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A Green Bill of Health – Can Vacant Lot Treatments Impact Mental Health?

The scientists who worked on this study wanted to focus on the effect of people’s environments on their mental health. The scientists identified vacant lots throughout Philadelphia. They wanted to study the effects of two kinds of vacant lot treatments—greening and trash cleanup—on nearby residents’ feelings about their own mental health.

A Green Bill of Health – Can Vacant Lot Treatments Impact Mental Health?

Meet the Scientists!

Michelle Kondo

Social Scientist

Charles Branas

Professor of Epidemiology

Eugenia South

Physician-Scientist

What Kinds of Scientists Did This Research?

Social Scientist: This scientist studies the values, opinions, beliefs, attitudes, and actions of individuals and groups of people.

Professor of Epidemiology (e pǝ dē mē ä lǝ jē): This scientist teaches and conducts research at a university. Epidemiology is a branch of public health science that deals with the occurrence, distribution, and control of disease in large populations.

Physician-Scientist: This is a research scientist who is also a medical doctor. In this study, this scientist studies the impact of neighborhood environments on human health and safety with a particular interest in urban nature.

Did You Know?

A pocket park (mentioned in Charles Branas’ bio above), or minipark, is a small, neighborhood park. These parks can be built on small lots within a city.

Thinking About Science

While scientists may work alone some of the time, many scientists work together to conduct their research. Sometimes the scientists working together may be similar kinds of scientists. For example, scientists researching an invasive insect might all be entomologists (scientists who study insects).

Research can also involve different kinds of scientists. For example, research into how an invasive insect impacts its environment might involve not only entomologists, but also ecologists, foresters, soil and water scientists, and more!

Collaboration is an important part of science. Different scientists can bring different skills and knowledge to a research project. Collaborating with different scientists can help scientists explore new ideas and share resources.

In this research study, a Forest Service scientist who studies the environment in cities worked with medical doctors, epidemiologists, and public health experts to find out how urban green spaces may impact human health. Collaboration can help scientists answer some of their most challenging research questions.

Thinking About the Environment

Creating or preserving green space is a priority in many communities around the world. Green spaces can be large, like national forests and national parks, or they can be small, like a tree-lined street or a yard of grass, shrubs, or flowers. We know that green spaces provide many important ecosystem services. Trees and other plants can store carbon, provide clean air to breathe, protect watersheds, and provide important habitats for other living things. We are also learning more about how green spaces contribute to human health.

A small city lot that has been planted with grass and flowers and is surrounded by a low wooden fence. The building next door features a large mural of hands.

What Is Green Space?

The definition of green space can be slightly different in different situations. In this study, green space is a place in the city that is covered in some kind of vegetation, like grass or shrubs, and that has no buildings.

Many scientists all over the world are studying the impacts green spaces might have on humans. Some studies have shown that spending time in and around green spaces may help people concentrate better, think more creatively, work more cooperatively, and feel less stressed.

Being in and around green spaces has been shown to increase people’s feelings of community and social connection; those feelings have been related to lower rates of mental illnesses like depression. Some scientists have even found evidence that green spaces can lower rates of crime and violence in neighborhoods. Scientists are learning more all the time about the ways green spaces can impact people and their communities (figure 1). How do you feel when you are spending time outdoors? Can you think of any other impacts of green spaces?

An empty city lot with grass and plantings, a colorful wooden fence, and a small lending library. — **Figure 1**. This neighborhood green space includes a small lending library where residents can both donate books to their neighbors and also pick up free books to read.

Courtesy photo by the Pennsylvania Horticultural Society.

Introduction

Many people are interested in learning about and improving mental health. Mental health is an important part of overall human health. Scientists are working to understand the causes of mental illnesses and poor mental health as well as the best treatments. Some scientists study medications that might help improve mental health. Some scientists study types of therapy or counseling to improve mental health. Other scientists study ways the environment can improve mental health.

The scientists who worked on this study wanted to focus on the effect of people’s environments on their mental health. They were specifically interested in people who live in low-resource neighborhoods in urban areas. Low-resource neighborhoods have fewer resources for their residents. They might have fewer parks or playgrounds, less funding for schools and libraries, and fewer opportunities for work and recreation. These conditions can contribute to people’s feelings of stress, fear, and overall poor mental health.

Many people in the United States live in urban areas, and some of those urban neighborhoods have little or no green space. The scientists in this study knew about previous research on the health impacts of green space (see Thinking About the Environment). Previous research showed that spending time in and living near green space was associated with various improvements in mental health. The scientists wanted to conduct an experiment in Philadelphia, Pennsylvania, to test this previous research (figure 2).

An aerial view of Philadelphia — **Figure 2**. (A) In this photo of Philadelphia, you can see that many buildings stand close together. There are some trees and other vegetation, but the majority of the space is taken up by buildings.

Adobe Stock photo.

A map showing the location of Philadelphia in Pennsylvania. — (B) Philadelphia lies on the western coast of the Delaware River in Pennsylvania.

FIND Outdoors map by Leslie Shaw Design.

The scientists focused on vacant lots throughout Philadelphia. They wanted to study the effects of two kinds of vacant lot treatments—greening and trash cleanup—on nearby residents’ feelings about their own mental health.

A vacant lot between two brick buildings. The lot has overgrown vegetation and a chain link fence. A caution barrier stands in front of the fence.

What's the big deal about a vacant lot?

Vacant lots are lots without buildings or other development. Many cities have ordinances, or rules, about how lots in the city must be cared for. The city might have a rule against dumping trash on these lots or about how tall the grass can grow. If the owners do not follow city ordinances, the lots can become untended and collect garbage and other debris. Many community organizations see the potential to turn these vacant lots into beneficial places for the community.

Reflection Section

Methods

The scientists obtained a list of all vacant city lots in Philadelphia from city records. Of these vacant lots, the scientists made a list of vacant lots eligible for their study. To be eligible, the lots had to have visible signs that they were not maintained, such as illegally dumped trash and debris, abandoned cars, and/or vegetation that was not being cared for (figure 3).

To be eligible, the lots also had to be abandoned; either their owners did not respond to messages from the scientists or the owners gave their permission to be included in the study. The scientists did not include lots that were well cared for, were not abandoned, were bigger than 5,500 square feet, or were fully paved parking lots.

An abandoned lot in a city. Grass and other plants are overgrown, and trash is accumulating. — **Figure** 3. The condition of this vacant lot in Philadelphia is similar to the condition of the vacant lots included in the study. The plants are overgrown, and trash has collected in the lot. This particular lot was not included in this study.

Courtesy photo by the Pennsylvania Horticultural Society.

Once they had a list of eligible lots, the scientists divided the lots into clusters that were randomly assigned to one of three study groups (table 1). In one group, vacant lots received a “greening” treatment. In a second group, vacant lots received a trash pickup treatment. A third group served as the control; vacant lots in this group received no treatment.

Table 1. In the study, vacant lots were randomly sorted into one of three groups. The treatments were done by the Pennsylvania Horticultural Society over a 2-month period in the spring of 2013.
Greening Treatment	Trash Pickup Treatment	Control
Removed trash and debris	Removed trash and debris	No changes were made to the vacant lots
Graded, or leveled off, the land	Mowed grass where possible
Planted new grass and a small number of new trees	Performed regular maintenance
Installed a low wooden perimeter fence with openings
Performed regular maintenance

Once the scientists narrowed down the list of eligible vacant lots and randomly assigned them to clusters and then to study groups, they had 541 vacant lots to include in the study (figure 4). They made sure that the three study groups (greening, trash pickup, and control) had similar characteristics in terms of size, number of residents, and other community characteristics.

A map of Philadelphia showing the lots chosen for the study. Each is marked with a different colored dot to denote which study group the lot belonged to. — **Figure 4**. This map of the city of Philadelphia divides the city into four sections. The dots represent vacant lots included in the study: green dots for the greening treatment, yellow dots for the trash pickup treatment, and gray dots for the control lots that received no treatment. The dots are not the exact locations of the vacant lots to protect the privacy of people who live in these neighborhoods.

USDA Forest Service map by Michelle Kondo.

Scientists used a process to randomly sample residents living near each kind of vacant lot. They interviewed 342 residents both before the treatments took place and after the treatments had been completed.

The residents answered questions about their perceptions of their own mental health over the last 30 days. The questions were from the Kessler 6 Psychological Distress Scale (known as the K6), a commonly used community screening tool (see below). Residents answered six questions about how often they felt nervous, hopeless, restless, depressed, that everything was an effort, and worthless.

Using the K6, scientists gave each resident a score anywhere from 0 to 24. Scores of 13 or higher on the K6 indicated that the resident suffered from more feelings of poor mental health than those with lower scores.

What's the difference between a screening test and a diagnostic test?

The Kessler-6 Psychological Distress Scale (or K6) is a community screening tool. The K6 is not a diagnostic tool, meaning it is not used to formally diagnose someone with poor mental health. Instead, the K6 provides information about how people feel and can be used as an informational tool. Screening tests can be used to determine if someone is at risk of developing a disease or condition.

Scientists compared the K6 scores of residents in the greening treatment group with the control group. They also compared the K6 scores of residents in the trash pickup treatment group with the control group. They looked at whether either treatment was related to improved mental health scores or not. They also looked at whether one type of treatment was associated with better mental health scores than the other.

Reflection Section

Findings

When the scientists compared the K6 scores of residents in the greening treatment group with those in the control group, they found a significant decrease in feelings of depression and feelings of worthlessness. For residents in the trash pickup treatment group, there was no significant difference in their K6 scores compared to the control group.

What makes an observed change significant?

When scientists are fairly certain that the observed change (in this case, improved K6 scores) was not caused by chance, the change is considered significant. Scientists do not just decide for themselves whether a change is significant. Scientists use mathematical equations to determine whether a change is significant.

When most people say that something is significant, they mean that the event or object has a great amount of importance. When scientists say that an observed change is significant, they mean that it is very likely the change was not caused by chance.

Reflection Section

Discussion

The greening of vacant lots in the city was associated with significant improvements in some aspects of the nearby residents’ mental health. Even though the greening treatments required more work and materials than the trash pickup, the treatments were still a relatively affordable option for helping improve the mental health of residents (figure 5). On each vacant lot, the greening treatment cost approximately $1,597. Scientists estimated that maintaining each lot will cost around $180 a year. The relatively low cost may make greening treatments a possibility for improving residents’ mental health in urban areas.

An empty lot in a city that has green grass, a newly planted young tree, and an open wood fence. — **Figure 5**. Remember the vacant lot in figure 3 (*see above*)? This is a photo of the same lot. The lot received the same greening treatment as part of a different community project by the Pennsylvania Horticultural Society. They cleared out the trash, planted new grass and a few trees, and built a low fence. The greening treatment was a relatively inexpensive treatment. Many of the lots are maintained by landscape crews made up of residents of the neighborhood. This lot was not included in this particular study.

Courtesy photo by the Pennsylvania Horticultural Society.

Number Crunch

Scientists proposed a few reasons why the greening treatment was associated with more improvements in mental health than the trash pickup treatment. One reason may be that the greening treatments created new green space that didn’t exist previously, while the trash pickup treatment just cleaned existing lots. Other studies have shown the positive health effects associated with green spaces, so having more green spaces would seem to benefit people’s overall health.

Another reason that the greening treatment was associated with better mental health outcomes may be that green spaces encourage more people to go outside to enjoy them (figure 6). The scientists did not specifically track how or if people used the greened lots. However, the scientists found some signs that people had been using them for recreation or gatherings. Sometimes there was a barbeque grill or a kiddie pool on a greened lot, or scientists saw people sitting on the fence and talking.

People can enjoy social activities with one another in green spaces, and these activities can help people feel a greater sense of community and connection with one another. Those feelings of connection have been shown to help improve mental health.

A small city lot planted with grass and other plants. A large mural borders one side of the lot, and there are benches and a picnic table. — **Figure 6**. The Ed Bradley Community Oasis was created as a joint project between the Pennsylvania Horticultural Society and the National Wildlife Federation. The formerly vacant lot, which was not part of this study, now has benches and picnic tables as well as a pollinator garden. These features encourage nearby residents to use the lot as a gathering place.

Courtesy photo by the Pennsylvania Horticultural Society.

Two children stand outdoors at a wooden railing and look at a waterfall.

Did You Know?

Some studies have shown that green space may help us recover from mental fatigue. Mental fatigue happens when our brains get tired and overwhelmed from processing so much information all the time. That information isn’t just what we’re learning in school or what we’re thinking about at work. We also process information when we watch things on TV or on our computers and phones, when we listen to people talk, or when we read books, magazines, or even signs! Green space provides a place where our brains can rest from processing all that information.

Interestingly, scientists think the fences that were part of the greening treatments may have had an impact on residents’ feelings of better mental health. They think the fence showed that the lot was being cared for, but because the fence was low and had openings, the lots looked welcoming and people felt they could enter (figure 7). The fence also somewhat prevented other people from dumping trash on the lot illegally. Showing that the lots were being cared for may have made residents feel like they were being cared for, too.

An abandoned city lot full of overgrown vegetation and trash, surrounded by a broken chain link fence. — **Figure 7**. (A) Before the greening treatment, this lot was enclosed by a chain-link fence that had fallen into disrepair.

Courtesy photo by the Pennsylvania Horticultural Society.

An empty city lot with green grass and a tree, surrounded by a low and open wooden fence. — (B) After the greening treatment, this lot has a low, open fence that is typical of the greened lots in the study. This particular lot was not part of this study.

Courtesy photo by the Pennsylvania Horticultural Society.

The scientists propose that greening vacant lots may be one important tool for communities to address mental health issues. Many health professionals and urban residents are concerned about the impact of people’s environments on both their physical and mental health. Even small green spaces may contribute to people’s overall sense of well-being (figure 8).

A community garden with many different plantings and a wooden pergola. — **Figure 8**. The Tioga Hope Garden and Park is located in the Nicetown-Tioga neighborhood in Philadelphia. Work on the garden is supported by the local community members, local organizations like Nicetown Community Development Corporation and Tioga United, as well as the Pennsylvania Horticultural Society. The garden was created to help the local community be “nourished by nature.” This garden was not part of this study.

Courtesy photo by Pennsylvania Horticultural Society.

After the study had concluded, the Pennsylvania Horticultural Society went back and also cleaned and greened the control lots, which were the lots that received no treatment for the study. These treatments are part of their LandCare Program that works to green other vacant lots in Philadelphia.

Learn More about the LandCare Program

Reflection Section

Adapted from South, E.C.; Hohl, B.C.; Kondo, M.C.; MacDonald, J.M.; Branas, C.C. 2018. Effect of greening vacant land on mental health of community dwelling adults. JAMA Network Open. 1(3): e180298.

Part Of

A Green Bill of Health - Vol. 1 No. 26

Explore Full Monograph

Michelle Kondo

Social Scientist

My favorite science experiences have involved observing the positive things that can come from neighborhood greening. Greening can bring jobs to a community. In addition, learning about trees, participating in...
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Charles Branas

Professor of Epidemiology

One of my favorite experiences as a scientist was a few years ago. A group of neighbors approached our study team—we thought they were going to complain about the noise...
View Profile
Eugenia South

Physician-Scientist

My favorite science experience was working with an awesome team to study the impact of different urban greening treatments on health and safety, including trees, vacant lot greening, and community...
View Profile

Standards addressed in this Article:

Next Generation Science Standards

ESS3.C-H1
ESS3.C-M1
ESS3.C-M2
ETS1.A-H2
ETS1.B-H1
ETS1.B-M1
ETS1.B-M2
LS2.A-M1
LS4.D-H2

Social Studies Standards

Individual Development and Identity
People, Places, and Environments
Science, Technology, and Society

Note To Educators

The Forest Service's Mission

The Forest Service’s mission is to sustain the health, diversity, and productivity of the Nation’s forests and grasslands to meet the needs of present and future generations. For more than 100 years, our motto has been “caring for the land and serving people.” The Forest Service, an agency of the U.S. Department of Agriculture (USDA), recognizes its responsibility to be engaged in efforts to connect youth to nature and to promote the development of science-based conservation education programs and materials nationwide.

What Is the Natural Inquirer?

Natural Inquirer is a science education resource journal to be used by students in grade 6 and up. Natural Inquirer contains articles describing environmental and natural resource research conducted by Forest Service scientists and their cooperators. These scientific journal articles have been reformatted to meet the needs of middle school students. The articles are easy to understand, are aesthetically pleasing to the eye, contain glossaries, and include hands-on activities. The goal of Natural Inquirer is to stimulate critical reading and thinking about scientific inquiry and investigation while teaching about ecology, the natural environment, and natural resources.

Natural Inquirer bee sitting at a desk with paper and pencil

Meet the Scientists

Introduces students to the scientists who did the research. This section may be used in a discussion about careers in science.
What Kinds of Scientist Did This Research?

Introduces students to the scientific disciplines of the scientists who conducted the research.
Thinking About Science

Introduces something new about the scientific process, such as a scientific habit of mind or procedures used in scientific studies.
Thinking About the Environment

Introduces the environmental topic being addressed in the research.
Introduction

Introduces the problem or question that the research addresses.
Method

Describes the method the scientists used to collect and analyze their data.
Findings & Discussion

Describes the results of the analysis. Addresses the findings and places them into the context of the original problem or question.
Reflection Section

Presents questions aimed at stimulating critical thinking about what has been read or predicting what might be presented in the next section. These questions are placed at the end of each of the main article sections.
Number Crunches

Presents an easy math problem related to the research.
Glossary

Defines potentially new scientific or other terms to students. The first occurrence of a glossary word is bold in the text.
Citation

Gives the original article citation with an internet link to the original article.
FACTivity

Presents a hands-on activity that emphasizes something presented in the article.

Science Education Standards

You will find a listing of education standards which are addressed by each article at the back of each publication and on our website.

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Education Files

Project Learning Tree

If you are a trained Project Learning Tree educator, you may use “Are Vacant Lots Vacant?,” “Sounds Around,” “I’d Like to Visit a Place Where . . .,” and “Planning the Ideal Community” as additional resources.

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