Lanark County Ecology

Lanark County is a mostly forested and rocky region of the Ottawa Valley, about an hour west of the City of Ottawa. In many ways, this county represents the natural environment of the entire Ottawa Valley: a mixture of forest and wetlands, with scattered fire barrens and alvars. You can enjoy a one hour video introduction here.

Lanark County has large areas of deciduous forest that provide nesting habitat for many species of migratory birds.

Thirty natural areas for protection

The Green Gems of Lanark County

These important natural areas need protection to benefit wildlife, store carbon, and encourage tourism.

An introduction to the environment of Lanark County:

Lanark County has mostly Precambrian rock in the north and west, as you find in the upper Ottawa Valley (including Algonquin Provincial Park). In the south and east there is limestone, as you find in much of the lower Ottawa Valley (including the City of Ottawa).  There are also extensive areas of marble.


Granite and gneiss are commonly seen along road cuts in the northwestern regions of Lanark County. These rocks are part of the ancient Canadian Shield, and often have a distinctive rust red colour. They are the remains of a mountain range that existed about a billion years ago. (P. Keddy)

Limestone is commonly seen along road-cuts in
the southeastern regions of Lanark County. This exposure is just west of Carleton Place along Highway 7 and it shows the typical colour and layering. These are young rocks formed in the bottom of a shallow ocean aboout half a billion years ago. (P. Keddy)

Some regions of the county are flat due to thick clay deposits that originated more than ten thousand years ago. The western side of Lanark County was flooded by an enormous glacial lake, so these clay areas originated under fresh water. The eastern side of the county was flooded by the Champlain Sea, so many of these deposits resulted from more saline conditions. The eastern clay plains extend from Lanark County all the way to Montreal. The old shoreline of the Champlain Sea can still be found, and is mapped in my guide to the county. A colour soil map for the county is provided later on this page. 

Lanark County is just west of Ottawa, and lies betwen the Ottawa River in the north and the St. Lawrence River in the south.

When the first Europeans arrived, the area was mainly deciduous forest (shown above in the first photo), but there were also fire barrens and pine ridges, as well as lakes, beaver ponds and extensive swamps.  The history is also typical: indigenous peoples were replaced by Europeans, predominantly Scottish and Irish settlers, who logged the forests and cleared for farms.  On deeper soils there are now prosperous communities, while on shallow and rocky soils, farming collapsed and the forests are recovering. You can read a description of the original forests of Lanark County here.

In spite of two centuries of human settlement, there are still important natural areas left.  These include old forets, wetlands, rock barrens, and alvars.  There are also distinctive southern species including Five-lined Skinks, Gray Ratsnakes and Southern Flying Squirrels. Shagbark Hickories have crept as far north as some rocky south-facing hillsides, while a stand of Hackberry trees clings to the limestone cliffs along the rapids in Carleton Place. A list of 30 of the most important natural areas, including habitat for species-at-risk, is here.

This page is intended to provide residents with an introduction to the natural environment of the county and to encourage the protection of important natural areas. It is also a guide for visitors who wish to explore the natural environment. Below are sources of information on the ecology of Lanark County, including a guide to our priority natural areas, which I call the thirty Green Gems.

My Resources on Lanark County

A Guide to the Natural Environment of Lanark County, will introduce you to the natural environment of the county, and guide you on local excursions to wild places. This book has won three prizes. It can now be delivered directly to your home.

A video introduction to the natural environment of Lanark County. I invite you to sit back and enjoy this one-hour video recording about the natural environment of the county. If you teach biology or ecology in a local school, you may wish to share this with your class.

A video introduction to the wetlands of Lanark County. Meet some of our provincially significant wetlands and the wild species that live in them.

The frogs of Lanark County. There are eight species of frogs, and one toad species found in the wetlands of Lanark County. There is even a species of tree frog that does indeed call from trees in May and June. This chart shows when you can hear each species calling. The frog chorus starts each spring with spring peepers in April, and ends each summer with bullfrogs in July. All of these frogs depend upon healthy wetlands and forests.

Ground nesting birds. There are about 50 species of birds in Lanark County that nest on the ground. These native birds are particularly sensitive to human activities. Some, like the whip-poor-will and the black-and-white warbler, are declining in numbers. These birds illustrate why some natural areas need protection from human recreation or logging during the spring and summer.

30 Green Gems

The thirty Green Gems of Lanark County: priority areas for protection.

Green gems of Lanark County
Click for a larger sized map


Some external resources for Lanark County

Living with wetlands and forests: How Much Habitat is Enough?

The Plants of Lanark County by David White

Some guidelines for restoring forests

The Scotch Corners Wetland

The Burnt Lands Alvar

Help protect wild places: The Mississippi Madwaska Land Trust.

Learn about nature and help protect wild places: The Mississippi Valley Field Naturalists. Become a member and enjoy guided tours, public talks, and more.

Soil map for Lanark County

Northern half: enlarge
Southern half: enlarge