Excess phosphorus runoff and emissions from urban areas and croplands, animal feedlots, sewage treatment plants, and combustion of fossil fuels has been blamed for the dead zone in the Gulf of Mexico, toxic algal blooms in Lake Erie and problems in numerous other lakes and rivers around the world.

For years unwanted nutrients were also choking the Florida Everglades, but in a surprising reversal, phosphorus levels have been reduced 79 percent this year — more than three times the state requirement — compared to the annual average runoff in the 1980s, according to an announcement from University of Florida’s Institute for Food and Agricultural Sciences. The average decrease in recent years has been around 50 percent annually.

The reductions have been achieved through a combination of best management practices targeting agriculture, including soil testing before fertilizer is applied, regulation of when and how much water can be pumped off of farms and into local waterways, and clearing sediment from canals that lead to the Everglades. All told, farmers have spent nearly $US200 million on improvements, according to the South Florida Water Management District.

Some think the reductions haven’t gone far enough, though. As the South Florida newspaper the Sun Sentinel reported earlier this month, representatives of Audubon Florida and the Sierra Club say phosphorus runoff needs to be reduced even further to comply with federal water quality standards.

Still, phosphorus levels are heading in the right direction. This year they are down to 94 parts per billion, compared with 500 parts per billion in 1986.