The phrase "butterfly populations" refers to the number or amount of butterflies in a specific area or region. It tells us how many butterflies are present in a particular place at a given time. Full definition
Facing challenges from climate change and increasing loss of habitat, butterfly populations worldwide have been affected one way or another. (treehugger.com)
A lifetime of research points to changes in butterfly populations due to a warming climate. (livescience.com)
They reported this year that the blue butterfly population reached 20,000. (discovermagazine.com)