A new study from the American Geophysical Union (AGU) finds that, if global warming persists, blue lakes worldwide are at risk of turning green-brown.

Shifts in lake water color can indicate a loss of ecosystem health. The study presents the first global inventory of lake color.

While substances such as algae and sediments can affect the color of lakes, the new study finds air temperature, precipitation, lake depth, and elevation also play important roles in determining a lake’s most common water color.