Pollution: Crash Course Ecology #11


I think we should do this one outside. This is better. This is beautiful.
Just, oh, of course… except for this. Litter – is a kind of pollution, but like
barely. Like, I would rather it not be here. It makes me kind of angry and it makes nature
less pretty, but environmentally, there’s a pretty low
chance that this can, or even a million more like it is going to
have a significant negative impact on an ecosystem. The kind of pollution that we really have
to worry about is the kind that we don’t see, either because it is invisible, or because it’s being done in places that are way out of the way that we’re less likely to encounter. That’s by design, of course. Because when people actually see the impact
that their lifestyle can have on the world, they tend to sometimes change the way that
they live. And also the way that they buy, and we can’t
have that! So, it’s time to get our hands dirty. [Theme Music] Pollution is a kind of catch-all term for
any substance that’s in the wrong place or in the wrong concentrations in the environment. Trash in the environment, that’s pollution. But chemicals, both naturally occurring and
synthetic, those are the real killers. Now, we tend to think of pollution in terms
of weird synthetic chemicals made in big chemical processing plants and
they’re certainly a problem. But as we’ll see in a bit you’ve got to understand
that natural compounds in the wrong concentrations can do just as much damage as whatever petro-insecticides we’re making. One of the main ways we’re altering concentrations
of natural compounds is by messing with the bio-geo-chemical cycles
that we talked about a couple of weeks ago. You’re probably tired of hearing about it, but the most obvious cycle that we’re screwing up is the Carbon Cycle, which shuffles carbon around the planet into
various reservoirs. The atmosphere, the oceans, rocks, the bodies
of living things. The cycle keeps going on thankfully. But we’re overloading it by digging up all
that carbon-rich coal and oil and gas, and burning it to fuel our 21st century lifestyles. All of a sudden there’s more carbon getting
released than the reservoirs can handle. Plants and animals are like “We’re cool, we
got all the carbon we need” And the oceans are like “Yeah, we’re good
on carbon too!” And it can’t just go back into the rock. So, it hangs around in the atmosphere as a greenhouse gas, insulating our planet and changing the climate. We’ve also been tampering with the nitrogen
and phosphorus cycles to similar effect. Nitrogen and phosphorus are nutrients which
we, and other organisms, need, like, really need in order to grow and respire
and exist. But when we go and make , like, ludicrous amounts of these nutrients available, ecosystems get very confused. It’s like the day in fifth grade when I realized
that I could spend my entire allowance on Cadbury Creme Eggs at the After-Easter
candy sale at Walgreens. It was fun at first, then it was not. Phosphates and Nitrates are basically the
main ingredients in fertilizers. And phosphates are also found in some detergents. So when waste water from our houses or run
off from farms, washes those compounds into rivers and streams, it can cause huge algal blooms that choke out the rest of the plants and animals in the stream. It’s totally gross-looking.
But that’s not the end of it. When all the phosphorus and nitrogen are used
up, the algae die, and then bacteria gets started on decomposing
that dead algae. But of course, the decomposers need oxygen, which they take out of the water and then
the oxygen levels in the water plummet, killing all the fish and just about everything
else that needs oxygen. This is how phosphate and nitrogen pollution
causes dead-zones. The biggest example of this happening right
this very minute is in the Gulf of Mexico, at the mouth of the Mississippi River. The Gulf of Mexico Dead-Zone covers 18,000
square kilometers of river delta and coast-line, and is basically a swathe of totally de-oxygenated
water caused by all the fertilizers from the entire
Mississippi River basin which drains 2.6 million square kilometers of land drained into this one point in the Gulf. The size of the dead-zone fluctuates seasonally, as it depends on how much fertilizer is being
used by pretty much half of the farms in America. So yeah, pollution isn’t just synthetic compounds
with just like 17-syllable-long names, sometimes they’re just imbalances of chemicals
that we need for our survival. However not all chemicals found in nature
are good for us. In fact, sweet, old Mother Earth comes up with some of the most toxic stuff that you’ve ever heard of. Take cyanide for instance. It’s in a lot of stuff that we come in contact
with everyday, foods like almonds, spinach and Lima beans
contain cyanide, and so do the seeds of apples, which you have
heard, and the pits of peaches. Cyanide is useful to plants because it’s a
primitive insecticide, causing a sort of molecular asphyxiation, preventing a bug’s cells from being able to use oxygen. Now it takes a lot more cyanide than you’d find in an almond to finish off a human, but guess what? We figured out how to collect a whole bunch of cyanide in one place because we really love gold. Gold! My precious! Mining operations use cyanide in large quantities in order to separate gold, silver, and other precious metals from the ore. In the cyanide process of ore extraction,
ground up ore is sprayed with a cyanide solution, which dissolves the metal in the ore and draws
it out. The solution is then collected and the precious
metal is taken out. But the by-product of all of this is, of course,
a big pile of cyanide-laced rock powder, a.k.a. hazardous waste to deal with.
Or try to deal with anyway. Mines do all kinds of stuff to reduce the concentration of cyanide in these leftovers, called tailings. Or they try and convert the cyanide into less-toxic
cyanate, but the toxin is never totally eliminated. So then it can end up leaking into the groundwater
supply. Or it can just sit there and keep dissolving
other toxic metals out of the rock that also end up in our water, like mercury. And mercury is another important pollutant,
it’s a super-toxic, naturally-occurring metal found in coal, among
other places. And it’s just fine when it’s hanging out underground
in a coal seam, but when that coal is burned to make electricity,
the mercury is released into the air. And then the mercury falls on the land, where
it makes its way into groundwater, and eventually into the food chain, especially
into the marine food chain. As a result, only about 25% of the mercury
released by U.S. power plants and factories actually ends up in the U.S. The rest enters the global cycle, which most
people end up ingesting by eating fish. And mercury acts as a powerful neurotoxin in animals, interfering with our brains and our nervous systems. Finally, two more naturally-occurring compounds that we keep pumping out are sulfur dioxide and nitrogen dioxide. The most common natural sources of these things
are volcanic eruptions, or the waste of some algae and bacteria. But we release millions of tons of these things into the environment every year by burning fossil fuels like coal. And when these compounds react with water
vapor in the atmosphere, they turn into sulfuric acid and nitric acid,
and then return to the surface as acid rain. In soils, these acids can cause the release
of natural, but toxic, elements like aluminum. In water, they can poison aquatic wildlife,
and on land, the acidity can cause animals’ eggs to not
hatch and plants to lose nutrients. Now, things have gotten significantly better since a lot of countries put emissions controls into place, but for a while there, back in 1980, rain in much of North America had the same pH as tomato juice, which, objectively speaking, is the grossest. So. That’s how we’re amping up the levels of naturally-occurring chemicals to toxic levels. But, of course, we’re also synthesizing chemicals
that Mother Nature never even dreamed of, and they wreak their own special brand of
havoc. The problem here is choosing just one as an
example, because there are so many chemicals out there,
doing so many different things. There’s a whole class of chemicals called
endocrine disruptors, which we put in pharmaceuticals, pesticides
and plastics, but some of them are also just byproducts
of industry and agriculture. Endocrine disruptors, like bisphenol A or
BPA, which baby bottle manufacturers have been scrambling to take out of their products in recent years, hang out in plastics and leach into our drinks or are flushed off of agricultural fields and into rivers or are just flushed down toilets when we pee them out because they’re in some drug that we’ve been taking. The result is that they get into waterways,
sometimes in high concentrations, and the animals there, they just soak ’em
all in. The endocrine system, basically just your hormones, controls a vast array of an organism’s functions. And as concentrations of EDCs have increased, we’ve spotted male fish in rivers all over
the world with female reproductive tracts or testes that make eggs. Those fish are living in the water, but we…we’re
drinking it. People of all ages are susceptible to EDCs, but research suggests that those most at risk are fetuses and infants, because their organ and immune systems are
still forming. Scientists are still studying the developmental,
reproductive, and neurological effects that these compounds
are having on us. And as far as I’m concerned they can’t do
it fast enough. So, the chemicals we’re making are affecting
us in ways that we could guess, and also probably ways that we’ve never even
dreamed of. At the same time, we’re rearranging where and how much some naturally occurring compounds are showing up and that adds to those 5 other impacts that
we’re having on the biosphere. And yeah, the past two weeks have been a real
bummer. But hopefully an enlightening bummer. And this leads us to the next stage of ecology,
and the last lesson in this course: conservation biology and restoration ecology, which together comprise the science of saving
our planet, and ourselves from…ourselves. Thank you for watching this episode of Crash
Course Ecology and thanks to everyone who helped us put it
together. If you want to review any of the stuff that
we covered this episode, there’s a table of contents over there that
you can click on, or down in the description. And if you have questions or comments for
us, we’re on Facebook and Twitter and of course,
down in the comments below.

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