According to the United Nations Environment Programme: One hectare of trees can absorb 6 tonnes of CO2 a year, at about 100 trees per hectare.
By reducing the amount of carbon fuels burnt for space heating, the amount of CO2 emitted is reduced. The amount reduced can be equated to that absorbed by a tree in a year, and hence the reduction in the number of trees we have to plant to bring our planet back to equilibrium.
According to the UN Billion Tree Campaign: See their Fast Facts here
To make up for the loss of trees in the past decade, we would need to plant 130 million hectares (or 1.3 million km2), an area as large as Peru. Covering the equivalent of 130 million hectares would entail planting approximately 14 billion trees every year for 10 consecutive years.
The net forest loss per day is 20,000 hectares or the equivalent of an area twice the size of Paris. This adds up to 7.3 million hectares per year.
We calculate that a representative house emits 3.7 tonnes of CO2 a year from heating. That would require about 60 trees to absorb the CO2. Use of Hydromx® could save up to 35%, that's about 20 trees per house.