Performance Benchmark L.12.C.4
Students know the unique geologic, hydrologic, climatic, and biological characteristics of
Nevada’s bioregions. E/S
When one views the biodiversity in Nevada it is surprising to note that only ten states are richer
in their biodiversity. Nevada lists 3,872 species in the state, of which, plants are the most
common with 2,875 species. In addition Nevada ranks sixth in terms of endemic species (native
species not found elsewhere) with 309 species found only in Nevada. The chart below shows the
taxa where these endemic species are distributed.
Figure 1. Endemic species in Nevada by major taxa.
http://dcnr.nv.gov/nrp01/figure3-1.gif
To learn more on Nevada’s biodiversity go to
http://heritage.nv.gov/reports/scor2006.pdf
and, http://www.natureserve.org/Reports/stateofunions.pdf
At the same time Nevada has 25 species that are on the Federal List of Endangered. Of these are
17 fish which include a number of pupfish in Ash Meadows.
To find the names of endangered species in Nevada go to
http://heritage.nv.gov/endanged.htm
The names of additional threatened species in Nevada are found at
http://www.fws.gov/nevada/protected_species/nevada_species_list.html
A map of threatened and endangered species is located at
http://ecos.fws.gov/tess_public/StateListing.do?state=all
The question then becomes, why does Nevada have so much biodiversity relative to the other 50
states? Size alone is not the answer considering Texas the second largest state in area is second
in biodiversity, while the largest state, Alaska ranks 49 in biodiversity. Of more importance is the
geographical diversity in the state. Nevada lies in a geological region known as Basin and Range
(see map below) which is vast system of valleys and mountain ranges. This area extends east-
west from the Colorado Plateau to the Sierra Nevada, while stretching south from the borders of
Nevada, Washington and Idaho to the northern parts of Mexico.
Figure 2. Extent of the Basin and Range topography in North America.
http://en.wikipedia.org/wiki/Basin_and_Range
The Basin and Range topography has resulted from the extension or pulling apart of the earth’s
crust in this area of North America. This stretching occurred as the North American and Pacific
Plates have moved apart over of the last 20 million years. As a result Nevada has hundreds of
active extension faults which results in earthquake activity in most parts of Nevada. This
stretching and pulling has also produced some of the thinnest crust on the earth.
This pulling continues today and the direction of this pulling can be seen in the map below.
Figure 3. Direction of tectonic plate separate between the Pacific and North American Plates.
http://www.seismo.unr.edu/ftp/pub/louie/class/100/plate-tectonics.html
To learn more about plate tectonics, go to
http://www.ucmp.berkeley.edu/geology/tectonics.html
The formation of this geological feature has left Nevada with 314 named mountain ranges and
232 hydrographic basins. Twenty-five of these mountain ranges have peaks over 10,000 feet,
while elevations of the larger valleys range from 500 to 6,800 ft above sea level. As can be seen
in the map below these mountains and valleys tend to run in a north south direction. (Note in
Spanish “Nevada” means “snowcapped”.)
Figure 4. Topography of Nevada
http://geology.com/state-map/nevada.shtml
The photo of the Kingston Range from Emigrant Pass illustrates this system of mountains and
valleys.
Figure 5. Kingston Mountain Range.
http://commons.wikimedia.org/wiki/Image:Kingston_Range_from_Emigrant_Pass.jpg
In addition, climate changes over the past 10,000 years have produced many freshwater lakes
that have developed and disappeared along with other ecosystems such as mountain coniferous
forests and riparian zones. These changes have provided the raw materials for evolution and
natural selection. As ecosystems developed, disappeared or became isolated selective pressures
were place upon organisms to adapt or become extinct. Nevada biodiversity can therefore be
seen as a direct interaction between geological and biological evolution.
The geological action that created the basin and range topography also formed a number of
mountain peaks which are isolated by broad valleys which surround them. An example of this
“sky island” ecosystem can be seen in the Spring Mountains which is typically 20-30°F cooler
than the valleys below. In this sky island biologists have identified nearly 40 endemic species of
plants and animals including the Palmer chipmunk, the prairie falcon, spotted bat and blue
mountain butterfly. This is the highest number of endemic species of any mountain range in the
Great Basin. Ash Meadows (see below) is another example of this oasis of species in Armargosa
Valley. Ash Meadows contained numerous artesian springs that sustained isolated populations
of endemic fish. However, due to extensive ground water pumping many of the artesian springs
have stopped flowing, resulting in the extinction or near extinction of their endemic populations.
Ecoregions of Nevada
The Basin and Range topography of Nevada is divided into four ecoregions. These include the
Great Basin, Mojave Desert, Columbia Plateau and the Sierra Nevada.
Figure 6. Major Ecoregions of Nevada
http://dcnr.nv.gov/nrp01/bio01.htm
A more detailed map of Nevada ecoregions can be found at:
http://www.fws.gov/nevada/habitats/documents/na_eco.pdf
Great Basin Ecoregion
Figure 6. Central Basin Topography
http://www.fws.gov/nevada/habitats/ecoregions_html.htm
The middle of the state is dominated by the Great Basin ecoregion. In fact over 68% of Nevada
is covered by this ecoregion which also extents into Utah and parts of southern California. This
area is also part of the larger Great Basin Desert. Compared with other ecoregions in the U.S. the
Great Basin ranks fifth in total species richness. In the higher valleys sagebrush (The Nevada
State Flower) dominates, while creosote bush can be found in the lower valleys. Salt flats are
scattered throughout this region. In the lower mountain elevations single-leaf pinyon (One of
Nevada’s state trees) and juniper are common. In the widely dispersed higher mountainous
elevations conifers and woodlands occur. Most of the yearly precipitation falls in the winter. As
such the Great Basin is often termed a “cold desert”.
Figure 7a and 7b. Sagebrush
http://www.netstate.com/states/symb/flowers/images/sagebrush2.jpg
The Great Basin makes up a landlocked drainage basin. The rivers in this ecoregion have no
natural outlets to the ocean. It is bordered by the Rocky Mountains to the east and the Sierra
Nevada to the west.
Figure 8. North American Basins
http://en.wikipedia.org/wiki/Image:Basin_New.png
For a map showing the major rivers of Nevada go to:
http://geology.com/state-map/nevada.shtml
Mojave Ecoregion
The Mojave Desert (the smallest of the four major deserts found in the U.S.) is found in the
southern part of the state.
Figure 9. Deserts of North America
http://www.birdandhike.com/Veg/Veg_index.htm
In the Mojave Desert valleys are broader and mountain ranges are fewer as compared to the
Great Basin. The area around Las Vegas illustrates the variety of life zones of the Mojave Desert.
These life zones can be seen in Figure 15 below. In the Lower Sonoran life zone (below 4000 ft)
creosote bush and White Bursage are the dominant plants with Mojave Yucca found at higher
elevations. This area is also home to the endangered Desert Tortoise. The non-endemic red
brome grass can be common, especially in high rainfall years. Temperatures range in excess of
110oF in the summer to 25oF in the winter.
As one moves up the slopes (from 4000 to 5000 ft) one enters the Upper Sonoran life zone. Here
creosote bush, Joshua Tree (which is the indicator plant for this desert, as it is naturally found no
place else in the world), various yucca and a mixture of shrub and cacti are found. One can find
the Big Horned Sheep (The Nevada State Animal) in this zone.
Figure 10: Creosote bush
http://www.americansouthwest.net/slot_canyons/photographs700/creosotebush.jpg
To learn more about the creosote bush, go to
http://www.birdandhike.com/Veg/Species/Shrubs/Creosote/Larr-trid.htm
Figure 11. Joshua Tree
http://i1.trekearth.com/photos/8168/joshua_tree.jpg
To learn more about the Joshua Tree, go to
http://www.birdandhike.com/Veg/Species/Yucca/Y_brev/Y_brev.htm
As one moves out of the Mojave Desert into lower mountainous elevations (5500-7500 ft)
pinyon pine and juniper can be found. Pines and firs are limited to higher elevations sometimes
with sages and bunchgrasses. At lower elevations one can find Blackbrush and Rabbit Brush.
Throughout this region numerous cacti such as Prickly Pear, Hedgehog Cactus and various
varieties of cholla can be found. Generally less than 5 inches of precipitation falls during the
summer monsoons and in winter. During the winter several feet of snow can sometimes occur at
the highest elevations.
Figure 12. Pinyon Pine in the Sheep Range in southern Nevada
http://www.birdandhike.com/Veg/Species/Conifers/Pine_Pinyon1/Pine_Pinyon1.htm
To learn more about pinyon pine trees, go to
http://www.birdandhike.com/Veg/Species/Conifers/Pine_Pinyon1/Pine_Pinyon1.htm
In the higher mountainous (over 7000 ft) areas within the Mojave Desert ponderosa pine become
the dominate vegetation type. Other plants found in this area include sagebrush, Manzanita,
shrub Live Oak and Quaking Aspens.
Figure 13. Mary Jane trailhead, Kyle Canon, Mt. Charleston
http://www.birdandhike.com/Veg/HabType/YellowPine/YellowPine.htm
As move up mountains beyond 8000 ft conifers continue to change until one reaches the alpine
tundra. If you were to climb some of the higher elevation trails in Mt Charleston you would see
white fir and Bristlecone Pine (Nevada’s second state tree). In the alpine tundra sedges and
bunchgrasses would be seen.
Figure 14. Alpine Life Zone on Mt. Charleston
http://www.birdandhike.com/Veg/Veg_index.htm
To learn more about the vegetation zones around Las Vegas, visit
http://www.birdandhike.com/Veg/Veg_index.htm
The idea of life zones was developed at the end of the 19th century by C. Hart Merriam, who was
the first director of the U.S. Biological Survey. This scheme of life zones was developed in
studies of the Grand Canyon and nearby San Francisco Mts. These life zones were developed to
identify belts of vegetation and animals. They were expressed with increases in altitude. In
addition annual totals in precipitation were considered.
To learn more about the concept of life zones, go to
http://www.cpluhna.nau.edu/Biota/merriam.htm
And, http://www.runet.edu/~swoodwar/CLASSES/GEOG235/lifezone/merriam.html
Figure 15. Life Zones of Mt. Charleston and the Las Vegas Valley.
http://www.birdandhike.com/Veg/Veg_index.htm
Columbia Plateau
Figure 16. The Columbia Plateau Ecoregion, Jarbidge Mts.
www.fws.gov/nevada/habitats/ecoregions_html.htm
In the northern part of Nevada the Great Basin Desert mixes in and joins the Columbia Plateau
ecoregion. Geologically this region contains tablelands, intermountain basins, dissected lava
plains and scattered mountains. With a cooler climate and volcanic soils a sagebrush steppe
ecosystem prevails containing numerous perennial grasses. Near the Idaho border open prairie is
evident with such large mammals as Mule Deer, Antelope and Elk being found here. Juniper
woodlands and mountain mahogany tend to replace the salt desert scrub and pinyon woodlands
of the Great Basin at lower elevations. At higher elevations Douglas-fir and aspen are common.
Sierra Nevada
Figure 17. Jeffrey Pines
The Sierra Nevada ecoregion is found near Carson City and Reno. Lake Tahoe lies on the border
between Nevada and California. Vegetation is mainly mixed conifer consisting of white fire and
lodgepole pine on western slopes and Jeffery pine and lodgepole pine on eastern slopes. In
higher elevations red fir, mountain hemlock and western white pine are seen.
These higher elevations receive more precipitation and are the source of rivers like the Truckee
and Walker. These rivers provide water to lower elevations in the Great Basin. There are many
mountain lakes and meadow/riparian areas. At the highest elevations alpine conditions exist.
Other areas
Within these four major ecoregions several other micro-regions can be identified including
riparian zones and wetlands. In each case these add to the biodiversity of Nevada. Riparian zones
are quite diverse and include short or tall grasses, shrubs and trees including willow, cottonwood
or aspen.
Figure 18. Riparian Habitat
http://dcnr.nv.gov/nrp01/bio08.htm
One of the unique micro-regions in Nevada is its numerous wetlands. These include thousands of
springs that are found throughout Nevada. A number of these springs are “left-overs” from the
last ice age. As the last North American Ice Age was in retreat 10,000 years ago, numerous
isolated springs were created. Of particular interest is Ash Meadows in the Armargosa Valley of
southern Nye County. Today Ash Meadows supports 24 species of plants and animals (including
the pupfish) that are found nowhere else in the world. This area represents the highest
concentration of indigenous species in the United States and second greatest in North America.
Figure 19. Ash Meadows
http://ndep.nv.gov/admin/ash.jpg
Figure 20. Desert Pupfish
http://sciences.unlv.edu/desertsurvivors/Pages/episode4.htm
Figure 21. Pupfish Distribution in North America
http://sciences.unlv.edu/desertsurvivors/images/episodepictures/e4/distribution.jpg
To learn more about Ash Meadows visit
http://www.fws.gov/desertcomplex/ashmeadows/
To learn more about the desert pupfish, go to
http://sciences.unlv.edu/desertsurvivors/Pages/episode4.htm
Other useful information
Figure 22. Precipitation Map of Nevada
http://www.ocs.orst.edu/pub/maps/Precipitation/Total/States/NV/nv.gif
Figure 23. Relief Map of Nevada
http://www.netstate.com/states/geography/mapcom/nv_mapscom.htm
Performance Benchmark L.12.C.4
Students know the unique geologic, hydrologic, climatic, and biological characteristics of
Nevada’s bioregions. E/S
Common misconceptions associated with this benchmark
1. Students mistakenly believe that there is little biodiversity in Nevada.
Biological surveys of United States have shown that Nevada shows more biodiversity than most
states. In fact only ten states show more biodiversity than Nevada and it ranks sixth in terms of
endemic species. At present 309 species are located in Nevada and nowhere else. Of particular
interest is the desert pupfish located in southern Nevada.
To learn more on Nevada’s biodiversity, go to
http://heritage.nv.gov/reports/scor2006.pdf and
(http://www.natureserve.org/Reports/stateofunions.pdf)
For a checklist of wildlife in Nevada visit
http://heritage.nv.gov/spelists.htm
Images of Nevada’s wildlife can be found at
http://heritage.nv.gov/images.htm#vascplants
2. Students incorrectly believe that Nevada shows very little variation in plant life and is
mostly desert.
While a large percentage of Nevada can be classified as desert the diversity of plant life has been
greatly increased because of Nevada’s location in the Basin and Range geographical region. This
geologically diverse region of mountains and valleys has produced many ecoregions within
Nevada. As a result of isolation and time 3,872 species (including 2,875 species of plants) are
now found in Nevada.
The four major ecoregions are subdivided into smaller ecological regions as can be seen in the
map below. Each of these major ecoregions should not be viewed as one region, but seen as
“micro regions” which are often sub-divided from one another. This isolation is important in the
evolution of species.
Refer to L.12.D.5 for a discussion on how isolation is important in the evolution of species.
Figure 24. Ecoregions of Nevada
http://www.fws.gov/nevada/habitats/documents/na_eco.pdf
For a detailed discussion of vegetation in the Great Basin, go to
http://www.fs.fed.us/pnw/lagrande/sagebrush/docs/Gr%20Basin%20PDF%20Sept03/Ch03_Veg
etation_Sept03.pdf
3. Students confuse the Great Basin Desert with the Basin and Range geographical region.
The Basin and Range geographical region is a broad area in the western part of the United States
(Refer to Figure 2) of valleys and mountains ranges. This area has resulted from tectonic actions
of the Pacific and North America Plates. Within this geographical area are several large deserts
including the Great Basin Desert (Refer to Figure 9), sometimes called the Great Basin. The
Great Basin is an inland drainage basin located in the northern region of the Basin and Range
geographical region and centered in Nevada. This basin also extends into surrounding states of
California, Oregon, Idaho and Utah.
Performance Benchmark L.12.C.4
Students know the unique geologic, hydrologic, climatic, and biological characteristics of
Nevada’s bioregions. E/S
Sample Questions
1. Which of the following statements most accurately described the biodiversity in the state of
Nevada?
a) Compared to most states Nevada shows the least biodiversity.
b) Compared to most states Nevada shows the most biodiversity.
c) Compared to most states Nevada ranks near the top ten in biodiversity.
d) Compared to most states Nevada rank in the bottom ten in biodiversity.
2. The area with the highest concentration of endemic species in the United States is
a) The wetlands in Ash Meadows
b) The Florida Everglades
c) The Great Plains
d) The Mississippi River Delta
3. The most common type of endemic species in Nevada belong to which taxa listed below?
a) Fish
b) Plants
c) Reptiles
d) Birds
4. You would know that you are located in the Mojave Desert if you were surround by
a) Saltbush
b) Sagebrush
c) Joshua trees
d) Pinyon Pine trees
Performance Benchmark L.12.C.4
Students know the unique geologic, hydrologic, climatic, and biological characteristics of
Nevada’s bioregions. E/S
Answers to Sample Test Questions
1.
2.
3.
4.
(c)
(a)
(b)
(c)
Performance Benchmark L.12.C.4
Students know the unique geologic, hydrologic, climatic, and biological characteristics of
Nevada’s bioregions. E/S
Intervention strategies and resources
The following is a list of intervention strategies and resources that will facilitate student
understanding of this benchmark.
1. Plate tectonics that shaped the SW region
The geography of Nevada is a major reason for the biodiversity of the state. The forces that
caused those changes are still at work today.
To learn more about plate tectonics, go to
http://www.ucmp.berkeley.edu/geology/tectonics.html
2. Geology of the Basin and Range
The Basin and Range topography is the dominate topography of the State of Nevada. Its “Sky
islands” mountains, and desolate valleys help to isolate species and provide the raw materials
for evolution and speciation to occur.
To learn more about the geology of the Basin and Range one might investigate John
McPhee’s book by the same name.
An example of such speciation is the Joshua Tree. To learn more about the Joshua Tree, go to
http://www.birdandhike.com/Veg/Species/Yucca/Y_brev/Y_brev.htm
3. Vegetation Zones
Vegetation zones are used to group plants and animals found at given elevations and climate
zones. It is useful to refer to these zones when discussing the endemic species of Nevada.
To learn more about the vegetation zones around Las Vegas, go to
http://www.birdandhike.com/Veg/Veg_index.htm
http://www.cpluhna.nau.edu/Biota/merriam.htm
and, http://www.runet.edu/~swoodwar/CLASSES/GEOG235/lifezone/merriam.html
For a detailed discussion of vegetation in the Great Basin visit
http://www.fs.fed.us/pnw/lagrande/sagebrush/docs/Gr%20Basin%20PDF%20Sept03/Ch03_
Vegetation_Sept03.pdf
Ash Meadows is one of the most diverse micro-regions in the Untied States. Nevada’s great
biodiversity can be brought into almost any discussion of the various Taxa that are required
to be taught. Providing “local” examples from our state’s diverse species is an excellent way
to help students develop a sense of community.
Detailed information about Ash Meadows can be found at
http://www.fws.gov/desertcomplex/ashmeadows/
To learn more about the desert pupfish, go to
http://sciences.unlv.edu/desertsurvivors/Pages/episode4.htm
To further explore Nevada’s biodiversity visit
http://heritage.nv.gov/reports/scor2006.pdf and
and, http://www.natureserve.org/Reports/stateofunions.pdf
For a checklist of wildlife in Nevada, go to
http://heritage.nv.gov/spelists.htm
Images of Nevada’s wildlife can be accessed at
http://heritage.nv.gov/images.htm#vascplants