So a mature forest can soak up the equivalent of 440 tonnes of atmospheric carbon dioxide per hectare in the 50-100 years it takes to reach maturity - that's a one-off total - not per year and will take several decades at least to get there.

This is approximately equivalent to the entire land area of Spain, twice as big as the United Kingdom and bigger than any US state other than Texas (696,621 sq km.) or Alaska (1,717,854 sq. km.) To be forested anew each year and held as such forever.

It would appear therefore than planting trees alone other than on a colossal scale  is not going to even allow us to stand still, let alone start to reverse the effects of global warming.