The Wildlife Crossing Problem
What do wildlife crossings and underpasses actually cost, what does the international HSR evidence say about whether they work — and are the A2A Collaborative’s mitigation recommendations adequate, or even likely to be adopted?
A new high-speed rail line is an absolute linear barrier — fully fenced, grade-separated, and impassable. Mitigation through wildlife crossings is possible but expensive, imperfect, and species-specific. On the Frontenac Arch section of ALTO’s southern corridor, the scale of adequate mitigation is far larger than anything ALTO’s consultation documents acknowledge. The most ambitious independent programme proposed — that of the A2A Collaborative — would, by A2A’s own admission, fail to fully restore connectivity.
The A2A Collaborative’s mitigation recommendations would cost hundreds of millions of dollars for the Frontenac Arch section alone, are unlikely to be adopted at that density under a DBFOM P3 structure, and would still fail to fully restore ecological connectivity for many species.
For several SARA-listed species — the Eastern Loggerhead Shrike, four bat species at the Moira Karst hibernaculum, and the karst-dependent Grey Ratsnake — crossing structures cannot mitigate the harm at all. Route avoidance is the only adequate response for those species.
What a wildlife crossing actually costs
Wildlife crossing structures range enormously in scale and cost — from small amphibian culverts costing tens of thousands of dollars to major vegetated overpasses exceeding $100 million. Four benchmark cases illustrate the cost range for structures capable of accommodating large mammals.
Wallis Annenberg Wildlife Crossing — California (US 101)
Originally budgeted at $92M for a single vegetated overpass spanning ten lanes of the 101 Freeway. Ran $21M over budget by early 2026 — a 23% overrun — bringing the total to approximately $114M. Expected completion late 2026, four years after groundbreaking. The 2018 estimate for the same project was $4M — a 2,750% underestimate at 30% design stage.
Caltrans / Governor of California, 2022–2026I-25 Greenland Wildlife Overpass — Colorado (6-lane interstate)
At 200 × 209 feet, North America’s largest wildlife overpass by surface area. Completed December 2025 on time and under budget at $15M. Specifically designed for elk and pronghorn — large mammals that refuse enclosed underpasses. Expected to reduce wildlife-vehicle collisions by 90%. Part of a 30-year, $300M+ corridor investment.
Colorado Department of Transportation, 2025Ojibway Parkway Wildlife Crossing — Windsor, Ontario
Preferred option estimated at $13M. Critical limitation noted in planning documents: the crossing stops at the railway tracks that border the parkway, providing no crossing of the railway itself. The railway is identified as a separate and unresolved barrier. This is the exact planning gap ALTO reproduces — road crossings are costed; railway barriers are deferred.
Windsor Star, 2025Banff National Park System — Trans-Canada Highway
44 crossing structures + 88 km of exclusion fencing along 82 km of highway. Built over 25 years at a total corridor investment exceeding $300M. Wildlife-vehicle collisions dropped 80% overall, 96% for elk and deer. This system is on a 4-lane highway operating at 110 km/h — not a 300 km/h fenced HSR line with up to 72 trains per day.
Clevenger & Waltho, 2005; TransCanada data| Structure type | Typical cost (USD) | Target species | HSR suitability |
|---|---|---|---|
| Small amphibian/reptile culvert | $50K – $200K | Frogs, snakes, turtles | Partial — needed every 300–500m; does not address large mammals |
| Wildlife underpass (medium) | $500K – $2.7M | Deer, bears, medium mammals | Limited — elk avoid enclosed tunnels; effective for mesopredators if correctly sized |
| Large vegetated landscape bridge | $15M – $30M | Elk, bear, wolf, full community | Most effective; European standard for HSR through sensitive corridors |
| Major ecoduct (Netherlands standard) | $50M – $114M+ | Full species community | Gold standard; Zanderij Crailoo (800m, spans highway + railway) is the benchmark |
| Elevated viaduct (per km, HSR) | $30M – $80M/km | All species — natural movement underneath | Eliminates barrier for most species; A2A recommends for most sensitive areas |
| Exclusion fencing (per km, both sides) | $100K – $350K/km | All species — mandatory for HSR | Without crossings, creates absolute permanent barrier; funnels animals toward adjacent roads |
Costs in USD; Canadian equivalent approximately 35–40% higher. Costs from Large Landscapes Coalition (2021), CDOT (2025), Caltrans (2026).
What other countries have learned from HSR and wildlife
92
Vertebrate deaths per km/yr on HSR
vs. 36.5 on conventional rail — a 2.5× increase (Spanish HSR study, cited by A2A 2026)
646
Wildlife deaths at Banff (24 years)
On a conventional freight railway — including 106 bears. ALTO proposes 300 km/h and up to 72 trains/day
0
Deer/wild boar crossings recorded
In 2-year study of 15 underpasses + 2 overpasses on a 25 km Spanish HSR section (Rodriguez et al. 1996)
10+ km
Sensory impact radius
A2A primer: impacts “extend up to over 10km.” Crossings address physical barrier; not noise and vibration
600+
Wildlife tunnels in Netherlands
Under roads and railways since 1988. Includes the 800m Zanderij Crailoo ecoduct spanning highway + railway
25 yrs
Time to build Banff system
Infrastructure of this complexity requires commitment before construction — not as an afterthought
A2A Collaborative’s own admission — February 2026
The A2A Collaborative’s ecological primer states directly: “Without (and potentially even with) robust mitigation, rail will significantly impact connectivity, necessitating new connectivity studies after the rail is completed and potential remapping of protected areas.” That is the organisation advocating for the Frontenac Arch corridor acknowledging that even its own recommended mitigation programme may not be sufficient.
France: fencing and crossings as a planning precondition
France’s lignes à grande vitesse are fully fenced and require a “double series of measures” — full-length species-appropriate fencing plus ecological permeability structures at ecologically determined intervals. The UIC (International Union of Railways) 2011 report calls this “state of the art to fulfil all obligations in order to secure planning permission.” France treats this as a precondition, not a post-route mitigation option.
Spain: deer and wild boar crossed zero times
A study along 25 km of Spanish HSR monitored 15 underpasses and two overpasses over two years. Reptiles used the structures; deer and wild boar made zero crossings. Large ungulates consistently avoid enclosed tunnel structures. Only wide, open, vegetated overpasses at $15M–$30M+ each attract these species — and those are exactly the structures a DBFOM contractor has maximum incentive to eliminate.
Why ALTO’s corridor is especially difficult to mitigate
ALTO’s southern corridor traverses the Frontenac Arch — a 2,700 km² UNESCO Biosphere Reserve identified by conservation scientists as the most important remaining wildlife movement corridor in northeastern North America. The A2A Collaborative’s own primer describes it as a “Double Barrier” problem: an HSR line running just north of Highway 401 creates a trapped zone where animals surviving a highway crossing face immediate re-entrapment against HSR security fencing.
Nine Carleton University ecologists and conservation scientists, in an open letter released February 24, 2026, explicitly warned that the project “could disrupt ecological and hydrological connectivity in the Frontenac Arch Biosphere Reserve” and called for mitigation planning to begin before routes are finalized.
Species for which crossing structures are not sufficient
Eastern Loggerhead Shrike
SARA Endangered · ~40 wild individuals · ~22 breeding pairs at Napanee
Breeds within Napanee limestone plain habitat — it does not cross the rail line. Noise, vibration, and artificial light from HSR degrade habitat quality across a wide zone. No crossing structure is relevant to its survival.
Four SARA-Listed Bat Species
SARA Endangered / Threatened · Moira Karst hibernaculum
Bat foraging habitat within range of hibernacula is degraded by railway noise and vibration at HSR speeds. Wildlife crossings are entirely irrelevant — the problem is habitat quality, not physical crossing.
Grey Ratsnake
SARA Threatened · SARA Critical Habitat formally mapped
Critical habitat is mapped along the Frontenac Arch. Population connectivity requires multiple underpasses within each home range. A2A recommends reptile tunnels every 300–500m — for 100km of corridor, 200–333 structures.
Salmon River Alvar
Unique · Sole Canadian Juniper Sedge population
Alvar cannot be recreated or transplanted. Construction through or adjacent to this site constitutes permanent loss. Route avoidance is the only option — no crossing structure restores alvar habitat.
Blanding’s Turtle & Freshwater Turtles
SARA Threatened
Require seasonal overland movement between wetlands. Culverts can work if paired with drift fencing and placed based on pre-construction movement surveys — surveys ALTO has not conducted for this section.
Black Bear, Moose, White-tailed Deer
Ecologically critical for corridor function
The Frontenac Arch’s continental function depends on their movement. The Spanish HSR data shows these species require wide vegetated overpasses. Based on Banff data, adequate crossing density is approximately one structure per 2 km.
What A2A recommends — and what it would cost
The A2A Collaborative published a background ecological primer in February 2026 with specific mitigation standards. Their recommended crossing densities for the Frontenac Arch section:
Herpetile tunnels — every 300–500m
Dedicated amphibian/reptile tunnels throughout critical corridor sections to prevent entrapment and facilitate seasonal migrations. For 100km of sensitive corridor: 200–333 structures at $135K–$270K CAD each. Subtotal: $27M–$90M per 100km.
Medium mammal culverts — every 1–2km
Large box culverts for mesopredators and forest-dwelling species. For 100km: 50–100 structures at $675K–$3.6M CAD each. Subtotal: $34M–$360M per 100km.
Large mammal landscape bridges — every 5–8km
Massive vegetated overpasses for apex predators and large ungulates. For 100km: 12–20 structures at $20M–$40M CAD each. Subtotal: $240M–$800M per 100km.
Ecological buffer zones + viaducts
400m exclusion zones around forest interior and wetlands. Elevated viaduct construction through highest-sensitivity areas at $40M–$108M/km. For 10km of viaduct: $400M–$1,080M.
ALTO is a DBFOM P3. Cadence — the consortium bearing construction cost risk — has a direct financial incentive to minimise crossing structures. Under a DBFOM structure, crossing commitments must be contractually specified before financial close. ALTO has made no such commitment. The public consultation closes April 24, 2026. No contract terms have been disclosed. No crossing density has been committed. ALTO’s stated position: mitigation will be determined “community-by-community after route selection.” That sequencing is the inverse of what international standards, the A2A, and nine Carleton University ecologists all require.