Things I am Thinking About Right Now...

  • 1. Finally Updated; A busy ( and not-so-birdy fall ) fall
  • 2. A smew in Ontario ??? And I got to see it !
  • 3. Thinking about summer vacation...
  • 4. And Sping trips too !
  • 5. Quite a few Winter rarities around. May try to add a few more to the list
  • 6. Still no snow on the ground...
  • 7. Project FeederWatch is going strong. Two eports submitted...
  • 8. I think I have convinced my wife to visit Cape May next summer !
  • 9. The Elephant Pepper Development Trust ( Check out their site ! )
  • 10. Tying to decide how to spend my remaining gift certificates !

Wednesday, 8 June 2011

What is an Alvar ?

For anyone visiting the Carden Nature Festival or visiting the Carden area on their own, they are destined to run into the term Alvar. Alvar habitats are globally rare, found in the Great Lakes basin, Quebec, the United Kingdom and Baltic Europe. From the North American perspective, Ontario has 75 % of the alvar habitat with notable alvars scattered around the provice from the Napanee Plain to the Bruce Peninsula to Pelee Island. The Carden Alvar ( with respect to the others ) may be the most significant alvar in the province. It is identified as an Important Bird Area and has been the focus of conservation efforts from a number of different organizations.

A typical alvar habitat in the Carden area
  So what is an alvar ?

The key characteristic of an alvar is an extremely thin layer of soil over a base of bedrock. In the case of the Carden alvar, the bedrock is limestone. The habitat is harsh for plant communities. During the spring, the area is flooded. During the summer, the heat is oppressive, baking the vegetation. Therefore, the plant communities on an alvar are survivors; evolved to deal with environmental extremes. These areas also tend to be open and dominated by grasses, low-growing plants and in some areas, even lichens and mosses.

Prairie Smoke at Windmill Ranch
Typical alvar wildflowers including some bright orange Indian Paintbrush
The biodiversity seen on alvars is very important. Plants like Prairie Smoke, Indian Paintbrush, Early Saxifrage, Shrubby Cinquefoil and Balsam Ragwort are specialists on alvars. Insects are also prolific. The Carden Alvar is an amazing area for butterflies and dragonflies ( Check out the parking area of Prairie Smoke Nature Reserve for  an impressive display of the latter ). Research is also revealing many alvar-specific invertebrates that are adapted to and only found within this habitat. Herpetologists have a good chance of finding numerous snakes, frogs and turtles including rarer species like Blanding's turtles or Milk snakes

A Grey Tree Frog at Windmill Ranch
The Carden Plain is identified as an Important Bird Area frequented by birdwatchers. Many of the declining grassland species like Bobolink, Eastern Meadowlark and Upland Sandpiper are easy to find. Breeding Eastern Loggerhead Shrikes, endangered species in Ontario, can also be reliably found here The shrubby alvar habitats hold a number of songbirds including the Golden-Winged Warbler. A knowledgeable birder may be able to find 8 sparrow species in a day including Vesper, Grasshopper and Clay-Coloured. The wetlands can be possibilities for Rails, Bitterns and Sedge Wrens.

The Carden area is also considered a part of "The Land Between", the area that borders the Canadian Shield to the North and the Mixed-Wood Plains to the south. As result, mammal species like Black bears, Wolves and Moose that are typical farther north wander into this area frequently.
Lichens and Wildflowers at McGee Creek Nature Reserve
The Carden Alvar is relatively well-protected. Conservation organizations like the Nature Conservancy of Canada and Couchiching Conservancy have purchased large amounts of land for the purpose of protection. However, there are threats to this ecosystem that still exist. The demand for limestone makes the Carden area a popular region for quarries. Thus any land acquisitions become bidding wars between conservation organizations and quarriers ( guess who tends to win... )

From a biological perspective, alvar habitat can become overrun with shrubby vegetation very easily. Under natural circumstances, fire would prevent this succession from happening. As humans moved into the area, they suppressed fire. However, they used these areas as ranches and the cattle helped to hold back the advance of shrubby vegetation. As the ranches disappear, so do the forces that keep shrubs in check. Some of the Nature Conservancy properties like Cameron Ranch and Windmill Ranch are still active cattle ranches, maybe the first time that cattle have been used to preserve a natural habitat.

Invasive Species also pose a threat to the Carden alvars. It is plants that pose the biggest threat as they move in to ecologically fragile alvar communities. The area is somewhat isolated but invasive species are moving in. One noxious example is Dog-Strangling Vine. DSV can choke out native alvar vegetation, growing quickly, while withstanding the harsh conditions. There are programs that work to eradicate the weed but as with all invasives, the challenge is daunting.
Wylie Road - One of the best birding locations in Ontario
Despite the issues, the Carden Plain is an excellent example of an alvar. Events like the Carden Nature Festival allow us to get different perspectives on this unique environment. However, the Carden area can be visited anytime. There are many areas that have been conserved, hiking trails and Wylie Road, a wonderful example of "road birding" that has been highlighted in Birder's World magazine. There are also many enterprises that continue to promote conservation including the Nature Conservancy of Canada, the Couchiching Conservancy and events like the Carden Challenge. Supporting the conservation of this unique habitat ensures birders and nature-lovers will enjoy this area for a long time to come.

I have some more material from my Carden weekend. Check out some of my pictures of the alvar wildflowers here. My birding success at the Carden Nature Festival is summarized here. THE DAUGHTER and I had a great time exploring aquatic wildlife too ( Posting still to come ... )

1 comment:

  1. Hello,

    Would you be able to post a way to contact you? I would like to get some more information from you regarding alvars for a project I am working on for a university class (also any information I collect will be shared with Manitoba conservation since there is one with a proposed development here now). I just don't want to post my email on a public comment.


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