{{Short description|Structures enabling wildlife to safely cross human-made barriers}} {{Use mdy dates|date=October 2023}} [[File:WildlifeCrossingA1IsraelSept202022 01.jpg|thumb|right|Wildlife crossing, Highway 1 (Israel)]] [[File:Bear underpass écoducOurs.jpg|thumb|right|Florida State Route 46 was elevated over this underpass. There are channeling fences on either side of the crossing.]] thumb|Drone video of Kolu wildlife overpass in Estonia (September 2021) '''Wildlife crossings''' are structures that allow animals to cross human-made barriers safely. Wildlife crossings may include underpass tunnels or '''wildlife tunnels''',<ref>{{Cite journal|last1=Van Der Ree|first1=Rodney|last2=Heinze|first2=Dean|last3=McCarthy|first3=Michael|last4=Mansergh|first4=Ian|date=December 2009|title=Wildlife Tunnel Enhances Population Viability|url=https://www.ecologyandsociety.org/vol14/iss2/art7/ES-2009-2957.pdf|url-status=live|journal=Ecology and Society|volume=14|issue=2|page=7|doi=10.5751/ES-02957-140207|jstor=26268295|archive-url=https://web.archive.org/web/20200709120735/https://www.ecologyandsociety.org/vol14/iss2/art7/ES-2009-2957.pdf|archive-date=July 9, 2020|doi-access=free|jstor-access=free |bibcode=2009EcSoc..14Tar.7V }}</ref> viaducts, and overpasses or '''green bridges'''<ref>{{Cite press release|url=https://www.gov.uk/government/news/green-bridges-safer-travel-for-wildlife|title=Green bridges: Safer travel for wildlife|publisher=Natural England|date=July 31, 2015|url-status=live|archive-url=https://web.archive.org/web/20200806125055/https://www.gov.uk/government/news/green-bridges-safer-travel-for-wildlife|archive-date=August 6, 2020}}</ref> (mainly for large or herd-type animals); amphibian and reptile tunnels; fish ladders; canopy bridges (especially for monkeys and squirrels); tunnels and culverts (for small mammals such as otters, hedgehogs, and badgers); and green roofs (for butterflies and birds).<ref>{{cite web |url=http://www.greenroof.se/?pid=28&sub=19 |title=About Green Roofs: Advantages |publisher=Scandinavian Green Roof Association |access-date=July 20, 2012 |quote=In the places where there isn’t enough ground space for green space, the green corridors, and the habitats for animals don’t have to be discontinued, if the flat roofs are used.}}</ref>
Wildlife crossings are a practice in habitat conservation, allowing connections or reconnections between habitats, combating habitat fragmentation. They also assist in avoiding collisions between vehicles and animals, which in addition to killing or injuring wildlife may cause injury or death to humans and property damage.
Similar structures can be used for domesticated animals, such as cattle creeps.
== Roads and habitat fragmentation== [[File:Camels crossing.JPG|thumb|Camel crossing in Kuwait]] Habitat fragmentation occurs when human-made barriers such as roads, railroads, canals, electric power lines, and pipelines penetrate and divide wildlife habitat.<ref name="Primack 2006">{{harv|Primack|2006}}</ref> Of these, roads have the most widespread and detrimental effects.<ref name="Spellerberg 1998">{{harv|Spellerberg|1998}}</ref> Scientists estimate that the system of roads in the United States affects the ecology of at least one-fifth of the land area of the country.<ref>{{harv|Forman|2000}}</ref> For many years{{Quantify|date=December 2020}} ecologists and conservationists have documented the adverse relationship between roads and wildlife,<ref>{{harvtxt|Jaeger et al.|2005}}</ref> and identify four ways that roads and traffic detrimentally affect wildlife populations: (1) they decrease habitat amount and quality, (2) they increase mortality due to wildlife-vehicle collisions (road kill), (3) they prevent access to resources on the other side of the road, and (4) they subdivide wildlife populations into smaller and more vulnerable sub-populations (fragmentation). Habitat fragmentation can lead to extinction or extirpation if a population's gene pool is restricted enough.
The first three effects (loss of habitat, road kill, and isolation from resources) exert pressure on various animal populations by reducing available resources and directly killing individuals in a population. For instance,<ref>{{harvtxt|Bennett|1991}}</ref> found that road kills do not pose a significant threat to healthy populations but can be devastating to small, shrinking, or threatened populations. Road mortality has significantly affected a number of prominent species in the United States, including white-tailed deer (''Odocoileus virginianus''), Florida panthers (''Puma concolor coryi''), and black bears (''Ursus americanus'').<ref>{{harv|Clevenger et al.|2001}}</ref> In addition, habitat loss can be direct, if habitat is destroyed to make room for a road, or indirect, if habitat quality close to roads is compromised due to emissions from the roads (e.g. noise, light, runoff, pollution, etc.).<ref>{{harv|Jaeger et al.|2005}}</ref> Finally, species that are unable to migrate across roads to reach resources such as food, shelter and mates will experience reduced reproductive and survival rates, which can compromise population viability.<ref>Noss et al., 1996</ref>
In addition to the first three factors, numerous studies have shown that the construction and use of roads is a direct source of habitat fragmentation.<ref name="Spellerberg 1998"/> As mentioned above, populations surrounded by roads are less likely to receive immigrants from other habitats and as a result, they suffer from a lack of genetic diversity. These small populations are particularly vulnerable to extinction due to demographic, genetic, and environmental stochasticity because they do not contain enough alleles to adapt to new selective pressures such as changes in temperature, habitat, and food availability.<ref name="Primack 2006"/>
The relationship between roads and habitat fragmentation is well documented. One study found that roads contribute more to fragmentation in forest habitats than clear cuts.<ref>{{harv|Reed et al.|1996}}</ref> Another study concluded that road fragmentation of formerly contiguous forest in eastern North America is the primary cause for the decline of forest bird species and has also significantly harmed small mammals, insects, and reptiles in the United States.<ref name="Spellerberg 1998"/> After years of research, biologists agree that roads and traffic lead to habitat fragmentation, isolation and road kill, all of which combine to significantly compromise the viability of wildlife populations throughout the world.{{citation needed|date=January 2022}}
== Wildlife-vehicle collisions ==
Wildlife-vehicle collisions have a significant cost for human populations because collisions damage property and injure and kill passengers and drivers.<ref>{{harv|Clevenger et al.|2001}}</ref> Research in the 1990s estimated the number of collisions with ungulates in traffic in Europe at 507,000 per year, resulting in 300 people killed, 30,000 injured,<ref>{{harvtxt|Bruinderink|Hazebroek|1996}}</ref><ref name="conover">{{cite journal |last1=Conover |first1=M. R. |author2=W. C. Pitt |author3=K. K. Kessler |author4=T. J. DuBow |author5=W. A. Sanborn |year=1995 |title=Review of Human Injuries, Illnesses, and Economic Losses Caused by Wildlife in the United States |journal=Wildlife Society Bulletin |volume=23 |issue=3 |pages=407–414 |jstor=3782947}}</ref> and property damage exceeding $1 billion. In parallel, 1.5 million traffic accidents involving deer in the United States cause an estimated $1.1 billion in vehicle damage each year.<ref name="Donaldson 2005">{{harv|Donaldson|2005}}</ref><ref name="conover" /> On a larger scale, research indicates that wildlife-vehicle collisions in the United States result in 29,000 injuries and more than 200 fatalities per year.<ref>{{Cite book|date=April 1, 2015|editor-last=van der Ree|editor-first=Rodney|editor2-last=Smith|editor2-first=Daniel J.|editor3-last=Grilo|editor3-first=Clara|title=Handbook of Road Ecology|language=en|doi=10.1002/9781118568170|isbn=9781118568170}}</ref>
The conservation issues associated with roads (wildlife mortality and habitat fragmentation) coupled with the substantial human and economic costs resulting from wildlife-vehicle collisions have caused scientists, engineers, and transportation authorities to consider a number of mitigation tools for reducing the conflict between roads and wildlife. Of the currently available options, structures known as wildlife crossings have been the most successful at reducing both habitat fragmentation and wildlife-vehicle collisions caused by roads.<ref>{{harvnb|Knapp|Yi|Oakasa|Thimm|2004}}, Clevenger, 2006</ref> [[File:Animals bridge flathead reservation.JPG|thumb|right|"Animals' Bridge", on the Flathead Indian Reservation in Montana, used by grizzly and black bears, deer, elk, mountain lions, and others<ref> {{Cite news | last = Devlin | first = Vince | title = Cameras show wildlife use Highway 93 North overpass and tunnels | journal = The Missoulian | location = Missoula, MT | publisher = missoulian.com | date = October 3, 2010 | url = http://missoulian.com/news/state-and-regional/article_c2e10564-cea6-11df-9944-001cc4c002e0.html | access-date = February 28, 2011}} </ref>]]
Wildlife crossings are structural passages beneath or above roadways that are designed to facilitate safe wildlife movement across roadways.<ref name="Donaldson 2005"/> In recent years, conservation biologists and wildlife managers have advocated wildlife crossings coupled with roadside fencing as a way to increase road permeability and habitat connectivity while decreasing wildlife-vehicle collisions.<ref>{{Cite web|last=Machemer|first=Theresa|title=Animals Are Using Utah's Largest Wildlife Overpass Earlier Than Expected|url=https://www.smithsonianmag.com/smart-news/animals-are-using-utahs-largest-wildlife-overpass-earlier-expected-180976420/|access-date=December 3, 2020|website=Smithsonian Magazine}}</ref> Wildlife crossing is the umbrella term encompassing underpasses, overpasses, ecoducts, green bridges, amphibian/small mammal tunnels, and wildlife viaducts {{harv|Bank et al.|2002}}. All of these structures are designed to provide semi-natural corridors above and below roads so that animals can safely cross without endangering themselves and motorists.<ref>{{Cite web|last=Greenfield|first=Patrick|date=December 29, 2021|title=Animal crossings: the ecoducts helping wildlife navigate busy roads across the world|url=https://www.theguardian.com/environment/2021/dec/29/wildlife-bridges-saving-creatures-big-and-small-aoe|access-date=December 29, 2021|website=The Guardian|language=en}}</ref>
==History== Written reports of rough fish ladders date to 17th-century France, where bundles of branches were used to create steps in steep channels to bypass obstructions. A version was patented in 1837 by Richard McFarlan of Bathurst, New Brunswick, Canada, who designed a fishway to bypass a dam at his water-powered lumber mill.<ref>Mario Theriault, ''Great Maritime Inventions 1833–1950'', Goose Lane, 2001, p. 45</ref> In 1880, the first fish ladder was built in Rhode Island, United States, on the Pawtuxet Falls Dam. As the Industrial Age advanced, dams and other river obstructions became larger and more common, leading to the need for effective fish by-passes.<ref>Office Of Technology Assessment Washington DC (1995) [https://books.google.com/books?id=ctBsJJ0oKHEC&dq=%22Fish+passage+technologies%22&pg=PA9 ''Fish passage technologies : protection at hydropower facilities''] Diana Publishing, {{ISBN|1-4289-2016-1}}.</ref>
The first overland wildlife crossings were constructed in France during the 1950s.<ref name="Chilson 2003">{{harv|Chilson|2003}}</ref> European countries including the Netherlands, Switzerland, Germany, and France have been using various crossing structures to reduce the conflict between wildlife and roads for several decades and use a variety of overpasses and underpasses to protect and re-establish wildlife such as: amphibians, badgers, ungulates, invertebrates, and other small mammals.<ref>{{harv|Bank et al.|2002}}</ref><ref name="HS"/>
The Humane Society of the United States reported in 2007 that the more than 600 tunnels installed under major and minor roads in the Netherlands have helped to substantially increase population levels of the endangered European badger.<ref name="HS">[https://web.archive.org/web/20070927220358/http://www.hsus.org/wildlife/issues_facing_wildlife/wildlife_crossings_wild_animals_and_roads/index.html Wildlife crossings - Wild animals and roads], The Humane Society of the United States. Archived from [http://www.hsus.org/wildlife/issues_facing_wildlife/wildlife_crossings_wild_animals_and_roads/index.html the original] on September 27, 2007.</ref> The longest "ecoduct" overpass, Natuurbrug Zanderij Crailoo, in the Netherlands, runs {{Convert|800|meters|feet}} and spans a highway, railway and golf course.<ref>{{Cite web|date=July 16, 2019|title=Wildlife Crossings|url=http://www.nationalgeographic.org/article/wildlife-crossings/|access-date=April 22, 2021|website=National Geographic Society|language=en|ref=Nat Geo 2019-07}}</ref><ref>{{Cite web|last=Nuwer|first=Rachel|author-link=Rachel Nuwer |date=July 23, 2012|title=World's Coolest Animal Bridges|url=https://www.smithsonianmag.com/smart-news/worlds-coolest-animal-bridges-5774855/|access-date=April 22, 2021|website=Smithsonian Magazine|language=en|ref=Smithsonian 2012-07}}</ref>
[[File:Terrapin Crossing, FJ Torras Causeway, St. Simons, Georgia, USA.jpg|thumb|A terrapin crossing sign and a highway barrier designed for crossing at the end of the F.J. Torras causeway at St. Simons Island, Georgia, US (2015)]]
Wildlife crossings are becoming increasingly common in Canada and the United States. Recognizable wildlife crossings are found in Banff National Park in Alberta, where vegetated overpasses provide safe passage over the Trans-Canada Highway for bears, moose, deer, wolves, elk, and many other species.<ref name="Clevenger 2007">{{harv|Clevenger|2007}}</ref> The 24 wildlife crossings in Banff were constructed as part of a road improvement project in 1978.<ref name="Clevenger 2007"/> In the United States, thousands of wildlife crossings have been built in the past 30 years,{{When|date=December 2021}} including culverts, bridges, and overpasses. These have been used to protect mountain goats in Montana, spotted salamanders in Massachusetts, bighorn sheep in Colorado, desert tortoises in California, and endangered Florida panthers in Florida.<ref name="Chilson 2003"/> The Henry Street salamander tunnels are tunnels under Henry Street in North Amherst, Massachusetts: they help salamanders cross Henry Street to get to vernal pools that the salamanders use for breeding.<ref name="Hofherr">{{cite news |last1=Hofherr |first1=Justine |title=There Are Teeny Tiny Underpasses for Salamanders in Massachusetts |url=https://www.boston.com/cars/untagged/2015/03/25/there-are-teeny-tiny-underpasses-for-salamanders-in-massachusetts/ |access-date=21 May 2024 |work=www.boston.com |publisher=Boston globe Media Partners, LLC |date=25 March 2015}}</ref>
The first wildlife crossing in the Canadian province of Ontario was built in 2010, along Ontario Highway 69 between Sudbury and Killarney, as part of the route's ongoing freeway conversion.<ref>[https://www.cbc.ca/news/canada/sudbury/ontario-builds-first-bridge-for-animals-near-sudbury-1.1148087 "Ontario builds first bridge for animals near Sudbury"]. CBC News, March 20, 2012.</ref>
== Costs and benefits == The benefits derived from constructing wildlife crossings to extend wildlife migration corridors over and under major roads appear to outweigh the costs of construction and maintenance. One study estimates that adding wildlife crossings to a road project is a 7–8% increase in the total cost of the project {{harv|Bank et al.|2002}}. Theoretically, the monetary costs associated with constructing and maintaining wildlife crossings in ecologically important areas are trumped by the benefits associated with protecting wildlife populations, reducing property damage to vehicles, and saving the lives of drivers and passengers by reducing the number of collisions caused by wildlife.{{Citation needed|date=December 2020}}
A study completed for the Virginia Department of Transportation estimated that underpasses for wildlife become cost effective, in terms of property damage, when they prevent between 2.6 and 9.2 deer-vehicle collisions per year, depending on the cost of the underpass. Approximately 300 deer crossed through the underpasses in the year the study took place {{harv|Donaldson|2005}}.
== Effectiveness ==
A number of studies have been conducted to determine the effectiveness of wildlife corridors at providing habitat connectivity (by providing viable migration corridors) and reducing wildlife-vehicle collisions. The effectiveness of these structures appears to be highly site-specific (due to differences in location, structure, species, habitat, etc.), and also dependent on design, but crossings have been beneficial to a number of species in a variety of locations.<ref name="j961">{{cite journal | last1=Sijtsma | first1=Frans J. | last2=van der Veen | first2=Eelke | last3=van Hinsberg | first3=Arjen | last4=Pouwels | first4=Rogier | last5=Bekker | first5=Renée | last6=van Dijk | first6=René E. | last7=Grutters | first7=Mark | last8=Klaassen | first8=Raymond | last9=Krijn | first9=Margriet | last10=Mouissie | first10=Maarten | last11=Wymenga | first11=Eddy | title=Ecological impact and cost-effectiveness of wildlife crossings in a highly fragmented landscape: a multi-method approach | journal=Landscape Ecology | volume=35 | issue=7 | date=2020 | issn=0921-2973 | doi=10.1007/s10980-020-01047-z | doi-access=free | pages=1701–1720 | bibcode=2020LaEco..35.1701S | url=https://link.springer.com/content/pdf/10.1007/s10980-020-01047-z.pdf | access-date=2025-05-18}}</ref>
==Examples== === Banff National Park ===
Banff National Park offers one of the best opportunities to study the effectiveness of wildlife crossings because the park contains a wide variety of species and is bisected by the Trans-Canada Highway (TCH), a large commercial road. To reduce the effects of the four-lane TCH, 24 wildlife crossings (22 underpasses and two overpasses) were built to ensure habitat connectivity and protect motorists {{harv|Clevenger|2007}}. In 1996, Parks Canada developed a contract with university researchers to assess the effectiveness of the crossings. Subsequently, a number of publications have analyzed the crossings' effect on various species and overall wildlife mortality (see {{harvnb|Clevenger|Waltho|2000}}, {{harvnb|Clevenger et al.|2001}}, and {{harvnb|Clevenger|2007}}).
[[File:Wildlife overpass Trans-Canada Hwy between Banff and LakeLouise Alberta.jpg|thumb|Wildlife overpass on Trans-Canada Highway in Banff National Park]] Using a variety of techniques to monitor the crossings since the early 1980s, scientists report that 10 species of large mammals (including deer, elk, black bear, grizzly bear, mountain lion, wolf, moose, and coyote) have used the 24 crossings in Banff a total of 84,000 times as of January 2007 {{harv|Clevenger|2007}}. The research also identified a "learning curve" such that animals need time to acclimate to the structures before they feel comfortable using them. For example, grizzly bear crossings increased from seven in 1996 to more than 100 in 2006, although the actual number of individual bears using the structures remained constant over this time at between two and four bears (Parks Canada, unpublished results). A similar set of observations was made for wolves, with crossings increasing from two to approximately 140 over the same 10-year period. However, in this case the actual number of wolves in the packs using the crossings increased dramatically, from a low of two up to a high of over 20 individuals.
{{harvtxt|Clevenger et al.|2001}} reported that the use of wildlife crossings and fencing reduced traffic-induced mortality of large ungulates on the TCH by more than 80 percent. Recent analysis for carnivores showed results were not as positive however, with bear mortality increasing by an average of 116 percent in direct parallel to an equal doubling of traffic volumes on the highway, clearly showing no effect of fencing to reduce bear mortality (Hallstrom, Clevenger, Maher and Whittington, in prep). Research on the crossings in Banff has thus shown mixed value of wildlife crossings depending on the species in question.
Parks Canada is currently planning to build 17 additional crossing structures across the TCH to increase driver safety near the hamlet of Lake Louise. Lack of effectiveness of standard fencing in reducing bear mortality demonstrates that additional measures such as wire 'T-caps' on the fence may be needed for fencing to mitigate effectively for bears (Hallstrom, Clevenger, Maher and Whittington, in prep).
=== Collier and Lee Counties in Florida === Twenty-four wildlife crossings (highway underpasses) and 12 bridges modified for wildlife have been constructed along a 40-mile stretch of Interstate 75 in Collier and Lee Counties in Florida {{harv|Scott|2007}}. These crossings are specifically designed to target and protect the endangered Florida panther, a subspecies of cougar found in the Southeastern United States. Scientists estimate that there are only 80–100 Florida panthers alive in the wild, which makes them one of the most endangered large mammals in North America {{harv|Foster|Humphrey|1995}}. The Florida panther is particularly vulnerable to wildlife-vehicle collisions, which claimed 11 panthers in 2006 and 14 in 2007 {{harv|Scott|2007}}.
The Florida Fish and Wildlife Conservation Commission (FWC) has used a number of mitigation tools in an effort to protect Florida panthers and the combination of wildlife crossings and fences have proven the most effective {{harv|Scott|2007}}. As of 2007, no panthers have been killed in areas equipped with continuous fencing and wildlife crossings and the FWC is planning to construct many more crossing structures in the future. The underpasses on I-75 also appeared to benefit bobcats, deer, and raccoons by significantly reducing wildlife-vehicle collisions along the interstate {{harv|Foster|Humphrey|1995}}.
=== Southern California === Wildlife crossings have also been important for protecting biodiversity in several areas of southern California. In San Bernardino County, biologists have erected fences along State Route 58 to complement underpasses (culverts) that are being used by the threatened desert tortoise. Tortoise deaths on the highway declined by 93% during the first four years after the introduction of the fences, proving that even makeshift wildlife crossings (storm-drainage culverts in this case) have the ability to increase highway permeability and protect sensitive species {{harv|Chilson|2003}}. Studies by {{harvtxt|Haas|2000}} and {{harvtxt|Lyren|2001}} report that underpasses in Orange, Riverside, and Los Angeles Counties have drawn significant use from a variety of species including bobcats, coyotes, gray fox, mule deer, and long-tailed weasels. These results could be extremely important for wildlife conservation efforts in the region's Puente Hills and Chino Hills links, which have been increasingly fragmented by road construction {{harv|Haas|2000}}. Los Angeles County's first wildlife-purpose built underpass is at Harbor Boulevard.<ref>{{Cite web|url=http://www.habitatauthority.org/harbor-boulevard-wildlife-underpass/|title = Harbor Boulevard Wildlife Underpass: First in Los Angeles County | Habitat Authority}}</ref> It was built in partnership between Los Angeles County, California State Parks and the Puente Hills Habitat Preservation Authority.
The Wallis Annenberg Wildlife Crossing in Agoura Hills, California, will be the world's largest wildlife crossing once completed in 2026.<ref>{{Cite web |date=May 7, 2024 |title=World's largest wildlife crossing on track to open by early 2026 |url=https://www.gov.ca.gov/2024/05/07/worlds-largest-wildlife-crossing-on-track-to-open-by-early-2026/ |publisher=State of California |access-date=April 10, 2025}}</ref>
=== Ecoducts, Netherlands === thumb|One of the two wildlife crossings spanning the A50 highway on the Veluwe in the Netherlands The Netherlands has over 66 wildlife crossings (overpasses and ecoducts) that have been used to protect the endangered European badger,<ref>[http://www.mjpo.nl/nieuws-publicaties/publicaties/ MJPO annual report 2014]</ref> as well as populations of wild boar, red deer, and roe deer. As of 2012, the Veluwe, {{Convert|1000|km2|mi2|sp=us}} of woods, heathland and drifting sands, the largest lowland nature area in North Western Europe, contains nine ecoducts, {{Convert|50|meters|feet}} wide on average, that are used to shuttle wildlife across highways that transect the Veluwe. The first two ecoducts on the Veluwe were built in 1988 across the A50 when the highway was constructed. Five of the other ecoducts on the Veluwe were built across existing highways, one was built across a two lane provincial road. The two ecoducts across the A50 were used by nearly 5,000 deer and wild boar during a one-year period {{harv|Bank et al.|2002}}.
The Netherlands also boasts the world's longest ecoduct-wildlife overpass called the Natuurbrug Zanderij Crailoo (sand quarry nature bridge at Crailo) {{harv|Danby|2004}}. The massive structure, completed in 2006, is {{Convert|50|meters|feet}} wide and over {{Convert|800|meters|feet}} long and spans a railway line, business park, roadway, and sports complex {{harv|Danby|2004}}. Monitoring is currently underway to examine the effectiveness of this innovative project combining wildlife protection with urban development. The oldest wildlife passage is Zeist West - A 28, opened in 1988.
=== Slaty Creek Wildlife Underpass, Calder Freeway, Black Forest, Australia === Another case study of the effectiveness of wildlife crossings comes from an underpass built to minimize the ecological effect of the Calder Freeway as it travels through the Black Forest in Victoria, Australia. In 1997, the Victorian Government Roads Corporation built Slaty Creek wildlife underpass at a cost of $3 million {{harv|Abson|Lawrence|2003}}. Scientists used 14 different techniques to monitor the underpass for 12 months in order to determine the abundance and diversity of species using the underpass {{harv|Abson|Lawrence|2003}}. During the 12-month period, 79 species of fauna were detected in the underpass (compared with 116 species detected in the surrounding forest) including amphibians, bats, birds, koalas, wombats, gliders, reptiles, and kangaroos {{harv|Abson|Lawrence|2003}}. The results indicate that the underpass could be useful to a wide array of species but the authors suggest that Slaty Creek could be improved by enhanced design and maintenance of fencing to minimise road kill along the Calder Freeway and by attempting to exclude introduced predators such as cats and foxes from the area.
===I-70 Vail Pass, Colorado=== In 2005, area environmental groups floated the idea of a wildlife overpass west of Vail Pass.<ref>{{Cite web|last=Thompson|first=Cliff|date=April 5, 2005|title=Creating a safer crossing for wildlife|url=https://www.summitdaily.com/news/creating-a-safer-crossing-for-wildlife/|access-date=April 22, 2021|website=www.summitdaily.com|language=en-US}}</ref><ref>{{Cite web|title=Wildlife Overpass Proposed West of Vail Pass|url=http://www.safepassagecoalition.org/news/vail_pass.htm|access-date=April 22, 2021|website=www.safepassagecoalition.org}}</ref> In 2010, ARC Solutions – an interdisciplinary partnership – initiated the International Wildlife Crossing Infrastructure Design Competition for a wildlife crossing over Interstate 70<ref>{{Cite web|last=Glendenning|first=Lauren|title=Competition created to help design wildlife crossing over I-70 near Vail|url=https://www.postindependent.com/news/competition-created-to-help-design-wildlife-crossing-over-i-70-near-vail/|access-date=April 22, 2021|website=www.postindependent.com|date=December 17, 2009 |language=en-US}}</ref> in the high country west of Denver, Colorado; designers had to account for challenges unique to the area, including snow and severe weather, high elevation and steep grades, a six-lane roadway, a bike path, and high traffic volumes, as well as multiple species of wildlife, including lynx.<ref>{{Cite web|last=|first=|date=December 16, 2009|title=New designs for wildlife crossings sought|url=https://www.denverpost.com/2009/12/16/new-designs-for-wildlife-crossings-sought/|access-date=April 22, 2021|website=The Denver Post|language=en-US}}</ref>
After receiving 36 submissions from nine countries, a jury of international experts in landscape architecture, engineering, architecture, ecology and transportation selected five finalists in November 2010 to further develop their conceptual designs for a wildlife crossing structure.<ref>{{cite web | url=http://competition.arc-solutions.org/finalists.php | title=Finalists | publisher=Arc | access-date=March 3, 2013 }}</ref><ref>{{Cite web|last=Leib|first=Jeffrey|date=November 29, 2010|title=Finalists named for Vail Pass wildlife crossings|url=https://www.vaildaily.com/news/finalists-named-for-vail-pass-wildlife-crossings/|access-date=April 22, 2021|website=www.vaildaily.com|language=en-US}}</ref> In January 2011, the team led by HNTB with Michael Van Valkenburgh & Associates (New York) were selected as the winners.<ref>{{Cite web|title=Design selected for I-70 wildlife crossing near Vail|url=https://arc-solutions.org/article/design-selected-for-i-70-wildlife-crossing-near-vail/|access-date=April 22, 2021|website=arc-solutions.org}}</ref><ref>{{cite web| url=http://competition.arc-solutions.org/video.php | title=ARC International Wildlife Crossing Design Competition | access-date=March 3, 2013 }}</ref> The design features a single 100 m (328 ft) concrete span across the highway that is planted with a variety of vegetation types, including a pine-tree forest and meadow grasses, to attract different species to cross. A modular precast concrete design means that much of the bridge can be constructed offsite and moved into place.<ref>{{cite report| title=Designing the Next Generation of Wildlife Crossings | date=March 2011 | publisher=United States Department of Transportation - Federal Highway Administration }}</ref>
In late 2020, Summit County Safe Passages released the "I-70 East Vail Pass Wildlife Crossings Feasibility Study" for a wildlife overpass.<ref>{{Cite web|title=Vail Pass {{!}} Summit County Safe Passages|url=https://www.summitcountysafepassages.org/initiatives/vail-pass/|access-date=April 22, 2021|language=en-US}}</ref>
=== I-90 near Snoqualmie Pass === In 2005, the Washington State Department of Transportation received approval to begin a {{convert|15|mile|adj=mid}} safety improvement project through the Snoqualmie Pass area along the Interstate 90 corridor from Hyak to Easton, through the Central Cascades and Mountains to Sound Greenway National Heritage Area,<ref>{{Cite web|url=https://mtsgreenway.org/nha|title=National Heritage Area}}</ref> including a series of wildlife crossings.<ref>{{Cite web|url=https://wsdot.wa.gov/Projects/I90/SnoqualmiePassEast/Default.htm|title = I-90 - Snoqualmie Pass East project}}</ref> Wildlife habitat on either side of I-90 will be reconnected with the installation of new bridges and culverts, protecting both wildlife and the traveling public. The construction of the wildlife overcrossing began in 2015 and was completed in late 2019.<ref>{{Cite web|title=I-90 - Snoqualmie Pass East project|url=https://wsdot.wa.gov/Projects/I90/SnoqualmiePassEast/Default.htm|access-date=December 17, 2020|website=wsdot.wa.gov|language=en}}</ref> Work to restore habitat on the wildlife bridge over I-90 has continued throughout 2020, with 90,000 trees and shrubs planted on the overcrossing.<ref>{{Cite web|date=November 24, 2020|title=2020 Parade of Accomplishments|url=https://mtsgreenway.org/blog/2020parade/|access-date=December 17, 2020|website=Mountains To Sound Greenway Trust|language=en-US}}</ref>
=== Interstate 80 in Parleys Canyon === In 2018, the Utah Department of Transportation announced a wildlife crossing over Interstate 80 in Parleys Canyon.<ref name=":0">{{Cite news|last=Old|first=Jason|date=November 24, 2020|title=WATCH: Wildlife uses Utah's first interstate crossing just for them|publisher=WDTV|url=https://www.wdtv.com/2020/11/24/watch-wildlife-uses-utahs-first-interstate-crossing-just-for-them/|url-status=live|access-date=December 3, 2020|archive-url=https://web.archive.org/web/20201203173839/https://www.wdtv.com/2020/11/24/watch-wildlife-uses-utahs-first-interstate-crossing-just-for-them/|archive-date=December 3, 2020}}</ref> The project was completed in early 2019 and measures {{Convert|350|feet|meters|order=flip}} long by {{Convert|50|feet|meters|order=flip}} wide.<ref>{{Cite AV media|url=https://www.youtube.com/watch?v=UjNk6RG5pgc |archive-url=https://ghostarchive.org/varchive/youtube/20211212/UjNk6RG5pgc| archive-date=December 12, 2021 |url-status=live|title=#KeepitWild! - I-80 Wildlife Overpass|date=February 1, 2019|publisher=Utah Department of Transportation|access-date=December 3, 2020|via=YouTube}}{{cbignore}}</ref> It is currently the only wildlife overpass in the state, though Utah has more than 50 wildlife underpasses.<ref>{{Cite news|date=November 25, 2020|title=Watch: animals safely cross the Utah interstate with this specially designed bridge|publisher=KVUE|url=https://www.kvue.com/article/life/animals/wildlife-overpass-interstate-80-animal-crossing/95-58dd3f93-13bd-4e11-a7e6-c43936c5d3cf|url-status=live|access-date=December 3, 2020|archive-url=https://web.archive.org/web/20201126060025/https://www.kvue.com/article/life/animals/wildlife-overpass-interstate-80-animal-crossing/95-58dd3f93-13bd-4e11-a7e6-c43936c5d3cf|archive-date=November 26, 2020}}</ref>
=== Robert L.B. Tobin Land Bridge === {{Main|Robert L.B. Tobin Land Bridge}} On December 11, 2020, the Robert L.B. Tobin Land Bridge opened over Wurzbach Parkway in San Antonio, Texas' Phil Hardberger Park.<ref>{{Cite news|last=Kirkpatrick|first=Brian|date=December 10, 2020|title=Largest Wildlife Bridge In U.S. Opens Friday At San Antonio's Hardberger Park|publisher=Texas Public Radio|url=https://www.tpr.org/san-antonio/2020-12-10/largest-wildlife-bridge-in-u-s-opens-friday-at-san-antonios-hardberger-park|url-status=live|access-date=December 12, 2020|archive-url=https://web.archive.org/web/20201212160028/https://www.tpr.org/san-antonio/2020-12-10/largest-wildlife-bridge-in-u-s-opens-friday-at-san-antonios-hardberger-park|archive-date=December 12, 2020}}</ref> The project cost $23 million and is designed for both wildlife and pedestrians. Construction began on November 26, 2018,<ref>{{Cite web|date=July 17, 2019|title=Land Bridge Construction|url=https://www.philhardbergerpark.org/parknews/land-bridge-construction|url-status=live|archive-url=https://web.archive.org/web/20201212173354/https://www.philhardbergerpark.org/parknews/land-bridge-construction|archive-date=December 12, 2020|access-date=December 12, 2020|publisher=Phil Hardberger Park Conservancy}}</ref> originally expected to end in April 2020,<ref>{{Cite news|last=Donaldson|first=Emily|date=October 6, 2018|title=City Breaks Ground on $23M Land Bridge to Connect Hardberger Park|work=San Antonio Report|url=https://sanantonioreport.org/city-breaks-ground-on-23-million-land-bridge-to-connect-hardberger-park/|url-status=live|access-date=December 12, 2020|archive-url=https://web.archive.org/web/20201212173047/https://sanantonioreport.org/city-breaks-ground-on-23-million-land-bridge-to-connect-hardberger-park/|archive-date=December 12, 2020}}</ref> and opened in December 2020. At {{Convert|189|feet|meters|order=flip}} long and {{Convert|150|feet|meters|order=flip}} wide,<ref>{{Cite news|last=Rubalcaba|first=Samantha|date=August 17, 2020|title=Hardberger Park land bridge in final stretch of development ahead of fall opening|work=San Antonio Report|url=https://sanantonioreport.org/hardberger-park-land-bridge-in-final-stretch-of-development-ahead-of-fall-opening/|url-status=live|access-date=December 12, 2020|archive-url=https://web.archive.org/web/20200922111710/https://sanantonioreport.org/hardberger-park-land-bridge-in-final-stretch-of-development-ahead-of-fall-opening/|archive-date=September 22, 2020}}</ref> it was the largest wildlife bridge in the United States when it was constructed.<ref>{{Cite news|last=Ruiz|first=Elizabeth|date=December 11, 2020|title=Largest land bridge in the United States opens in San Antonio's North Side.|publisher=KTSA|url=https://www.ktsa.com/largest-land-bridge-in-the-united-states-opens-in-san-antonios-north-side/|url-status=live|access-date=December 12, 2020|archive-url=https://web.archive.org/web/20201212172125/https://www.ktsa.com/largest-land-bridge-in-the-united-states-opens-in-san-antonios-north-side/|archive-date=December 12, 2020}}</ref>
=== Canopy Bridge in Anamalai Tiger Reserve === Many endangered lion-tailed macaques used to be killed while crossing the highway at Puduthotam in Valparai, South India. Thanks to the efforts of NGOs and the forest department, several canopy bridges were installed, connecting trees on either side of the road. This helped to lower the numbers of lion-tailed macaques killed in the region. The Environment Conservation Group had initiated a national mission to increase awareness on the importance of adopting roadkill mitigation methods through their mission PATH<ref>{{Cite news | url=http://www.thehindu.com/todays-paper/tp-in-school/stop-the-animals-are-crossing/article8029760.ece | title=Stop! The animals are crossing| newspaper=The Hindu| date=December 25, 2015| last1=Jeshi| first1=K.}}</ref> traveling more than {{Convert|17,000|km|miles|sp=us}} across 22 states.<ref>{{Cite web | url=http://www.sanctuaryasia.com/magazines/conservation/10297-driven-to-protect-a-journey-across-india-to-document-wild-roadkills.html | title=Driven to Protect – A Journey Across India to Document Wild Roadkills | access-date=May 18, 2016 | archive-date=June 24, 2016 | archive-url=https://web.archive.org/web/20160624021532/http://www.sanctuaryasia.com/magazines/conservation/10297-driven-to-protect-a-journey-across-india-to-document-wild-roadkills.html | url-status=dead }}</ref>
==See also==
* Colored walls or corridors ** Aquatic organism passage ** Emerald network ** Wildlife corridor, green corridor
* Animal passages ** Amphibian and reptile tunnel ** Bat bridge ** Squirrel bridge ** Toad tunnel
* Ecological network ** Habitat destruction ** Rewilding ** Landscape connectivity
== References == {{Reflist|2}}
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==External links== {{Commons category|Wildlife crossings}} {{Wiktionary|wildlife crossing|ecoduct}}
*[https://web.archive.org/web/20191218071223/https://www.environment.fhwa.dot.gov/env_initiatives/eco-logical/report/eco_index.aspx Eco-Logical: An Ecosystem Approach to Developing Infrastructure Projects] - Federal Highway Administration (FHWA) *[https://web.archive.org/web/20100309044309/http://www.y2y.net/Default.aspx?cid=333&lang=1 Wildlife Crossing Structures] - Yellowstone to Yukon Conservation Initiative *[https://storyateverycorner.com/animal-crossings-in-banff/ Wildlife Crossings in Banff National Park] *[https://roadecology.ucdavis.edu Road Ecology Center, UC Davis] *[https://www.wildlifecrossing.net/california California Roadkill Observation System] *[https://www.wildlifecrossing.net/maine Maine Audubon Wildlife Road Watch] *[http://www.wildlifeconsultingresources.com/pdf/wildlife%20habitat%20linkages%20I-70_Final%2012_05_07.pdf An Assessment of Wildlife Habitat Linkages on Interstate 70, Utah] {{Webarchive|url=https://web.archive.org/web/20160304073913/http://www.wildlifeconsultingresources.com/pdf/wildlife%20habitat%20linkages%20I-70_Final%2012_05_07.pdf |date=2016-03-04 }} *[http://www.wildlifeconsultingresources.com Wildlife Consulting Resources] {{Webarchive|url=https://web.archive.org/web/20160304080857/http://www.wildlifeconsultingresources.com/ |date=2016-03-04 }} Wildlife Crossing and Linkage Information for New Highway Projects *[http://www.wcproject.eu Wildlife Crossings Project] - The Wildlife Crossings Project provides information about georreferenced wildlife crossings all around the world, and allow specialists to publish them.
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Category:Wildlife crossings Category:Bridges Category:Conservation projects Category:Ecological connectivity Category:Ecological restoration Category:Roadkill Category:Road traffic management Category:Subway (underpass) Category:Tunnels Category:Transport and the environment