Sunday, December 10, 2023

To reduce harmful algal blooms and dead zones, the US needs a national strategy to regulate agricultural pollution

The summer solstice is the time for forecasts of the size of this year’s “dead zones” and algal blooms in major lakes and bays. Will the Gulf of Mexico dead zone be the size of New Jersey, or just the size of Connecticut? Will the Lake Erie bloom become a human health crisis or simply devastate the coastal economy?

We are scientists who have spent nearly 50 years discovering what causes dead zones and what is needed to resurrect them and reduce the risks of toxic algal blooms. Researchers can forecast these events fairly well and have calculated the cuts in nitrogen and phosphorous pollution needed to reduce them.

These goals are now written into formal government commitments to clean up Lake Erie, the Gulf, and the Chesapeake Bay. Farmers and landowners across the country received $30 billion to support conservation, including practices designed to reduce water pollution, between 2005 and 2015, and are scheduled to receive an additional $60 billion between 2019 and 2028.

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But these efforts have fallen short, mainly because controls on nutrient pollution from agriculture are weak and ineffective. In our opinion, solutions to this problem are not lacking. What is needed is technological innovation and stronger political will.

Map Showing An Area With Low Oxygen Values ​​Along The Louisiana Coast.
The hypoxic (dead) zone of the Gulf of Mexico in 2021, which measured 6,334 square miles (16,400 square kilometers). Lower values ​​represent less dissolved oxygen in the water.
Louisiana Universities Marine Consortium, CC BY-ND

Trouble returns to Lake Erie

State and federal agencies have known since the 1970s that overloading lakes and bays with nutrients creates huge algal blooms. When the algae die and decompose, they deplete the oxygen in the water, creating dead zones that cannot support aquatic life. But in each of these “big three” bodies of water, efforts to curb nutrient pollution have been slow and halting.

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The US, Canada, and cities around Lake Erie began work to reduce phosphorous pollution in the lake from household and industrial waste in 1972. Water quality rapidly improved, dead zones were reduced, and the Harmful algal blooms became less frequent.

But the scourges of oxygen-poor waters and sometimes toxic algae made a comeback in the mid-1990s. This time, the source was primarily runoff from phosphorus-saturated agricultural soils from repeated applications of fertilizers and manure. Climate change made things worse: warmer waters contain less oxygen and lead to faster growth of algae.

Bar Graph Showing Phosphorus Entering Lake Erie Between 1967 And 2001.
Phosphorus loads to Lake Erie, 1967-2001. Nonpoint sources are large areas without a defined discharge point, such as farm fields.
Scavia et al., 2014, CC BY-ND

Slow progress on the Chesapeake Bay

Nitrogen and phosphorous reach the Chesapeake Bay from sources including sewage treatment plants; air pollution emitters such as factories and cars; and runoff from urban, suburban, and agricultural land. In 1987, the federal government and the states around the bay agreed to reduce these flows by 40% by the year 2000 to restore water quality. But this effort was based on voluntary action and did not make much progress.

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In 2010, states and the US Environmental Protection Agency signed a legally binding commitment to reduce pollutant loads below maximum prescribed levels necessary to restore water quality. If states make inadequate progress, EPA can limit or terminate their permitting authority, and states can lose federal funding.

Nitrogen and phosphorus pollution has been reduced primarily by tightening permit requirements and improving wastewater treatment plants. Air pollution controls for power plants and vehicles have also reduced the nitrogen reaching the bay. Water quality has improved and the annual dead zone has been modestly reduced.

But with the 2025 commitment deadline approaching, nitrogen loads have been reduced by less than 50% of projected amounts, phosphorus by less than 64%. Most of the remaining pollution comes from agricultural runoff and urban stormwater. The intensification of agriculture in rural areas and the expansion of urban areas are offsetting other cleanup efforts.

Cleanup of water bodies with large watersheds, such as the Chesapeake Bay (64,000 square miles/165,000 square kilometers), involves many states and thousands of sources of pollution.

Failure in the Gulf of Mexico

The Gulf of Mexico dead zone forms every year during the summer, fueled by nutrients washed down the Mississippi River from Midwestern farms. It usually covers at least 6,000 square miles, sometimes expanding up to 9,000 square miles (23,000 square kilometers), and affects an area very rich in fishing.

In 2001, the EPA and 12 states in the Mississippi River Basin agreed to take steps to reduce the Gulf dead zone by two-thirds by 2015. The researchers estimated that this would require reducing nitrogen loads reaching the Gulf by about 45 percent. , mainly from the corn belt. .

Now that deadline has been extended to 2035. Nitrogen and phosphorus loads at the mouth of the Mississippi River have not budged in 30 years, so measures taken to date have failed to reduce the Gulf’s dead zone.

Bar Chart Showing Measurements Of The Gulf Of Mexico Dead Zone Since 1985.
Since 2017, the Gulf of Mexico dead zone has covered an average of 5,380 square miles (14,000 square kilometers), which is 2.8 times larger than the 2035 goal set by a federal task force.

overwhelmed by agriculture

In 2020, the EPA and Ohio adopted a Chesapeake-like agreement to reduce phosphorus pollution below a prescribed maximum load from the Maumee River watershed at the western end of Lake Erie, where algal blooms occur most frequently. . To date, Mississippi River Basin states and even the EPA have similarly opposed requiring maximum pollution loads to reduce the Gulf of Mexico dead zone.

Despite substantial government subsidies to implement various farm management practices, nitrogen and phosphorous pollution in Iowa and Illinois streams has actually increased from the 1980-1996 Gulf settlement baseline.

Even with increased crop yields and more efficient use of fertilizers, the expansion and intensification of agriculture in the Midwest has outpaced any improvement in water quality. One driver is ethanol production, which has increased forty-fold since the Gulf Action Plan was adopted in 2001. Currently, more than 40% of the corn grown in the US is used to make ethanol , mainly in the Midwest, while most of the rest uses animals

In all three regions, the growth of large-scale livestock farms (pigs in the Midwest, poultry around the Chesapeake Bay) also contributes to nutrient pollution. Improper management of animal waste increases nitrogen and phosphorous loads in local soils and waters.

Studies show that agriculture contributes 85% of Lake Erie’s Maumee River phosphorus load, 65% of the Chesapeake Bay’s nitrogen load, and 73.2% of the nitrogen load and 56% of the phosphorous load of the Gulf of Mexico.

Incentives don’t work

We believe the evidence is clear that the largely voluntary approaches adopted to date, with substantial public funding and technical assistance, are not working.

Economists have called for a fundamental change in policies that control agricultural pollution. Instead of offering subsidies to polluters to clean up their operations, these experts argue, the strategy should be to pay farmers for their performance, based on environmental outcomes that can be measured or predicted at appropriate scales and specific locations.

Under this approach, the government would set limits on the amount of nutrients that can be lost to the environment, and farmers would choose how to achieve them, based on what type of action works best for their specific soils and climates. For example, restoring wetlands within the watershed could help capture nutrients that inevitably disappear from farmland.

The ongoing switch to electric vehicles offers the opportunity to grow much less grain for ethanol, which doesn’t even help the climate. And, in the long run, the development of efficient plant-based food systems would reduce nutrient pollution and limit climate change.

In June 2022, the Government Accountability Office concluded that federal agencies charged with preventing and controlling harmful algal blooms and dead zones under a 1998 law have failed to establish a national program to address these problems. Fifty years after the Federal Clean Water Act was enacted, we believe that such a program is long overdue.

Nation World News Desk
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