Last summer, southern Florida nearly ran out of water. It wasn’t drought—actually, the opposite. The state got way too much rain, which flushed nutrients from over-fertilized farms into its canals and reservoirs. All the extra food led to a massive algal bloom, a skim of blue-green slime that smells like rotten eggs and poisons humans. Governor Rick Scott declared a state of emergency in four counties.
Algal blooms aren’t new. In fact, they happen naturally. Florida’s was dangerous because of humanity’s industrial-strength thirst and hunger, leading to big, fertilizer-based agriculture. Add climate change to those pre-existing conditions, and you’ve got a water system primed to snap. More rain in already-wet agricultural areas will leach away even more nutrients, causing more blooms, leading to more water shortages—impacting fisheries, agriculture, and public health.
A new study published today in Science shows just how bad these algal blooms will be, based on three different carbon emissions scenarios. On the bright side, this means policymakers can start planning all sorts of ingenious new ways to curb fertilizer use. And that’s what they’ll do—right guys?
Scientists have known about the links between rain, nutrient runoff, and disaster for years. “Nutrients are essentially food to phytoplankton,” says Anna Michalak, a climate scientist at Stanford University’s Earth Systems Institute. “When a bunch of it leaches into the water, you stimulate these algae to grow. And when they eventually die, they decompose, and use up oxygen, creating dead zones.” One of the biggest dead zones occurs pretty much annually off the coast of Louisiana, fed by the Mississippi River’s runoff.
Likewise, scientists have long suspected that algal blooms would get worse as climate change brings more rain to already wet regions. “For close to 10 years we’ve been looking at how to better understand recurrence of hypoxic dead zones and algal blooms around the US,” says Michalak, who co-authored the new paper. During that time, she worked with her lab to develop a model linking rainfall to nutrient runoff, which she published last fall. This latest research links that model to the results of a massive database of climate change scenarios.
Those scenarios fall into one of three possible futures. In the first, humans continue with business as usual, emitting fossil fuels at a rate that follows the historical trajectory. This gets bad. The worst runoff will happen in the Mississippi-Atchafalaya watershed, and the Northeast region, from Maryland to Maine. This megaregion—encompassing much of the nation’s agricultural land, and most of its major population centers—could be hit with an 18 percent increase in nitrogen loading by the end of the century. The other scenarios are incremental versions of humanity cleaning up its act, leading to slightly less nitrogen runoff.
Even the rosiest scenario predicts runoff increases ranging around 5 to 10 percent, depending on the region and how far you project into the future. That means humans are going to have to make up the deficit by reducing how much fertilizer they use. Not an easy ask, even before you consider that the Earth’s population—and therefore its appetite—is growing. Remember that 18 percent increase Michalak’s group predicted for the Mississippi-Atchafalaya watershed? In order to counteract all that runoff, the region needs to dump 30 percent less nitrogen into its soil.
Impossible, you say? Well, before your reflex climate pessimism kicks in, consider this: The US EPA has already imposed a region-wide nitrogen reduction. The ultimate goal calls for a 62 percent cut. Currently, farmers are working towards 20 percent. They’ve done this by things like applying fertilizer directly to crops through precision agriculture, composting, or by sustainably tossing out livestock manure. “This is all the low hanging fruit. To really get to the next step, we need to talk about some of the more blue sky, high technology agriculture,” says Sybil Seitzinger, an environmental scientist, and director of the Pacific Institute for Climate Solutions at the University of Victoria.
For instance, cattle are a huge greenhouse gas emitter, plus their manure is a major source of nitrogen. Lab grown beef would take care of both problems. Another tech solution would be genetically modifying crops like corn or cereal grains, so they are capable of fixing their own nitrogen. This means they would be more efficient at taking up soil nutrients—farmers would need less fertilizer. The technological challenges are tough enough. These solutions would also be up against the monied meat industry, which isn’t so excited to cull its herds and leave the burgermaking to pencil-necked lab jockeys. And in case you haven’t been paying attention, genetically modified organisms don’t have the rosiest reputation in the US. Then again, the prospect of running out of clean drinking water might just inspire people to expand their palates.