Data story 02 ยท For all ages
How much forest do they fill?
Each winter, scientists in Mexico measure how much forest the monarch colonies cover. Last winter it was 2.93 hectares. That is hard to picture, so here it is as squares you can count, soccer fields you can imagine, and an estimate of the monarchs inside.
Read it right
Every chart has limits. Here is what this one can tell you, and what it cannot.
What this shows
- Forest area, as squaresThe forest covered by eastern monarchs each winter. One square is a tenth of a hectare.
- A soccer-field comparisonHow the area compares to a FIFA soccer field, about 0.714 hectares.
- An estimate of the monarchs insideUsing 21.1 million monarchs per hectare, a common middle value.
What it does not show
- An exact countScientists have measured from about 2.4 million to 80.7 million monarchs in a hectare, so any estimate has a wide range.
- Western monarchsThey winter on the California coast, not in these forests.
Sources. Forest area: WWF-Mexico and CONANP, compiled by Monarch Watch. Monarchs per hectare: Thogmartin and others (2017). A FIFA soccer field is about 0.714 hectares. The narrated tour is read by an AI voice (OpenAI gpt-audio, via OpenRouter) from the captions you see. See Data and credits. No endorsement implied.