Even agricultural conservation might not save Midwestern freshwater biodiversity

Sustainable Leaders | North America

By Hannah Corsini, Kingfisher Writer

Published March 13th, 2024

Agriculture is a major driver of land-use changes and can intensify the impacts of climate change on temperature and groundwater. The loss of riparian cover or vegetation can affect the ecosystem’s health of the Mississippi River Basin in the Midwestern US, particularly the fish population.

Freshwater ecosystems are among those most threatened on the planet. Humans depend on freshwater for many reasons, but water as a resource is becoming increasingly scarce due to overexploitation, pollution and climate change.

A new study surveyed a river of the Mississippi River basin to evaluate freshwater biodiversity changes. | SFWS Mountain-Prairie / Flickr.

Not only does this spell disaster for us but also for the species that rely on freshwater at the core of their ecosystems. Freshwater fish exhibit the highest extinction rates, with freshwater species as a whole showing an 83% decline since 1970.

Chemical inputs used on farms can drain off into waterways where they can accelerate plant growth to the point that algal blooms form. Algal blooms are caused by eutrophication, and when the algae die, their decomposition uses all of the available oxygen in the water, creating what is known as a ‘dead zone.’

A study published in 2023 suggests that although climate change will increase the severity of harmful algal blooms (HABs), full implementation of conservation practices can help offset their occurrence, suggesting that these practices may function best as a type of damage control for the effects of climate change.

Dead zones, being devoid of oxygen, are uninhabitable for plant and animal life. A 7,829 square mile dead zone in the Gulf of Mexico now exists as a direct result of nutrient runoff from Midwestern farms into the Mississippi River basin, which has seen its nitrogen levels triple since the 1950s due to agricultural pesticide and fertiliser use.

‘Climate change will increase the severity of harmful algal blooms.’

The reduction of riparian cover around the riverbanks of the Mississippi River basin has also led to negative impacts on fish communities downstream from the river. The loss of riparian cover can increase solar radiation exposure, alter river flow patterns and reduce habitat complexity.

Researchers recommend building wooded riparian zones to recover the river’s sinuosity. The riparian zone can also help buffer between aquatic communities and terrestrial agricultural production. Although there is uncertainty in farming communities the economic benefits from recovering riparian cover can be quantified.

Further remedies: Best Management Practices

‘Best Management Practices’ (BMPs) are voluntary practices with which farmers aim to maximise both productivity and sustainability. A key aim of several BMPs is to reduce eutrophication, either by reducing the amount of chemicals applied to farms, or reducing nutrient leaching: i.e. the amount of nitrogen and phosphorus draining off into waterways.

Largemouth Bass can be found in the Mississippi River basin.| SFWS Mountain-Prairie / Flickr.

One example of such practices is conservation tillage, where the residue from the previous year’s crops is left on the ground, as opposed to conventional tillage, where the soil is completely inverted with a tractor-pulled plough and then smoothed over before the new crops are planted.

The stated benefits of this are improved soil health and reduced nutrient leaching. A UK study disputed this claim, finding no benefit to soil quality or local freshwater biodiversity over five years of using conservation tillage, whilst evidence from a 15-year study taking place in Switzerland supported it, finding an increase in topsoil carbon and both microbial biomass and activity when the farm ceased ploughing and switched to conservation tillage.

‘Conservation tillage, where the residue from the previous year’s crops is left on the ground.’

Other BMPs have similar uncertainties behind them, perhaps owing to a lack of thorough research in this field, and the fact that different techniques work for different areas. During seven years of monitoring, scientists in Illinois found that despite high uptake of BMPs such as grassed waterways, strip tillage and stream buffers, there were no changes in nitrate-nitrogen or dissolved phosphorus content observed in the studied watershed.

A 2020 study of Lake Erie suggested that implementing conservation practices would likely be outweighed by the effects of climate warming since smaller, benthic (bottom-feeder) species will be better suited to warmer waters than larger, cool-bodied species that swim in open water.

Overgrowth of blue-green algae in irrigation drain. | Willem van Aken / CSIRO via Wikimedia Commons.

These small species—which feed on dead organic matter—can disturb sediment deposits, which could lead to an increase in nutrient flow through the lake and therefore an increase in eutrophication.

The United States Department of Agriculture (USDA) makes payments worth billions of dollars to farmers every year in indemnities, easing the burden of some farmers. But these payments are largely unequally distributed—with some regions receiving millions of dollars worth of funding each year, and some receiving none at all—and do little to address the real issue at hand: an inbuilt lack of resilience in the Western farming system.

The USDA has promised to address this issue—their National Institute of Food and Agriculture is now funding a five-year project called ‘Diverse Corn Belt: Resilient Intensification through Diversity in Modern Agriculture’ in Illinois, Indiana and Iowa.

The major point of the scheme is to grow a range of crops to replace the dominance of soy and corn, increasing both environmental and economic stability. But with the future of Midwestern agroecology looking the way it does—this may merely be another sticking plaster.

Recently, another group of scientists have assessed the effect BMPs could have on the Kaskaskia River watershed. This vast tributary to the Mississippi River spans 14,880 kilometres squared, a sizable 10.2% of the state of Illinois. Before the arrival of European settlers in the 18th century, this land consisted of sweeping prairies and forests alongside bodies of water. Now, like much of the Midwest, it contains little more than corn and soybeans. Many of its meandering streams and rivers have been channelised and dredged.

The scientists sampled fish from 91 sites across the Kaskaskia watershed to assess whether or not BMPs had an impact on the biodiversity of the freshwater fish. They modelled four key practices: crop rotation, cover crops, reduced tillage and reduced fertiliser application.

American White Pelicans on the Illinois River.| Ron Frazier / Flickr.

Contrary to other studies, they found that BMPs could reduce the nutrient and sediment input into the river. Local nitrate levels were predicted to reduce by up to 40% and 30% in the years 2020-2029 and 2030-2039 respectively. However when the scientists modelled the actual diversity of the fish, not a single conservation scenario was able to prevent the predicted decrease in biodiversity.

The most prominent species richness loss predicted at any single site was 22% from the year 2019 to 2049. The average loss predicted was 6%. The agricultural conservation scenarios made little to no difference—in every modelled scenario, the impact on freshwater biodiversity was less than 1%.

‘Best Management Practices could reduce the nutrient and sediment input into the river.’

On a more local scale, algal blooms present a problem for Midwestern waterways. Some algal blooms secrete toxins, which produce side effects in the unlucky few who swim in or drink this water.

These can include rashes, gastrointestinal symptoms like nausea and diarrhoea, muscle weakness and even kidney and liver damage. Multiple research centres in the US monitor the region’s HABs, which can be found, for example, in the Illinois River, Mozingo Lake, and the Mississippi River basin.

Along with creating dead zones, HABs secrete neurotoxins, which are capable of paralysing the central nervous system of fish and therefore causing death by asphyxiation, whilst others secrete hemolytic compounds which destroy blood cells, rupturing fish gills and starving them of oxygen. With cyanobacterial blooms exceeding WHO thresholds in Midwestern lakes, it is clear that both ecological and human health are under threat.

Algal blooms risk the entire aquatic environment, including the risk of neurological damage to fishes and animals. | Andrew Caldecott / Unsplash.

What is the future of farming in the Midwest?

Over the next two decades, the owners of 70% of the USA’s farmland are set to retire. However, the vast majority of this land will end up not in the hands of the next generation of farmers, but in those of property developers.

What’s more, climate events like floods and droughts—set to worsen as the world warms—and supply-chain issues like the global pandemic or the war in Ukraine jeopardise farmers’ livelihoods under the current agricultural system.

‘With cyanobacterial blooms exceeding WHO thresholds in Midwestern lakes, it is clear that both ecological and human health are under threat.’

The future for farming in the Midwest, therefore, may seem bleak. Although often maligned by environmentalists, it is important to recognise that farmers and farmworkers will be left vulnerable by these turbulent socio-economic and environmental conditions. According to the Purdue University horticultural architecture expert Linda Prokopy, farmer suicides and bankruptcies have risen in the last several years.

According to the Endangered Species Committee of the American Fisheries Society (AFS), 40% of American freshwater fish species are either endangered or already extinct. Declines are visible across America in species such as freshwater mussels and pallid sturgeon, but for the most part, the changes to freshwater ecology are out of sight.

Why are freshwater species declining?

Agriculture is responsible for 70% of freshwater consumption, and some estimates suggest that agricultural water consumption could increase by 50% by 2050.

Water stress occurs when a community has insufficient access to water due to a lack of supply or inadequate infrastructure. It is estimated by the Food and Agriculture Organization (FAO) that around 10% of the global population lives in water-stressed areas. In the vast majority of these areas, agriculture is the primary cause of water consumption.

Consequently, organisations such as the United Nations (UN) and the FAO have advised agricultural policy shifts and information campaigns to make agriculture more sustainable and far less water-intensive.

‘Agriculture is responsible for 70% of freshwater consumption.’

A sizeable percentage of the money spent on conservation by the United States Department of Agriculture (USDA) goes to states in the midwest, (Illinois, Indiana, Iowa, Michigan, Mississippi, Missouri, Ohio and Wisconsin), often referred to as the corn belt due to its vast agricultural production, which totals a $76 billion industry and 127 million acres of land, of which 75% of which is made up of corn and soybeans.

The Midwest is dominated by farmland, having the highest concentration anywhere in the United States, and consequently, less than 0.1% of the original Midwestern prairie remains.

With climate change, the future of agriculture in the Midwest may be at stake. | Don Sniegowski / Flickr.

So in the battle fought by BMPs to preserve fish biodiversity in the Kaskaskia watershed, it looks like climate change will win. They say never to bring a knife to a gunfight, and global warming is a behemoth that will take a lot more than individual conservation actions to confront.

However, that does not mean that these conservation actions have no value. As stated, in certain studies they were found to be of benefit to local ecology, and even in the Kaskaskia watershed, they were predicted to decrease nitrate levels, something which may aid fish abundance if not diversity.

The takeaway is that there is no one-size-fits-all approach to conservation and that mitigating global warming by ending the global fossil fuel hegemony should be one of our key priorities as ecologists.

If the latter proves impossible, conservation can salvage some of the ruins: the scientists studying the Kaskaskia watershed recommend prioritising key species and the cool-water species which will be most negatively affected by warming waters. With mass extinction and biodiversity loss looming on the horizon, conservationists may have to make more of these decisions.

Featured Image: Gary Leavens | Flickr

Centre for Disease Control (2023) ‘Avoid harmful algae and cyanobacteria.’ Center for Disease Control and Prevention. Available at: https://www.cdc.gov/habs/be-aware-habs.html [Accessed July 4th, 2023]

Cooper, R., Hama-Aziz, Z., Hiscock, K., et al. (2020) Conservation tillage and soil health: lessons from a 5-year UK farm trial. Soil and Tillage Research. Volume 202, Article 104648.

Cromwell, R. (2022) ‘More than 57 billion tons of soil have eroded in the U.S Midwest.’ ScienceNews. Available at: https://www.sciencenews.org/article/soil-erosion-rate-us-Midwest-unsustainable-usda [Accessed July 4th, 2023]

Dai, Q., Cao, Y., Chu, M., Larson, E. and Suski, C. (2023) Agricultural conservation may not help Midwestern US freshwater biodiversity in a changing climate. Science of the Total Environment. Volume 872, Article 162143.

Dudgeon, D. (2019) Multiple threats imperil freshwater biodiversity in the Anthropocene. Current Biology. Volume 29, Issue 19, Pages 960-967.

Dzombak, R. (2021) ‘Cyanobacteria blooms exceed WHO thresholds in Midwest lakes.’ PHYS ORG. Available at: https://phys.org/news/2021-11-cyanobacteria-blooms-thresholds-Midwest-lakes.html [Accessed July 4th, 2023]

EPA (2022) ‘The Sources and Solutions: Agriculture.’ EPA.gov. Available at: https://www.epa.gov/nutrientpollution/sources-and-solutions-agriculture [Accessed July 4th, 2023]

Food and Agriculture Organisation. (2021) ‘Progress on level of water stress: Global status and acceleration needs for SDG indicator.’ FAO. Available at: https://www.fao.org/3/cb6241en/cb6241en.pdf [Accessed July 4th, 2023]

FoodPrint (2021) ‘Biodiversity and Agriculture.’ FoodPrint. Available at: https://foodprint.org/issues/biodiversity-and-agriculture/ [Accessed July 4th, 2023]

Fraker, M., Aloysius, N., Martin, J., et al. (2023) Agricultural conservation practices could help offset climate change impacts on cyanobacterial algal blooms in Lake Erie.’ Journal of Great Lakes Research. Volume 49, Issue 1, Pages 209-219.

Fraker, M. Keitzer, S., Sinclair, J., et al. (2020) Projecting the effects of agricultural conservation practices on stream fish communities in a changing climate. Science of the Total Environment. Volume 747, Issue 141112.

Grooten, M. and Almond, R. (2018) ‘Living planet report - 2018: Aiming higher.’ WWF. Available at: https://c402277.ssl.cf1.rackcdn.com/publications/1187/files/original/LPR2018_Full_Report_Spreads.pdf [Accessed July 4th, 2023]

Howard, G., Burnett, E., Wilson, R., Roe, B., Irwin, E., Zhang, W. and Martin, J. (2016) ‘Farmers, Phosphorus and Water Quality, Part II: A Descriptive Report of Beliefs, Attitudes and Best Management Practices in the Maumee Watershed in Northwest Ohio.’ The Ohio State University, School of Environment & Natural Resources. Available at: https://www.researchgate.net/publication/303466847_Farmers_Phosphorus_and_Water_Quality_Part_II_A_Descriptive_Report_of_Beliefs_Attitudes_and_Best_Management_Practices_in_the_Maumee_Watershed_in_Northwest_Ohio [Accessed July 4th, 2023]

Keitzer, S., Ludsin, S., Sowa, S., et al. (2016) ‘Thinking outside the lake: Can controls on nutrient inputs into Lake Erie benefit stream conservation in its watershed?’ Journal of Great Lakes Research. Volume 42, Issue 6, Pages 1322-1331.

Klobucista, C. and Robinson, K. (2023) ‘Water stress: a global problem that’s getting worse.’ Council of Foreign Relations. Available at: https://www.cfr.org/backgrounder/water-stress-global-problem-thats-getting-worse [Accessed 5th July, 2023]

Krauss, M., Berner, A., Perrochet, F., Frei, R., Niggli, U. and Mader, P. (2020) Enhanced soil quality with reduced tillage and solid manures in organic farming - a synthesis of 15 years. Scientific Reports. Volume 10, Article 4403.

Krauss, M., Wiesmeier, M., Don, A., et al.. (2022) Reduced tillage in organic farming affects soil organic carbon stocks in temperate Europe. Soil and Tillage Research. Volume 216, Article 105262.

Lemke, A., Kirkham, K., Lindenbaum, T., Herbert, M., Tear, T., Perry, W., Herkert, J. (2011) Evaluating Agricultural Best Management Practices in Tile-Drained Subwatersheds of the Mackinaw River, Illinois. Journal of Environmental Quality. Volume 40, Issue 4, Pages 1215-1228.

Liu, T., Bruins, R. and Heberling, M. (2018) Factors influencing farmers’ adoption of best management practices: a review and synthesis. Sustainability. Volume 10, Issue 2, Page 432.

Mazure, J. (2023) ‘A lifetime of research links Gulf of Mexico ‘dead zone’ to Midwest fertiliser runoff.’ The Gazette. Available at: https://www.thegazette.com/environment-nature/a-lifetime-of-research-links-gulf-of-mexico-dead-zone-to-Midwest-fertilizer-runoff/ [Accessed July 4th, 2023]

NOAA (2016) ‘What is a harmful algal bloom?,’ National Oceanic and Atmospheric Association. Available at: https://www.noaa.gov/what-is-harmful-algal-bloom [Accessed July 4th, 2023]

Saenz, E. (2021) ‘Rethinking Midwestern Agriculture.’ Indiana Environmental Reporter. Available at: https://www.indianaenvironmentalreporter.org/posts/rethinking-midwestern-agriculture [Accessed July 4th, 2023]

Schechinger, A. (2022) ‘New EWG map highlights Mississippi river region crop insurance payout ‘hotspots’.’ Environmental Working Group. Available at: https://www.ewg.org/research/new-ewg-map-highlights-mississippi-river-region-crop-insurance-payout-hot-spots [Accessed July 4th, 2023]

Sha, J., Xiong, H., Li, C., Lu, Z., Zhang, J., Zhong, H., Zhang, W., Yan, B. (2021) Cyanobacterial Harmful Algal Blooms in Aquatic Ecosystems: A Comprehensive Outlook on Current and Emerging Mitigation and Control Approaches. Chemosphere. Volume 274, Article 129912.

Summers, K., Krempa, H., Garrett, J. (2022) ‘Central Midwest Water Science Center - Harmful Algal Blooms Fact Sheet.’ United States Geological Survey. Available at: https://pubs.er.usgs.gov/publication/fs20223011/full#:~:text=Algal%20blooms%20become%20harmful%20when%20the%20blooms%20add,thresholds%20for%20living%20organisms%20and%20cause%20fish%20kills. [Accessed July 4th, 2023]

Tolme, P. (2017) ‘The US biodiversity crisis.’ NWF. Available at: https://www.nwf.org/Magazines/National-Wildlife/2017/Feb-March/Conservation/Biodiversity [ [Accessed July 4th, 2023]

USDA (n.d) ‘Agriculture in the Midwest.’ United States Department of Agriculture. Available at: https://www.climatehubs.usda.gov/hubs/Midwest/topic/agriculture-Midwest [Accessed July 4th, 2023]

White, A. (2017) ‘Young Midwestern farmers want to grow sustainable food - but they need help.’ The Guardian. Available at: https://www.theguardian.com/sustainable-business/2017/apr/13/sustainable-farming-Midwest-food-organic-agriculture [Accessed July 4th, 2023]

Zohdi, E., Abbaspour, M. (2019) ‘Harmful algal blooms (red tide): a review of causes, impacts and approaches to monitoring and prediction,’ International Journal of Environmental Science and Technology. Volume 16, Pages 1789-1806.

Enbridge ignores Michigan’s shutdown deadline and continues to transport propane across Line 5.

Sustainable Leaders | North America

Is Brazil facing a water crisis?

Environment | Earth Systems