Here’s last year’s Gulf dead zone. How big will this year’s be? (Photo courtesy of NOAA.)

If you’re an underwater creature living in the Gulf of Mexico, summer is not your friend. All spring long, rain falls on America’s farmland and floods the waterways around factory animal farms, creating a steady stream of nitrogen from excess fertilizer and animal waste that heads down the Mississippi River and out to the Gulf. These nutrients create algae that sinks, decomposes, and eats oxygen. The result is an oxygen-free area or underwater desert — a dead zone.

This year, one study from the University of Michigan estimates the Gulf dead zone might be a lot smaller than it has been in recent years — a mere 1,200 square miles, compared to 6,765 square miles in 2011.