The Grand Canyon
Ecology, Humans, and Agriculture
By Keith Carlson
Dept. of Anthropology
University of Arizona
Objectives
• Introduce key concepts of ecology, environment,
climate, and ecosystem through introduction to the
Grand Canyon Region.
• Introduce the concept of climate change and how
scientists reconstruct past environments.
• Learn how long humans have lived in the Grand
Canyon region and how climate change affected
farming and foraging practices.
Where is the Grand Canyon?
• Located in Northern
Arizona
• Created by the Colorado
River
• 6000 Ft at its deepest
point!
• 277 miles long and 15
miles at its widest!
Key Terms
• Ecology: The scientific study of the
distribution of living things on earth
and their relationship with other
livings things and the environment.
• Ecosystem: What ecologists study –
the total group of organisms, climate,
and geology that interact in a
particular region.
Key Terms
• Climate: The temperature, rainfall (precipitation)
and wind conditions of a region
Key Terms
• Environment: The total living and nonliving things in a particular region,
including climate!
Key Terms
• Carrying Capacity: The amount of a
certain species or phenomenon that a
particular environment can support
• Limiting Factors: The environmental
factors such as rain that directly affect
the survivability of plants and animals
or activities of those organisms.
The Grand Canyon Ecosystem
• Temp – ranges from 41°
in January to 84° in July.
• Semi-arid (dry) desert.
– Average about 16 inches
per year (4 inches more
then Tucson!)
– Warmer and more moisture
at the bottom of the canyon
than at the top!
• High altitude
– Elevation at north and
south rim ranges from 7000
Ft to 8000 Ft
Environmental Zones of the Grand
Canyon
• Figure of Environmental zones of the
Grand Canyon – Cross Section
Elevation plays one of the largest role in defining ecological zones, as different areas
of different elevation have different climatic conditions.
1) Higher rainfall, the higher in elevation
2) Drier conditions the further down into the canyon
The Grand Canyon Ecosystem –
Major Plant Communities
Pinyon-Juniper Woodland
Aspen - Ponderosa Pine Forest
Mojave Desert Scrub Plants
The Grand Canyon Ecosystem –
Major Animals
Humans are a major part of the
Ecosystem too!
• People have lived in the Grand Canyon
region for more the 8000 years!!!
• Over this time, people:
– Hunted various animals.
– Gathered various plants.
– And Farmed corn, cotton
What is the major ‘limiting factor’
for the Grand Canyon
ecosystem???
WATER!!!
How people, plants, and animals are able to
live and survive around the Grand Canyon is
largely based on the amount of available
water!!!
Has the environment of the Grand
Canyon always been this way?
NO!!!
Climates and environments are always
changing
Climate change has had a major effect on how
humans have lived and used the Grand
Canyon environment!
How do scientists know that the
environment has changed?
• Pollen Analysis
– Most plants produce pollen
– Each plant produces a unique
pollen grain
– The pollen is spread in the air and
deposited in lots of different areas.
– Old pollen is recovered in
archaeological sites and is
identified under microscopes!
– This can tell scientists what
plants used to live in the region.
Pack Rat Middens
• Small Rodents
• They are Collectors –
they bring lots of stuff
back to their dens.
• Scientists can find very
old pack rat collections
and study them for old
plant and animal remains.
-- Usually found in caves
– These remains tell the
scientist what the climate
was like in the past!
Dendroclimatology
• The study of past climates
through the study of tree
rings.
• All trees produce annual
rings. These rings vary in
size depending on the
temperature and rainfall
• Scientists can study old trees
from archaeological sites and
see what the climate was like
when people used the wood!
What have scientists learned about
the history of the Grand Canyon
Environment?
• After 8000 years ago, the climate started to become warmer.
• 5500 to 2900 years ago – Very hot and dry!
– Plants and animals different from today, more dispersed
• After 2900 years ago, a lot more moisture.
– Change from warm, wet summers and cool, dry winters to warmer,
wetter winters and drier and warmer summers – more similar to today!
• After 1500 years ago, even more wetter, but big periods of drought
between 900 and 750 years ago that affected what plants and
animals could survive, including humans.
• After 750 years ago, true modern conditions in place.
How did Humans live in the Grand
Canyon Region?
• Hunters and Gatherers
– Archaic Period – 8000 to 1800
years ago.
– Very mobile. Moved around
the landscape in search for
food. Hunted animals and
gathered plants foods such as
pinyon nuts and cactus fruits
• Farming – Agriculture – Pueblo
Peoples, Anasazi
– Began about 2250 years ago
– Villages, settled life
– Corn, Cotton, Beans, Squash
How do scientists know when
People began to farm?
• Domesticated plants
versus wild plants
– Plants that are intensively
used by humans will
eventually begin to change
their genetic composition.
Modern corn is much
different than Ancient
corn!!!
– See these in pollen and
pack rat middens!!!
Maize versus Teosinte
• Have pictures of both
• Maize: Corn – domesticated in Mexico and
dispersed to Southwest.
– Very large ears with a high number of kernels.
– Cannot reproduce without aid of humans!
• Teosinte: Wild corn. Domesticated corn evolved
out of teosinte. Very small and hardy.
Reproduces by dispersing seeds in the air. Still
found in parts of Mexico and Central America.
Other indicators of Farming
• Archaeologists have
found the remains of
tools used by early
people for farming.
–
–
–
–
Manos and Metates
Hoes
Digging sticks
Pottery for cooking
and storage
Farmed crops
•
•
•
•
Corn (Also called Maize)
Beans
Squash
Cotton – used to make clothes!
Map of different farming zones in
Grand Canyon Region
• Figure that shows where prehistoric
farming activity took place.
• Have this superimposed on the map
showing the different ecological zones so
students can see relationship.
Also continued to use natural
resources!
• Pinyon nuts
• Mesquite pods
• Hunted animals – mule deer, jack rabbits
What are the ‘limiting factors’ on
farming in the Grand Canyon?
• Water: The amount of rainfall and when it falls
(seasonality) affects where and when people
can plant crops.
– Less water, or long periods between rains will
decrease what can be obtained from farming.
• Temperature/Seasons: Temperature and
seasons affects what crops can be grown as
well as their yield.
• Soils: The dirt! Farming can only be done
where the soils have the right nutrients to do so!
How did farming affect human
populations?
• Population Growth: The more people to feed,
the more likelihood that a year with bad crops
will impact the overall health of the farmers!
• Carrying Capacity: Just like with hunting and
gathering, the more people on the landscape,
the increased expansion of farming is necessary.
• Increased reliance on farming created a lot of
risk as the climate in the Grand Canyon is so
variable!
How did Climate affect farming in
the Grand Canyon Region?
• AD 950 to 1425
– Increasingly became wetter – Population expansion
and increased farming during wet periods!
• AD 1150 to 1300
– Periods of drought – Decreased population and
much less farming during dry periods! Much more
difficult to survive in the environment!
• After AD 1300
– Wetter climate, increased farming, but less population
than in the past. Havasupai and Hualapai peoples.
The impacts of Modern Farming in
the Grand Canyon region and
beyond today.
Bibliography – Books and Articles
References - Images
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•
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http://www.cpluhna.nau.edu/Biota/ponderosa_forest.htm
http://www.ags.uci.edu/~pkammer/pictures/cloudcr/
http://geography.otago.ac.nz/Courses/283_389/Resources/IntroDendrochronology.html