More than one million families live in single-family homes around Long Island Sound. Each of them makes decisions regarding their yards that influence the health of local rivers, streams, bays, and eventually the Sound.
People decide how much fertilizer to apply on their lawns and gardens or none at all. If they apply too much or apply at the wrong time the fertilizer they use will not be absorbed by all of the grass and plants. Instead, the excess nitrogen in fertilizer could end up in waterways—either carried away by stormwater into storm drains and streams or, more likely, transported underground through porous soils toward streams and other waterways that flow to the Sound. Instead of nitrogen fertilizer promoting a green lawn, it could feed the growth of microalgal blooms and thick mats of macroalgae seaweeds along the coast, and result in dangerously low oxygen conditions and harmful algal blooms for the Sound and coastal and fresh waters alike.
Typically, government and environmental groups provide communications materials such as brochures, posters, and web pages to tell homeowners about the need to control the amount of fertilizer to use, in order to protect the environment. But according to Dr. Robert Johnston, an environmental economist at Clark University in Worcester, MA, these types of general information campaigns may not be designed or targeted in ways that most effectively promote positive environmental practices and, ultimately, reduced nitrogen loads to Long Island Sound.
For the past six years, through two research projects funded by the Long Island Sound Study Research Grant Program, Johnston has worked with multidisciplinary teams of marine, environmental, and land use scientists to look for a better way. The latest project, which is to be completed this year, includes the creation of maps that will allow resource managers and policy makers to identify nitrogen “hot spots”— neighborhoods and communities where homeowners are both likely to apply large amounts of fertilizer and where there also is a high likelihood of nitrogen flowing directly to the Sound. “These are the areas where behavior change campaigns can have the greatest impact,” said Johnston. “Because there are large amounts of lawn fertilizer being applied and a large proportion of the nitrogen from that fertilizer is eventually reaching the Sound.”
To support this targeting guidance, he and the research team have created a supplementary model—based on household survey data—that predicts the likelihood that alternative types of policies and programs to reduce fertilizer use will be supported by watershed residents.
“What’s exciting about this project is that it provides outputs that have direct implications for actions,” said Johnston. “What we’re hoping to provide is clear guidance to identify how behavior change programs can be designed and targeted, given that you have limited budgets, to most effectively address nitrogen pollution in particular embayments.”
The issue is important for clean water in the Sound’s embayments—the bays, harbors, and coves that shape the Sound’s coastlines and where millions of people live in coastal communities. Fertilizer use accounts for about one-third of the nitrogen that ends up in embayments. The largest source of nitrogen—about 50 percent—is from human waste, including from discharges of treated sewage in wastewater treatment plants and individual septic tanks from homes. But some embayments receive much higher loads of nitrogen from fertilizer. “In some embayments it’s significantly more than one-third, it’s almost 100 percent fertilizer,” said Dr. Jamie Vaudrey, a marine scientist at the University of Connecticut and the developer of a Nitrogen Load Model for Long Island Sound. “Especially if a community is on sewer and that sewer outfall is somewhere else (discharging waste outside the embayment), then really the big player in those towns is fertilizer applied to households, but also to parks and recreational fields.”
Compounding the problem is a lack of effective policies and programs to address fertilizer use. This is not the case for controlling other sources of nitrogen entering the Sound. For example, billions of dollars have been invested to remove nitrogen into the Sound from human waste through wastewater treatment plant upgrades. Also, Suffolk and Nassau Counties have recently begun a program with support from the New York State Department of Environmental Conservation and the Long Island Sound Study to provide grants to encourage people to replace hundreds of thousands of antiquated septic tanks and cesspools with new systems that have advanced nitrogen reduction technologies.
“For most of these sources, we’re moving in a positive direction, and we have policy levers to control those sources of nitrogen,” said Johnston. “They might be expensive, but we can do it. But residential lawn care is one of the sources of nitrogen that we haven’t reduced very well.”
Johnston has been interested in the connection between the choices people make on land and how it affects water quality since he was a graduate student at the University of Rhode Island in the 1990s. It continued into his job in the 2000s as associate director of Connecticut Sea Grant, which is a member of the Long Island Sound Study’s Management Committee, when the primary focus on water quality in the Sound was the implementation of a federal and bi-state plan to reduce nitrogen loads through the upgrades of wastewater treatment plants. At the time, Sea Grant was funding extensive research on the impact of nutrients on aquatic life in the Sound, which it is still doing today. For Johnston, the opportunity to focus on lawn care arose in 2015 when he coordinated with environmental scientists to use his expertise in developing surveys for a study on residential lawn care practices in the Baltimore metropolitan area that impact Chesapeake Bay. When one of the lead scientists, Dr. Peter Groffman, relocated to New York City to join the City University of New York faculty, Johnston and Groffman decided it was a natural next step to focus on Long Island Sound. In 2018, the two scientists (one social and one environmental) along with Dr. Colin Polsky, an environmental scientist from Florida Atlantic University, received a $371,000 research grant from the Long Island Sound Study Research Grant Program to develop a survey for a model that predicts lawn care practices around Long Island Sound and what policy initiatives households might favor to reduce fertilizer use and improve water quality. They also collaborated on this study with Dr. David Newburn, an environmental economist from the University of Maryland, whose work also emphasizes household landscape decisions and impacts on water quality.
Using random sampling methods, Johnston invited 30,000 households by mail throughout coastal counties of Long Island Sound to answer a web-based survey. A total of 2,344 people responded and answered questions about their lawn fertilizer applications and other lawn management activities, household demographics, housing and yard characteristics, and whether they would support alternative types of policies to reduce the negative impacts of fertilizer use. Their responses were then used to produce predictions of various types of behavior for each household—for example how frequently a household will apply lawn fertilizer and how that fertilizer use would change in response to alternative types of behavior change campaigns.
With publicly available U.S. Census and geospatial data on parcel and household characteristics, the researchers are able to produce these predictions for any residential neighborhood or community within the Long Island Sound watershed—for example within the four Connecticut coastal counties or municipalities on Long Island that border the Sound. The researchers use high resolution land cover maps derived from aerial photos to distinguish the lawn area for each household. These predictions can be overlaid with maps showing how much fertilizer applied to each lawn contributes to nitrogen loading in Long Island Sound.
The survey data, said Johnston, reveals “major differences in how people apply fertilizer, how much of that fertilizer reaches the Sound, and how different households react to behavior change campaigns.” It also shows that one of the most significant lawn care decisions people make runs counterintuitive to the notion Americans are obsessed with a perfect green lawn. Almost half of survey respondents—46 percent—said they do not fertilize their lawns. It was a response that did not surprise Johnston. “This is very close to what we found in our prior work in Baltimore and is similar to other studies,” he said. “Most places you look, give or take, roughly 50 percent of the people fertilize their lawn and roughly 50 percent don’t.”
Johnston said that other studies also show that people who choose to fertilize are often influenced by neighborhood norms. “If all else is equal, if your neighbor fertilizes, you are more likely to fertilize,” he said.
For the people who apply fertilizer in the Long Island Sound survey, the most common frequency is between one and three applications a year, although some households apply more frequently. New York residents apply more than Connecticut residents, an average of 1.53 times a year compared to 1.26 times. Generally, households in urban areas with smaller older homes in the region are less likely to fertilize their lawn and have a lower number of fertilizer applications than those in exurban areas. Households in suburban and exurban municipalities closer to New York City in Connecticut or Long Island, especially those with newer larger homes and larger lots, have the highest probability of lawn fertilization and the highest number of fertilizer applications.
“On average, we find that homeowners with larger and newer homes tend to fertilize more,” said Johnston. Because these types of homes tend to cluster in neighborhoods, “these patterns lead to fertilizer hot spots, or areas where people fertilize a lot compared to other areas.”
The survey also helps to provide insight into the extent to which households in New York and Connecticut support policies and programs designed to reduce household fertilizer use—such as possible regulations that would restrict the number of fertilizer applications per year.
The survey also helps to provide insight into the extent to which households in New York and Connecticut support policies and programs designed to reduce household fertilizer use—such as possible regulations that would restrict the timing or number of fertilizer applications per year.
Johnston said that the households can be broadly divided into two groups. About 61 percent fall into the “environment and cost” group that supports either moderate or strict limits on fertilizer use. In contrast, about 39 percent fall into a group Johnston calls “lawn people” that does not favor strict regulations on lawn care. Despite their differences, said Johnston, most people have common ground. For example, all groups are more likely to support regulations that improve Long Island Sound water quality, holding all else constant, and all groups support moderate restrictions on fertilizer use.
He also found that homeowners were willing to participate in government incentive programs to convert a portion of their lawns into native plants and rain gardens, which reduce stormwater runoff and provide habitat for pollinators. To increase homeowner participation, program enrollment barriers need to be minimized including reducing the paperwork needed to get a rebate that adds time and cost to a gardening project. Homeowners also preferred getting the rebate upfront to pay for supplies rather than waiting for a municipality to approve the funds after getting confirmation that the planting occurred. “What we’re finding, and perhaps this is obvious, is that many households do not have the free cash flow to front all that money in the hopes that they’ll pass inspection and be reimbursed later,” said Johnston.
Many people, across the two major groups, also were concerned about applying chemicals from fertilizer or pesticides on their lawns. “If you give people information on reductions in chemical exposure to children and pets, it turns out that they’re more likely to indicate that they would reduce their fertilizer use,” he said.
A noticeable finding also might surprise people who believe that cost is the primary factor in people’s decision-making. Johnston said that most people did not believe that a tax or surcharge on fertilizer (ranging from 10 to 30 percent) would discourage them from using fertilizer.
“We could find no evidence that it made a difference,” said Johnston. “What we think is happening is that the price of fertilizer is low enough that (a modest additional surcharge) will not have a major effect on fertilizer use for most households.”
Johnston presented findings from the first research project at the Long Island Sound Biennial Research Conference in Bridgeport in May 2022. In attendance were staff from the University of Connecticut’s Center for Land Use Education and Research, or CLEAR, which developed the Nitrogen Sink tool, a model of nitrogen flow to the Sound that predicts what areas of the Sound’s watershed are either “sinks” absorbing nitrogen or are “leaky,” providing an easy transport through porous soils to streams and the Sound. Examples of nitrogen sinks are ponds, wetlands, and vegetated buffers along streams and rivers. After the presentation Chet Arnold, then the director of CLEAR, and Dave Dickson, a land use scientist who is now the director of CLEAR, approached Johnson with an idea to combine forces. “We just got the idea, wouldn’t it be cool to combine the fertilizer application data with N-Sink, which follows the path and shows where leaky areas of nitrogen are on the landscape as a way to better target nitrogen fertilizer outreach campaigns,” said Dickson.
Before the research conference, CLEAR and Jamie Vaudrey, the developer of the Nitrogen Load Model, had been trying to get research grants to combine their models to gain a better understanding of the sources of nitrogen entering Long Island Sound. After the conference, Vaudrey, CLEAR and Johnston decided to team up to submit a proposal for the 2022 Long Island Sound Research Grant competition. They received a $406,000 grant to integrate their models to help resource managers develop effective nitrogen-reduction behavior change campaigns. While the project is expected to be completed by the year’s end, Vaudrey previewed some of their combined maps showing the nitrogen hot spots at the 2024 Long Island Sound Biennial Research Conference in Port Jefferson on May 15.
Johnston is optimistic that Long Island Sound and its embayments will be better off as a result of social and natural scientists working together.
“It’s been really beneficial working with Jamie and also with CLEAR because their work is such a natural fit with the work that we are doing as economists. Integrated modeling like this allows us to understand entire systems through which human behaviors influence the environment, rather than each piece in isolation.”
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