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Rapid expansion of industrial farming in U.S. contributes to increased pollution, harmful algal blooms

September 10, 2020

A recent paper by University of Maryland Center for Environmental Science phytoplankton ecologist Pat Glibert sheds light on the impacts of both crop and animal industrial farming in the United States on nutrient pollution. The sharp increase in number and concentration of animals farming operations may lead to further human health and environmental issues, including increased nutrient pollution and harmful algal blooms.

“In order to maximize production and profit for the meat companies, what goes by the wayside is the nutrient pollution. That is the cost that we pay for food that is comparatively cheap,” said study author Pat Glibert. “We need to be looking more seriously at these animal operations from the perspective of the nutrients that they are putting off and the fact that they are now concentrated in parts of the country in such densities that we really have localized these pollutants.”

This review highlights the sources of nutrient and greenhouse gas pollution from farms in the United States by source, form and location, and how these sources have changed over recent years using data that are all available to the public. While nitrogen pollution from crop farming fertilizers exceeds that of animal manure and human waste, phosphorus pollution from manure and fertilizer use are comparable in the U.S. Understanding what sectors are contributing most to nutrient pollution and how they are doing can help managers understand where to focus efforts of ecosystem management.

The review also found an increase in the proportion of nitrogen to phosphorus pollution through farming practices, which can lead to larger, more toxic harmful algal blooms.

“In both fresh and marine systems nutrient pollution is increasing, harmful algal blooms are increasing, hypoxic zones around the world are now found, all related to nutrient sources,” said Glibert.

The number of concentrated animal feeding operations (CAFOs), the main source of meat production in the United States, has increased almost 10% in the last decade alone leading to a sharp increase in nutrient pollution in the areas surrounding these facilities. In 2019, the U.S. produced almost 8.7 billion animals from concentrated animal feeding operations, localized in a small number of regions in the country, creating localized sources of pollution that can threaten the health and safety of their communities.

Crop agricultural practices are also major sources of nutrient pollution. Managers have been focusing on working with farmers to reduce runoff from fertilizers, the major contributor to pollution in waterways. In terms of nitrogen pollution, agricultural fertilizer sourced pollution exceeds that of manure and human waste several fold. About half of nitrogen and phosphorus used in soils ends up in the surrounding environment through runoff and volatilization.

Runoff associated with fertilizers use has improved with best management practices, but reducing the growing waste from concentrated animal feeding operations is essential if eutrophication and its effects on fresh and marine waters are to be reduced.

Pat Glibert

Excess nutrients released into freshwater systems and marine systems yield somewhat different negative effects, but both can lead to harmful algal blooms. For freshwater sources that are victim to nutrient pollution and the harmful algal blooms that result from it, the risk to human health from cyanobacteria blooms is more apparent, while the harmful algal blooms that form in marine systems can have a significant impact on the ecological system as well as a delayed human health effect through contamination of seafood.

When excess nutrients run off into fresh water systems, an issue on the rise as pollutant sources such as concentrated animal feeding operations increase in density, harmful algal blooms in drinking water supplies have led to health consequences ranging from skin irritation to liver cancer and failure after long term exposure.

Waste from hog and dairy farms is often kept in open lagoons that are susceptible to flooding and extreme storms, a phenomenon on the rise as climate change intensifies. The nitrogen and phosphorous from the waste lagoons is spread to surrounding fields at levels that can no longer be absorbed, leading to contamination of water used both recreationally and for human consumption.

 “There are many of these operations located near freshwater and we are seeing more outbreaks of toxic cyanobacteria, the culprits responsible for freshwater harmful algal blooms in the surrounding areas,” commented Glibert.

Understanding the ways that different sources of nutrient pollution are contributing to the problem can help managers zero in on what industries need to be focused on in terms of best management practices.

To protect waterways from nutrient pollution, many solutions have been focused on controlling phosphorus input rather than nitrogen, but numerous studies outlined in this review show that the increasing ratio of nitrogen to phosphorus can cause harmful algal blooms to grow more abundantly and more toxic. Glibert highlights the need to work towards environmental strategies that tackle reducing both nitrogen and phosphorus nutrient pollution from both crop agriculture and animal production even though the costs to reduce and mitigate nutrient pollution are extremely high.

From hogs to HABs: impacts of industrial farming in the U.S. on nitrogen and phosphorus and greenhouse gas pollution” by Patricia M. Glibert was published in Biogeochemistry.