Warming rivers are quietly losing their breath

A global analysis of 21,000 river systems reveals that nearly 80 percent of them are steadily losing their breath. While we often worry about water levels or clarity, the real crisis is hidden in the chemistry of the water itself. Dissolved oxygen—the tiny fraction of gas that fish actually breathe—is highly sensitive to temperature. As water warms by just one or two degrees, its physical ability to hold onto oxygen drops sharply, much like how a warm soda quickly turns flat and lifeless.