We are entering the era of geography, an era when geographical thinking is essential for
making sense of a globally interconnected world, a bold claim for a discipline that
is defined more by a perspective than by a particular topic.
But it's an integrated perspective that can help us understand everything from the
movement of the tiniest grain of sand, to the clashing of continents, to the rise and
fall of nations, to the trekking of hurricanes, to the distribution of material wealth across
the globe.
I am Alec Murphy, and I'm going to show you how this much ignored subject in 20th century
America rose to a position of prominence in the 21st century.
This is the story of physical geography, making sense of planet Earth.
Changing the physical landscape has accompanied every major human development, from the early
emergence of hunter-gatherer societies, to tribal communities, to agrarian communities,
to industrial nation states.
All of these developments have involved major changes to the natural environments in which
these human organizations existed.
In this 8th and final program, human impacts on the natural environment, we will look at
humanity's increased ability to modify the planet's physical spheres, landscape, soils,
water, atmosphere, and I'll show you how understanding this increased capacity of humans
has become critical to geographical thinking, geographical thinking that helps us understand
why things are the way they are.
We passed a point just a few years ago where the bulldozer became the primary shaper of
the United States of our landforms.
More Earth was moved by bulldozers than by natural processes.
There has never been a time where humans have been able to modify the physical landscape
more than today.
We have a tremendous capacity to change the landscape.
We changed the landscape to such a degree, for example, the construction of dams.
There's over 80,000 dams in the United States today, large dams.
The dams across the northern hemisphere hold back so much water that they've actually
changed the rotation of the Earth.
And that's just one rather extreme example of the human capacity to change the physical
environment.
This process of humans transforming the physical landscape, the physical geography planet is
not a new thing.
We've already done enormous changes to the land cover of the planet.
Well over half of the planetary surface has changed from what it was prior to modern
humans.
That's amazing.
This capacity to change the physical landscape began with the end of the last ice age 10,000
years ago.
At that time, humans had already started organizing themselves in small hunter-gatherer groups.
Groups capable of altering the geographical character of their settings beyond what a
single individual or family could do.
Notably, they were able to manufacture tools, tools that allowed them to manipulate their
environment.
One of the most useful of these were spearheads made from rock.
Rock found in flint quarries sometimes miles away from their hunter-gatherer homelands.
These manufactured spearheads permitted them to hunt larger gain than had previously been
possible.
At the same time, many of these hunter-gatherers began using hides and other material to craft
simple clothing, clothing which allowed them to survive in a greater range of climates.
It is even claimed that these paleolithic tribal hunters became so effective that they
wiped out the megafauna of North America.
Cracked out animals such as mammoths and mastodons, horses and the saber-tooth tiger, producing
the first extinction event attributable to humans.
Even if true, by present standards, humans imprint on the physical landscape was minimal
until 4,500 years ago, when structures like Stonehenge began appearing on the southern
plains of present-day England.
By this time, human organizations had grown beyond simple tribes of hunter-gatherers into
the beginnings of agrarian communities.
The emergence of Stonehenge and other similar structures heralded the rearrangement of the
physical landscape.
A rearrangement that previously had only been brought about by geological forces.
Long before any megalith would be placed at Stonehenge, the site had already been selected
5,000 years ago by the Neolithic people in southern England on the Salisbury Plain for
a burialhenge.
Neolithic hinges were circular or semicircular ditches.
The one at Stonehenge contained the bones of dead cattle.
This was the first phase in the building of Stonehenge.
However, the villages of Stonehenge were not the first recognized inhabitants of Britain
after the last ice age.
3,000 years earlier, a Paleolithic culture had migrated to this cold and wet land.
It was a land rich in game and heavily timbered.
And as it is today, some of the land was ideal for agricultural settlement.
During this time, the land bridge between England and the rest of Europe disappeared
as the English channel filled up in the wake of melting ice sheets, protecting these first
Britons from invading peoples from the continent.
Then around 6,500 years ago, a remarkable transformation took place, a transformation
that changed the landscape.
These ancient Britons began an aggressive clearing of the forest with more advanced stone tools,
axes and knives made of flint.
This was the start of the Neolithic or New Stone Age.
Small settlements and farmsteads made their appearance.
Animal husbandry was in full swing, and planted fields flourished throughout the land.
It was against the backdrop of this new and successful agricultural economy that the building
of Stonehenge took place.
This is important for burials. Stonehenge's purpose probably changed over thousands of
years of use.
As I say, the purpose fair is, astronomy comes into it. Astronomy is important in laying out
some of the stones. They're concerned with the midsummer sunrise and the midwinter sunset.
But what they do with that, we don't know, but astronomy is important.
You can use Stonehenge for telling time, but whether this was a purpose, I'm not sure.
Interesting ideas that have been raised recently within the last couple of years is that Stonehenge
may have been an oracle as well, and possibly a healing centre, which is very little evidence
for this. In fact, it's just one sixth skeleton.
But it's a nice idea that Stonehenge was a famous place for healing, because a lot of
Greek and Roman temples, the healing was important there as well, so possibly Stonehenge is a
big healing centre as well.
There is a common theme that runs through human society's ever greater capacity to alter
the natural landscape. The changes made on the environment change the society. They change
how people think, how they go about their daily business, what they worship, and how
they see and make sense of themselves. It is impossible to think about the Egyptians
without their pyramids, the ancient Greeks without their Parthenon, the Romans without
their Forum and Colosseum, the Maya without their temples.
All of these great ancient cultures were based on one particularly profound way of modifying
their environment, preparing land to grow crops. Indeed, the development of agriculture
represented one of the most important shifts in human environment relations and led to
massive human-induced changes to the physical geography of the planet.
Perhaps no great ancient civilization was more ingenious in producing a surplus agriculture
capable of supporting a grand empire than the Inca who thrived in the harsh high altitude
environment of South America's Andes.
Tucked in an Andean mountain valley is the modern-day city of Cusco. It is a city of
300,000 and was once the capital city of the Inca Empire. Nearly two miles high, the central
plaza of Cusco is still where it had been nearly 500 years ago, when the empire was
at its zenith. Not only was Cusco setting part of the Andes, but nearly the whole Inca
Empire was part of this rugged mountain chain. Starting from modern-day Colombia, down to
the tip of Chile, the region is dominated by the Andes, rising up almost immediately
from the Pacific coast of South America. A series of different mountain environmental
zones are encountered as one climbs toward the magnificent snow-capped peaks of the high
Andes. The climates here range from Mediterranean to tropical to temperate. Climate are not marked
by winter and summer, but by dry and rainy seasons. Coming down the eastern side of
the Andes, one encounters the tropical Amazon River Basin. This was once all part of the
Inca Empire. How the Incas rose from a society with a simple
chieftain to one with a complex imperial ruling elite remains a mystery. What is clear, however,
is their rise was accompanied by modifying the landscape. The Peruvian government has
given Ruth Wright and her husband, Ken, special permission to study Inca engineering. Ruth
has written a guidebook to Machu Picchu. She is impressed by the Incas agricultural accomplishments.
The miracle of the Incas was, was their ability to grow food, agriculture. And you go along
the Urabamba River on your way to Machu Picchu, and there's terraces after terraces after
terraces in the floodplain of the Urabamba River. They were able to grow so much food
that they had extra food, not only on an annual basis, but they would have storehouses
all over the empire. It was almost a social contract. You will not go hungry if you will
be good citizens of the empire. So you look at these storehouses and usually up on a hill,
they would have corn and potatoes. They had hundreds of different kinds of potatoes.
They would grow those, take them up to high altitudes, and freeze-dry them. And you can
still buy freeze-dried potatoes in the stores, and you just put it in hot water and they puff
up again. So these could last for years. So there's plenty of food for the Inca Empire
to not only have an army, but all the other things that an empire needs, the priests and
the educators and the people who do the stonework, and who do all the water, engineering, and
so forth. So that society, as was Egypt, was built on excess agriculture.
In addition to potatoes, the Inca successfully grew corn, beans, and squash. And like nowhere
else in the Americas, the people of the Andes had for over 1,000 years domesticated beasts
of Burton, alpacas and llamas. These camel-like animals were primarily pack animals, carrying
goods and supplies from one place to another. So a key foundation for the builders of the
Inca Empire was their ability to grow excess food. And that success was based on their
unique social organization, a unique organization of human power and knowledge. Human power and
knowledge that enabled the Incas to modify their geographical setting. They tear us the
mountain slopes to grow and harvest food. Built roads connecting the farthest outposts
of their vast empire and engineered grand cities and marvelous palaces. And just as amazing,
this unique organization brought together over 7 million people, speaking many different
languages, and spanning over 2,000 miles, all working toward a common purpose. The Inca
exhibited a kind of ability to modify their environment and geography that became one
of the cornerstones of industrialized societies. Each step in the increased capacity to rearrange
the landscape brought greater interconnectivity between more and more groups and their activities.
No story brings this point home better than the dramatic changes made to the Colorado
River.
Both cruises across a beautiful lake in the high desert of present-day Utah. The glitz
and glamour of America's third city, Las Vegas, Nevada. Multiple bumper crops of every fruit
and vegetable imaginable in California and Arizona's Imperial Valley. None of this would
have been possible without dramatically altering the Colorado River. Much of this change is
the result of two great dams on the river. Hoover Dam completed in 1935. England Canyon Dam finished
31 years later. Mike Gillieri is an ecologist who has been studying the environmental impact
of these dams on the Grand Canyon.
It's been said more than once that the entire Colorado River system, which is only number
26 in the United States, in actual volume of water, but the only big river in the southwest,
it's so valuable that for various political reasons, the river has been converted from
a river to a chain of megalithic plumbing.
The Colorado River originates high in the Rocky Mountains and flows south through the Colorado
Plateau, creating these spectacular canyon lands. In northern Arizona, it has cut one
of the seven wonders of the natural world, the Grand Canyon. There is no place like it
on the planet. Leaving the canyon, it continues to flow south, finally emptying into the Gulf
of California. As the 20th century dawned, humans had achieved through engineering and
construction the ability to build massive dams, dams that would totally alter the nature
of the river and its ecosystems.
Be that as it may, both these big dams and there are 26 dams at least on the Colorado
River system. They're all controlled by human beings and they're all controlled primarily
for the purpose of generating the greatest money from hydropower. Both the big dams,
both Hoover Dam and Glen Canyon Dam were built before the National Environmental Policy
Act was passed, so neither dam had to justify or examine the consequences of what the river
would experience, ecologically or otherwise, after the dams were up. It was irrelevant
in those days. And the reality is, of course, many species of native fish and otters and
so on have got extinct in Grand Canyon because of these dams. But the most noticeable effect
is that the river doesn't flood anymore.
Indeed, by the time the lower dams along the river siphon water for irrigating crops in
the Imperial Valley, barely a trickle of water flows into the Gulf of California.
The Colorado River story graphically illustrates how the physical geography of a region was
so drastically changed by human engineering that it transformed an even larger region.
A region so large it encompassed the whole of the desert southwest, all the way to the
Los Angeles basin. A larger region. A larger region that now plays a major role in global
economics, supporting shipments of goods to and from Asia, and tourists from around
the world.
The next case brings the whole range of the new geographical thinking into play. Into
play in understanding why there is a lake district in the center of America's agricultural
bread basket. Beautiful cottages rest beside Sun Drench Lakes in central Illinois and
Indiana.
Land that just 200 years ago was tall grass prairie. And more recently, prime agricultural
land used for growing corn and soybeans.
In order to understand how these cottages came to be, we have to go back 300 million
years during the Pennsylvanian period, at a time when the North American continent looked
like this. Through the forces of plate tectonics, it was part of a supercontinent called Gondwana.
In fact, Illinois and Indiana sat on the equator.
It was a region dominated by prolific swamps. Swamps that built up huge amounts of dead
plant material. Then over millions of years, massive amounts of sediments covered and compressed
the dead plant material until it became fossilized. It became coal.
In the process, the Illinois basin was formed, a paleozoic, depositional, and structural
basin, underlying most of the state of Illinois, and extending into southwestern Indiana and
western Kentucky.
Over millions of years, the sediment eroded away, exposing the ancient Pennsylvanian coal.
Coal that was discovered by cartographers mapping the region in the early 19th century.
As the nation prospered, coal was needed to fuel the economy, heat homes, and stoked the
engines of America's great industrial expansion. Real roads were propelling America into an
industrial powerhouse connecting the nation from sea to sea.
At the beginning of the 20th century, there was a boom in coal mining.
Strip mining the coal in Illinois basin back then was much the same as it is today.
The topsoilers removed, huge machines scooped up the coal from the old Pennsylvanian layer,
and send it on its way to markets.
After the coal was all mined, depressions or holes in the land were left behind. In a
few years, the depressions filled with water. A few more years, and vegetation began growing
around what had now become man-made lakes and ponds.
Gradually, the ponds became the center of new wetland ecosystems. From there, the beautiful
new lakes became prime real estate for recreational activities. That's how the cottages got there.
Interestingly, a region that had fallen on hard times as the need for coal diminished
was suddenly brought back to life by higher prices brought on through new market demands
for coal in the 21st century. Coal needed by China for its own industrial expansion.
So once again, the big machines are working the land.
One day coal from the Illinois basin may be shipped to China.
What does this all mean? This ever-increasing capacity by human societies to change the
physical landscape.
We are the biggest geomorphic agent on the planet. So how far can we take it? I think
very far, and I think we are just at the tip of the iceberg, especially in terms of biological
alteration of the planet. I mean, we've already seen massive landscape changes. I'm speaking
to you from Southern California. This is a semi-arid desert. My water comes from the
Colorado River several hundred miles away. The California Water Project enables agriculture
and the growth of cities on a scale that's totally impossible based on the climatology
of where I live. So that was all done in the early part of the 20th century. This is old
news, all right? But the real frontier now, which is both terrifying and exciting all
at the same time, will be genetic alteration of the planet's animals. I mean, it's already
happening with genetically modified foods. It would be very interesting to see what kind
of world we're living in, 50 or 100 years from now, as our ability to really play ***
with altering species just on a much faster time scale than has been enabled so far by
natural selection. I think that the planet is really poised on the brink of some very
radical transformations. Geographic information, our understanding of a landscape, is the primary
method by which we understand to be able to make predictions about how we make management
decisions. For example, if we build a dam, what will happen to our physical environment?
For example, if we build large scale roads, where will that energy come from and where
where the materials go? At the same time that understanding allows us to make intelligent,
informed decisions about when our management decisions are bad, where we can look for places
where habitat is being destroyed or where we can look for areas where there are problems
very quickly, both of those require the highest level of our geographic knowledge that we
have today. So if we look to the future of our species on the planet, on our impact on
the planet, unless something catastrophic occurs, we're going to add another couple
billion people between now and about the middle of the century. At the same time, individuals
in the developing world are demanding more resources to live a lifestyle, I must say,
not unlike the one that I enjoy or that we enjoy in the so-called developed world. So
not only will there be more people, but the demand for resources will increase as people
are basically working towards a higher standard of individual living. They say that by 2050
then, human population size will begin to, human population growth will begin to decline
and that we might reach a steady state and maybe even decrease numbers a little bit.
That might remove some of the pressure, but I don't think we can count on that. I think
we have to plan now and I think by being able to integrate the hydrosphere, lithosphere,
the atmosphere, the biosphere, by being able to look at all of the issues and challenges
we have spatially, the connectedness between space and place and by being able to look
a little bit over the horizon. Geographers can play a really important role in managing
our planet through what could be a crisis point over the next 50 years.
As this and other programs in this series have shown, we live in a world of constant
change. Part of that change is driven by humans themselves, whose impacts have now become
so great that leading edge thinkers argue humanity has become a geologic force, propelling
us into a new age, the Anthropocene. It is increasingly clear that we need to see the
environment not just as a blank stage on which the human drama plays out, but as an
inextricable part of that drama. By the same token, we need to understand not just the
individual components of the environment, its geological, biological, atmospheric and
human features, but the places and patterns that are created by the interaction of these
features. This is the essence of geography. Geography helps us understand the diversity
of the planet and the ways in which where something happens influences what unfolds.
In a world being remade by far reaching environmental changes and rapidly shifting patterns of
human interaction, a grasp of how Earth's surface is organized and how geographical
context shapes what happens, is essential if we are to confront the most pressing challenges
of our time. Thanks for watching Physical Geography. I'm Alec Murphy.
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