During the last COSEWIC meeting (Committee on the Status of Endangered Wildlife in Canada) in November, 2007, the risk to wood turtles was upgraded from "Special Concern" to "Threatened", indicating that their populations continue to decline.
Algonquin has one of the last self-sustaining populations left in Ontario. While it's the largest remnant population there is, it's estimated that there are only about 500 individuals left in the park.
It's known that wood turtles are killed by traffic on roads and by road-building. The more roads there are, the greater the roadkill.
There is an illegal pet trade going on because of their attractive appearance, with individuals being captured and some being sent to overseas markets. Others are taken home by those who don't know any better. In Algonquin, all wildlife are protected, but it's probably obvious by now, that laws aren't always effective at preventing abuse.
Loss of habitat is another cause in the decline - wood turtles occupy lands along streams and rivers, and often these are developed or logged, with damage being done by heavy machinery. In Algonquin, additional buffers along all streams, large or small, are needed to protect habitat.
Photos for ID... the concentric growth rings on the carapace give the appearance of wood, and the orange-yellow colors near the throat are distinctive.