Where did all the calcium go?
A century of acid rain and historically poor logging practices have flushed calcium from the soil and from the lakes and rivers. Most of Muskoka’s lakes have lost 25% to 50% of the calcium they need. Even though acid rain has largely stopped, and forestry practices have improved, without intervention it will take centuries for calcium levels to rebound.
Why is this a problem?
All life needs calcium. In Muskoka, forests are about 2% calcium by weight, and when calcium isn’t available, the trees and other forest plants can’t grow as quickly or efficiently. Many aquatic creatures – particularly hard-shelled creatures like crayfish, turtles and molluscs – are even more dependent on calcium. Crayfish diversity in many lakes has already declined by 25%.
When trees aren’t growing as quickly, they can’t capture carbon as efficiently, impacting their ability to help fight climate change. In lakes, the tiny crustacea and molluscs are often filter-feeders, performing a vital function in cleaning our waterways. Just one group of species filters the entire volume of Lake Muskoka every week in the summer.
Is this a problem everywhere?
No. The problem is most severe in areas with thin soils, granite bedrock, and a history of being exposed to acid rain. Muskoka and other parts of central Ontario are uniquely positioned to feel the brunt of this problem.
What will wood ash do?
Wood ash is about 1/3 calcium by weight, and also contains many other key nutrients. Much of it is absorbed into the soil and quickly taken up by trees and other plants. What isn’t absorbed by the plants will make its way into the lakes.
How much ash will it take?
It will take roughly four tonnes of ash per hectare over many thousands of hectares to restore the calcium balance. That is far more ash than Muskoka residents produce. The lessons learned in this three-year study will be used to help develop a province-wide ash recycling program, to bring wood ash from southern Ontario.
