One possible casualty of the endless U.S. budget fight may be the federal subsidy for corn ethanol production. There's been a lot of quiet, and some not-so-quiet, cheering from the environmental community, based on the premise that eliminating the subsidy will lessen nutrient pollution from growing so much corn.
In reality, cutting or repealing the 45-cents-per-gallon ethanol tax credit is unlikely to have much of an effect on planting decisions. As a recent article in the NY Times nicely explained last week, the subsidy is, at this point, unnecessary. Between laws requiring blending of ethanol into gasoline, the federal ethanol mandate, the tariff on imports, the size of the ethanol production industry, and the high price of corn, there's already enough incentive to maintain the status quo in corn production and corn ethanol production.
There are certainly good reasons to eliminate the subsidy. No one should pretend that doing so will solve of the problem of nutrient levels in the Mississippi River and the Gulf of Mexico. That is a far greater challenge.
Sunday, July 17, 2011
Eliminating the US corn ethanol subsidy is no panacea
Sunday, July 05, 2009
Abuse of science and logic by the National Corn Growers Association
The National Corn Growers Association released a report arguing that there is no connection between the use of nitrogen fertilizers on corn in the Midwestern US and the seasonal “Dead Zone” in the Gulf of Mexico.
There is no point mincing words about what this “analytical white paper”. It is the corn equivalent of irrational climate change skepticism. This is one truly shoddy piece of work. I encourage others in the scientific community to respond either independently or to append the critique offered here.
First, let’s review the actual science.
The “dead zone” in question, discussed many times before on this blog, is generated most summers on the continental shelf of the northern Gulf of Mexico. Nutrients originating in the Mississippi River Basin in the spring fuel the production of algae (primary production) in the surface waters along the continental shelf. The algae die and sink to the bottom, or something else eats the algae and the fecal matter from the something else sinks to the bottom. All that organic matter needs to decompose, and the process of decomposition (respiration) consumes oxygen. So the bottom waters on the continental shelf during the summer become very depleted in oxygen, or “hypoxic”.
Scientific research over the last few decades has shown that the increase in nitrogen flow from the Mississippi and neighbouring Atchafalaya Rivers since the 1950s has driven the development of these large seasonal periods of hypoxia. The evidence comes from basic ecological theory on nutrient limitation, lab experiments, tracking of the Mississippi River plume, long-term data analysis, sediment cores, isotopic analysis and mathematical modeling. While other nutrients like phosphorus and silica are important, nitrogen is the primary culprit.
There are many possible explanations for the increased flow of nitrogen out of the Mississippi-Atchafalaya River Basin (MARB) including fertilizer use, manure use, NOx emissions from cars and sewage. A simple nutrient budget shows nitrogen fertilizer use in the MARB has increased 20-fold since the 1950s. And today, most of that nitrogen fertilizer is applied to corn fields. Measurements and mathematical modeling of nitrogen loss from corn fields show that corn production is a primary source of nitrogen to the Mississippi and Atchafalaya Rivers, and hence, a primary driver of the development of what's come to be called the “Dead Zone”.
The author of the NCGA report (from the consulting firm StrathKirn Inc.) attempt to counter the mass of scientific evidence with the following largely baseless and unscientific arguments. Basically, he throws a bunch of stuff at the wall to see if anything sticks. I’ll go one by one through the report's chain of five incorrect and comically inconsistent assertions:
Assertion #1: Oxygen levels on the continental shelf are not low in comparison to other parts of the ocean.
This is misleading and irrelevant. First, the large regions of upwelling in the open ocean have low oxygen concentration due to high primary production. There’s no sense in contrasting the naturally and persistently low oxygen levels in the eastern Pacific to the intermittent, seasonal hypoxia on the continental shelf of the Gulf of Mexico. Second, even if there were some sense in this comparison, the data resolution of these maps is far too poor to capture a hypoxia area, which, while among the largest in the world, is still at its largest on the order of 20,000 km2 [here’s a test – can you clearly delineate New Jersey on that map?]. The global map of marine nitrogen concentrations is even more ridiculous. The data is far too coarse to capture the plume of the Mississippi River.
Assertion #2: Hypoxia doesn’t affect the fishery (not there is any hypoxia).
The report shows no change in fish catch over the years. As Steve Carpenter of the University of Wisconsin mentioned in an e-mail, the problem is the report analyses data on fish landings, not fishing effort. The boats may come back with the same weight in fish – but it takes more time and money to get those fish.
Assertion #3: Nitrogen from the Mississippi and Atchafalaya doesn’t cause the hypoxia (not that the hypoxia affects the fishery, or that there is any hypoxia in the first place).
This argument is advanced through a series of graphs relating annual nitrogen export, annual river flow and the annual extent of the hypoxic zone. There are a number of problems here. The nitrogen and flow data are shown only since 1985, despite data existing back to the 1950s. If the graph went back thirty years, you’d see the 2-3fold increase in nitrogen export occurred between the 1950s and the 1980s. Instead, the author reports no evidence of a trend in nitrogen of hypoxia since 1993. That’s not the issue – the issue is the hypoxic zone began growing large in the 1980s because fertilizer use increased between the 1950s and the 1980s, and further increases in corn planting, say for ethanol production, may further increase the average annual extent of hypoxia.
The other glaring problem with this argument is that the report uses no statistics whatsoever. For example, after a chart of nitrogen export and hypoxia extent since 1985 is this unsupported passage:
Again, there appears to be an association between water flow and the amount of nitrite (NO2) plus nitrate (NO3), but these do not relate well to the size of the hypoxic zone (except that they are all low in the year 2000). Thus, many of the statements about the relationship between water flow, nitrogen, and the size of the hypoxic zone are inaccurate.
Some actual statistical analysis, or frankly, just eyeballing the graph, would suggest that there is a significant relationship between the annual nitrogen export from the MARB and the annual extent of the hypoxic zone. It is not a perfect one-to-one relationship between nitrogen and the extent of hypoxia because of how the weather effects mixing of oxygen in the Gulf, the load of other nutrients and a myriad of other mitigating factors. If the author had done any research, they’d find proper statistical analysis and explanations in dozens of published papers, including this one of from my own work, a 2007 paper in Limnology and Oceanography:
Between 1985 and 2004, there is a significant relationship (r2 > 0.61) between midsummer hypoxia area and the May + June nitrate flux (Fig. 1). The strength of this relationship is limited by a number of other variables, including the advection of sub-pycnoclinal waters on the continental shelf, summer tropical storms that increase vertical mixing, recycling of N sequestered in shelf sediments during previous years, and the input of other nutrients such as phosphorus (Rabalais et al. 2002; Scavia et al. 2003; Wawrik et al. 2004).
Assertion #4: Not very much nitrogen is applied to corn (not that nitrogen causes hypoxia, or that hypoxia affects the fishery, or that there is any hypoxia in the first place).
The report displays a graph illustrating that non-crop uses of nitrogen fertilizer, like fertilizer used on lawns, is equal to or greater than the use of nitrogen fertilizer on corn. The problem, or I should say, the most glaring problem? It is national data. Over 90% of the corn grown in the US, and over 90% of the nitrogen fertilizer applied to corn in the US, is grown in the MARB. A 1999 EPA report estimated that non-agricultural fertilizer use is only 5% of total U.S fertilizer use - and that percentage of total fertilizer use in the major producing states of the Corn Belt.
Assertion #5: No nitrogen runs off of corn fields (not that much nitrogen is applied to corn, or that nitrogen causes hypoxia, or that hypoxia affects the fishery, or that there is any hypoxia in the first place).
The report proudly claims that the same amount of nitrogen is now removed during the corn harvest (i.e. in the grain) than is applied as fertilizer, so there can’t be any extra nitrogen left over to run off into the river. Fertilizer use efficiency has indeed increased over the years thanks to genetic technology and improved management. In other word, farmers are getting higher yields with the same amount of nitrogen fertilizer. That is positive news.
But the calculation in the paper is full of flaws. To name just one: the contention that fertilizer inputs = crop outputs = no nitrogen runoff only makes sense if fertilizer were the one and only source of nitrogen to the crops. For one, there is the mineralization of nitrogen in the soil – plant matter on the ground is naturally broken down by microbes, a process that released nitrogen from the plant matter to replenish the soil. This is a fundamental part of soil chemistry. The whole reason the Midwest is good land for growing corn is the high natural mineralization rates!
Final take-home message of the report: The US has a lot of golfers.
The report concludes that all other analyses are ignoring all the fertilizer applied to lawns and present maps and data to support this conclusion. The calculations are extremely suspect. First, the author assumes that the fraction of land devoted to lawns is greater in the MARB than in the rest of the country. Analysing the lawn data, eyeballing the national map, or simply reflecting about the fact that 4/5ths of the US population live outside the MARB, shows that this is a ridiculous assumption. Second, the report assumes that all the fertilizer not applied to corn, wheat, soybeans or cotton – which amounts to about 25% of annual fertilizer sales - is applied to lawns. This ignores all other crops grown in the United States, as well as all the fertilizer applied to rangelands and forests.
The report goes on to argue:
Since most lawns are cut and mulched there is relatively little removal of N, unlike the grain in corn. Consequently, a major portion of the N applied to lawns may be available for leaching… the net N available for leaching per acre is almost infinitely higher for lawns than from corn.
Not only does this argument incorrectly imply that no plant residue whatsoever is ever left behind after harvest to replenish the soil, it ignores the fact that unlike lawns, many corn fields are artificially drained by pipes or drainage tiles, such that excess nitrogen easily leaches to the nearest stream.
All told, the NCGA report is an embarrassment.
There are some legitimate outstanding questions about the nitrogen-hypoxia problem and definitely some legitimate critiques of the media coverage. In particular, the coverage often gives the mistaken impression that corn is the only source of nitrogen, that the hypoxic zone covers a large fraction of the Gulf of Mexico, that water at all depths is hypoxia, and that hypoxia is a permanent phenomena, rather than a seasonal occurrence. The NCGA could have issued on a report on those real concerns. Instead, it issued this dishonest mess of half-truths and pseudo-science.
Tuesday, June 17, 2008
A perfect storm for the Dead Zone
The massive floods in the Midwestern US are likely to fuel the largest Gulf of Mexico Dead Zone in recorded history. The image at right is from the NY Times and the National Weather Service.
Nitrogen applied to crops like corn in the Midwest is the major driver of the now famous Dead Zone, as I've described in a number of previous posts and this Google News commentary. The blame for the high nitrogen levels in the Mississippi and this year's record Dead Zone forecast is being placed on the production of more corn for ethanol. A more complete explanation would be that the surge in corn production, and, hence, fertilizer use, the past few years has made nitrogen pollution more sensitive to the climate than ever.
Nitrogen and hydrology are tightly linked in the Mississippi River Basin, and other agriculturally intensive river basins, thanks to nature and to humans. Several nitrogen 'species' like nitrate are highly soluble. What has exacerbates things in the Mississippi is activities like wetlands, installing artificial drainage under fields and channelizing rivers that reduce chances for nitrogen to be consumed before moving downstream. The result is the amount of nitrogen that the Mississippi sends to the Gulf can actually be predicted from the rainfall in the Corn Belt.
In coverage of our recent paper on corn and the Dead Zone, the prediction that the US Energy Policy would increase average nitrogen loading by 10-34% drew most of the attention. What might be missed is that the nitrogen loading could be much higher if the conditions are wetter.
The reason this matters is the the continental shelf of the Gulf of Mexico has a memory. The usual tale is that the Dead Zone grows each spring and summer when the big flood of Mississippi nitrogen arrives weather and water conditions are ripe for algae growth (it breaks up in the fall when the waters cool and mix, reintroducing oxygen to the bottom waters). However, nitrogen from previous years that is deposited in the sediments can also be recycled and feed algae growth. In other words, the system remembers a big flood of nitrogen. For example, during the 1993 Mississippi floods, the Dead Zone grew to a then-record 17,600 km2; the next year, it grew to an almost equal 16,600 km2, despite 31% less nitrate flowing down the Mississippi. That's just one reason why it is critical to consider climate and climate variability in ecological management and policy.
This year, the Dead Zone is projected to reach over 25,000 km2 in size, 20% greater than the previous maximum. What will that mean for 2009? For 2010? The longer you wait, the harder problems like the Dead Zone are to solve.
Wednesday, April 09, 2008
Growing ethanol on conservation lands
One of the assumptions in our recent paper on the impact of increasing corn ethanol production on the Gulf of Mexico Dead Zone is that farmers could start to plant crops on land enrolled in a federal conservation program.
The latest data shows that may be happening. The area of U.S. croplands enrolled in the federal Conservation Reserve Program decreased from by 2.12 million acres since July of last year (using February data), a drop of 6%. The NY Times reports that the drop was caused by high commodity prices, driven in part by the ethanol boom.
Farmers sign a ten-year contract when entering land in the CRP. As it stands, that land cannot be returned to cultivation until the contract expires. It is worth remembering that, despite the headlines and echoing blog posts, the area of CRP lands had been increasing for the past ten year, reaching an all-time high last year. This recent drop does not negate those changes. So the real question is what happens to the 9.5 million acres of land for which the contracts expire in the next three years.
Monday, March 17, 2008
Hypoxic zones around the world
The World Resources Institute and scientist Bob Diaz of Virginia Marine Institute have compiled a new map of the world's coastal hypoxia zones like the famous Gulf of Mexico "Dead Zone" we discuss in the recent PNAS paper on nitrogen pollution and corn production for ethanol. The new map includes 169 documented hypoxic areas, 233 are areas of concern and 13 areas in recovery.
Bottom-water hypoxia can develop when high input of nutrients like nitrogen promote the excessive algae growth. When algae eventually dies and sinks to the bottom, it decomposes, and that process depletes oxygen from the water.
It is worth noting hypoxia will not arise anywhere simply because nutrients are added. To get things started, you still need to feed the algae, and nutrient pollution does the trick. But certain
coastal areas are more naturally prone to hypoxia.
If, for example, the water column is highly "stratified", by that I mean less dense water lying above more dense water there is little mixing between the surface and the bottom waters (think of making a simple oil and vinegar salad dressing). It is then difficult for oxygen from the air to diffuse to the bottom and replace the oxygen consumed by decomposition.
The outlet of big rivers like the Mississippi can be ideal for hypoxia development because the fresh and therefore lighter water introduced by the river creates a stratified water column. That explains some of the year-to-year dynamics of the hypoxic zones like the Gulf Dead Zone. First, hypoxia development can be much worse in a wet or flood year because of the addition of more nutrients and the increased stratification. Second, if a hurricane blows through the Gulf, it encourages mixing just like you do by shaking that bottle of salad dressing, and can break-up the Dead Zone.
The new map supposedly includes only human-driven cases of hypoxia. Which raise the question, what is the cause of the zone between very sparsely populated Somerset and Cornwallis Islands in Nunavut, in the Canadian Arctic? If you have an answer, let me know.
Monday, March 10, 2008
Corn ethanol production will worsen the Dead Zone
A new paper by my colleague Chris Kucharik and I looks at the new US Energy Policy, will calls for growing more corn to produce ethanol, will affect the "Dead Zone" in the Gulf of Mexico. For a quick summary, see Reuters, the CBC or AFP (or my 15 Minuten ruhm on German ARD). Wired and Scientific American go into more detail.
The Mississippi dumps a massive amount of nitrogen, largely in the form of the soluble ion nitrate, into the Gulf each spring. It promotes the growth of a lot of algae, which eventually sinks to the bottom and decomposes. This consumes much of the oxygen in the bottom waters, making life tough for bottom-dwelling fish and creatures like shrimp. The Dead Zone has reached over 20,000 km2 in recent years.
The primary source of all that nitrogen is fertilizer applied to corn grown in the Midwest and Central US. Reducing the Dead Zone to less than 5000 km2 in size, as is suggested in US policy, will require up to a 55% decrease in nitrogen levels in the Mississippi.
The new US Energy Policy calls for 36 billion gallons of renewable fuels by the year 2022. Of that, 15 billion can be produced from corn starch. Our study found meeting those would cause a 10-34% increase in nitrogen loading to the Gulf of Mexico.
Meeting the hypoxia reduction goal was already a difficult challenge. If the US pursues this biofuels strategy, it will be impossible to shrink the Dead Zone without radically changing the US food production system. The one option would be to dramatically reduce the non-ethanol uses of corn. Since the majority of corn grain is used as animal feed, a trade-off between using corn to fuel animals and using corn to fuel cars could emerge.
Monday, July 30, 2007
Dead Zone in Gulf is third largest since 1985
Though I'm reticent to link to any news article under the cable-TV-news-ish heading "Planet in Peril", CNN reports that this summer's Gulf of Mexico dead zone has been measured at about 20, 460 km2 in size. That makes it the third largest since measurement began in 1985.
The hypoxic zone was expected to be unusually large this year because of the high flux of nitrogen -- the nutrient that fuels the high productivity on the continental shelf that leads to the consumption of oxygen from the bottom waters -- from the Mississippi River this spring. The blame can likely be placed on the weather and possibly even the increase in corn planting (due to high prices / ethanol demand).
Now off to grab my cape. The planet is in peril.
Wednesday, December 20, 2006
The plan to protect New Orleans and the Gulf Coast
Back to the Gulf Coast... The NY Times earlier this week that US Army Corps of Engineer Plans to build a costly and complicated systems of levees and mechanical barriers, and to replenish offshore barrier islands in an effort to protect the Gulf Coast has come under fire from scientitst.
How's this for a quote:
“The most shocking thing to me is that they would even consider some of the things that they are considering,” said Robert J. Young, new director of the Program for the Study of Developed Shorelines, a project of Duke and Western Carolina universities.
At a special session about the corps’s proposals at a meeting of the Geological Society of America in October, Dr. Young said his fellow scientists “were just stunned.” Dr. Young, who helped organize the session, added, “I saw mouths dropping open at the scale of proposed coastal engineering.”
Friday, December 15, 2006
The ongoing recovery in New Orleans
Almost 16 months after Hurricane Katrina struck the Gulf Coast, many parts of New Orleans are still putting the pieces together. I spent part of Thursday cleaning up yards in the Lakeview neighbourhood with the Beacon of Hope Resource Center.
Lakeview is adjacent to the 17th Street Canal levee, one of three levees that breached during Katrina. This NASA image from after the storm shows the Canal stretching into the city from Lake Ponchotrain (middle-left), and the flooding of the neighbourhoods (to the right).
For a sense of the scale of the flooding, you only have to see the yellowish line along the outer walls of many of the remaining homes that marks the maximum height of the floodwaters.
Few of the residents of this area returned to New Orleans after the storm. The old neighbourhood was now a patchwork of empty streets full of abandoned and badly damaged homes. The eerie quiet was interrupted only by the sound of sound of houses being razed and debris being removed.
Denise Thornton and the founders of the Beacon of Hope wanted their old neighbourhood back, but found little help from the government. So they started on their own, raised money for equipment to clean up yards, remove dead tress, replace storm drains and gut old houses, one by one. Thanks to outside donations and support from the United Way, the grassroots clean-up organization is now expanding to other parts of the city.
From a distance, it is hard to truly appreciate not just the physical, but the social devastation caused by Hurricane Katrina and the levee failures. The clean-up effort not only makes life more palatable for those that are there now, but it may encourage others to return. This is not just about the comfort of seeing people walk by your house or some lights on down the street; with so few people in these neighbourhoods, the property tax base has collapsed, making it even harder for the city to provide any services to the community.
If you’re in New Orleans, give the volunteer coordinator, Liz Widener, a call. They appreciate when out-of-towners spend even half a day (like me) removing weeds, debris and mowing lawns. If you want to plan a special trip to volunteer, they can even get you a discount at a local B&B.
