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Aliso and Wood Canyons Wilderness Park is a major
regional park A regional park is an area of land preserved on account of its natural beauty, historic interest, recreational use or other reason, and under the administration of a form of local government. Definition A regional park can be a special park distri ...
in the
San Joaquin Hills The San Joaquin Hills are a low mountain range of the Peninsular Ranges System, located in coastal Orange County, California. They extend in a northwest–southeast direction, starting in the northwest in Newport Beach at the southern edge of t ...
of
Orange County Orange County most commonly refers to: *Orange County, California, part of the Los Angeles metropolitan area Orange County may also refer to: U.S. counties *Orange County, Florida, containing Orlando *Orange County, Indiana *Orange County, New ...
,
California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...
in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...
. Comprising of rugged coastal canyons, open grassland, and
riparian A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks a ...
woodland, the park borders the suburban cities of
Aliso Viejo Aliso Viejo (Spanish for "Old Sycamore") is a city in the San Joaquin Hills of southern Orange County, California. It had a population of 47,823 as of the 2010 census, up from 40,166 as of the 2000 census. It became Orange County's 34th city on ...
,
Dana Point Dana Point () is a city located in southern Orange County, California, United States. The population was 33,107 at the 2020 census. It has one of the few harbors along the Orange County coast, and with ready access via State Route 1, it is a po ...
,
Laguna Beach Laguna Beach (; ''Laguna'', Spanish for "Lagoon") is a seaside resort city located in southern Orange County, California, in the United States. It is known for its mild year-round climate, scenic coves, environmental preservation efforts, and a ...
,
Laguna Hills Laguna Hills (; ''Laguna'', Spanish for "Lagoon") is a city in south Orange County, California, United States. Its name refers to its proximity to Laguna Canyon and the much older Laguna Beach. Other newer cities nearby—Laguna Niguel and Lagun ...
and
Laguna Niguel Laguna Niguel () is a city in Orange County, California, United States. The name Laguna Niguel is derived from the words "Laguna" (Spanish for "lagoon") and "Niguili" (the name of a Native American village once located near Aliso Creek). As of ...
and lies within a portion of the ancestral homeland of the indigenous Acjachemen people. Aliso and Wood Canyons is part of a larger park complex known as the
South Coast Wilderness Laguna Coast Wilderness Park is a wilderness area in the San Joaquin Hills surrounding Laguna Beach, California. This park features coastal canyons, ridgeline views and the only natural lakes in Orange County, California. Trails are maintained f ...
. Surrounded by heavy suburban development and the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...
, it is an important regional
wildlife preserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological or ...
. The park includes trails for hiking, mountain biking, and horseback riding; a
greenbelt A green belt is a policy and land-use zone designation used in land-use planning to retain areas of largely undeveloped, wild, or agricultural land surrounding or neighboring urban areas. Similar concepts are greenways or green wedges, which h ...
and bikeway along Aliso Creek; and various geological features such as caves, springs, and exposed marine
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
beds. The park is administered by the County of Orange under the OC Parks Department. The name ''Aliso'' originated in the 18th century when
Spanish explorers Exploration refers to the historical practice of discovering remote lands. It is studied by geographers and historians. Two major eras of exploration occurred in human history: one of convergence, and one of divergence. The first, covering most ...
named Aliso Creek, probably for the ''
Alnus rhombifolia ''Alnus rhombifolia'', the white alder, is an alder tree native to western North America, from British Columbia and Washington east to western Montana, southeast to the Sierra Nevada, and south through the Peninsular Ranges and Colorado Desert oa ...
'' (white alder) tree native to the area. Wood Canyon was likely named for the groves of California live oak and
sycamore Sycamore is a name which has been applied to several types of trees, but with somewhat similar leaf forms. The name derives from the ancient Greek ' (''sūkomoros'') meaning "fig-mulberry". Species of trees known as sycamore: * ''Acer pseudoplata ...
s that are found in the canyon. In 2021, the park was designated by the Old Growth Forest Network for its old live oak and sycamore trees.


History

The park was originally inhabited by the Acjachemen and
Tongva The Tongva ( ) are an Indigenous people of California from the Los Angeles Basin and the Southern Channel Islands, an area covering approximately . Some descendants of the people prefer Kizh as an endonym that, they argue, is more historically ...
Native Americans who used Aliso Creek as the boundary between their respective territories to the south and north. The relationship between the two tribes was mostly peaceful. Because Aliso Canyon was one of the few places in what is now south Orange County with perennial streams and springs – as well as providing easy access from inland areas to the Pacific Ocean – it was a major wintering spot for native peoples. The Acjachemen village of Niguili was located in what is now the park, near the confluence of Aliso Creek and Sulphur Creek. The 1769 Spanish
Portola expedition Portola may refer to: * ''Portola'' (album), a 1998 album by Rose Melberg * Portola, California * Portola, San Francisco, California People with the surname * Gaspar de Portolá Gaspar de Portolá y Rovira (January 1, 1716 – October 10, 1 ...
was the first European party to explore the area. Spanish ships were also known to anchor in the bay at the mouth of Aliso Canyon and sailors "harvested large timbers from the river area". In the following decades the Spanish colonized California they established missions to convert the Native Americans to Christianity with varying degrees of success. The peoples who once lived in Aliso Canyon were moved by the Spanish to the nearby Mission San Juan Capistrano. After Mexico's independence from Spain in 1821 the missions were
secularized In sociology, secularization (or secularisation) is the transformation of a society from close identification with religious values and institutions toward non-religious values and secular institutions. The ''secularization thesis'' expresses the ...
and mission lands were divided into private
land grant A land grant is a gift of real estate—land or its use privileges—made by a government or other authority as an incentive, means of enabling works, or as a reward for services to an individual, especially in return for military service. Grants ...
s. The Rancho Niguel, which included most of what is now the park, was granted to
Juan Avila ''Juan'' is a given name, the Spanish and Manx versions of ''John''. It is very common in Spain and in other Spanish-speaking communities around the world and in the Philippines, and also (pronounced differently) in the Isle of Man. In Spanish, ...
in 1842. After the
Mexican–American War The Mexican–American War, also known in the United States as the Mexican War and in Mexico as the (''United States intervention in Mexico''), was an armed conflict between the United States and Mexico from 1846 to 1848. It followed the 1 ...
in 1850, California became part of the United States; after a severe drought Avila sold the ranch in 1865. Rancho Niguel changed hands multiple times until it was acquired by Lewis Moulton and Jean Pierre Daguerre in 1895. During the 19th century, others also took advantage of the shelter and seclusion offered by Aliso Canyon. Dripping Cave (once used by the local Native Americans as a shelter), tucked into a sheltered part of Wood Canyon, became a "base of operations" of outlaws, led by Juan Flores, who robbed stagecoaches traveling between
Los Angeles Los Angeles ( ; es, Los Ángeles, link=no , ), often referred to by its initials L.A., is the List of municipalities in California, largest city in the U.S. state, state of California and the List of United States cities by population, sec ...
and
San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the eighth most populous city in the United State ...
. Long after the bandits were arrested, it retains the nickname "Robbers Cave". In 1871 Eugene Salter, the first white settler along Aliso Creek, claimed in the canyon just outside the Rancho Niguel. The next year, the homestead was taken over by the Thurston family who irrigated an orchard using water from Aliso Creek. Aliso Canyon was used for sheep ranching through the first half of the 20th century, although tourism was also growing due to the popularity of Aliso Beach at canyon's end, and the establishment of the Aliso Creek Inn and Golf Course on the old Thurston property in 1950. During the 1960s, the Rancho Niguel was sold for residential suburban development in the
planned cities A planned community, planned city, planned town, or planned settlement is any community that was carefully planned from its inception and is typically constructed on previously undeveloped land. This contrasts with settlements that evolve ...
of Aliso Viejo, Laguna Hills and Laguna Niguel. The Aliso Canyon was the proposed location of a "much publicized national fitness center headed by former Los Angeles Rams coach
George Allen George Allen may refer to: Politics and law * George E. Allen (1896–1973), American political operative and one-time head coach of the Cumberland University football team * George Allen (Australian politician) (1800–1877), Mayor of Sydney and ...
." A six-lane highway was proposed to run the length of the canyon, to link inland communities with Laguna Beach. The canyon was spared from development when about 40 land parcels were acquired by the county for use as a park, the largest in 1979 when the Mission Viejo Company donated . The park officially opened on March 31, 1990 as Aliso and Wood Canyons Regional Park; it was later designated a Wilderness Park to better preserve native habitat. Continued land acquisitions and donations since then brought the park to its current size.


Features and characteristics

The park encompasses the dramatic Aliso Canyon, which is the valley formed by Aliso Creek as it slices through the San Joaquin Hills on its way from the
Cleveland National Forest Cleveland National Forest encompasses 460,000 acres (), mostly of chaparral, with a few riparian areas. A warm dry mediterranean climate prevails over the forest. It is the southernmost U.S. National Forest of California. It is administered by ...
to the Pacific Ocean. Wood Canyon is formed by Wood Canyon Creek as it flows south to join Aliso Creek in the center of the park. Another tributary, Sulphur Creek, joins Aliso Creek at the eastern end of the park. Elevations within the park range from above sea level to at Temple Hill in Laguna Beach (colloquially "Top of the World"), on the park's western boundary. On a clear day, most of Orange County can be seen from Temple Hill and the other ridge tops surrounding Aliso Canyon. Aliso and Wood Canyons links two major park systems in Orange County. The South Coast Wilderness, which protects much of the San Joaquin Hills ecosystem, includes
Laguna Coast Wilderness Park Laguna Coast Wilderness Park is a wilderness area in the San Joaquin Hills surrounding Laguna Beach, California. This park features coastal canyons, ridgeline views and the only natural lakes in Orange County, California. Trails are maintained f ...
which borders Aliso and Wood Canyons to the north. The Aliso Creek Corridor, a greenbelt stretching along Aliso Creek to national forest lands in the
Santa Ana Mountains The Santa Ana Mountains are a short peninsular mountain range along the coast of Southern California in the United States. They extend for approximately southeast of the Los Angeles Basin largely along the border between Orange and Riverside c ...
, also terminates in Aliso Canyon.http://scc.ca.gov/webmaster/ftp/pdf/sccbb/2013/1306/20130620Board09_Aliso_and_Wood_Canyons_Public_Access.pdf Aliso and Wood Canyons very nearly touches the popular Aliso Beach County Park on its southern end; however, the two are separated by the private Ranch at Laguna Beach (formerly Aliso Creek Inn and Golf Course), preventing visitors from accessing the beach using park trails. A plan to extend a public trail through this property was indefinitely suspended in 2009 after the
global financial crisis Global means of or referring to a globe and may also refer to: Entertainment * ''Global'' (Paul van Dyk album), 2003 * ''Global'' (Bunji Garlin album), 2007 * ''Global'' (Humanoid album), 1989 * ''Global'' (Todd Rundgren album), 2015 * Bruno ...
. The park contains a large number of artifacts from past inhabitants of the area. Many types of these prehistoric artifacts are found throughout the park. These include, but are not limited to, open air shell middens, rock shelters, stone tools, and their production sites. There is also historic farm equipment and buildings dating from the Rancho Niguel period. Such historical sites include the Moulton Cement Plant, Bacon House site, and Tischler Rock.


Climate

The park has a warm, dry
Mediterranean climate A Mediterranean climate (also called a dry summer temperate climate ''Cs'') is a temperate climate sub-type, generally characterized by warm, dry summers and mild, fairly wet winters; these weather conditions are typically experienced in the ...
, with mild winters and hot summers. Most of the annual rainfall occurs between December and March. The average annual precipitation is .


Trails and access

The park is open from 7 AM to sunset. The main entrance and parking are located off Alicia Parkway at AWMA Road in Laguna Niguel. There is no entrance fee, but a $3 fee applies for parking. About of recreational trails wind through the park. The most prominent include the paved Aliso Creek Trail, which travels the length of the park, and the unpaved Wood Canyon Trail which terminates at Canyon View Park in Aliso Viejo. The Aliso Creek Trail continues north along the creek towards
Laguna Hills Laguna Hills (; ''Laguna'', Spanish for "Lagoon") is a city in south Orange County, California, United States. Its name refers to its proximity to Laguna Canyon and the much older Laguna Beach. Other newer cities nearby—Laguna Niguel and Lagun ...
as a paved walking/biking path. The more enclosed and shaded Wood Canyon is a popular location for horseback riding; the hills bordering Wood Canyon include many mountain biking paths, such as the Mathis Canyon and Rock-It trails, ranging in difficulty from beginner to advanced. Many of the names for smaller trails in the park are from the Acjachemen language, including ''Aswut'' ("golden eagle"), ''Toovet'' ("brush rabbit"), ''Alwut'' ("crow") and ''Hunwut'' ("black bear"). Dripping Cave is a popular beginner's hike and was once used as a hideout by local cattle and stagecoach thieves during the 1800s. The Aliso Summit and West Ridge trails hug the ridge lines on the park's eastern and western boundaries, respectively.


Geology

Aliso Canyon began forming about 1.2 million years ago, as Aliso Creek carved its way through the hills at the same time the hills experienced geological uplift. During the
pluvial In geology and climatology, a pluvial is either a modern climate characterized by relatively high precipitation or an interval of time of variable length, decades to thousands of years, during which a climate is characterized by relatively high ...
Ice Age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gre ...
, ending about 10,000 years ago, Orange County had a much wetter climate and sea levels were lower; the valley is a relic of a time when much more water flowed through Aliso Creek as it cut its way to the sea. At the end of the Ice Age sea levels rose, backfilling the canyon and creating a shallow
fjord In physical geography, a fjord or fiord () is a long, narrow inlet with steep sides or cliffs, created by a glacier. Fjords exist on the coasts of Alaska, Antarctica, British Columbia, Chile, Denmark, Förden and East Jutland Fjorde, Germany, ...
. Sediment deposited by Aliso Creek slowly filled the canyon to depths of and created the flat valley floor seen today. The creek remains as an
underfit stream A misfit stream is a river that is either too large or too small to have eroded the valley or cave passage in which it flows. This term is also used for a stream or river with meanders that obviously are not proportional in size to the meanders ...
whose present size, in today's semiarid climate, appears too small to have cut the canyon through which it flows. The San Joaquin Hills consist of marine
sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
that originally lay at the bottom of the Pacific Ocean before being uplifted above sea level. As the creek cut through the hills it exposed strata of the
Monterey Formation The Monterey Formation is an extensive Miocene oil-rich geological sedimentary formation in California, with outcrops of the formation in parts of the California Coast Ranges, Peninsular Ranges, and on some of California's off-shore islan ...
dating to the
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
(5-23 million years ago) and the
Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...
(34–56 million years ago).
Limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
outcrops in the northeast section of the park, part of the Pecten Reef, have yielded thousands of fossils including Miocene dolphin and whales, preserved
invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s,
plankton Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
,
bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...
, and red, blue and brown algae. Much of the scientific understanding for evolution, paleoenvironments and paleoclimates during the Miocene period in Orange County is based on the specimens collected from the Pecten Reef.


Ecology

The plant and animal species in the park are split between three major plant communities covering approximately equal acreage within the park. These are
coastal sage scrub Coastal sage scrub, also known as coastal scrub, CSS, or soft chaparral, is a low scrubland plant community of the California coastal sage and chaparral subecoregion, found in coastal California and northwestern coastal Baja California. It is ...
, chaparral, and annual
grassland A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...
. Chaparral often co-exists with sage scrub on the hills and slopes of the park; mostly in the southern extreme of the park. The grassland covers the valley floor, with
riparian zone A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks a ...
s along the park's perennial streams. The park, a designated wildlife sanctuary, protects the habitat of 137 species of nesting and migratory birds.


Plants

The Aliso Canyon bottom is seasonal grassland, which flourishes in spring and diminishes by late summer or fall. The park protects habitat for a number of sensitive plant species, including many-stemmed
dudleya ''Dudleya'', commonly known as liveforevers (Spanish: ''siemprevivas'') is a genus of succulent plants in the stonecrop family, Crassulaceae, consisting of about 68 taxa in southwestern North America and Guadalupe Island. The species come in mu ...
, Pomona rattleweed, Orange County Turkish rugging, Palmer's grapplinghook, aphanisma, Laguna Beach dudleya,
scrub oak Scrub oak is a common name for several species of small, shrubby oaks. It may refer to: *the Chaparral plant community in California, or to one of the following species. In California *California scrub oak ('' Quercus berberidifolia''), a wides ...
, western dichondra, hummingbird sage, ocean spray, and crown-beard.
Oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...
and
sycamore Sycamore is a name which has been applied to several types of trees, but with somewhat similar leaf forms. The name derives from the ancient Greek ' (''sūkomoros'') meaning "fig-mulberry". Species of trees known as sycamore: * ''Acer pseudoplata ...
are found in Wood Canyon, and marshes and grassy wetlands are found along Aliso Creek. Native grassland ecosystems in the less visited south-western portion of the park are considered largely intact.


Animals

The park is one of the largest sanctuaries in coastal Orange County for mammals such as coyotes and bobcats. Several sensitive bird, small mammal, and reptile species find refuge in the park, including
California gnatcatcher The California gnatcatcher (''Polioptila californica'') is a small long insectivorous bird which frequents dense coastal sage scrub growth. This species was recently split from the similar black-tailed gnatcatcher of the Sonoran and Chihuahuan ...
, pond turtle,
San Diego horned lizard The San Diego horned lizard or Blainville's horned lizard (''Phrynosoma blainvillii'') is a species of phrynosomatid lizard native to southern and central California in the United States and northern Baja California in Mexico. Taxonomy Descri ...
, orange-throated whiptail,
Pacific pocket mouse The Pacific pocket mouse, ''Perognathus longimembris pacificus'', is endemic to California. It lives in sandy coastal soils of the coastal sage scrub ecoregion. It eats seeds and some insects. It was believed to be extinct until 1993, when a smal ...
,
great egret The great egret (''Ardea alba''), also known as the common egret, large egret, or (in the Old World) great white egret or great white heron is a large, widely distributed egret. The four subspecies are found in Asia, Africa, the Americas, and ...
,
white-tailed kite The white-tailed kite (''Elanus leucurus'') is a small raptor found in western North America and parts of South America. It replaces the related Old World black-winged kite in its native range. Taxonomy The white-tailed kite was described in ...
,
northern harrier The northern harrier (''Circus hudsonius''), or ring-tailed hawk, is a bird of prey. It breeds throughout the northern parts of the northern hemisphere in Canada and the northernmost USA. The northern harrier migrates to more southerly areas ...
,
sharp-shinned hawk The sharp-shinned hawk (''Accipiter striatus'') is a small hawk, with males being the smallest hawks in the United States and Canada, but with the species averaging larger than some Neotropical species, such as the tiny hawk. The taxonomy is fa ...
,
Cooper's hawk Cooper's hawk (''Accipiter cooperii'') is a medium-sized hawk native to the North American continent and found from southern Canada to Mexico. This species is a member of the genus ''Accipiter'', sometimes referred to as true hawks, which are f ...
,
ferruginous hawk The ferruginous hawk, (''Buteo regalis''), is a large bird of prey and belongs to the broad-winged buteo hawks. An old colloquial name is ferrugineous rough-leg, due to its similarity to the closely related rough-legged hawk (''B. lagopus''). ...
,
cactus wren The cactus wren (''Campylorhynchus brunneicapillus'') is a species of wren endemic to the deserts of the southwestern United States and northern and central Mexico. It is the state bird of Arizona, and the largest wren in the United States. ...
,
yellow warbler The yellow warbler (''Setophaga petechia'') is a New World warbler species. Yellow warblers are the most widespread species in the diverse genus ''Setophaga'', breeding in almost the whole of North America, the Caribbean, and down to northern S ...
, and
yellow-breasted chat The yellow-breasted chat (''Icteria virens'') is a large songbird found in North America, and is the only member of the family Icteriidae. It was once a member of the New World warbler family, but in 2017, the American Ornithological Society mov ...
. Up to five bald eagles have been counted in Aliso Canyon, and peregrine falcons have been sighted flying along the canyon walls.


Fish

Aliso Creek was formerly a major
steelhead Steelhead, or occasionally steelhead trout, is the common name of the anadromous form of the coastal rainbow trout or redband trout (O. m. gairdneri). Steelhead are native to cold-water tributaries of the Pacific basin in Northeast Asia and ...
stream. Dam construction, upstream channelization, pollution, invasive plant species such as giant reed, as well as severe
erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...
problems that have in some places undermined the Aliso Creek Trail, have essentially eliminated steelhead with only occasional anecdotal sightings. Near the mouth, there was also a large population of
tidewater goby ''Eucyclogobius newberryi'', the Northern tidewater goby, is a species of goby native to lagoons of streams, Marsh, marshes, and creeks along the coast of California, United States. The Northern tidewater goby is one of six native goby species to ...
(an endemic species to California) which have largely disappeared with human development. Carp of up to 18 inches (1.5 feet, 45 cm) have been taken from the creek; they are among the few fish species that thrive in the warm, silty and nutrient-rich waters.


Environmental issues

Among the most long-running problems afflicting Aliso and Wood Canyons is the presence of invasive species, many introduced by former ranching activities, and later, exotic ornamental plants imported for gardens. Plants such as giant reed (Arundo donax) and pampas grass crowd out native vegetation and provide less nutritional value to animals that frequent the park. Giant reed in particular has invaded many riparian zones along Aliso Creek and reduced the biodiversity of these habitats. There are also numerous invasive animal species, including the
Brown-headed cowbird The brown-headed cowbird (''Molothrus ater'') is a small, obligate brood parasitic icterid native to temperate and subtropical North America. It is a permanent resident in the southern parts of its range; northern birds migrate to the southern ...
, a brood parasite which lays its eggs in native birds' nests. Recent mitigation projects have utilized herbicides and trapping to reduce the population of invasive species within the canyon. Another issue affecting the park are hikers and mountain bikers who create unauthorized trails as shortcuts. Even before the opening of the park in 1990, motorcyclists would frequently trespass inside the boundaries, damaging sensitive habitat and slopes; in part because of this, motorized vehicles with the exception of maintenance and emergency workers are banned in the park. Rangers regularly block and re-plant unofficial trails, and visitors are urged to stay on the designated trails to prevent erosion.


Erosion

The Aliso Wastewater Management Agency (AWMA) was created in 1974 to reclaim domestic sewage for irrigation; a
water treatment Water treatment is any process that improves the quality of water to make it appropriate for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, inc ...
facility was established inside the future park as the overflow into Aliso Creek when the volume of reclaimed water exceeds demand in nearby cities. Since then, the population of south Orange County has grown faster than projected, increasing the volume of wastewater entering Aliso Creek and causing erosion problems inside the park. In the 1990s Orange County and the Mission Viejo Company constructed a dam on Aliso Creek inside the park, which was intended to control erosion and help restore riparian habitat. About 10,000 trees were planted to enhance habitat conditions. This project was known as the Aliso Creek Wildlife Habitat Enhancement Project (ACWHEP). However, after flooding damages in 1997-98 the dam was severely damaged, and has led to significant
degradation Degradation may refer to: Science * Degradation (geology), lowering of a fluvial surface by erosion * Degradation (telecommunications), of an electronic signal * Biodegradation of organic substances by living organisms * Environmental degradatio ...
of the river bed such that the creek now flows in a gully below the surrounding land. This has caused further environmental problems along the creek, and dried up former riparian habitat and wetlands. Further efforts to control erosion along the creek in the park, both to restore habitat and protect nearby waste-water pipelines,https://www.socwa.com/Planning/documents/LowerAlisoCreekErosionAssessmentSOCWAFINAL_041912.pdf have been controversial as they would severely impact the existing habitat in the canyon. A 2008 proposal by the
U.S. Army Corps of Engineers , colors = , anniversaries = 16 June (Organization Day) , battles = , battles_label = Wars , website = , commander1 = ...
, would have "locked" the creek in place by building 20
drop structure A drop structure, also known as a grade control, sill, or weir, is a manmade structure, typically small and built on minor streams, or as part of a dam's spillway, to pass water to a lower elevation while controlling the energy and velocity of the ...
s and underground concrete walls to counter channel migration. The works would have involved moving as much as of earth and affected of the park. In 2009 a study submitted to the City of Laguna Beach suggested that the creek should be allowed to reach natural equilibrium with its surroundings, as additional human interference would likely lead to further unexpected damages. Due to environmental concerns, no such project has been attempted to date.


See also

* Crystal Cove State Park


References

{{Commons category, Aliso and Wood Canyons Wilderness Park Parks in Orange County, California Regional parks in California San Joaquin Hills