. We also have irrigation, the use of pesticides that target different
things. The major ones are herbicides and insecticides. We use fertilizers. Some of
those are going to be organic, like manure. But a lot of those are going to be synthetic.
And now we have the arrival of genetically modified organisms. All of these together
have allowed us to create more food than we ever have. But each of them have draw backs.
Mono cropping for example, when you harvest all of those plants, it can lead to soil erosion
and a lack of biodiversity. How could we prevent soil erosion? Things like contour plowing.
Irrigation depletes aquifers and can lead to salinization. So we could maybe have the
arrival of new salt tolerant crops. Pesticides have a double problem. Pests are going to
become resistant to the pesticides and also those chemicals are going to bioaccumulate
within the food web. What can we do? We can use processes like integrated pest management
to try to mediate those problems. Fertilizers require a lot of energy. They require fossil
fuels to make and also they will run off the fields and enter into the food web causing
things like eutrophication. So what can we do? We can use other crops as fertilizers
using something called intercropping. Genetically modified organisms, most of the studies are
saying are not harmful to humans to eat, but they can lead to a decrease in biodiversity.
And so there is a big push away from industrial agriculture towards alternative (or sustainable)
agriculture. We still have to feed the humans on our planet, but we can do it in a smarter
way. And so if we look at the history of farming, most of it has been subsistence. So this is
over 3000 years old in a burial tomb. And so this is an early farmer plowing his field.
And so what has happened is as the population has grown exponentially, we have only been
able to create food in a linearly increasing fashion. And so eventually what you have is
this catastrophe where you cannot make enough food to feed everyone. And this happened in
the last century. So we could see that the food growth was quickly going to be outpaced
by the exponential growth of the population. And so biologists like Norman Borlaug, farmers
brought forth these industrial ways, called the green revolution, of providing more food.
You could see this in wheat yields. So this is in developing countries. Back in the last
century it was increasing in a linear fashion and then we had this green revolution. Places
like India and Mexico. So what are the characteristics of industrial agriculture? One big one is
mono cropping. It is when you plant just one crop. So this is corn for example. What is
great about that? You become really good at planting corn and taking care of corn. It
is easier to plant this way. It is easier to harvest it as well. What are some of the
problems? Well we have a decrease in biodiversity and it can lead to things like soil erosion.
You have to harvest all of that food at the same time. Rain can wash that really valuable
soil away. So what could we do to prevent that? Things like contour plowing where you
are plowing with the contour of the field. It keeps it flat, the surface is flat so we
have less of that runoff. Irrigation has allowed us to farm in areas where we never could of
in the past. So this is in Kansas for example. What are some problems with irrigation? Well
you are going to deplete, this is the Ogallala Aquifer that this sits on, so eventually that
will run out. You also have the problem of salinization. So rain water will generally
wash the natural salts away. But if you start pumping water out of the ground, that is ground
water. And it is going to contain salt. Those drops of water have salt in it and so we are
going to have an increase in salt. Salinization over time. How do we solve this? Well we could
try varying the crops that we have. We could limit irrigation. Or we could start to evolve,
through artificial selection, salt tolerant crops. Another major part of industrial agriculture
is the use of pesticides. The major ones are going to be herbicides that kill other plants
or weeds. We have insecticides, fungicides and other biocides. Now why are farmers using
them? It is because they can get return on their investment. For every dollar they spend
on pesticides they get four dollars in higher crop yield. So an example. If we look at one
of the most popular herbicides in America, Atrazine, it is a broad leaf plant killer.
So it is going to kill the weeds in crops like corn. And so you can see it is going
to be aggregated where we are growing a lot of corn. And the reason why is that they can
get more corn back. Now what are the problems with this? One is bioaccumulation. Those chemicals
do not just go away. They are going to build up in the food pyramid. And so pests are killed
but they are eaten by other consumers and other consumers. Like the example that we
are familiar with is DDT aggregating inside and eventually killing things like bald eagles.
Another problem is resistance. If you spray pesticides, what pests are you killing? The
ones that are least resistant. So if you spray it the first time you will kill a lot of those
insects. But the ones that survive are resistant. And over time through natural selection those
pesticides do not work anymore. So how do we solve this problem? Well if we look at
the population of the pest itself, so one individual pest, it is going to undergo exponential
and then logistic growth. So right down here in this area it does not make sense, financial
sense, to spray pesticides. The numbers are not large enough. We have not gone over what
is called the economic injury level. And so farmers are constantly monitoring the fields,
figuring out what pests do I have? What is the level of them? They can use other things
beside pesticides. We can mechanically remove those pests. We could use things like traps.
We could use other life. We could use things like this lace wing larva to kill other aphids.
And then we could monitor it to the point where maybe it is going to a level where it
is going to hurt us. So then we could use pesticides but we could use pesticides wisely.
Another characteristic of industrial agriculture is the use of fertilizers. It puts those important
nutrients that plants need, like nitrogen, potassium, phosphorus, into the soil. And
so this right here is spraying anhydrous ammonia into the soil. That is a process that humans
have invented to take nitrogen out of the air using the Haber process and making ammonia
out of it. You can spray it on the fields and the plants are going to grow more quickly
with a higher yield. What is the problem? As we have rain that runoff is going to push
those fertilizers into the water supply and it can lead to problems like eutrophication.
How could solve this problem? Well we could start using other crops. And so this is intercropping
where we are having beans mixed in with corn. And so the beans are providing manure, essentially
green manure for that corn to grow. A growing characteristic of industrial agriculture is
the use of genetically modified organisms. Now we have always been breeding plants, but
recently we are taking genes from one organism and inserting them in another. An example
could be golden rice. And so you are inserting genes into rice so they produce vitamin A.
Why is this a big deal? Over a 500,000 children under the age of 5 die each year due to vitamin
A deficiency. So we could insert those genes, they can eat the rice and that is not going
to be a problem. Another example could be Bt corn. We are taking genes from a bacteria
and inserting it into corn and it produces a natural pesticide so things like a corn
bore cannot eat it. Now most of the studies are saying that this food is generally safe
for humans to eat. But depending on where you are, in the US we use lots of GMOs but
in Europe not so much. And so there is controversy over the effects to the environment through
the use of genetically modified organisms. And so the current push is towards sustainable
agriculture. We do not want to have such an impact on our planet. And what is interesting
is a lot of these practices will return us towards our subsistence farming roots. And
so did you learn the following? Could you pause the video at this point and fill in
all of the blanks? Well let me do it form you. So malnutrition is a lack of calories.
The green revolution led to industrial agriculture. Some of the characteristics are mono cropping,
irrigation, pesticides, fertilizers and GMOs. Herbicides are the most popular type of pesticides.
Our fertilizers can be either organic or synthetic. And what are we moving towards? Alternative
agriculture, where we do not have so much of an impact on our planet. And I hope that
And I hope was helpful.