Thousands of kilometers of ditches have drained large parts of Finland’s forests. Why, you ask? Landowners wanted to be able to grow more fast-growing conifers such as spruce in order to increase profits and make forestry work easier. As a result, the swamps, which are among the world’s most effective carbon sinks, have been greatly reduced. In recent decades, these environmental changes have released more carbon into the atmosphere than all of Finlands traffic has caused in the same period.
Heikki Susilouma is taking the initiative to reverse these mistakes of the past. As a young boy, he spent a lot of time in marshlands. Already 50 years ago, he collected signatures to stop the draining of marshes.
To decide where to close the trenches, you need to analyze the topography of the area and find the best and most effective location for building a dam. An expert had mapped the area and marked the possible sites on the map.
On site, Heikki made a precise decision very close to the mark on the map where the ditch becomes narrower and steeper, causing the water to drain away more quickly.
Once we had found a suitable location, we began our work. The trunks of the spruce pillars need to be sharpened so that they can be driven into the ground of the trench more easily.
We cut down two strong spruce trees for the side walls and then placed shorter trees as a barrier.
The sledgehammer is an important tool used to hammer the logs into the trench floor.
At the same time, we began shoveling suitable soil to fill the dam. Sand, clay, and rotted peat are the best materials, but they are not always easy to obtain under the roots of trees.
The walls of the dam are sealed with branches. The dam should be slightly higher than its surroundings so that floodwater in winter flows further to the sides and damage to the dam is prevented.
All the small spruce trees that we had to cut down for the dam were growing right next to it and are surplus material. Even though it seems cruel to cut down young trees, the carbon that is prevented from escaping from the soil by this wooden dam far outweighs the environmental benefits of these small trees.
We are ready to leave the construction site for now. Next time, we will need to fill the inside with more sand and soil until it rises above the surrounding area.
Water is already slowly collecting on the upstream side of the dam. We threw the remaining branches into the ditch to protect the dam from the flow of water. There was a pile of stones next to the dam. When the earth layer of the dam is high enough, we can place these stones on top of it as weights. However, the expert says: Never put stones larger than a child’s fist in the earth!
Text by Maria L. Räihälä and Matthias Fritsch
Photos by Matthias Fritsch
The rewilding project Majava is an initiative by Maria L. Räihälä.
Visit http://morgenvogel.net/majava-workshop-25.html for more information and future workshops in Finnland.