Yellowstone Handbook 2019Greater Yellowstone Ecosystem |
Yellowstone Resources and Issues Handbook. Published by the National Park Service (NPS).
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Greater Yellowstone Ecosystem
At 3,437.5 square miles (8,903 km2),Yellowstone
National Park forms the core of the Greater
Yellowstone Ecosystem—one of the largest nearly
intact temperate-zone ecosystems on Earth. Greater
Yellowstone’s diversity of natural wealth includes
the hydrothermal features, wildlife, vegetation, lakes,
and geologic wonders like the Grand Canyon of the
Yellowstone River.
Heart of an Ecosystem
Yellowstone National Park was established in 1872
primarily to protect geothermal areas that contain
about half the world’s active geysers. At that time, the
natural state of the park was largely taken for granted.
As development throughout the West increased,
the 2.2 million acres (8,903 km2) of habitat that now
compose Yellowstone National Park became an
important sanctuary for the largest concentration of
wildlife in the lower 48 states.
The abundance and distribution of these animal
species depend on their interactions with each other
and on the quality of their habitats, which in turn
is the result of thousands of years of volcanic activity, forest fires, changes in climate, and more recent
natural and human influences. Most of the park
is above 7,500 feet (2,286 m) in elevation and underlain by volcanic bedrock. The terrain is covered
with snow for much of the year and supports forests
Quick Facts
Space and Ownership
•
12–22 million acres; 18,750–
34,375 square miles (Sizes,
boundaries, and descriptions of any
ecosystem can vary.)
•
States: Wyoming, Montana, Idaho
•
Encompasses state lands, two
national parks, portions of five
national forests, three national
wildlife refuges, Bureau of Land
Management holdings, private and
tribal lands.
•
Managed by state governments,
federal government, tribal
governments, and private
individuals
Wildlife
•
One of the largest elk herds in
North America
Management Challenges
•
Climate change
•
Invasive species
•
Managing an ecosystem across
political boundaries
•
Land use change
•
In Yellowstone:
•
Largest free-roaming, wild herd of
bison in United States
•
One of few grizzly populations in
contiguous United States
−− Grizzly bear management
•
Rare sightings of wolverine and
lynx
−− High visitation
−− Bison management
−− Native fish conservation
Greater Yellowstone Ecosystem 53
E CO S YS T E M
The Greater Yellowstone Ecosystem, with Yellowstone at its core, is one of the largest nearly intact temperatezone ecosystems on Earth.
the Yellowstone Plateau itself is a result of uplift due
to hot-spot volcanism. Today’s landforms even influence the weather, channeling westerly storm systems
onto the plateau where they drop large amounts of
snow.
The volcanic rhyolites and tuffs of the Yellowstone
Influence of Geology
Caldera are rich in quartz and potassium feldspar,
Geological characteristics form the foundation of
which form nutrient-poor soils. Thus, areas of the
an ecosystem. In Yellowstone, the interplay between
park underlain by rhyolites and tuffs generally are
volcanic, hydrothermal and glacial processes, and
characterized by extensive stands of lodgepole pine,
the distribution of flora and fauna, are intricate. The
which are drought-tolerant and have shallow roots
topography of the land from southern Idaho norththat take advantage of the nutrients in the soil.
east to Yellowstone probably results from millions of
In contrast, andesitic volcanic rocks that underlie
years of hot-spot influence. Some scientists believe
the Absaroka Mountains
Billings !
are rich in calcium, magLivingston
! Bozeman
!
nesium, and iron. These
minerals weather into
M O N T A N A
soils that can store more
water and provide better
Custer
Gallatin
Red Lodge
nutrients than rhyolitic
National Forest
!
National Forest
soils. These soils support
Gardiner
Cooke City
!
!
more vegetation, which
Beaverhead-Deerlodge
adds organic matter and
Yellowstone
National Forest
National Park
enriches the soil. You can
Red Rock Lakes
see the result when you
!
West Yellowstone
National Wildlife Refuge
drive over Dunraven Pass
! Cody
Shoshone
National Forest
or through other areas of
the park with Absaroka
Caribou-Targhee
National Forest
rocks. They have a more
diverse flora, including
John D. Rockefeller, Jr.
Memorial Parkway
mixed forests interCamas National
spersed with meadows.
Wildlife Refuge
Grand Teton
Rexburg
!
National Park
Lake sediments deposited
W Y O M I N G
during glacial periods,
National Elk
such as those underlying
Refuge
!
! Idaho Falls
Jackson
Hayden Valley, form clay
Bridger-Teton
soils that allow meadow
National Forest
I D AH O
communities to outcompete trees for water.
Grays Lake National
Wildlife Refuge
The patches of lodgepole
pines in Hayden Valley
Pocatello
!
grow in areas of rhyolite
rock outcrops.
Because of the influBureau of Land Management
Continental Divide
ence
rock types, sediFish and Wildlife Service
Rivers and Lakes
ments, and topography
Forest Service
0
50 Kilometers
State Boundary
North
National Park Service
have on plant distribuState
Land
0
50 Miles
tion, some scientists
theorize that geology
The Greater Yellowstone Ecosystem. Description of an ecosystem’s size, boundaries,
also influences wildlife
and characteristics can vary greatly.
E C O S YS T E M
dominated by lodgepole pine and interspersed with
alpine meadows. Sagebrush steppe and grasslands on
the park’s lower-elevation ranges provide essential
winter forage for elk, bison, and bighorn sheep.
l
54
Yellowstone Resources and Issues Handbook, 2019
distribution and movement. Whitebark pine nuts are
an important food source for grizzly bears during autumn. The bears migrate to whitebark pine areas such
as the andesitic volcanic terrain of Mount Washburn.
Grazing animals such as elk and bison favor the
park’s grasslands, which grow best in soils formed by
sediments in valleys such as Hayden and Lamar. The
many hydrothermal areas of the park, where grasses
and other food remain uncovered by snow, provide
sustenance for animals during winter.
The Clean Air Act Amendments of 1977 designated
Yellowstone and Grand Teton among the 156 national parks and wilderness areas that are Class I airsheds, requiring the most stringent air-quality protection within and around their boundaries. Yellowstone
and Grand Teton are in compliance with federal air
quality standards for human health. However, airquality trends may be affecting other aspects of the
ecosystem. Even at relatively low levels, such as those
found in the Greater Yellowstone Ecosystem, air pollution and the subsequent deposition of pollutants
in water and soil can leach nutrients from the Earth,
injure vegetation, and acidify and over-fertilize lakes
and streams.
The thin soils, sparse vegetation, short growing
seasons, and snow-based water supply of these high
elevation areas limit the amount of nitrogen that plants
can effectively use. These conditions make the area
more vulnerable to the effects of acidification and
nutrient enrichment from nitrogen deposition. For
example, nitrogen in precipitation has increased at
many western sites as a result of fertilizer use and feedlots. Although nitrogen is a nutrient needed for plant
growth, too much nitrogen disrupts native plant communities that are adapted to low-nitrogen conditions;
high nitrogen levels can advance the spread of nonnative species that increase fire frequency. Acidification
of high-alpine lakes from sulfur and nitrogen deposition can cause the loss of macroinvertebrates and fish.
Long-term changes in the composition of algae in
several alpine lakes in Yellowstone and Grand Teton
are correlated with increased nitrogen.
Naturally occurring ozone in the upper atmosphere protects life by absorbing the sun’s ultraviolet rays, while ground-level ozone is a pollutant
that forms when nitrogen oxides from vehicles,
power plants, and other sources combine with
volatile organic compounds. Ozone concentrations
Sources of Particulate Matter
The largest source of particulate matter in Greater
Yellowstone is smoke from wildland fires, which is
considered part of the area’s “natural background
conditions” and is taken into consideration in establishing the threshold for “good” visibility. Emissions
from prescribed fires have been relatively insignificant. Because of prevailing winds, Wyoming oil and
gas development has not had a detectable effect on
air quality in Yellowstone.
Soundscapes
The Greater Yellowstone Ecosystem has many biological sounds with important ecological functions
for reproduction and survival. Birds, mammals, amphibians, and insects often need to hear or produce
sounds to attract mates, detect predators, find prey,
and/or defend territories. The occurrence of sounds
in a particular area forms the soundscape.
The natural soundscape of the Greater
Yellowstone Ecosystem delights visitors during the
fall elk rut, during birds’ spring choruses, along
rushing streams, and in the still and profoundly quiet
days and nights of winter. Natural soundscapes are a
resource and are protected by National Park Service
policies. Many park visitors come to national parks
to enjoy serenity and solitude and expect to hear
sounds of nature. Sounds associated with human
activity, including road traffic, aircraft, and snowmobiles, often impact these natural soundscapes and are
a source of growing concern. Aircraft noise, which
is the most widespread human-caused sound in the
park, is heard on average for less than 10 percent of
the day. Yellowstone and Grand Teton national parks
initiated a soundscape monitoring program in 2003.
More Information
Ambrose, S, and S. Burson. 2004. Soundscape studies in
National Parks. George Wright Forum 21:1 29–38.
National Park Service Air Resources Division: www.nature.
nps.gov/air.
Greater Yellowstone Ecosystem 55
E CO S YS T E M
Air Quality
in Yellowstone typically peak in spring rather than
summer, indicating that human influences are less
significant than changes in atmospheric circulation
and lengthening daylight. Nonetheless, in addition to
potentially causing respiratory problems in people,
ozone levels during the growing season may be high
enough to prevent sensitive species, such as aspen,
from reaching full growth potential.
E C O S YS T E M
Yellowstone waters provide essential moisture to much of the American West and water resources provide
recreational opportunities, plant and wildlife habitat, and scenic vistas.
Water
The water that flows through Yellowstone National
Park and the Greater Yellowstone Ecosystem (GYE)
is a vital national resource. The headwaters of seven
great rivers are located in the GYE, and flow from
the Continental Divide through communities across
the nation on their way to the Pacific Ocean, the Gulf
of California, and the Gulf of Mexico. Precipitation
(rain and snow) in the mountains and plateaus of the
Northern Rockies flows through stream and river
networks to provide essential moisture to much of
the American West; and water resources provide
recreational opportunities, plant and wildlife habitat,
and scenic vistas.
Water also drives the complex geothermal activity in the region and fuels the largest collection of
geysers on Earth. Precipitation and groundwater
seep down into geothermal “plumbing” over days,
and millennia, to be superheated by the Yellowstone
Volcano and rise to the surface in the form of hot
springs, geysers, mudpots, and fumaroles.
Yellowstone contains some of the most significant,
Waters of Yellowstone
near-pristine aquatic ecosystems found in the
United States. More than 600 lakes and ponds
comprise approximately 107,000 surface acres in
Yellowstone—94 percent of which can be attributed
to Yellowstone, Lewis, Shoshone, and Heart lakes.
Some 1,000 rivers and streams make up approximately 2,500 miles of running water. Thousands of
small wetlands—habitats that are intermittently wet
and dry—make up a small (approximately 3%) fraction of the Yellowstone landscape.
Lakes
Yellowstone’s inland lakes are essential aquatic habitat for resident species. They are largely protected
from many of the environmental stresses to which
waters outside the park boundaries may be victim.
These lakes maintain freshwater biodiversity, support
elaborate food webs, and underpin plant and animal
communities. Understanding the complexities of
Yellowstone’s lake ecosystems allows park managers
to successfully conserve Yellowstone’s lake resources
in the face of nonnative invasive species, climate
change, and pollution.
Yellowstone Lake
Area of Yellowstone National Park
3,472 mi2
(8,991 km2)
Water surface area2,3
~5% of park area
Number of named lakes
150
1
Yellowstone Lake is the largest high-elevation lake
(above 7,000 ft) in North America, covering up to 139
square miles, with an average depth of 138 feet, and
just over 12,000,000 acre-feet of water. The lake is
covered by ice from mid-December to May or June.
Surface area of named lakes
24.7 mi2 (63.9 km2)
Number of lakes with fish2
~45
Number of named streams3
278
Total stream length3
2,172.52 mi
(3,496,329 m)
•
Elevation: 7,731 feet (2,357 m)
•
Surface area: 131.8–135.9 mi2 (341–352 km2)
~200
•
Perimeter (Shoreline): 141 miles (227 km)
•
Deepest point is due east of Stevenson Island at 430
feet (131 m)
1
Number of streams with fish2
Yellowstone Spatial Analysis Center data.
Varley and Schullery 1998.
3
GRYN Water Quality Report 2009.
1
2
56
Yellowstone Resources and Issues Handbook, 2019
Yellowstone Lake Quick Facts
So
da
B
utte C
r
r d ner R iver
i ver
Ga
eR
Rive
Firehole River
ID
ws
ton
r
Gi b b o n
Madison River
MT
lo
Yel
Shoshone
Lake
Lewis
Lake
West Yellowstone
Lake
Thumb
Heart
Lake
Snake
R
Major watersheds
Shoshone River
Missouri River
E CO S YS T E M
Lewis Lake is fed by the Lewis River and other tributaries. Shoshone Lake, the park’s second largest lake,
is located at the head of the Lewis River southwest
of West Thumb. Shoshone Lake is a valuable wilderness resource. Only accessible by foot, or by boat
through the Lewis River Channel, one of the park's
amazing geyser basins lies near the northwest shore.
Shoshone Lake is 205 feet at its maximum depth, has
an area of 8,050 acres, and contains lake trout, brown
trout (Salmo trutta), and Utah chub (Gila atraria).
Originally, Shoshone Lake was barren of fish owing
to waterfalls on the Lewis River. The two types of
r
MT
WY
ive
ar R
Lewis and Shoshone Lakes
eek
L am
Entering Yellowstone Lake are more than 141
tributaries, but only one river. The Yellowstone River,
which enters at the south end of the southeast arm,
dominates the inflow of water and sediment flows
out. The only outlet of the lake is at Fishing Bridge,
where the Yellowstone River flows north and discharges 2,000–9,000 cubic feet per second.
Powerful geologic processes in Yellowstone
National Park have contributed to the unusual shape
of Yellowstone Lake, which straddles the southeast
margin of the Yellowstone caldera. A smaller calderaforming event about 174,000 years ago, comparable
in size to Crater Lake, Oregon, created the West
Thumb basin. Several significant glacial advances and
recessions continued to shape the lake and overlapped the volcanic events. Glacial scour deepened
the central basin of the lake and the faulted south
and southeast arms. More recent dynamic processes
shaping Yellowstone Lake include currently active
fault systems, development of a series of postglacial
shoreline terraces, and postglacial hydrothermalexplosion events, which created the Mary Bay crater
complex and other craters. (See “Yellowstone Lake
Geology” in chapter four, for more information.)
Many of the area’s 1,000 to 3,000 annual earthquakes
occur under Yellowstone Lake, causing uplift and
subsidence events which continually reshape the
shoreline of the lake.
Yellowstone Lake is also the site of one of the most
extensive conservation efforts in the National Park
Service. Lake trout (Salvelinus namaycush) which
were illegally introduced to Yellowstone Lake have
jeopardized the survival of the native population of
cutthroat trout (Oncorhynchus clarkii bouvieri). See
“Native Fish Species” and “Lake Trout” in the wildlife chapter for more information.
i v er
0
0
10 km
10 mi
Snake River
Yellowstone River
trout were planted beginning in 1890, and the Utah
chub was apparently introduced by bait fishermen.
This large lake is the source of the Lewis River, which
flows to the Pacific Ocean via the Snake River system. The U.S. Fish and Wildlife Service believes that
Shoshone Lake may be the largest lake in the lower
48 states that cannot be reached by road.
Heart Lake
Heart Lake is located at the south end of the park
near the base of Mt. Sheridan. It sits in prime bear
habitat, and there are several thermal areas along the
northwest shore.
Rivers
Watersheds, or drainage basins, represent the surface area that contributes runoff to a particular river.
The boundaries of a watershed are ridges or elevated
areas which determine the direction surface water
will flow. Any rain or snow that falls within the watershed will flow downstream to the basin’s mouth,
unless it is removed from the flow by evaporation,
freezing, absorption as groundwater, or diversion for
human use.
Yellowstone River
The Yellowstone River is 671 miles long. It is the
longest undammed river in the lower 48 states.
The headwaters of the Yellowstone are outside the
Greater Yellowstone Ecosystem 57
corner of the park and flows to the
Missouri River. The Gardner flows
into the Yellowstone first, joining near
Rattlesnake Butte at the north entrance
to the park.
E C O S YS T E M
Snake River
Yellowstone River delta
southeast park boundary on Younts Peak (Wyoming)
and flows into Yellowstone Lake. It leaves the lake
at Fishing Bridge, and continues north-northwest
until it leaves the park near Gardiner, Montana. The
Yellowstone River continues north and east through
Montana and joins the Missouri River just across the
North Dakota state line. Its watershed drains onethird of the state of Montana. It carves out the Grand
Canyon of the Yellowstone in the middle of the park
and runs over the Upper and Lower Falls and is
home to Yellowstone cutthroat trout.
The Yellowstone River is among the top recreational river destinations in the US and provides opportunities for boating and fishing enthusiasts, birders, and for recreation. Additionally, the Yellowstone
River serves many downstream communities (e.g.,
Billings, Montana) and is recognized regionally and
nationally for economic importance to agriculture,
industry, and municipalities.
Lamar River
The Lamar River originates on the east side of the park.
Park boundaries were adjusted in 1929 to include the
entire Lamar watershed in order to protect this major
tributary of the Yellowstone River. The Lamar River
is joined by Soda Butte Creek as it flows across the
northern range to the outflow of Yellowstone Lake.
The Lamar River Valley is home to wild pronghorn,
bison rutting, bear habitat, the most consistent viewing
of wild wolves in the world, and first-rate fly fishing.
Gardner River
The Gardner River originates in the northwest
58
Yellowstone Resources and Issues Handbook, 2019
The Snake River—a major tributary
of the Columbia River—originates in
Yellowstone National Park, and then
turns south, passing through the John
D. Rockefeller, Jr., Memorial Parkway
into Grand Teton National Park. The
river flows through Idaho and joins
the Columbia River in Washington.
The Snake River is 1,040 miles long
(1,674 km); 42 miles (68 km) of it are
in Yellowstone National Park. The
river feeds Jackson Lake—a natural lake augmented
by a dam, resulting in regulated downstream flows
since 1907.
Visitors enjoy a multitude of recreational opportunities on the river such as rafting, fishing, and photography. The river is home to a wide variety of riparian
and aquatic species, including the native Yellowstone
cutthroat trout and an endemic variety, the Snake
River fine-spotted cutthroat trout (Oncorhynchus
clarkii behnkei). The 2009 Snake River Headwaters
Legacy Act designated the river above Jackson Lake as
a Wild and Scenic River. The Lewis River is a tributary
of the Snake River.
Firehole River
Home to several species of trout, the Firehole River
is a favored fly fishing spot. Most of the outflow from
the park’s geyser basins empties into the Firehole
River causing it to be warmer with larger concentrations of dissolved minerals (chemically richer) than
FREQUENTLY ASKED QUESTION
Does the Missouri River begin here?
No, but its three tributaries begin in the greater
Yellowstone area. The Jefferson River begins in the
Centennial Mountains, west of the park. The Madison
River forms inside the park at Madison Junction, where
the Gibbon and Firehole rivers join. The Gallatin River also
begins inside the park north of the Madison River. It flows
north through Gallatin Canyon and across the Gallatin
Valley, joining the Madison and Jefferson rivers at Three
Forks, Montana, to form the Missouri River.
other watersheds. The Gibbon and Firehole rivers
join to form the Madison River. The Madison flows to
Hebgen Lake, joins the Jefferson River and eventually
the Missouri River on its way to the Gulf of Mexico.
Water Quality
The quality of the nation’s waters is protected by
laws and policy at local, state, and federal levels. To
understand and maintain or improve water quality and aquatic ecosystems, resource managers take
inventory and actively monitor water resources
throughout the region. Water quality in a national
park may reflect activities taking place upstream of
the park’s surface waters as well as within the park.
The water quality in Grand Teton and Yellowstone
national parks, where most of the watersheds originate on federally protected land, is generally very
A volunteer collects a water sample at Soda Butte
Creek. Collection of water quality data has continued
at fixed sites since 2002.
Long-term Water Quality Monitoring
Monitoring water quality continues to be a high priority for Yellowstone, with standardized data collected
at fixed sites since 2002. This long-term data is used to
evaluate overall ecosystem health, ascertain impacts of
potential stressors (e.g., upstream impacts from legacy
mines), identify changes that may be associated with
water quality degradation, and guide resource management decisions related to water quality.
The characteristics of Yellowstone’s surface
waters are influenced by season, elevation, precipitation, and weather. Some waters are also affected by
the park’s geothermal features, generally resulting
in warmer temperatures and higher dissolved ion
concentrations. Park staff monitors water temperature, dissolved oxygen, pH, specific conductance,
turbidity, and total suspended solids at 11 stream sites
and 7 sites on Yellowstone Lake. Staff collect chemical parameters from 10 stream sites, including anions,
cations, and nutrients.
Most waters in Yellowstone meet or surpass national and state water quality standards. Geothermal
influence on some park waters can result in failure
to meet state drinking or recreational water quality
standards. For example, arsenic levels in the Madison
River at West Yellowstone exceeded the State of
Montana’s criteria on most sampling occasions.
Arsenic in the Madison River is likely naturally occurring from geothermal geology in the watershed.
Park staff also monitor three sites on the park
boundary where stream segments in the Yellowstone
River drainage have been listed as impaired by the
State of Montana.
Greater Yellowstone Ecosystem 59
E CO S YS T E M
Fishing on the Firehole River.
high. However, it is vulnerable to impacts such as
road construction, recreational activities, and deposition from atmospheric pollutants.
All Yellowstone waters are classified as
Outstanding National Resource Waters, which receive the highest level of protection for surface waters
under the Clean Water Act. Because of the relatively
pristine nature of the park’s surface waters, they are
often used to establish reference conditions for the
northern Rocky Mountain region. Although most of
the park’s watersheds originate within its boundaries
and are minimally affected by human activities, they
are vulnerable to impacts such as road construction,
dewatering, atmospheric deposition, sewage spills,
climate change, and runoff from mining sites outside
park boundaries.
Reese Creek
E C O S YS T E M
Irrigation by landowners north of the park has often
reduced the lowermost reach of the stream during
mid-summer and fall. The water flow becomes unsuitable for sustaining native trout and overall biological integrity. The adjudicated water rights stipulate
that the creek is to have a minimum flow of 1.306 ft3/
sec from April 15 to October 15. A stakeholder group
of federal agencies, private citizens, and conservation
organizations are working together on projects to
increase the flows in the main channel.
Soda Butte Creek
Soda Butte Creek is located near the park boundary, approximately 5 miles (8 km) downstream of the
former location of the McLaren Mill and Tailings
site. As a result of metal contamination from previous
mining activity, dissolved and total metals (arsenic,
copper, iron, and lead) persist in the floodplain. State
and federal agencies completed a three-year effort to
relocate mine tailings away from the floodplain and
to reconstruct the former channel in 2014. Results
from 2015 and 2016 monitoring activities in Soda
Butte Creek downstream of the reclamation work
show that iron levels associated with the former tailing site have been dramatically reduced.
The resulting data from recent monitoring also
led to a determination in November 2017 by the
Montana Department of Environmental Quality
(DEQ) that metals conditions in Soda Butte Creek
support designated beneficial uses. Montana DEQ
has now recommended removing Soda Butte Creek
from the state’s impaired water 303(d) list. The
60
Yellowstone Resources and Issues Handbook, 2019
reclamation of McLaren Mill and Tailings site and
subsequent removal from the 303(d) list represent
important milestones in the restoration of Soda Butte
Creek.
Yellowstone River at Corwin Springs
Similar to prior years, water samples were collected
on the Yellowstone River from late February to early
November 2017 and indicated that sites exceeded
the EPA drinking water standard of 0.01 mg/L total
arsenic but not the aquatic life criterion (0.15 mg/L).
The higher total arsenic values in this drainage may
be due to natural geological or geothermal influences
on water chemistry.
More Information
Gude, P.H., A.J. Hansen, and D.A. Jones. 2007. Biodiversity
consequences of alternative future land use scenarios
in Greater Yellowstone. Ecological Applications 17(4):
1004–1018.
Koel, T. et al. 2014. Yellowstone Fisheries and Aquatic
Sciences Report 2012–2013. National Park Service:
Yellowstone National Park.
Levandowski, M. and A. Ray. 2017. Water quality summary
for the Lamar River, Yellowstone River, and Madison
River in Yellowstone National Park: Preliminary analysis
of 2015 data. Natural Resources Report NPS/GRYN/
NRR-2017/1389. National Park Service, Fort Collins,
Colorado.
Marcus, W.A., J.E. Meacham, A.W. Rodman, A.Y. Steingisser.
2012. Atlas of Yellowstone. University of California Press.
Staff Reviewer
Andrew Ray, Ecologist, Greater Yellowstone Network.
Jeff Arnold, Fishery Biologist.
The ecological diversity of the Greater Yellowstone Ecosystem contributes to its value, and its controversy.
Yellowstone's northern range has been the focus of debate since the 1930’s.
Cycles and processes are essential connections within
an ecosystem. Photosynthesis, predation, decomposition, climate, and precipitation facilitate the flow
of energy and raw materials. Living things absorb,
transform, and circulate energy and raw materials
and release them again.
Life forms are active at all levels. Microbes beneath Yellowstone Lake thrive in hydrothermal vents
where they obtain energy from sulfur instead of the
sun. Plants draw energy from the sun and cycle nutrients such as carbon, sulfur, and nitrogen through the
system. Herbivores, from ephydrid flies to elk, feed
on the plants and, in turn, provide food for predators like coyotes and hawks. Decomposers—bacteria,
fungi, other microorganisms—connect all that dies
with all that is alive.
The ecosystem is constantly changing and evolving. A wildland fire is one example of an integral,
dynamic process. Fires rejuvenate forests on a grand
scale. Some species of plants survive the intense
burning to re-sprout. Some cones of lodgepole pines
pop open only in heat generated by fires, spreading
millions of seeds on the forest floor. After fire sweeps
through an area, mammals, birds, and insects quickly
take advantage of the newly created habitats. Fires
recycle and release nutrients and create dead trees
or snags that serve a number of ecological functions,
such as the addition of organic matter to the soil
when the trees decompose.
These cycles and processes are easily and frequently observed on Yellowstone’s northern range,
which refers to the broad grassland that borders the
Yellowstone and Lamar rivers in the northern portion of the park and into Montana. This area sustains
one of the largest and most diverse communities of
free-roaming large animals seen anywhere on Earth.
Many of the park’s ungulates spend the winter here.
Elevations are lower, and the area receives less snow
than elsewhere in the park. Often, the ridge tops and
south-facing hillsides are clear of snow, a result of
wind and sun. Animals take advantage of this lack of
snow, finding easier access to forage.
As a result of its incredible biodiversity, relatively
complete ecosystem integrity, and year-round access, research conducted on the northern range has
informed much of our current scientific understanding of native species and the ecological processes that
sustain them.
Biodiversity
Each species—no matter how small—has an important role to play in a functioning ecosystem. They all
participate in various ecosystem processes like transferring energy, providing nutrient storage, or breaking down pollutants. That is why biological diversity,
or biodiversity, is a benchmark for measuring the
health of an ecosystem. Biodiversity can be measured
in many ways, including the number of different species (also called richness) and the abundance of each
species (also called evenness).
The biodiversity and ecological processes that
are protected in the park support a healthy ecosystem. Significantly, Greater Yellowstone’s natural
diversity is essentially intact. The region appears to
have retained or restored its full historical complement of vertebrate wildlife species—a condition
unique in the wildlands of the contiguous 48 states.
The extent of wildlife diversity is due, in part, to
the different habitats found in the region, ranging
from high alpine areas to sagebrush country, from
hydrothermal areas, to forests, meadows, and other
habitat types. All of these are connected, by landforms, through links provided by streams and rivers
that course through the changing elevations, and by
the air that circulates between them.
Greater Yellowstone Ecosystem 61
E CO S YS T E M
Cycles and Processes
Gardiner
Mammoth
Hot Springs
Yellowst
on
e
La
m
ar
Ri
v
er
E C O S YS T E M
ver
Ri
Tower
Junction
= Yellowstone's northern range
The northern range is a broad grassland that borders
the Yellowstone and Lamar rivers in the northern
portion of Yellowstone and into Montana.
Biodiversity also supports the resilience of an
ecosystem. When a variety of organisms contributes
to ecosystem processes, an ecosystem can be more
flexible through dynamic events like floods or fire.
Knowledge of the park’s biodiversity expanded in
2009 with Yellowstone’s first bioblitz.
Intricate Layers
The reintroduction of the wolf to Yellowstone
restored an important element of ecological compl