I believe that birch is considered a renewable resource.
It grows very quickly, and based on the size of the trees, harvesting seems very practical.
I don't think oak and hickory fall into that category.
Average wage in Estonia is $ 7.00 per hour vs $ 18 or so per hour in the US..one can only guess what the minimum wage is over there.
*Don't have to guess...minimum wage is 2.40 per hour.
There might come a day that we are buying our dirt from somewhere else.
At least we Americans are making the money and jobs by importing it, trucking it, distributing it, and making pizzas with it.