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Have you ever heard the song “Big Yellow Taxi?”
It’s one of our favorites.
It was originally written and recorded by Joni Mitchell back in the seventies, and there
are lots of singers who have their own recordings of her song.
Great song.
The song has this verse in it that asks “farmers to put away their DDT.”
You know when you’re young and you don’t understand a lyric in a song---you kind of---make
up what that might mean in your head?
….Ok maybe that’s just us.
We didn’t really get that lyric until we got older--- now we do---and it’s so much
more powerful now.
So of course, it deals with science.
DDT is a chemical pesticide, and it is called DDT because it stands for this.
Yeah…so we’re going to call it DDT.
Its use really sparked in the 1940’s as a powerful chemical pesticide---meaning it
was used to kill insect pests.
Often the types of insect pests that destroy crops so it was popular in agriculture.
DDT was very popular.
But DDT soon came under some scrutiny.
It became evident that pesticide was having negative environmental effects.
In 1972, the EPA issued a cancellation order of DDT and the EPA still works with other
countries to control substances such as DDT and similar chemicals.
DDT is used in other parts of the world, such as areas that are battling malaria and therefore
looking for mosquito control options with indoor residual spraying.
It is definitely far more regulated and controlled in its use today.
One thing that DDT really taught us is that the effects went far beyond the little insects
that it may be targeting.
Some high level consumers, such as bald eagles for example, really took a bad hit from DDT.
For bald eagles, this affected reproductive abilities, including severe thinning of bald
eagle egg shells.
But why?
After all, bald eagles do not typically eat the small insects that the DDT targeted.
This takes us into our topic of biomagnification.
And biomagnification doesn’t just involve DDT.
There are many chemicals and toxins that can be biomagnified.
Mercury is another example that you may hear about.
When you think of anything being magnified, you think of it getting bigger.
Biomagnification describes what happens when toxins become more and more concentrated in
the living tissues of organisms as you go up in the food chain.
But why does this happen?
Take a look at these little bugs here.
Imagine that perhaps these insects have been poisoned.
Here are some still living poisoned insects.
Weakened, some may make easy targets for predators.
This poison is killing off a lot of the insects but not all of them.
Each of these insects will contain one triangle, which represents a concentration of that toxin.
Now imagine these insects are eaten by secondary consumers such as lizards or rodents.
As those secondary consumers eat those insects, the toxin concentration level increases in
the secondary consumers.
Why?
Well recall in the energy pyramid, that organisms only keeps 10% of the energy from the trophic
level below.
The remaining is lost as heat or undigested.
That means that as you move up trophic levels, the animals will have to consume far more
biomass from the level below to be able to compensate for this and survive.
And everything it consumes from that trophic level below could have that toxin stored in
its tissues---which now, is an unwanted gift.
It’s adding up.
Now if a predatory bird begins to eat these secondary consumers, this concentration further
increases.
Remember it only gets 10% of the energy from the trophic level below----and so as a tertiary
consumer----it must eat a significant amount of secondary consumer biomass to survive.
Increasing toxin concentration in the tissues!
The problem with many toxins or chemicals is that if they are not controlled well, they
can get into the air, the soil, the water.
With DDT, it was able to get into the water supply.
Primary consumers, such as small fish, began to feed on those producers.
The concentration in body tissues of the poison in the primary consumers increased due to
biomagnification.
Secondary consumers, such as larger fish, feed on those primary consumers.
The concentration in body tissues of the poison in the secondary consumers increased due to
biomagnification.
Tertiary consumers, such as bald eagles, feed on the secondary consumers.
The concentration in body tissues of the poison in tertiary consumers increased due to biomagnification.
In summary, biomagniciation is a major factor to consider for any pesticide or chemical
toxin that humans may make.
We need people like you to come up with new solutions!
If you take a look at the end of our virus video, you can learn about a virus that has
been used as a pesticide as it only attacks specific types of pest insects.
What if viruses were manipulated to attack specific pests to avoid the use of toxin?
But even then, could there be consequences for taking out specific types of pest insects?
One last thing to mention.
Animals face additional problems such as habitat destruction, habitat loss, and poaching.
There are ecologists who devote their lives to helping these organisms and raising awareness
among people like you.
Truly, a career for the brave and bold.
That’s it for the amoeba sisters and we remind you to stay curious!