Using wood ash to restore calcium in lakes and forests
By Jenn Watt
Published June 21, 2018
Years of acid rain have left some lakes in central Ontario with “ecological osteoporosis,” a term scientists use to paint a picture of what happens to the environment when not enough calcium is present.
In May, Dr. Norman Yan of the Friends of the Muskoka Watershed gave a presentation to representatives from Haliburton County lakes about the importance of calcium and what can be done when a lake is discovered to have too little of the mineral.
With more than $74,000 in funding from the Ontario Trillium Foundation, the Muskoka watershed group was able to begin work on a wood ash recycling program, which would help correct the calcium problem.
Yan and his research colleague Dr. Shakira Azan presented at the Stanhope Firefighters’ Community Hall to a meeting of the Coalition of Haliburton Property Owners Associations on May 25.
Plants and animals need calcium to grow, but the amounts differ between species. The crayfish, for example, is between 10 and 30 per cent calcium. Fish are between two and eight. Wood is .1 per cent calcium, but bark is three per cent.
“Forests need it. Lakes need it for sure. And there’s a problem,” Yan told the group.
“There’s been, in the main Dorset study lakes, a 35 to 40 per cent decline in calcium over the last 35 years. … These are very serious declines.”
When the level of calcium drops below 1.5 milligrams per litre, things start going wrong, he said.
The Dorset study lakes include Blue Chalk, Chub, Crosson, Dickie, Harp, Heney, Red Chalk and Plastic, which are studied by the Ministry of the Environment through the Dorset Environmental Science Centre.
“These data sets are a provincial treasure, in my opinion,” Yan said in a follow-up email with the paper.
In Plastic Lake, five species of daphnia were lost when calcium levels hit the 1.5 mg/l threshold.
The loss of daphnia can be a problem as the little water flea eats algae and algal blooms can reduce water quality.
Lack of calcium on the land can also slow the growth of trees, particularly sugar maple.
“The nearshore waters of lakes support many species with high calcium demands including amphipods (commonly called scuds) and crayfish, and their populations are in decline or disappearing in several lakes,” reads a booklet produced by Friends of the Muskoka Watershed.
Yan said their focus has been on the Dorset study lakes, which were chosen because there is a range of development along the shorelines and range in sensitivity to acid deposition.
“The quite sensitive lakes also turn out to be quite vulnerable to calcium decline. While calcium is falling in most lakes in the area, it’s reaching levels that are damaging biota [regional plant and animal life] only in the particularly acid sensitive lakes,” he said by email.
What the average person might notice about a lake with declining calcium levels would be fewer clams and crayfish and more algae, Yan said.
“This change has been seen in lakes in the Maritimes when calcium levels fell,” he said.
In order to determine whether wood ash collected locally would be of use in restoring calcium levels of the forests and lakes in the Muskoka area, research was conducted by Yan and Azan, who works for the Muskoka watershed group.
Azan spent a week in Yan’s garage sifting through wood ash, removing foreign matter, to study the calcium and other components of the ash. The ash was used to test whether it would be toxic to daphnia when mixed with water. They found there was little impact to the water fleas, except when introduced in high concentrations.
The group says wood ash would be spread in forests (not directly into the water) and would make its way into the trees and the lakes through the soil.
With this information in mind, the group is now embarking on educational campaigns to spread the word about the uses of wood ash.
Among the benefits: reduction of waste in landfills, improving forest growth and productivity, and protecting and enhancing populations of calcium-rich creatures in lakes.
A survey of Muskoka residents found that of those who heat with wood, most produce about 20 buckets of ash per heating season, which researchers estimated would mean about 36,500 buckets from all Muskoka residents. In the survey, two-thirds of respondents said they would transport their ash to the landfill or a transfer station – ash that could be recycled in the forests.
The group has applied for grant funding to continue their work, which would expand the program’s footprint into Haliburton County.
Wood ash spreading does come with a few risks. Ash must be entirely cool before it’s used or it could start a fire. There is also the possibility of heavy metals in wood ash, which researchers recommended should be tested on a regular basis. Fine ash particulate should also not be breathed in. And wood treated with preservative should not be used in the recycling program.
Recycling and Reusing Wood Ash
(The following information is from the Friends of the Muskoka Watershed and used with permission.)
Wood ash can be used in many ways. Here are some ways you can reuse/recycle your wood ash:
Use cold wood ash in your gardens, on driveways, and on forest soils.
Use ash from wood that is not pressure-treated, contains preservatives, insecticides, metals, or plastic products, or any foreign matter (e.g., nails, staples).
Spread wood ash widely on your woodlot, focusing on sugar maple trees that may well receive the most benefit from it. Do not concentrate in any one area.
Do not sprinkle wood ash in any waterbody on or near your property.