Do Phosphate Ordinances Make a Difference?
Municipalities around the country are banning or restricting the use
of phosphorus-containing lawn fertilizers, which can kill fish and cause
algae blooms and other problems when the phosphorus washes out of the
soil and into waterways.
Do the ordinances really help reduce phosphorus pollution? That was the
objective of a research project conducted at the University of Michigan
by John Lehman, professor of ecology and evolutionary biology at the
University of Michigan and students Douglas Bell and Kahli McDonald.
Their paper, appearing in the journal Lake and Reservoir Management,
published online Aug. 14, shows that phosphorus levels in the Huron
River dropped an average of 28 percent after Ann Arbor adopted an
ordinance in 2006 that curtailed the use of phosphorus on lawns.
"Right away, we started to see decreases," Lehman said. After the first
year of data collection, it was clear that phosphorus concentrations
were lower after the ordinance was enacted than before.
But did the ordinance cause the drop? Though that explanation seems
likely, public education efforts and general increased environmental
awareness among Ann Arbor residents also may have entered in.
The Southeast Michigan Council of Governments (SEMCOG), invited
Lehman to present the study results at a meeting earlier this year. Due
to the importance of the data, the study may well generate interest
beyond Michigan's borders.
"Although the science wasn't difficult, its ramifications in a
political sense and in an environmental sense will not be
insignificant," Lehman said.
Photo shows the Huron River.
ANN ARBOR, Mich.—In an effort to keep lakes and streams clean,
municipalities around the country are banning or restricting the use of
phosphorus-containing lawn fertilizers, which can kill fish and cause
smelly algae blooms and other problems when the phosphorus washes out of
the soil and into waterways.
But do the ordinances really help reduce phosphorus pollution? That's
been an open question until now, says John Lehman, professor of ecology
and evolutionary biology at the University of Michigan.
"It's one of those things where political organizations take the action
because they believe it's the environmentally conscious thing to do, but
there's been no evidence offered in peer-reviewed literature that these
ordinances actually have a salutary effect," Lehman said.
Now, such evidence exists in a study published by Lehman and students
Douglas Bell and Kahli McDonald in the journal Lake and Reservoir
Management. The paper, published online Aug. 14, shows that phosphorus
levels in the Huron River dropped an average of 28 percent after Ann
Arbor adopted an ordinance in 2006 that curtailed the use of phosphorus
on lawns. Phosphorus is naturally plentiful in southeast Michigan soils,
so fertilizing established lawns with the nutrient is generally
unnecessary.
Lehman was in an ideal position to assess the effectiveness of the Ann
Arbor ordinance because he and undergraduate student Julie Ferris were
already studying nutrient levels in the Huron River and two downstream
lakes, Ford Lakes and Belleville Lake, for a different research project.
Ferris used some of the data from that project in her senior honors
thesis, and she and Lehman published a paper on the Ford Lake and
Belleville Lake research, but they weren't sure what to do with the rest
of the data from the Huron River around Ann Arbor.
"As we were talking about it, I got a phone call from Ann Arbor
environmental coordinator Matt Naud, who knew about the work we had been
doing," Lehman said. "He said the city council had enacted an ordinance
that would reduce the use of phosphorus-containing fertilizers, and he
wondered if we would be able to detect any change that might occur as a
result."
Using statistical models, Lehman and Ferris figured out how much
sampling would be required to confidently detect a 25 percent decrease
in phosphorus concentrations. "We came up with the result that for most
of the river that runs through Ann Arbor, we should be able to detect a
change of that magnitude by sampling once a week for one summer or two
summers, depending on the sampling station."
Naud found funding to pay a student to do the work over the next two
summers. By that time, Ferris had graduated and gone on to medical
school, so Lehman recruited Bell to do the sampling and chemical
analyses. When Bell graduated and took a job measuring phosphorus on
research cruises around Bermuda, McDonald joined the project.
"Right away, we started to see decreases," Lehman said. After the first
year of data collection, it was clear that phosphorus concentrations
were lower after the ordinance was enacted than before. But did the
ordinance cause the drop? Though that explanation seems likely, public
education efforts and general increased environmental awareness among
Ann Arbor residents also may have entered in.
At any rate, the study already has attracted the attention of the
Southeast Michigan Council of Governments (SEMCOG), which invited Lehman
to present the study results at a meeting earlier this year, and may
well generate interest beyond Michigan's borders.
"Although the science wasn't difficult, its ramifications in a political
sense and in an environmental sense will not be insignificant," Lehman
said.
The research was funded by the Environmental Protection Agency, the U.S.
Department of Agriculture and the city of Ann Arbor.
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