Once again, agriculture in Eastern Canada is under fire, this time in the Great Lakes basin. Already bearing media scorn for neonicotinoid seed treatments and biotech innovations, now farmers are getting blamed for Great Lakes pollution.
To be specific, the type of pollution in the headlines is eutrophication. It’s a phosphorus enrichment of waterways, and it creates the conditions for harmful algal blooms.
And there’s little doubt that this pollution is real, and it’s serious.
In 2012, the International Joint Commission (IJC) created the Lake Erie Ecosystem Priority (LEEP), with the goal of responding to what has been identified as a growing challenge in Ontario and in all states bordering the Great Lakes.
The driver was the algal bloom in Lake Erie in 2011, described in the report as the “largest in history.”
The report blamed both rural and urban sources, along with changes in climate and the presence of invasive aquatic species.
These aren’t the first algal blooms on the lakes. Such blooms were on the front pages in the 1970s too, with the finger pointed mainly at municipal sewage treatment plants rimming the lake.
The difference now, the IJC report says, is the combination of intensive farm management and its allegedly heavier applications of phosphorus combined with more severe and intense weather events, such as heavy spring and summer rains.
Make no mistake, there have also been media reports that blame the cities and towns within the Great Lakes watershed. A story in the London Free Press in August 2013 cited Windsor and London as the two worst polluters in the region, with both cities regularly discharging partly treated or raw sewage into adjacent water courses. Sarnia and Toronto were also listed in the study. The combined result of these mismanaged practices was billions of litres of sewage finding their way into the Great Lakes.
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But then in August 2014, an algal bloom formed at the southwestern end of Lake Erie, forcing the closure of water treatment plant intakes near Toledo, Ohio. According to media reports, scientists and farmers agreed that phosphorus from run-off of farm fields was the primary cause of that bloom. They added that more intense storms are washing away topsoil and phosphorus, turning watercourses and lake fronts brown and murky, and promoting the growth of harmful cyanotoxins.
Not so fast…
One of the paradoxes with that 2014 algal bloom is that sales figures from the fertilizer and inputs sector show that farmers have actually cut their fertilizer use. In the case of the Toledo-based bloom, the stats show that Ohio farmers used less than half as much P-based fertilizer in 2011 as in the mid-1990s.
Another claim is that large-scale livestock operations, particularly along the Maumee River watershed, are flushing more phosphorus into watercourses, a claim which one researcher deems unfounded. He says that without soil tests, there’s no way to determine whether those so-called “megafarms” are responsible.
“If we really want to fix whatever the issue is, however it’s happened, make it very focused on where it’s occurring,” says Dale Cowan, senior agronomist with AGRIS and Wanstead Co-operatives in Chatham, Ont. “These broad, sweeping gestures of ‘We have to reduce tillage,’ or, ‘you have to cut phosphorus levels back’ are premature.
“You often don’t get the desired effect,” Cowan says. “It must be science and technology based.”
Cowan also wants to avoid a witch hunt. He says spring run-off doesn’t come off in waves, but usually from a corner of a field that runs for a couple of days. These areas can be identified, and Cowan asks if it’s possible to put together strategies to mitigate against those areas rather than imposing new regulations on all cropland.
“It’s probably a small percentage of the land base that’s contributing to most of the run-off issue,” Cowan says.
Cowan is also quick to mention the decreasing sales figures in Ohio, and says that farmers are poised to do more with less as long as productivity is increased by way of precision agriculture systems. Gone are the days when farmers ramped up their P applications, and the same is true with nitrogen and potash. There also have been improvements in feed efficiencies for phosphorus with Phytase reducing phosphorus release by 30 per cent.
“It’s not like we’re increasing our fertilizer use every year,” says Cowan. “We’re putting it where it’s needed.”
No single cause; no silver bullet
An emerging consensus is that there is no one single cause, which also means there can be no one single “cure-all” solution. That’s why a collaborative approach to assessing and overcoming the challenges is so important.
Great Lakes pollution is more complicated than farmers and consumers may want to believe, says Jackie McCall, a geographer with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). For every answer that researchers and industry specialists produce, another question comes to light.
For instance, why are some isolated lakes in northern Ontario and in northern Russia, which are low-nutrient (oligotrophic) in nature, showing signs of algal blooms for the first time in their recorded histories?
Scientists are questioning possible climate change links, but there are also invasive species and the physical structure of Lake Erie itself that may be part of the puzzle. Erie is the shallowest of the Great Lakes, which might make it more prone to phosphorus enrichment, depending on a certain set of weather parameters.
Interestingly, the Lake Simcoe watershed has developed a phosphorus-reduction strategy, and McCall refers to efforts to verify different sources of phosphorus. There have been at least two studies on that watershed, one started in the late 1990s, and the latest in 2011 by the University of Guelph. In the earlier of the two studies, tributary and atmospheric sources were identified as the greatest contributors. Atmospheric deposition of phosphorus attached to windblown soil accounted for up to 49 per cent of the loadings from 1999 to 2000. In the Guelph study, atmospheric deposition was identified as a “major non-point source” with very similar findings of roughly 25 to 50 per cent of the total phosphorus entering the lake.
“That’s controversial because most of the scientific world discounts atmospheric loading of phosphorus as a significant source,” says McCall. “At the time they were collecting that information and making those extrapolations, Lake Simcoe was one of the most heavily urbanizing watersheds in Canada. Barrie was rapidly growing, and Newmarket and Aurora were rapidly growing, and a lot of dirt was being blown around.”
McCall adds that recent research in Ohio has also identified storm events as playing a significant role in phosphorus loading of the lakes, and in particular Lake Erie. In November 2013, the Ohio Phosphorus Task Force issued Phase II of its assessment of the Lake Erie watershed. Although it determined that roughly 20 per cent of phosphorus from the Maumee came from livestock and nearly 80 per cent from commercial fertilizer use, the report also cited major rain events, coupled with pre-existing short-term land and soil conditions, as key factors in phosphorus deposition.
“That’s maybe a new piece of science that we’re trying to grapple with,” says McCall. “How do we incorporate that new information into the way that we’ve traditionally done best management practices in agriculture?”
Variety of measures
Some may recommend on-farm projects such as berms, buffer strips and riparian zones as helpful measures to reduce phosphorus contamination. Yet there has been some recent research, albeit in Manitoba, that suggests buffer strips and riparian areas are not as effective filters as previously believed. It needs to be emphasized that Manitoba has different watershed dynamics compared to Ontario, and that research in that province has found the on-farm constructs are less effective in spring; it doesn’t say that they do not function at other times of the year.
There are also conflicting opinions on the value of tile drainage, and whether it’s a contributor to pollution in general and phosphorus loading, in particular. In the past three years, there have been stories in U.S. farm media sources that place the majority of blame for a seasonal “dead zone” at the mouth of the Mississippi River on overuse of fertilizers and tile drainage.
Dr. Merrin Macrae is an associate professor at University of Waterloo’s department of geography and environmental management, specializing in research on the movement of nutrients in water and soil, including the use of tile drainage. Like McCall, she believes there are many potential contributors to eutrophication, including golf courses and urbanizing landscapes, in addition to agricultural lands. But she also contends that it’s more difficult to pinpoint the exact percentages that each may contribute. And as non-farming interests line up and demand answers, she says, nothing happens quickly.
“If you look at the last three years for example, we have had very different weather from year to year,” says Macrae. “The fact is, in Ontario, and really anywhere around the Great Lakes, our climate is so incredibly variable that you can get a huge range of temperatures or rainfall, and yet it’s all within the range of the norms that we get in this region. This variability is why it often takes many years to be able to answer questions with confidence.”
Another important point is that phosphorus loading — when it comes — isn’t like a dripping tap. These rain events that have been identified as major contributors are not always predictable, and a storm may occur in one region but not another. So the idea of doing research in one place where a heavy rain event is occurring sounds simple, but it isn’t.
“We often find that what comes out of one field may not come out of a different field, whether or not you are in agriculture or urban landscapes. You go from one place to the next, and you can find a lot of differences,” says Macrae. “We have to make sure that we capture this range in conditions in our water sample collection to get a good picture of what is really happening in watersheds.”
There’s also the notion that these studies are easy to fund. Cowan proposed a paired watershed study to the provincial government years ago. He recommended getting a set number of farmers to follow an optimal plan for reducing run-off, while a second set of farmers worked their ground as usual. Then, water quality would be assessed, and after five or six years it would be possible to determine which practices work best.
There are two problems though, says Macrae. One is money. The second is variability. Besides, it’s a lot to ask farmers to commit to such a project, especially during a five- or six-year period.
“We do have some paired study sites that have been sampled now for three or four years, and even with that, you can have two fields or plots within a field that seem to be perfectly identical but they’re not always,” says Macrae. It is important to be certain that differences between sites are caused largely by management and not just natural variability. She adds that the complexity of measuring and gathering relevant data increases once you take the research out of a lab to a “real farm” setting, but notes that capturing data from real farms is highly valuable.
Over or under?
Much of Macrae’s work focuses on the use of tile drainage, and when it comes to managing run-off, she maintains that it’s best to help water flow under the soil rather than over it. Whatever farmers can do to reduce the loss from erosion at the surface is the best plan, she says, and tile drainage may be one of those measures.
“Tile drains are controversial because there have been studies that have shown that tile drains can lose a fair bit of phosphorus,” says Macrae. “The question is, is that something that’s happening here in Ontario? It is true that you may catch blips of phosphorus in tile drainage following a summer thunderstorm, but how do those losses compare to very wet periods of the year such as springtime when the potential for run-off over the surface is high, since those wet periods are when most run-off and phosphorus are lost?”
What Macrae finds is that the phosphorus losses are low from sites where farmers carefully manage their fertilizer application, they’re careful with their tillage, and they apply their fertilizer in bands, rather than surface broadcasting. These growers are using multiple bundles of BMPs, using everything available to them.
Macrae stands firmly behind the science associated with tile drainage. Much of what has been learned and documented, and the practices that have resulted in the past 10 to 20 years have done more to keep the water on the land and avoid or at least reduce surface erosion.
That’s a sentiment that Cowan echoes. “Nothing’s better for the environment than high-yielding crops, and what drainage has done is to improve our land quality, so we actually have less run-off,” says Cowan. “Certainly people argue that we’re now allowing more through the tile, but it’s a very small amount of water that actually ends up going through the tile. And the soluble P — and that’s one of the main contributors — is a very small amount.”
Cowan adds that increased soil testing would help, to match a plant’s nutrient demand with available soil nutrient levels. This is one of the tenets of the 4R Nutrient Stewardship program being supported by many stakeholders who are embracing the idea of source, rate, time and place of nutrient applications. More farmers are banding and incorporating their fall P applications, there’s more interest in no till or zone or strip tillage, and there’s the move to precision placement of fertilizers.
From her vantage point, McCall advocates for an “all for one and one for all” approach, noting that one significant change has to take place, and that is the finger pointing that may be occurring between all interested parties. Urbanites want clean water, she says, but so do the farmers, and everyone involved wants workable solutions.
“All sectors have to talk to each other,” Macrae says. Not only do we need more science on how we as humans contibute to the problem, climate change may be a factor too, she adds.“If that’s the way things are going, we have to collectively get around a table and say, ‘OK, we’re in a new world here.’”
This article was originally published as, “The sick lakes” in the October 2014 issue of Country Guide