Toxic Algae Blooms and Agriculture: 5 Things to Know About Their Connection

Toxic Algae Blooms and Agriculture: 5 Things to Know About Their Connection

The increase in frequency and severity of harmful algal blooms are a reminder that we need to make significant and lasting changes to the way we farm and produce our food, especially in reducing nutrient pollution.

5 Things to Know About The Connection Between Toxic Algae and Agriculture

Those who follow environmental or climate news have probably seen reporting about harmful algal blooms (aka toxic algae or HABs). Over the past few decades, scientists have observed a surge in the frequency of these blooms around the planet as well as an increase in their severity and geographic distribution. 

Blooms happen when an excess of nutrients like nitrogen and phosphorus feed algae causing them to ‘bloom’. When the blooms die, the decomposition processes use up available oxygen in the water, creating a dead zone where no aquatic life can survive. 

According to the US Environmental Protection Agency (EPA), the blooms – known as everything from red tides to blue-green algae or cyanobacteria – have been cropping up across the country and are now, in fact, in all 50 states

For example, the Summer 2022 dead zone in the Gulf of Mexico, which has been monitored for a little over 30 years, was larger than an area the size of Rhode Island and Delaware combined. The Gulf’s largest dead zone on record, in Summer 2017, covered 8,776 square miles, an area about the size of New Jersey.

Most news stories understandably focus on the negative – and sometimes severe – impact these blooms can have on humans and animals, but give short shrift to what is causing the blooms. While this is a scientifically complex issue and there are a number of factors that have been linked to the blooms and their toxin production, there is a strong linkage between industrial agriculture and toxic algae outbreaks that we must not overlook. 

Here are 5 things to know about the connections between agriculture and algal blooms:

First and foremost, these blooms are yet another reminder that we need to make significant and lasting changes to the way we farm and produce our food, especially in reducing nutrient pollution. According to the EPA, “animal manure, excess fertilizer applied to crops and fields and soil erosion make agriculture one of the largest sources of nitrogen and phosphorus pollution in the country.” 

It is this nutrient pollution and over-enrichment that is primarily fueling the harmful algal blooms. Thanks to the important work of NOAA and other federal and state agencies, we know a lot more today about the growing threat that these blooms pose to the nation’s aquatic ecosystems, public health and local and regional economies.

Pollution associated with industrial animal production or concentrated animal feeding operations (CAFOs) without a doubt contributes to nutrient over-enrichment which can be a factor in harmful algal bloom outbreak frequency and toxin production. North Carolina – home to a large number of industrial poultry and hog farms (third largest producer of poultry products and second largest pork producer in the US) – provides a unique window into this environmental problem. 

In June 2016, Waterkeeper Alliance, North Carolina Riverkeeper organizations and Environmental Working Group released a first-of-its-kind interactive map that documented the approximate locations of more than 6,500 CAFOs – large swine, poultry and cattle operations – across the state of North Carolina. 

All those CAFOs must generate a lot of poop, right? Yes, they do. 

The researchers estimated that these CAFOs annually produce more than 10 billion pounds of wet animal waste and 2 million tons of dry animal waste in North Carolina. Aerial views of the CAFOs reveal manure lagoons (aka waste ponds) from swine operations and their proximity to rivers, streams and other vital public water sources. These lagoons are often unlined, and nutrients can leach out and find their way into nearby waterways or aquifers.  Farms are often sprayed with the manure depositing nutrients that are easily washed away in heavy rains. But that’s not the only way nutrients can get into the waterways. 

When storms bring heavy rains, like from Hurricane Matthew in 2016, rivers overflow their banks, flooding the lagoons and washing large amounts of animal waste downstream. While this can have an immediate impact on communities that depend on certain rivers – like the Neuse and Cape Fear – for their drinking water, in the longer term, the pollution caused by such flooding can also fuel harmful algae blooms that result in drinking water bans (among other negative impacts).

Crop production can also play a role. For example, the harmful algal blooms that plague Lake Erie are fueled in part by fertilizer runoff from industrial corn and soybean farms.

2. The Climate Piece

Just as industrial agriculture is intimately tied to toxic algae blooms, it is also closely connected to climate change… which is inextricably linked to the toxic algae crisis.

One primary source of greenhouse gas emissions (GHG) in the US is agriculture – in particular, animal agriculture and livestock production. Cows and other ruminant animals produce methane, a powerful GHG gas, during a digestive process known as enteric fermentation. Another source of methane from ruminant animals is the massive amounts of decomposing manure being stored in the lagoons used by factory farming operations. 

According to the Food and Agriculture Organization of the United Nations, global livestock production represents 14.5 percent of all anthropogenic GHG emissions. It doesn’t have to be this way. 

Livestock farming that makes use of regenerative agriculture techniques has the potential to absorb more greenhouse gasses than it currently does – with the added benefit of curtailing nutrient pollution.

What about the link between climate change and toxic algae blooms?

According to the US Environmental Protection Agency, research indicates that the “impacts of climate change may promote the growth and dominance of harmful algal blooms through a variety of mechanisms including warmer water temperatures, changes in salinity, increases in atmospheric carbon dioxide concentrations, changes in rainfall patterns, intensifying of coastal upwelling and sea level rise.” 

Indeed, there is already evidence of climate change exacerbating the toxic algae problem. For one, toxic algae outbreaks are arriving earlier and staying longer (partly due to warmer water temperatures); a NOAA scientist noted this trend following the 2013 algae outbreak in Lake Erie. Another example is the trend towards more intense storms and precipitation (and the subsequent flooding) and the role they play in harmful algal blooms. 

Citing North Carolina’s experience with two 500-year floods (linked to Hurricanes Matthew and Floyd) in the last 20 years, Cape Fear Riverkeeper Kemp Burdette warned that “as the world continues to experience climate change and rising sea levels, we’re going to see more and more and more flooding brought on by these stronger storms.”In groundbreaking research led by Dr. Christopher Gobler, the recent intensification of toxic algae events – along with their distribution and frequency – in the North Atlantic and North Pacific Oceans has been linked directly to warming ocean temperatures (brought about by climate change).

3. The Economic Connection

If agricultural runoff and toxic algae blooms aren’t reined in, then communities across the US will continue to experience the negative impacts to the environment, human health and the economy. 

Some of the economic impacts will be seen in our fisheries and drinking water supplies. Tom Philpott wrote that the annual damages caused by toxic algae blooms nationwide, “everything from increased [drinking water] filtration costs to declines in fish populations,” amounts to about $2 billion in costs to the US economy. Philpott points to Lake Erie and its surrounding communities as a “stark example” of the threat posed by polluted agricultural runoff and harmful algal blooms. 

On the other hand, properly funding initiatives that seek to reduce nutrient pollution, including from agricultural land, will help to boost the economy including sectors related to our food system.

4. Farms Can Be Part of the Solution

While some farms are a big part of the nutrient pollution problem, all farms can be a big part of the solution. A large majority of farmers are willing (and, in some cases, already doing) the right thing and we need to provide the necessary support to help them keep nutrients in the field and out of our waterways. As noted in Scientific American, one way to cut back on nutrient runoff is somewhat simple: “apply only the right amount of fertilizer in a targeted way at the appropriate time exactly where it can do the most good for crops and have the least likelihood of simply running off in the rain.”

That said, a bigger picture and more effective approach is regenerative agriculture. Regeneration International describes regenerative agriculture as “farming and grazing practices that, among other benefits, reverse climate change by rebuilding soil organic matter and restoring degraded soil biodiversity – resulting in both carbon drawdown and improving the water cycle.” In regards to the latter, regenerative agriculture practices result in increased water percolation and retention and cleaner (and safer) water runoff.

5. Your Food Choices Make a Difference

Among the most important decisions you make every day are your choices about the food you eat. Given the intense focus on climate change you may already be thinking about how to leverage your personal food choices in the fight to reduce greenhouse gas emissions. 

Fortunately, in addition to the important role that these decisions play in combating climate change, they can also help tackle the toxic algae problem. 

For instance, you could eat a little less meat – try Meatless Monday. While Americans are eating less beef in recent years, the Natural Resources Defense Council observes that we still consume much more than most countries. In fact, the US ranks fourth globally in per capita beef consumption – we’re eating twice as much red meat as advised by USDA’s dietary guidelines. For those who still have a hankering for meat, make sure it comes from a sustainable farm. 

In addition, choose sustainably grown produce as much as possible. Both of these choices will translate to less polluting nitrogen and phosphorus runoff, and the benefits don’t end there. Some of these food choices can shrink personal water footprints and improve animal welfare, public health and labor conditions.

Originally published at GRACE’s former blog Ecocentric by Kyle Rabin on 07.05.2017. Updated on 01.12.2023.
Image: Algae Bloom in Lake St. Clair Credit: NASA/USGS