The Grand Canyon

Ecology, Humans, and AgricultureBy 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 non-living 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 areasof different elevation have different climatic conditions.

1) Higher rainfall, the higher in elevation2) 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

• 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