In December last year a project was announced to plant one million trees in the Brecon Beacons National Park, which is where I live. I wondered, how much land would one million trees take up? Assuming 2250 trees per hectare, it works out at just over 4 square kilometres, which is a tiny fraction of the park. I made this map to illustrate:

Visualization type: map

Data source: data.gov.uk, KML, 1.4 MB

Technical notes: generated using Leaflet; code

See also: “One Million Trees in the Brecon Beacons National Park” Facebook page