Learn about the ecology of Grand Canyon National Park.
Although many people may only think of bare rock when they picture the Grand Canyon, this area is actually teeming with life. The Grand Canyon is both incredibly wide and deep, creating a variety of habitats. The extreme range of elevation in the Grand Canyon creates a variety of distinct ecosystems. Life here comes in many forms, from aquatic to desert to forest ecosystems. The great variation in elevation, and the movement of the river, foster a diversity of organisms in five major ecosystems, with different species thriving under particular conditions in each: The mixed conifer forest, the ponderosa pine forest, the pinyon juniper woodland, the desert scrub, and the riparian (river-edge), from highest to lowest elevation. Some organisms, such as the desert bighorn sheep, can travel between ecosystems to get the resources they need, others are confined to a narrow range based on available water and conditions.
Five Major Ecosystems
The mixed conifer forest or boreal forest ecosystem is only found at the highest elevation of the Grand Canyon, at the North Rim, from 8,200-9,200 feet. Deciduous trees (those that lose their leaves seasonally), like aspen, are common, as are evergreen trees (those that do not lose their leaves) like the Douglas fir and Englemann spruce. The trees provide a thick forest cover that shelters animals from intense storms. Small mammals like voles and squirrels are common, as are deer. This ecosystem receives more rain than any other in the Grand Canyon, and averages 11 feet of snow a year. Animals here are adapted to survive the cold, harsh winters. When spring comes, the snow melts and creates small lakes in the meadows, which eventually continue down the canyon to the other ecosystems.
The Ponderosa Pine Forest is found on both the South and North Rims, and is at the second highest elevations. It receives an average of five feet of snow each year, but in the summer is subjected to intense thunder storms that create flash floods. The tall trees are common targets of lightning, often causing forest fires that are a natural part of the ecosystem. The ponderosa pine tree is the most common plant here, and is relied upon by many creatures. The Kaibab squirrel is endemic (only found in one location) to this ecosystem, and relies on the pine cones for food and the branches for shelter. Sapsuckers are birds that create holes in the bark of the ponderosa pines, drawing insects to the sap, which then become the meal of the sapsucker. Small flowering plants called lupine are also common on the forest floor.
The Pinyon Juniper Woodland is found in sunny areas below the North and South rims that receive about half as much rainfall as the Ponderosa Pine Forest, and has drought-resistant plants, the most common being Utah juniper and pinyon pine. The leaves on the plants here have certain adaptations to capture and retain water, including being scale shaped or needle-like. The prickly pear cactus is also common, and provides an important source of hydration for many animals. The Pinyon Juniper Woodland is sometimes referred to as a pygmy woodland, because trees do not grow more than 20 feet tall. This ecosystem gets quite hot in the summer, with these short trees providing the only shade. Bobcats are common, as are small mammals like rabbits, mice, and skunks.
The Desert Scrub is the hottest and driest of the five Grand Canyon ecosystems. It is found only at very low elevation, and all the water from the higher elevations has evaporated before reaching here. The harsh conditions dictate the life that can live here. Plants are adapted to unpredictable and scarce water supply, and tend to be smaller, with agave being an exception. Cacti, sage, yucca, and blackbrush are common. Mammals like the bighorn sheep and mice are also found here, but the Desert Scrub ecosystem is home to most of the reptiles in the canyon, including the collared lizard.
The Riparian ecosystems are found along the banks of the Colorado River at the bottom of the canyon. Riparian ecosystems are also found by small creeks or springs around the Grand Canyon, independent of elevation. Their defining characteristic is a constant presence of water, so they are composed of lush vegetation, including cottonwood trees. While the smallest Grand Canyon ecosystem, the greatest biodiversity is supported here in both aquatic and terrestrial organisms. The ecosystem provides food, water, and shelter to support the lives of animals, including some that are also found in other areas of the canyon, like the skunk. Other animals, like the canyon tree frog, can only be found in the riparian zone because they depend on a constant supply of water.
Some species native to the Grand Canyon are threatened and are in danger of going extinct, due to a variety of factors. Changing environmental conditions and competition from other species can drive out native populations. Below are some endangered species of the Grand Canyon, including descriptions of the work scientists are doing to protect them.
The Humpback Chub is a large freshwater fish that only lives in the Colorado River basin. Scientists think that its population decline was likely caused by changes in the river due to the construction of the Glen Canyon Dam, as well as the introduction of nonnative fish like rainbow trout. Nonnative fish have fewer natural predators, and in this case are thought to outcompete the humpback chub for food resources. In recent years, however, the humpback chub population has been growing, in part because of efforts by the Grand Canyon Monitoring and Research Center (GCMRC). Teams of scientists have been carefully monitoring the population and potential risks, and have taken steps to increase humpback chub numbers. Some of these include removal of the rainbow trout and other nonnative species, breeding and reintroduction, and natural causes such as river warming due to drought.
Sentry milk-vetch is an endemic herb (it only lives at the Grand Canyon) that lives on the rim, in shallow cracks in the Kaibab limestone. It can be part of the Pinyon Pine forest. They grow to only about one inch tall, and have small, lavender flowers. This plant is particularly in danger of extinction due to its seed and germination cycle, that makes it rare for any seed to sprout. There are many pollinators that visit the early blooms of sentry milk-vetch, before any other plants are in bloom. These include mason bees, flies, and ants. Now, places where plants are growing are often marked off to avoid accidental harm. Since 2006, researchers have been working to protect and regrow the population through projects like monitoring soil conditions, hand-pollinating plants in greenhouses, and replanting them on the rim of the Grand Canyon.
The USGS Grand Canyon Monitoring and Research Center monitors Colorado River flow patterns and the important natural resources to inform government about practices to sustain management and conduct research on local ecology.
The USGS Southwest Biological Science Center conducts research on the terrestrial and aquatic ecosystems of the Southwest U.S.. This research can assist decision makers to best manage, conserve, and rehabilitate this part of the country and works closely with the GCMRC.