Streams are abruptly acidifying and turning orange or milky-white across vast regions of North America’s northwest. This is caused by permafrost thaw — an outcome of a warming climate that has immediate consequences for water and wildlife.
Stream acidification is driven by the weathering of naturally occurring sulphide minerals, which release acid, sulphate and toxic metals into groundwater and streams. This is known as acidic drainage. Water can become “rusty” for several kilometres downstream as iron and aluminium minerals enter streams.
