The Napanee Plain: Why This Land Matters
What the proposed southern rail corridor would cross — and what would be lost
Plain-language overview. This page explains the environmental and engineering risks of the Alto southern corridor through the Napanee Limestone Plain. All factual claims are drawn from cited published sources. Nine sections cover geology, alvar ecosystems, species at risk, hydrology, invasive plants, and the compounding effects that make this landscape uniquely difficult to build through.
Under much of the Napanee area, the bedrock is limestone — a rock that slowly dissolves in rainwater over thousands of years. This process creates what geologists call karst: a landscape riddled with underground caves, hidden rivers, sinkholes, and tunnels. In the Napanee Plain, this underground cave system is well developed. There are documented sites like the Roblin Hell Holes — a limestone cliff area with caves and sinkholes near the Salmon River — and the Moira Karst, which contains a large cave used every winter by five species of bats as a hibernation site. Both are recognized as Areas of Natural and Scientific Interest (ANSI).9
Lennox & Addington Stewardship Council (2022): “The underground drainage, flooding and potential collapse of underground rock masses make karst dangerous to build on.”1
High-speed rail is extremely sensitive to the ground beneath it. Unlike a highway, a high-speed rail track must stay almost perfectly level and stable — tolerances smaller than the width of your thumb. Any ground movement can cause serious safety problems at 300 km/h. Karst terrain creates several risks that are very hard to manage:
- Sinkholes can open without warning as underground caves gradually dissolve and collapse.
- The ground shifts unpredictably. Limestone and underlying shale layers vary so much over short distances that building a stable, level foundation is extremely difficult.
- Flooding is erratic. Water surges through underground channels and surfaces unpredictably, putting pressure on any embankment or cutting.
- Drainage work can make things worse. Digging ditches or culverts can accidentally redirect underground flows, potentially triggering new sinkholes nearby.
Engineers do have ways to build on karst — but they are expensive. Options include injecting cement grout into underground cavities, drilling deep steel piles to solid ground, or building on elevated viaducts. A useful comparison: when the UK’s HS2 project crossed a geologically similar area in Cheshire, an independent assessment found the extra engineering would nearly double the cost per kilometre for that section — adding roughly £750 million for just 20 kilometres of track.14
The catch-22. The engineering fixes for unstable karst ground — filling caves with cement, redirecting water, deep excavation — are exactly the things most likely to destroy the rare wetland habitats and bat caves that depend on that underground water system. The more you stabilize the ground for the train, the more you damage the ecology.
An alvar is a type of habitat found only in two places on Earth: the Great Lakes region of North America, and parts of Scandinavia. It forms on flat limestone bedrock where the soil is paper-thin or absent entirely. Because of the bare rock and shallow soil, these landscapes experience extremes that most plants can’t survive: deep flooding in spring, intense drought in summer, and hard frost in winter.
85 percent of all alvar habitat in North America is found in Ontario, and despite over 120 identified sites across the Great Lakes region, alvars cover only 0.2 percent of the landscape.2 They are globally imperiled. The Napanee Plain has approximately 50 alvar sites — one of the most significant concentrations in the world.2
Ontario MNRF (2007): “Almost all alvar types found in the Great Lakes region are considered globally imperiled and under stress. They are irreplaceable repositories of biodiversity adapted to the specific conditions of limestone bedrock environments.”2
Alvars support remarkable life: rocky pavements covered in mosses, lichens, and rare tiny flowering plants; alvar grasslands with up to 20 grass species and 12 sedge species supporting large populations of grassland birds; and alvar savannas with scattered Red Cedar. What makes alvar biodiversity possible is the extreme flood-and-drought cycle. If you change the water patterns — by cutting ditches, burying culverts, or cementing underground channels — the alvar plants cannot survive. Once destroyed, this habitat does not come back.1
About 2 km southwest of Lonsdale, Ontario, lies the Salmon River Alvar — an 847-hectare site that provincial ecologists describe as one of the richest alvars in all of Ontario.4 Unlike most alvar sites, the Salmon River Alvar contains the full range of habitat types: bare pavements, open grasslands, savanna, woodland, riverside marsh, and dry forest, all within one connected landscape. It holds the second-highest plant species diversity of any alvar in Ontario4 and is recognized as an ANSI.
A plant that exists nowhere else in Canada. The Salmon River Alvar woodland is home to the only known population of Juniper Sedge (Carex juniperorum) in Canada.4 If the habitat at this site is destroyed, Juniper Sedge disappears from Canada entirely — not locally, not regionally, but from the country. As the Lennox & Addington Stewardship Council states: “Destruction of this habitat through corridor construction would result in national extirpation of the species.”1
The Salmon River Alvar has already been cut in two by Highway 401 and its concrete barriers.4 Wildlife that needs to move across the landscape — including bobcat — are already squeezed by this barrier. Adding a second major barrier — a high-speed rail corridor with fencing, noise walls, and maintenance roads — would cut the remaining habitat into pieces too small to sustain the species that depend on it.
Canada’s Species at Risk Act (SARA) makes it illegal to destroy the critical habitat of listed species or to kill, harm, or harass individuals of those species. The southern corridor passes through habitat supporting multiple such species. The table below lists species documented in the Napanee Plain alvar system directly affected by southern corridor construction.
| Species | Status | Federal Protection | What They Need |
|---|---|---|---|
| Eastern Loggerhead Shrike | Endangered | SARA Schedule 1 | Open alvar grassland with scattered shrubs for nesting |
| Bobolink | Threatened | SARA Schedule 1 | Meadows and hay fields |
| Eastern Meadowlark | Threatened | SARA Schedule 1 | Open grassland and alvar |
| Grasshopper Sparrow | Special Concern | SARA Schedule 1 | Alvar grassland — a habitat specialist |
| Short-eared Owl | Special Concern | SARA Schedule 1 | Open grassland; nests on the ground |
| Upland Sandpiper | Special Concern | SARA Schedule 1 | Open alvar grassland; nests on the ground |
| Juniper Sedge | Endangered | Federal assessment required | Salmon River Alvar woodland — sole Canadian population |
| Henslow’s Sparrow | Endangered | SARA Schedule 1 | Tall-grass alvar meadow; formerly bred here, suitable habitat remains |
The Eastern Loggerhead Shrike is one of Canada’s most endangered birds. Fifty years ago, shrikes were found across eastern North America. Today, fewer than 30 breeding pairs remain in Ontario, and the species breeds regularly in only two places in Canada: the Napanee Plain and the Carden Plain.5 The total wild Canadian population is now estimated at roughly 40 individuals.10
The shrike is specifically dependent on open alvar grassland. It needs large areas with scattered shrubs and fence posts for hunting and nesting; grasshoppers, crickets, frogs, and small mice; quiet during April–June nesting season (construction noise and vibration would disrupt breeding directly); and freedom of movement across open landscape, which fencing and noise barriers would block.
Surveys from 2004 found 150–200 pairs of Upland Sandpiper breeding in the Napanee Plain IBA each year — about 2% of the entire Canadian population — as well as 150–200 pairs of Grasshopper Sparrow and 200–400 pairs of Eastern Meadowlark.9 All of these species are in national decline. All nest on or near the ground.
The rare plants of the Napanee Plain alvars don’t survive despite the extreme flooding and drought — they survive because of it. The spring floods kill off competitive plants that would otherwise crowd them out. Disrupt the water cycle and the alvar ecosystem collapses, even if the physical ground is untouched.
This water cycle is driven by an intricate underground plumbing system: caves, cracks, and channels in the limestone that carry water across the landscape, well beyond the boundaries of any individual property. Because everything is connected underground, a change in one place can affect alvar communities hundreds of metres or even kilometres away.1
The Ontario Ministry of Natural Resources has identified changes to water flow as one of the top ten threats to alvar ecosystems.2 Rail construction through this landscape would trigger multiple changes simultaneously: earthworks cutting through underground drainage pathways; ditches redirecting where and when water flows; paved surfaces stopping rain from soaking into the ground; and cement grouting of underground cavities permanently sealing cave systems used by bats. The particular problem is that the underground system is mostly unmapped. Engineers cannot predict with confidence where the connections run or how far a disruption would travel.
Invasive plants are one of the top ten documented threats to alvar ecosystems.2 The same conditions that make alvars so distinctive — bare soil, extreme flooding and drought — also make them vulnerable when those conditions are disturbed. Any event that exposes fresh soil gives aggressive invasive plants like common buckthorn, dog-strangling vine, garlic mustard, and giant phragmites a foothold they would otherwise struggle to find. Once established, these species form dense monocultures that crowd out the rare native plants.
Linear infrastructure is one of the most effective ways invasive plants spread across a landscape. A high-speed rail corridor through the Napanee Plain would function as a continuous weed-introduction pathway: construction equipment carries seeds between sites; freshly disturbed fill provides ideal bare-soil conditions for invasive annuals; drainage ditches connect previously isolated patches; and maintenance vehicles travelling the corridor over decades continue introducing new propagules long after construction is complete. The Lennox & Addington Stewardship Council specifically identifies infrastructure access as a current threat to the remaining alvars.1
The Salmon River Alvar meets all five ANSI criteria and is recognized as one of Ontario’s most ecologically significant sites. Yet the Lennox & Addington Stewardship Council states plainly that an ANSI designation “no longer defends that area from development.”1 Most of it is privately owned farmland, and it continues to face incremental threats from rural subdivision, off-road vehicles, and agricultural intensification.
For the Alto consultation process, this matters in a specific way. A federal environmental assessment triggered by SARA would require Alto to demonstrate that the project would not destroy or damage the critical habitat of listed species. Given how many SARA-listed species live in this landscape, and how thoroughly aligned the southern corridor is with their documented habitat, that would be an exceptionally difficult case to make.
Each of the concerns described above would individually be a significant obstacle for a project like Alto. What makes the Napanee Plain especially problematic is that these issues don’t sit side by side — they feed into each other:
- The engineering solutions for unstable karst ground (Section 1) require altering underground drainage — which directly destroys the alvar ecosystems (Section 5) that those solutions were supposed to avoid disturbing.
- Destroying alvar habitat (Section 2) eliminates food sources and nesting sites for Species at Risk grassland birds (Section 4), while the construction zone simultaneously becomes the entry point for invasive plants that degrade the surrounding alvar (Section 6).
- The Salmon River Alvar (Section 3) is already damaged by Highway 401. A second corridor would isolate the remaining fragments, cutting off movement for bobcat, grey ratsnake, and Blanding’s Turtle.
- Existing protections (Section 7) offer no effective backstop, which means the environmental assessment process is the only real check on these risks — and that assessment would need to address all of these overlapping issues simultaneously.
- The Juniper Sedge’s only Canadian population, Ontario’s most endangered bird, and an unstable karst geology all overlap in the same small area. A bad outcome in any one of these areas makes all the others worse.
The combined picture. Taken together, these interlocking risks mean that a southern corridor through the Napanee Plain would face one of the most complex and costly environmental assessment processes imaginable — with a high probability of legal challenges under the Species at Risk Act that may not be resolvable through mitigation measures, on ground that poses ongoing structural hazards to the infrastructure itself.
The southern corridor for Alto would pass through a landscape that is, simultaneously: geologically dangerous to build on, home to globally rare ecosystems found nowhere else in similar concentrations, the last stronghold in Canada for an endangered bird, and the only place on Earth where a rare plant still grows in this country.
These are not contested claims. They come directly from government ministries, conservation authorities, species recovery programs, and the naturalists who have worked in this landscape for decades. They are part of the public record.
We believe the Alto consultation process must engage seriously with this evidence. A route choice that ignores these conditions — or treats them as problems to be engineered around — would be environmentally irresponsible and would likely face insurmountable legal and regulatory obstacles. There is a northern corridor option that avoids these issues. That option deserves full, fair, and transparent analysis.
All facts on this page are drawn from published government documents, conservation authority reports, and peer-reviewed research.
This plain-language overview was prepared as part of a public consultation submission. All factual claims are drawn from cited published sources. This document does not constitute legal or engineering advice.