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Science and Children >  > The Colorado Plateau > Ecological Diversity: Then and Now 

Ecological Diversity: Then and Now

Photo by Jerry Sintz
Rock eroded by water shaped dramatic landforms of Colorado Plateau.
Water is the primary agent of erosion on the Colorado Plateau, sculpting dramatic surface landforms.
The Colorado Plateau is indeed one of the world's premier natural showcases for earth history.  A canyon hiker can literally take a trip through time, descending through layers of rock representing progressively earlier geologic periods.  Scattered through these layers are fossil life forms such as tracks, shells, bones, leaves, and petrified wood – from single celled organisms to dinosaurs.  At the Cleveland-Lloyd Dinosaur Quarry in northeastern Utah, scientists have uncovered 18,000 bones from 70 different dinosaurs and other species.  Fossils of some of the earliest mammals, the size of small mice, have been found here in 225 million-year-old Triassic rock.  The remains of large amphibians and armored crocodile-like phytosaurs, some exceeding 9 m in length, have been found amidst petrified trees.  Dinosaurs from the Triassic to the Late Cretaceous (65 million years ago) have left their traces on the Plateau.  Fossil sea life from algal heads to “Loch Ness Monster”-like marine reptiles, sharks and squid-like creatures occur near ancient clam and oyster beds.  Ancient insects, archaic sabre-toothed mammals, and even mammoths, camels, and musk and shrub oxen once lived here.

Photo by Jerry Sintz
Different erosional patterns reflect variations in rock properties.
Variations in the properties of rock formations are reflected by different erosional patterns.

 Today, great ecological diversity is the Plateau’s signature; high alpine tundra, boreal forest, salt deserts and cryptobiotic crusts are each established here.  Climate, elevation, and soil combine to create many micro-zones that support an amazing range of plants and animals.  Six of the seven North American life zones are represented on the Plateau (only subtropical is absent), a rare biological occurrence.

Tope Elementary School
Microbiotic crusts composed of lichens, fungi, and algae
Microbiotic crusts, dark carpets of lichens, fungi, and algae, help to prevent erosion and act as seedbeds for desert plants.

Living creatures in this strange landscape are diverse and exceptional, largely because of the Plateau’s singular geologic features.  Some of the Plateau’s inhabitants are the collared lizard, jackrabbit, coyote, mule deer, bobcat, cougar, bighorn sheep, elk, quail, mourning doves, gray fox, and rattlesnakes.  Stellar jays, Clark’s nutcrackers, red-tailed hawks, falcons, and a myriad of small migratory birds soar the Plateau’s azure skies.  Water always attracts plant and animal life and in the arid West, rivers and small streams is their very lifeblood.  Cottonwoods trees and hanging gardens fringe the waterways that thread throughout the Plateau, hosting frogs, toads, snails, beavers, dragonflies, and fish.

Photo by Jerry Sintz
Deep, steep-walled canyons formed by rivers and uplift of Colorado Plateau
Deeply incised, steep-walled canyons were formed by the increased velocity of rivers as the Colorado Plateau was uplifted.

 

The plant life of the Plateau is equally varied and remarkable.  Low-lying rocky areas support desert shrubs like saltbush and greasewood.  Stands of pinyon pine and several species of juniper blanket much of the Plateau.  This “pygmy forest”, as it is often termed, is interspersed with grasses, herbs, and shrubs like sagebrush.  At higher elevations, forests of ponderosa pine, Douglas fir, lodgepole pine and aspen dominate.  Numerous species of cacti grow throughout the Plateau, and some of them are found nowhere else.  Even documenting their presence is challenging; some lay dormant, desiccated and nearly invisible until environmental conditions are just right.  Recently, six new cacti species were discovered on the Plateau.

Photo by Jerry Sintz
Narrow trail in "slot canyon" created in walls of amber sandstone
A hiker squeezes through a narrow trail bounded by steep, wavy walls of amber sandstone.

The sandstone formations of the Colorado Plateau hold a fascinating and unusual habitat: potholes.  Depressions ranging in size from no bigger than a teacup to a two-car garage, potholes dimple the sandstone.  They form through either chemical erosion along fault lines, or from the persistent erosion of cascading water.  They are filled by rainfall, which has no outlet except evaporation, and potholes are ephemeral.  In a sense, potholes are like temporary aquariums in the rock; they support a remarkable miniature ecosystem that is virtually independent of other ecosystems.  The lifeforms dependent upon potholes have adaptive strategies to cope with the unreliability of water.  Creatures like toads, birds, and insects can simply leave when the water dries up.  They are adapted to
Photo by Jerry Sintz
Photo of "hanging garden" where vegetation grows on damp rockface
Damp rockfaces host hanging gardens, miniature oases of lush vegetation.
reach maturity before leaving, and reproduce the next generation.  Some creatures produce a protective covering that conserves cell moisture.  Snails have a hard shell and they cover their operculum with a waxy sealant.  Mites manufacture a fatty substance that is excreted in a shingle-like fashion.  This covering slows water migration from their cells.  Snails and mites move to the deepest sediment where the temperature is coolest, and reduce their metabolic rate.  Fairy shrimp go with the flow (or lack of it!) and adapt to moisture loss.  Shrimp eggs can tolerate a loss of 92% of their cell moisture and still be viable when the potholes refill.  It seems they use a substitute sugar molecule (trehalose) that mimics the shape of a water molecule.  The sugar molecule maintains the shape of the cells’ components so that they will function again when rehydrated. 

 

 

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Last updated: 11-13-2009