Nouabale-Ndoki National Park in Central Africa, site of the scientists' research. Credit: Wikimedia Commons

Ecologists discover when, how tropical trees regenerate

Nouabale-Ndoki National Park is a tree-dotted enclave in Central Africa’s Republic of Congo. Heavy logging surrounds the park, but it still has one of the largest intact forests in Africa. In recognition, it recently became a UNESCO World Heritage Site.

Trees–thousands of them–make up a forest. How did Nouabale-Ndoki’s trees become so numerous, and how do they stay that way?

The answer, say biologists, lies far below the tree canopy, in the soil where seedlings sprout.

Reaching toward the sky: a canopy tree in Nouabale-Ndoki National Park. Credit: Connie Clark

Recently, in the journal PLOS ONE, scientists report results of an extensive seedling experiment in Nouabale-Ndoki National Park. The research, which involved sowing 40,000 seeds of five tree species, is a new look at “seeing the forest for the trees.”

The findings, which show what limits seedling growth, are important to reforestation efforts in areas that have been logged.

Every tree can produce hundreds of thousands of seeds in its lifetime, but on average, only one seed survives to adulthood, says John Poulsen of Duke University, a co-author of the journal paper.

Other paper co-authors are Connie Clark, also of Duke, and Doug Levey, formerly of the University of Florida and now a program director in the National Science Foundation’s (NSF) Division of Environmental Biology.

Which seeds have the best chance of making it to old age?

“There are basically two ways to look at successful seedling recruitment [survival],” says Levey. “Species may be seed-limited or establishment-limited.”

Two-year-old seedlings of a species known as African mahogany survive in the tropical forest. Credit: Connie Clark

A tree species is seed-limited if its ability to grow is determined by whether its seeds reach a particular location on the ground. The seeds may arrive on the wind or simply by falling from trees.

Establishment-limited trees are those that depend on the environment around them, rather than on seeds landing in just the right spot. If the soil is too wet or there is too much shade, a species is establishment-limited.

To test the importance of these two limitations on seedling recruitment, the scientists sowed tens of thousands of seeds. They chose the species randomly, which allowed the results to be generalized to all tree species, not just the most common ones, says Poulsen.

The seeds were planted in different amounts in plots that stretched across an area the size of the state of Rhode Island. Latter-day Johnny Appleseeds, the researchers couldn’t do it alone, however.

Gaston Abeya, a Mbendzele research assistant, measuring tree seedlings. Credit: Connie Clark

“We hired a small army of indigenous, Mbendzélé hunter-gatherers,” says Clark. “These families could easily locate seeds, and we were the beneficiaries of their intimate knowledge of the forest’s natural history.”

After the seeds were planted, the ecologists watched them grow into seedlings over two years.

They found that only a small fraction of seeds, some 16 percent, became seedlings. An even smaller amount, about six percent, survived to reach their second birthdays.

When numbers of seeds were at one end of a spectrum–rare or abundant–the trees’ recruitment was seed-limited.

“When seeds were at intermediate densities,” says Levey, “the chance of recruitment was influenced by environmental factors such as soil type and sunlight.”

The importance of seed- and establishment-limitation changes over time, Levey says. “As individual trees get older, they need the correct soil and light exposure [become more establishment-limited].”

Not that different from our changing needs for the right nutrients and enough light as we reach our sunset years.

Source: National Science Foundation

In Zambia, as in many third world countries, charcoal is a major source of heating and cooking fuel. But it is also one of the major deforestation causes, as trees of all sizes and species are cut and burned in earthen pits. The majority of charcoal is produced by poor rural villagers and is a source of income for them. There are laws in place to stop the practice but with limited resources to enforce them, the devastation continues.

But one charcoal burner, Lloyd Maanyina, has taken an enormous step in creating a tree nursery to replace the trees he’s burned during his life. This short film, Amazing Grace by Makulu, shows how dedication, and a conscience, can make a difference.

Amelia and the Moments

Passing on the stories of individual or collective plant species occurs daily for me. It may be for a semi-permanent interpretative sign for a plant in the glasshouse collections of the National Botanic Gardens, Glasnevin in Dublin, where I work, a page of a book on native Irish orchids, a speciality of mine, or in a chat with a neighbour. The selection of an appropriate image can make or break the efficacy of the words.

When I met Amelia Stein in the Gardens an autumn day in 1999, a joint project was conceived. Neither of us knew it at the time.

There was method to Amelia’s arrival in Glasnevin that first day. It was to document, for generations to come, an extinction event. It was a necessary extinction, one that would avoid an untimely and more unsightly one.

The necessity was the dismantling of a glass, iron and wooden structure that protected a semi-tangible creation. This structure had a name and that name became the title of the project – The Palm House.

The physical were the plants, pots, tubs, soil and even the birds that flew through cracked panes to nest in crevices in the warm blackstone wall that supported the lattice of ironwork.

Less tangible was the atmosphere created by heat, moisture and modest decay. It was something I loved.

Amelia’s arrival coincided with the declaration of the imminent restoration of this great, graceful, grande dame of Irish glasshouses.

Moving

The collections within were to be removed, transported to temporary accommodation, to be returned sometime later. The temporary accommodation was tight; necessitating cramped quarters, narrow maintenance aisles and the banishment of public visitors.

This huge task required great planning and careful execution, it was an exile. The return from this exile would gauge the success of the planned procedures. Unforeseen complications fortunately stalled the restoration date giving Amelia more time to engage with the house, the plants and me.

It was both a challenge and a joy to be involved with Amelia and The Palm House project. Part of the joy was that there were few written words and the challenge, exactly the same.

The Palm House

For The Palm House, my task was to tell tales. They were tales of characters in a play that was on show every day for public viewing. The play was in its final run. The cast came from far and wide yet lived in harmony, their shared heritage was one of warmth.

The photographic process at the hands of Amelia and her Hasselblad camera would capture the leading men and their ladies. These would include the lonely man cycad from the Ongoye forest of KwaZulu-Natal, the long and lanky Asian giant bamboo that towered over everyone else and the graceful, arching North African date palm delivering sweet treats to those who cared for them. But I digress, these are tales for another time!

Amelia’s portraits of moments in time in the Palm House at Glasnevin would accumulate and then be sorted, discussed, discarded and reprieved, as the selection for final line up proceeded.

Captured

Through Amelia’s art, her patience, listening, watching and waiting, moments from that magical world appear in duotone.

The images are evocative and informative.

To some they awaken buried memories, to others create unique scenes.

For me she has captured the impossible! The warmed atmosphere, infused with the heady scents from the flowers of spathe and swamp lilies, decaying leaves and wet soil, carried to your face on moisture laden air.

And there are the sounds from the house. Foliage rustling as the cool outdoor air rushed through on a door opening or the cries of exclamation from a young visitor. The tactile and olfactory palpably evoked in print.

Realized

It is a glimpse into the creation and working of a century old collection of foreign tropical plants in a foreign temperate country. Generations of gardeners took charge to grow these plants, most which were single specimens, cosseting them as seedlings, increasing their pot size as they grew from year to year and finally planting them in wooden barrels, recycled whiskey casks, when their rootballs exceeded the size of the largest clay pot.

The behemoths were suspended on large steel tripods as their containers were replaced, roots freshly encased in rich soils until size or exhaustion necessitated another change.

Some plants escaped their containers and sunk their roots into the gravel and clinker floor, an achievement, impossible to reverse. They had customised concrete forms, cast around them.

The magic of light was captured too.

The low winter trajectory absorbed and partitioned by the variety of forms created a leafy kaleidoscope.  It is these images that I cherish most, remembrances of frosty, winter mornings standing alone in the warm air, watching the play from the sidelines as the characters prepared for another performance.

The Show Goes On

One day, following the final exits, Amelia and I recollected our thoughts, now that the time had come to hand over the burdensome task of restoration to the contractors. There is an image from that day that I frequently revisit. It shows me sitting on the steps of the main entrance to the Palm House, the benches empty, pots and tubs removed. Pushing its way through the gravel is a shoot of a banana, a remnant of the clump that had been removed, defying the events of the past month while the house was cleared. In revisiting, I see captured, fleeting moments. The shoot, the defiance of plants in the face of man’s destructive qualities, the miracle of rebirth, that most things do not end, they continue in some form or other.

And it is in that vein that I end this lament and transform it to a celebration. For the grande dame has returned clothed in new silks of modern design. She has not changed much, her warm embrace as strong as ever, her protective stance warding off danger, her comforting world coaxing new fronds from aged stems. Her corridors are as luxuriant as ever, the exiles finding firm root in the new, deep beds of fertile soil.

They have returned, we exclaim success!!

 Visit Amelia Stein Gallery: The Palm House in ecoArts. a companion piece to this article, to see beautiful selections from Amelia Stein’s  ”The Palm House” photographic exhibition in Ireland, and exquisite hardcover book of the same title.

The Palm House: Photography by Amelia Stein; foreword by John Banville, text by Brendan Sayers; published by The Lilliput Press Ltd., printed on Garda Pat Klassica and bound by Editoriale Bortolazzi Stei, Verona, Italy.

This fine monograph of duotone photographs taken in the great Palm House at the National Botanical Gardens in Glasnevin, Dublin, beautifully illustrates the house prior to its restoration, and its unique patina acquired over a period of time that spans three centuries. Amelia captures the relationships between the luxuriant tropical plantings and the time-worn fabric of the building, the seasonal changes in light. Brendan’s narrative text brings a light touch and a deep knowledge to Amelia’s lush visual exploration of The Palm House, and all its living charges.

Brendan Sayers is Glasshouse Foreman in The National Botanic Gardens in Glasnevin, Ireland. Brendan specializes in Belizean and Irish orchids. His previous published collaborations include the much-coveted and awarded duo of Ireland’s Wild Orchids and Ireland’s Wild Orchids – A Field Guide.

In 2011 he received the H.H. Bloomer Medal from the Linnean Society of London for raising the profile of Irish orchids. He is currently writing his next wild and wonderful publishing project, Transformations.

Born in New York City to Irish parents, Brendan was raised in County Kerry, which he considers one of the most beautiful places in Ireland. Brendan was educated in horticulture at The National Botanic Gardens, Glasnevin. He worked in professional horticulture in New York and New Jersey, before returning permanently to Ireland in 1993. Brendan is one of Planting for the Planet’s earliest contributors, starting with Our Step Forward: Botanical Pursuits of the Human Kind.

Rows of tall buildings can create a unique urban habitat known as a street canyon. These canyons trap traffic pollutants, limiting their dispersal into the atmospheric boundary layer that extends as high as 2,000 meters above the ground. A new study suggests that vegetation in street canyons may reduce air-pollutant concentrations much more than previously reported and suggests innovative planting configurations to improve city pollution hot spots.¹

NYC street canyon

Outdoor air pollution is believed to cause an estimated 1.3 million annual deaths worldwide,² as well as an increased risk of respiratory and cardiovascular diseases.³ Plantings are often promoted as a partial solution, because leaves absorb gaseous pollutants through their pores and capture particulate matter on their surfaces.^{4,5,6,7,8,9,10,11} Yet modeling studies of the vegetation across entire cities have estimated that existing green cover reduces air pollution concentrations by less than 1.5%.^4,5,9

For the current study, researchers developed a computer model to calculate how much pollution is captured by vegetation in the much smaller, somewhat isolated space of a street canyon. “We argue that for urban air quality these effects will be much more important because people aren’t found five hundred meters up in the atmosphere; they’re found down at street level,” says lead author Thomas Pugh, a postdoctoral researcher in atmospheric chemistry now at the Karlsruhe Institute of Technology.¹²

Green wall, Pittsburgh PA, photo by Eugene McCarthy

The team estimated that street-canyon vegetation may reduce concentrations of two of the most harmful urban air pollutants, nitrogen dioxide (NO2) and coarse particulate matter (PM10), by as much as 40% and 60% respectively, although average reductions over a year were in the range of 7–30%. Because air lingers in street canyons, it stays in contact with pollutant-scrubbing vegetation, Pugh says.

David Nowak, who studies how urban forests affect environmental quality for the U.S. Forest Service, likens the effect to that of an air purifier running in a small, enclosed room as opposed to a large, open space. He points out that the new results are not entirely unexpected—at least one other study showed similar reductions in the air pollutant ozone, although those measurements were made in an urban forest, not a city.⁵

The study is limited by the model’s reliance on data with only modest experimental support, including the rates at which plants capture pollutants and air flows in and out of street canyons, says Pugh. Moreover, experimental research in vegetated street canyons is needed to verify the results. This lack of validation makes Max Zhang, an associate professor of engineering at Cornell University who studies traffic emissions, question the size of the pollutant reductions the paper reports. “I still believe the argument is very good,” says Zhang, “I believe there are definitely reductions, but the problem is the magnitude.”

Nevertheless, Pugh says city planners may be able to design plantings that significantly improve air quality in highly polluted street canyons. The model results suggest that plants growing vertically on building walls could remove nearly 10 times as much NO2 and nearly 12 times as much PM10 from street-canyon air as horizontally grown rooftop vegetation. The researchers even propose adding “green billboards” to rooftops to increase the time polluted air spends within a canyon, maximizing its exposure to vegetation.

Green wall, Paris

Whether green billboards or green walls are practical on a large scale remains to be seen. Walter Warriner, community forester for the city of Santa Monica, California, and a board member of the National Urban and Community Forestry Advisory Committee, is unaware of any plantings specifically targeted at urban pollution hot spots in the United States. But he says they may soon be possible given advances in air-quality monitoring technology and a recent focus among urban foresters on quantifying environmental benefits.

Trees are a more familiar solution, but although Pugh and colleagues did not directly model how trees capture airborne pollutants,13 they predict that in highly polluted street canyons, trees may actually do more harm than good. That’s because in those circumstances, trees’ ability to capture pollutants may be outweighed by their tendency to trap vehicle emissions near street level, right where people can breathe them in.^14,15

“That’s not to say you should go and chop down all the trees in busy street canyons,” says Pugh, but planners contemplating planting new trees in these settings should proceed with caution to make sure they don’t inadvertently increase ground-level pollution while trying to address some other issue, such as rainwater runoff or beautification. Where traffic is light, trees offer clear benefits, the researchers write.

Nowak notes that although plants can certainly help reduce urban air pollution, reducing emissions is a more effective, if not necessarily an easy, first step. In the worst cases, he says, “We’re not going to plant our way out of this problem.”

Rebecca Kessler, based in Providence, RI, writes about science and the environment. She is a member of the National Association of Science Writers and the Society of Environmental Journalists.  

References and Notes

1. Pugh TAM, et al. Effectiveness of green infrastructure for improvement of air quality in urban street canyons. Environ Sci Technol 46(14):7692−7699 (2012); http://dx.doi.org/10.1021/es300826w.

2. WHO. Public Health and Environment (PHE): Health Impacts—How Large Is the Disease Burden from Urban Outdoor Air Pollution? [website]. Geneva, Switzerland:World Health Organization (2012). Available: http://www.who.int/phe/health_topics/outdoorair/databases/health_impacts/en/index1.html [accessed 30 Nov 2012].

3. WHO. Public Health and Environment (PHE): Health Impacts—Are There Health Effects from Both Short and Long Term Exposure to Urban Outdoor Air Pollution? [website]. Geneva, Switzerland:World Health Organization (2012). Available: http://www.who.int/phe/health_topics/outdoorair/databases/health_impacts/en/index2.html [accessed 30 Nov 2012].

4. Nowak DJ. Air pollution removal by Chicago’s urban forest. In: Chicago’s Urban Forest Ecosystem: Results of the Chicago Urban Forest Climate Project. USDA Forest Service General Technical Report NE-186 (McPherson EG, et al. eds.). Radnor, PA:Northeastern Forest Experiment Station, Forest Service, U.S. Department of Agriculture (1994). Available: http://www.nrs.fs.fed.us/pubs/gtr/gtr_ne186.pdf [accessed 30 Nov 2012].

5. Nowak DJ, et al. Air pollution removal by trees and shrubs in the United States. Urban Forest Urban Green 4(3–4):115−123 (2006); http://dx.doi.org/10.1016/j.ufug.2006.01.007.

6. Currie BA, Bass B. Estimates of air pollution mitigation with green plants and green roofs using the UFORE model. Urban Ecosys 11(4):409−422 (2008); http://dx.doi.org/10.1007/s11252-008-0054-y.

7. Donovan RG, et al. Development and application of an urban tree air quality score for photochemical pollution episodes using the Birmingham, United Kingdom, area as a case study. Environ Sci Technol 39(17):6730−6738 (2005); http://dx.doi.org/10.1021/es050581y.

8. Yang J, et al. Quantifying air pollution removal by green roofs in Chicago. Atmos Environ 42(31):7266−7273 (2008); http://dx.doi.org/10.1016/j.atmosenv.2008.07.003.

9. Tallis M, et al. Estimating the removal of atmospheric particulate pollution by the urban tree canopy of London, under current and future environments. Land Urban Plan 103(2):129−138 (2011); http://dx.doi.org/10.1016/j.landurbplan.2011.07.003.

10. Escobedo FJ, Nowak DJ. Spatial heterogeneity and air pollution removal by an urban forest. Land Urban Plan 90(3-4):102−110 (2009); http://dx.doi.org/10.1016/j.landurbplan.2008.10.021.

11. McDonald AG, et al. Quantifying the effect of urban tree planting on concentrations and depositions of PM10 in two UK conurbations. Atmos Environ 41(38):8455−8467 (2007); http://dx.doi.org/10.1016/j.atmosenv.2007.07.025.

12. At the time this study was conducted Pugh was a postdoctoral researcher at Lancaster University, United Kingdom.

13. Steffens JT, et al. Exploration of effects of a vegetation barrier on the dispersion of pollutants in a near road environment. Atmos Environ 50:120–128 (2012); http://dx.doi.org/10.1016/j.atmosenv.2011.12.051.

14. Gromke C, Ruck B. On the impact of trees on dispersion processes of traffic emissions in street canyons. Bound-Lay Meteorol 131(1):19−34 (2009); http://dx.doi.org/10.1007/s10546-008-9301-2.

15. Gromke C. A vegetation modeling concept for building and environmental aerodynamics wind tunnel tests and its application in pollutant dispersion studies. Environ Pollut 159(8–9):2094−2099 (2011); http://dx.doi.org/10.1016/j.envpol.2010.11.012.

TREES IMPROVE THE ENVIRONMENT

Air Quality/Pollution Reduction

• Trees help to clean the air by “catching” airborne pollutants such as ozone, nitrogen oxides, sulfur dioxides, carbon monoxide, carbon dioxide, and small particulates less than 10 microns in size.3

• Planting trees remains one of the cheapest, most effective means of drawing excess CO2 from the atmosphere.15

• There is up to a 60% reduction in street level particulates with trees.1

• One tree that shades your home in the city will also save fossil fuel, cutting CO2 buildup as much as 15 forest trees.16

• Each year an average acre of mature trees absorb up to 26 pounds of carbon dioxide from the air, which is equal to the amount of Co2 produced by driving a car 26,000 miles.8

Water Quality/Erosion

• Trees reduce topsoil erosion, prevent harmful land pollutants contained in the soil from getting into our waterways, slow down water run-off, and ensure that our groundwater supplies are continually being replenished. For every 5% of tree cover added to a community, storm water runoff is reduced by approximately 2%.1

• Trees help communities across the country avoid millions of dollars in storm water management costs.18

• Trees reduce soil erosion when planted along streams and waterways.18

• Trees can intercept between 7 percent and 22 percent of storm water runoff from impermeable surfaces.17

Energy Savings

• Homeowners that properly place trees in their landscape can realize savings up to 58% on daytime air conditioning and as high as 65% for mobile homes. If applied nationwide to buildings not now benefiting from trees, the shade could reduce our nation’s consumption of oil by 500,000 barrels of oil/day.12

• Projections suggest that 100 million additional mature trees in US cities (3 trees for every unshaded single family home) could save over $2 billion in energy costs per year.10

A CANOPY FOR COMMUNITY AND SOCIETAL WELL-BEING

Urban Trees Reduce Crime, Increase Public Safety and Build Community

• A University of Illinois study finds that trees in urban areas are directly correlated with lower levels of fear, fewer incivilities, and less violent and aggressive behavior.4

• In an inner-city neighborhood, the greener the residence, the lower the crime
  rate. Residents reported fewer violent crimes and property crimes in green neighborhoods as compared to those that were barrern.4

• Researchers found fewer reports of physical violence in homes that had trees
  outside the buildings. Of the residents interviewed, 14% of residents living in
  barren conditions have threatened to use a knife or gun against their children
  versus 3% for the residents living in green conditions.15

The Healing Power of Trees

• School children with ADHD show fewer symptoms and girls show more academic self-discipline if they have access to natural settings.19

• Researchers found fewer reports of physical violence in homes that had trees outside the buildings. Of the residents interviewed, 14% of residents living in barren conditions have threatened to use a knife or gun against their children versus 3% for the residents living in green conditions.15

• Studies have shown that hospital patients with a view of trees out their windows recover much faster and with fewer complications and require fewer pain-killing medications than similar patients without such views.13

• A Texas A & M study indicates that trees help create relaxation and well being.18

• A U.S. Department of Energy study reports that trees reduce noise pollution by acting as a buffer and absorbing 50% of urban noise.18

• Reduced air pollution from the presence of trees helps to ameliorate respiratory problems, such as asthma—the leading serious chronic illness among children.17

• Trees can provide protection against skin cancer by reducing UV-B exposure (the most damaging type of solar radiation) by about half, according to a study by Richard Grant, Purdue University; and Gordon Heisler, USDA Forest Service.17

• Time spent in nature reduces mental fatigue, restoring the ability to concentrate and pay attention.4

• Exposure to even small amounts of trees and grass aids concentration, leading to greater effectiveness.4

MONEY DOES GROW ON TREES!

• Large, mature street trees are found to be the most important indicator of attractiveness in a community.17

• Property values increase 5-15% when compared to properties without trees (depends on species, maturity, quantity and location)18

• Shoppers are willing to pay up to 11 percent more for products purchased in shops along tree-lined streets than they would pay for the same item in a barren setting.17

• The quality of products were perceived as being better in shopping districts having trees versus those with barren sidewalks.17

• Shoppers stay longer in plazas that have trees.17

• Appraised property values of homes that are adjacent to parks and open spaces are typically 8-20% higher than those of comparable properties elsewhere.17

• Strategically placed trees can cut summer air conditioning costs for businesses by as much as 50 percent or more.17

• Rental rates of commercial office properties were approximately 7% higher on sites having quality landscape, including trees.17

• Office workers with a view of nature are more productive, report fewer illnesses, and have higher job satisfaction.17

• Trees have the potential to reduce social service budgets, decrease police calls for domestic violence, strengthen urban communities, and decrease the incidence of child abuse according to the study. Chicago officials heard that message in 2005. The city government spent $10 million to plant 20,000 trees, a decision influenced by Kuo’s and Sullivan’s research, according to the Chicago Tribune.

What are the threats facing Indianapolis trees?

• Pollution and urban sprawl. As cities and suburbs expand, our forests shrink – meaning all of the benefits of those trees are lost.

• Indianapolis ranks 8th worst in the country for fine particulate matter pollution.

• American Forests recommends that a city have an average tree cover of 45%. Currently, Indianapolis has a tree cover of 24%. Center Township has a tree cover of 15%.

• In Indianapolis, there has been a 25% loss in tree canopy measured during the last three decades. An IUPUI study using aerial photography measured changes in the urban forest from 1962 to 1993 in 41 randomly selected census tracts.

• There has been a 37% loss in wooded lands in Marion County from 1980 to 2000. IUPUI measured this loss by using Landsat Thematic Mapping technology. The equivalent of 20 square miles of woods has been lost in Marion County since 1980.

• IUPUI Research shows a direct correlation between income and tree canopy. A study of 41 census tracts found lower income neighborhoods often have significantly less canopy cover.

• The emerald ash borer is decimating Indiana ash trees, estimated at 6% of Indiana’s trees, and is at Marion County’s doorstep.

• The IUPUI/Center for Urban Policy and the Environment forecasts that growth in Central Indiana over the next 40 years will outpace development since Indianapolis was founded. In 2000, 1076 square miles of land were urbanized. By 2040, and additional 1,167 square miles will be developed.

References
1. Coder, Dr. Kim D., “Identified Benefits of Community Trees and Forests”, University of Georgia, October, 1996.
2. USDA Forest Service Pamphlet #R1-92-100
3. International Society of Arboriculture Tree Care Bulletin, Benefits of Trees
4. Kuo, F.E. 2001, “Environment and Crime in the Inner City: Does Vegetation Reduce Crime?” Environment and Behavior, Volume 33, Number), pp
343-367.—www.herluiuc.edu
5. Kuo, F.E., 1998 Fertile Ground for Community: Inner-City Neighborhood Common Spaces. American Journal of Community Psychology, 26 www.herluiuc.edu
6. Georgia Urban Forest Council; University of Illinois at Urbana Champaign; www.cucf.com
7. Kuo , F.E. 2003. The role of arboriculture in healthy social ecology. Journal of Arboriculture, 29, 3, 148-155
8. Nowak, David J., “Benefits of Community Trees”, (Brooklyn Trees, USDA Forest Service General Technical Report, in review)
9. Galveston-Houston Association for Smog Prevention (GHASP), “Trees and Our Air”, January, 1999.
10. McAliney, Mike. Arguments for Land Conservation: Documentation and Information Sources for Land Resources Protection, Trust for Public Land,
Sacramento, CA, December, 1993
11. Michigan State University Extension, Urban Forestry #07269501, “Benefits of Urban Trees”
12. American Forests, “The Case for Greener Cities”, Autumn 1999.
13. American Forests, “How Trees Fight Climate Change”, 1999.
14. Crompton, J.L. 2001. Parks and Economic Development. Chicago, IL. American Planning Association
15. Prow, Tina., “The Power of Trees”, Human Environmental Research Laboratory at University of Illinois.
16. National Arbor Day Foundation pamphlet #90980005
17. Georgia Urban Forestry Publication, Shade-Healthy Trees, Healthy Cities, Healthy People, 2004
18. www.colorado trees.org, Benefits of Trees
19. Coping with ADD: The Surprising Connection to Green Play Settings, Environment and Behavior. Vol. 33 No. 1. January 2001. 54-77, 2001 Sage
Publications, Inc.

The 9.0 earthquake triggered a powerful tsunami that reached heights of up to 130 ft. (40.5 meters) and which traveled up to 6 miles inland (10km). Over 20,000 died in the devastation along the Pacific coastline of Japan’s northern islands.

This exquisite natural monument serves a dual purpose, both practical and symbolic. While creating a touching memorial to victims of the disaster, the planned 105 mile (170 km) row of pink blossoming cherry trees along the tsunami’s high water line will also stand as a potentially life-saving reference, showing residents how far to evacuate from the coast in the event of a future tsunami warning.

There were a few forgotten stone monuments marking high water points of past tsunamis in Rikuzentakata, known as Takata. Had residents been aware of their history more lives may have been saved. This new demarcation will not be so easily overlooked as the progress of debris removal and reconstruction softens the edge of the devastation. The trees of the Sakura Line 311 will grow in stature and beauty, standing as a timeless reminder for future generations.

The project started in August 2011 with 259 Sakura trees planted to date, at 60 locations in the city. In 2012 350 more Sakura trees will be planted in November and December. The goal of the non-profit group, to eventually plant about 17,000 cherry trees, one every 11 yards, in a line some 105 miles long, may require more than 10 years to complete. As word of the project spreads, individuals and businesses across Japan have donated cherry saplings, landowners in Takata have given the group permission to plant the saplings, and hundreds of volunteers have participated.

Though it was expected to take 4 years for the Sakura saplings to bloom, many of the trees have bloomed the first spring after planting – a rare and inspiring occurrence.

“Having lost many friends and acquaintances due to the tsunami, I regret that we had no knowledge of inland points where waves had reached in the past. I don’t want future generations to feel the same way,”

Takumi Hashizume, President, “Sakura Line 311″

Reconstruction of Rikuzentakata is in progress, 18 months after the tsunami

Sakura Line 311 volunteers prepare for planting

300 Sakura Line 311 volunteers support planting event

2~3 year old seedlings were chosen which are easy to handle

Volunteers plant a seedling

A precious Sakura blossom on a tree planted in November, 2011

It is considered rare for the Sakura to start blooming a year after planting

Photos courtesy of Sakura Line 311

For More information:

The Sakura Line 311
Save Takata
 



Excerpt from the upcoming video “one day, everything will be free”, a feature length documentary about Sadhana Forest in Ansapit, Haiti, by Joseph Redwood-Martinez.

“It’s the mother. Without good soil, there won’t be a good crop.”

Nancy Gammons, Four Sisters Farm

When you buy a head of lettuce, you may not think about the soil it grew in, but soil is an ever-present concern for farmers. Nancy Gammons of Four Sisters Farm sums up the significance of soil: “It’s the mother. Without good soil, there won’t be a good crop.” The quality of a farm’s soil makes a big difference in yield, water use, and even the taste of the harvest.

Healthy soil is rich in organic matter, which helps store water, air, and nutrients efficiently. It has the right amount of each nutrient needed for plant growth—not too little, and not too much. Healthy soil teems with life and supports beneficial organisms like earthworms, which aerate and fertilize the soil. A healthy soil produces plants that are more resistant to disease, and it can even yield better tasting, nutrient-rich food.

Caring for the soil is good for the land and the crop, but it can also have an even farther-reaching impact. Sustainable soil management can help mitigate global warming by removing carbon dioxide from the atmosphere and storing it in the soil as carbon.

As Many Ways as There Are Farmers

While each farm has its own unique soil, and every farmer has a different approach to soil care, perhaps the most important distinction is between conventional and organic soil management methods. Conventional farmers may use chemical fertilizers to deliver nutrients to their crops and synthetic pesticides to remove pathogens from the soil, substances that are prohibited on certified organic farms. These conventional practices can provide a quick fix, but they can also have long-lasting, damaging effects on the soil, such as reduced fertility, increased erosion, and elimination of beneficial soil organisms. Gammons explains, “If it’s going to poison a bug, it’s going to poison everything. Poison is poison.”

Whereas a conventional farmer may think about feeding the plant the nutrients it needs, organic and sustainable farmers think about feeding the soil. They support the overall health of the soil by adding compost, rotating crops, planting cover crops, and, in some cases, integrating animals into the farm.

Sustainable Farmers Grow Soil

The way farmers treat their soil reflects their farming philosophy and sense of environmental responsibility. Using organic practices and a whole lot of care and effort, Gammons and her family have grown the topsoil at Four Sisters Farm by a whopping 20 inches in the last 20 years. Joe Schirmer of Dirty Girl Produce has a similar goal. He says, “When I leave these fields, I want them to be in better shape than when I got them.”

Carl Rosato of Woodleaf Farm practices organic no-till farming. He avoids plowing or turning the soil, thus preventing erosion, preserving soil structure, and allowing fungal webs to develop. According to Rosato, fungal webs pull nutrients from long distances toward crops. Although no-till is not the typical way farming is done, it helps build soil, stores carbon, and requires less work over time. Some no-till farmers rely on herbicides for weed control, but Rosato and others are doing it the organic way. To control pests and diseases while keeping the soil as “alive” as possible, he creates habitat for beneficial insects and uses methods like crop rotation.

He says, “It is the way we need to figure out how to farm, but it is difficult,” especially on bigger farms. It requires a healthy soil to begin with and calls for specialized techniques, so it isn’t for everyone. Rosato, a veteran organic farmer, is up to the task. “It works great. I don’t have insect problems. I don’t use sprays. I’ve got a system that functions.” His yields may not be large, but he gets high-quality, flavorful produce.

Be a Soil Supporter

Farmers market customers can encourage environmentally friendly soil practices by asking farmers about their techniques and buying from those who take good care of the soil. The organic label means that no synthetic fertilizers or sewage sludge are used on the soil.

At the Ferry Plaza Farmers Market, eaters can reduce waste and return nutrients to the earth by composting their plates, biodegradable cutlery, and food scraps (learn more about our Waste Wise Initiative). Composting at home is easy with San Francisco’s curbside green waste collection through Recology, or if you want to keep that black gold for your garden plants, you can maintain a backyard compost pile or a worm bin. Together, farmers and eaters can build healthy soil, a healthy planet, and healthy communities.

CUESA – The Center for Urban Education about Sustainable Agriculture

CUESA thanks recent volunteer intern Grace Dover for contributing to this piece.

“People garden for the same reasons they go to the farmers market. You see your friends and neighbors. You talk about the weather and what’s in season. It not only allows people to have a broader connection to food, but it also builds community.”

Andrea Jadwin – Founding member, San Francisco Gardening Resource Organization

Mary Davis started feeling the squeeze of city life about a year ago. She had grown up gardening and spent a stint working on an organic farm while attending grad school in Missouri. Now an architect living in San Francisco’s Mission District, she longed to reconnect with her gardening roots, but her small apartment was lacking in the dirt department. “There was no garden, no outdoors,” she says. “I really wanted a place with some soil.”

She started looking around her neighborhood and fell in love with the historic Dearborn Community Garden. But when she inquired about getting a plot, she was told there was a 22-year waiting list.

She signed up nonetheless and continued her search, adding her name to the Potrero Hill Community Garden’s list as well, which had a comparatively modest seven-year wait. Since then, Davis has moved into a house with a shared backyard garden, but she still longs for a plot of her own.

Davis’s experience is not uncommon among would-be gardeners in San Francisco. Most of the city’s community gardens have waiting lists of two years or more, according to Public Harvest, a new report by San Francisco Urban Planning + Urban Research Association (SPUR). The most comprehensive report of its kind in recent years, it paints a sweeping portrait of the current urban agriculture landscape and presents a bold agenda to help San Francisco meet the demands of a burgeoning movement.

From commercial urban farms to rooftop plots and shared gardens, more than two dozen private and public urban agriculture projects have sprouted up in the City over the last four years as a result of the resurgence of interest in gardening. “We need to start looking to our public land to meet this demand,” said SPUR program manager Eli Zigas at a recent press event at Michelangelo Playground Community Garden in Nob Hill.

Since the dissolution of the San Francisco League of Urban Gardeners (SLUG) in 2004, there have been no centralized city-funded efforts to maintain or expand urban agriculture. Residents hoping to start new projects face many bureaucratic hurdles, since public land and urban agricultural activities are managed by multiple agencies, with little coordination.

While San Francisco Recreation & Parks oversees 35 community gardens on public land, those gardens are generally operated by volunteers, not staff. “The gardens are run by gardeners,” says Andrea Jadwin, a founding and active member of San Francisco Gardening Resource Organization (SFGRO), which offers support and training for community gardeners throughout the city. “That’s good and that’s bad because some gardens aren’t very well run.” Garden managers are often inadequately prepared to deal with issues like vandalism or garden members who neglect their plots while waiting lists grow. “If there were an agency helping people run the gardens better, it’d be easy to keep them going with minimal budget,” she adds.

According to SPUR’s findings, San Francisco’s urban agriculture program is middling compared to other large cities. With an annual operating budget of $800,000, or about $6,615 per site, San Francisco spends more than New York but far less than Seattle, which invests $11,940 per site.

Taking SPUR’s findings and recommendations to heart, District 3 Supervisor David Chiu has proposed new legislation that would create a strategic plan and a centralized program to streamline the management of urban agricultural projects, either through the city or a city-funded nonprofit.

The proposed ordinance includes a six-month audit of city-owned building rooftops that could be used for urban agriculture, the creation of a “one-stop shop” for individuals and organizations looking to engage in agricultural activities, and the establishment of garden resource centers that would provide residents with compost, seeds, and tools. By 2014, Chiu aims to develop at least 10 new urban agricultural projects on public land and reduce waiting lists for plot-based gardens to one year.

Zigas emphasizes the minimal cost of such a program for the returns it offers to the city of San Francisco, such as greening the urban landscape and reducing storm-water runoff, which in turn reduce public spending on landscaping and sewage treatment.

He also notes the benefits of urban agriculture for San Francisco residents and the food system at large, connecting city dwellers with the miracles and challenges of growing food. “I think many gardeners in San Francisco have a great appreciation for a fresh tomato because they know how hard it is to grow a tomato,” says Zigas. “There are a lot of people in the city who learn about food and how it’s produced through that process.”

Having been a member of White Crane Springs Community Garden in the Sunset for nine years, Jadwin has witnessed the benefits that such spaces offer by bringing neighbors together.

“People garden for the same reasons they go to the farmers market,” she observes. “You see your friends and neighbors. You talk about the weather and what’s in season. It not only allows people to have a broader connection to food, but it also builds community.”

CUESA

Yards with plants that mimic native vegetation offer birds “mini-refuges” and help to offset losses of biodiversity in cities, according to results of a study published today in the journalPLOS ONE.

A xeric, or desert, yard in Phoenix: This yard with native vegetation is a mini-refuge for birds. Credit: Susannah Lerman

“Native” yards support birds better than those with traditional grass lawns and non-native plantings.

Researchers conducted the study through the National Science Foundation’s (NSF) Central Arizona-Phoenix Long-Term Ecological Research (LTER) site, one of 26 such sites around the globe in ecosystems from coral reefs to deserts, from forests to grasslands.

“To a desert bird, what’s green is not necessarily good,” says Doug Levey, program director in NSF’s Division of Environmental Biology. “Arizona birds don’t view lush urban landscapes as desert oases. The foraging behavior of birds in greener yards suggests that there’s less food for them there than in yards with more natural vegetation.”

This mesic yard in Phoenix, with its non-native grass lawn, is less attractive to native birds. Credit: Susannah Lerman

The research, led by scientists Susannah Lerman and Paige Warren of the University of Massachusetts-Amherst, and Hilary Gan and Eyal Shochat of Arizona State University, looked at residential landscape types and native bird communities in Phoenix, Ariz.

It’s among the first to use quantitative measures and a systematic approach–including 24-hour video monitoring–in yards to assess and compare foraging behavior of common backyard birds.

The scientists found that desert-like, or xeric, yards had a more even bird community and superior habitat compared with moist, or mesic, grass lawns.

“We already know that bird communities differ, and that there are more desert birds found in a desert-type yard,” says Lerman.

“With this study, we’re starting to look at how different yards function–whether birds behave differently by yard type. We’re doing that using behavioral indicators, especially foraging, as a way of assessing birds’ perceptions of habitat quality between differing yard designs.”

Lerman and colleagues conducted the experiment in 20 residential yards at least 1.8 miles apart, making it unlikely that the same birds would visit more than one study yard.

Half the yards were desert-like, while the others had green lawns.

From February through April 2010, homeowners removed bird feeders before and during a 24-hour experimental data collection period.

The researchers set up feeding stations–seed trays–in each yard to simulate resource patches similar to ones where birds feed in the wild. Plastic trays contained 0.70 ounces of millet seed mixed into six pounds of sand. The trays were placed on low stools and left out for 24 hours.

The experimental set-up used to determine that native vegetation is more attractive to birds. Credit: Susannah Lerman

Later, Lerman removed the trays, sifted out and weighed uneaten seed to the nearest 0.01 gram. The amount of seed remaining quantified the giving-up densities (GUD), or the foraging decision and quitting point for the last bird visiting a seed tray.

Trays were videotaped for the entire 24-hour experiment.

The experiment assumed that an animal behaving optimally would stop foraging from a seed tray when its energy gains equal the “costs” of foraging, Lerman says.

Costs include predation risk, digestion and missed opportunities to find food elsewhere.

As time spent foraging at a seed tray increases, so do the costs associated with foraging. When a bird first arrives at the tray, seeds are easy to find, but that gets harder as the tray becomes depleted.

Each bird makes a decision about whether to spend time searching in the tray or to move on to a new patch in the yard.

The “giving up” point will be different for different species and in different environmental conditions. Birds visiting seed trays in yards with more natural food available will quit a tray sooner than birds in resource-poor yards.

Since the method only measures the foraging decisions for the last species visiting the seed tray, the researchers devised a mathematical model for estimating the foraging decisions for all visiting species.

Using the videotapes, they counted every peck by every bird for each tray to calculate the relationship between the number of pecks and grams of seed consumed for each seed tray. This was the GUD-peck ratio for the last species visiting the seed tray.

They then estimated the seed consumption–GUD ratio for all other species visiting the seed tray based on the number of pecks per tray when each species quit.

“We know how many pecks each species had and can put that number into the model and calculate the number of grams at that point,” Lerman says. This greatly enhances the GUD method by expanding the ability to assess foraging decisions for all species visiting trays.

A curve-billed thrasher, a Sonoran desert species, forages in a xeric yard in Phoenix. Credit: Eyal Shochat

In all, 14 species visited the trays, 11 of which visited both yard types. Abert’s towhee, curve-billed thrasher (a species unique to the Sonoran desert), house finch and house sparrow were the most widespread tray visitors.

Species that visited trays in both yard designs consumed more seed from trays placed in mesic yards, indicating lower habitat quality compared with xeric yards.

Similarly, foragers in the desert-like yards quit the seed trays earlier due to greater abundance of alternative food resources in those yards, spending more time foraging in the natural yards and less at the seed trays.

Lerman says that by videotaping the trays, counting pecks and measuring giving-up points by species, the research also advanced the GUD method, allowing researchers to disentangle some of the effects of bird community composition and density of competitors, and how these factors affect foraging decisions between two different landscape designs.

The results build upon evidence that native landscaping can help mitigate the effects of urbanization on common songbirds, she says.