Increase biomass means younger 100-year forests are maturing, but there's still a decrease in acreage (even if only slightly in the last decade or so). We've seen a larger decrease in forest area since the 60s.

https://harvardforest1.fas.harvard.edu/exist/apps/datasets/showData.html?id=hf013

https://www.fs.usda.gov/ne/newtown_square/publications/other_publishers/OCR/ne_2003_brooks001.pdf

We're actually going through a second phase of deforestation. Woodlands have been declining since the 80s due to development.