Trees do 8 times better in the New York City Urban Heat Island

From the The Earth Institute at Columbia University

Do urban ‘heat islands’ hint at trees of future?

Barnard College student Acadia Roher counts leaves of experimental red oak seedlings at Lamont-Doherty Earth Observatory.

Common oaks get a boost in New York’s Central Park

City streets can be mean, but somewhere near Brooklyn, a tree grows far better than its country cousins, due to chronically elevated city heat levels, says a new study. The study, just published in the journal Tree Physiology, shows that common native red oak seedlings grow as much as eight times faster in New York’s Central Park than in more rural, cooler settings in the Hudson Valley and Catskill Mountains. Red oaks and their close relatives dominate areas ranging from northern Virginia to southern New England, so the study may have implications for changing climate and forest composition over a wide region.

The “urban heat island” is a well-known phenomenon that makes large cities hotter than surrounding countryside; it is the result of solar energy being absorbed by pavement, buildings and other infrastructure, then radiated back into the air. With a warming climate, it is generally viewed as a threat to public health that needs mitigating. On the flip side, “Some organisms may thrive on urban conditions,” said tree physiologist Kevin Griffin of Columbia University’s Lamont-Doherty Earth Observatory, who oversaw the study. Griffin said that the city’s hot summer nights, while a misery for humans, are a boon to trees, allowing them to perform more of the chemical reactions needed for photosynthesis when the sun comes back up.

With half the human population now living in cities, understanding how nature will interact with urban trees is important, the authors say. “Some things about the city are bad for trees. This shows there are at least certain attributes that are beneficial,” said lead author Stephanie Y. Searle, a Washington, D.C., environmental researcher who was a Columbia undergraduate when she started the research.

In spring 2007 and 2008, Searle and colleagues planted seedlings in northeastern Central Park, near 105th Street; in two forest plots in the suburban Hudson Valley; and near the city’s Ashokan Reservoir, in the Catskill foothills some 100 miles north of Manhattan. They cared for all the trees with fertilizer and weekly watering. Maximum daily temperatures around the city seedlings averaged more than 4 degrees F higher; minimum averages were more than 8 degrees higher. By August, the city seedlings had developed eight times more biomass than the country ones, mainly by putting out more leaves. The researchers largely ruled out other factors that might drive tree growth, in part by growing similar seedlings in the lab under identically varying temperatures, and showing much the same result. Due to air pollution, the city also has higher fallout of airborne nitrogen—a fertilizer—which could have helped the trees as well, said Searle, but temperature seemed to be the main factor.

Seedlings did eight times better in New York City's Central Park than at comparable suburban and rural sites.

Other experiments done in Japan and Arizona have shown that higher temperatures, especially at night, may promote growth of rice plants and hybrid poplar trees. A 2011 study by a Lamont-based group showed that conifers in far northern Alaska have grown faster in recent years in step with rising temperatures. Some Eastern Seaboard trees also seem to be seeing growth spurts in response to higher carbon-dioxide levels alone, according to a 2010 study by scientists at the Smithsonian Institution. However, heat can cut both ways; in lower latitudes, rising temperatures and shifting weather patterns appear to be pushing some species over the edge by causing ecological changes that stress them; massive die-offs are underway in the U.S. West and interior Alaska. There is already some evidence that with warming climate, New York area forest compositions are already changing, with northerly species dwindling and southerly ones that tolerate more heat coming in, said Griffin. Red oaks are probably not immune to increasing heat, so there is no guarantee that they would do well in the New York City of the future.

New York City has some 5.2 million trees and is in the midst of a campaign to plant more. “Cities are special places—they might be laboratories for what the world will look like in coming years,” said Gary Lovett, a forest ecologist at the Cary Institute of Ecosystem Studies in Millbrook, N.Y., some 90 miles north of Manhattan. With temperatures projected to rise, he said, “what kinds of trees are doing well there now might be related to what kinds might do well up here in a number of years.”

###

The study’s other authors are affiliated with the University of Canterbury in Christchurch, New Zealand; Black Rock Forest Consortium in Cornwall, N.Y.; and Weizmann Institute of Science in Rehovoth, Israel.

The paper, “Urban environment of New York City promotes growth in northern red oak seedlings,” is at: http://treephys.oxfordjournals.org/content/early/2012/04/05/treephys.tps027.full?sid=ca754aba-06b3-4ae7-bc0e-f3d2e2847b60, or available from the authors.

Author contacts:

Stephanie Y. Searle stephanie@theicct.org 202-534-1612

Kevin Griffin griff@ldeo.columbia.edu 845-365-8371

More information: Kevin Krajick, Senior Science Writer, The Earth Institute kkrajick@ei.columbia.edu 212-854-9729

The Earth Institute, Columbia University mobilizes the sciences, education and public policy to achieve a sustainable earth. www.earth.columbia.edu

Lamont-Doherty Earth Observatory seeks fundamental knowledge about the origin, evolution and future of the natural world. Its scientists study the planet from its deepest interior to the outer reaches of its atmosphere, on every continent and in every ocean, providing a rational basis for the difficult choices facing humanity. www.ldeo.columbia.edu

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tokyoboy

‘The “urban heat island” ….. is the result of solar energy being absorbed by pavement, buildings and other infrastructure, then radiated back into the air.’
I guess the intensive energy use in big cities is much more effective in raising temp.
For example, a normal-sized car is equivalent to a 30-50 kW heater by driving.

Anything in the study as to how high the CO2 concentration was in relation to the other sites? Are they only studying temp variations? What about nitrogen, ozone, CO2 and oxygen concentrations etc.?

markx

The system seems horribly self regulating! I trust word will not get out.
But, what a wonderful laboratory do these sites provide! Here we have day time maximums of 4 F hotter, and night-time minimums of 8 F hotter than surrounding areas. Doing these experiments is just what is needed to see what a warmer world would bring! (be that hypothesis correct, or not.)

pat

Yes, heat helps. So does the elevated CO2.

dp

Regarding park trees within the city I would not misunderestimate the power of irrigation, frequent fertilization, and the nurturing hand of the local arborists.
The trees in my suburban Seattle back yard, far from UHI effects, are doing far better than their country cousins for the reasons I’ve mentioned. Never attribute to UHI that which can be lain at the foot of nurturing care and preventative maintenance. The primal forest is a harsh world for all living things.
I’m skeptical.

AndyG55 (from down-under)

The medieval Warm Period and the Roman Warm Period were both known to be very fruitful time for plant life.. Why should the smaller warm period we are currently experiencing be any different.
So long as they have water, nutrients and CO2, a couple of degrees extra will help most plants along quite nicely !.

newtlove

“The “urban heat island” is a well-known phenomenon that makes large cities hotter than surrounding countryside…”
But that is hotly denied by the CAGW alarmists. Since urban heat islands are a myth, these trees and shrubs are not growing better than their cousins in nearby rural areas. This is impossible, and Manny and Trenbirther can prove it by running your data through their Hockey Stick model. /sarc

kbray in california

Farmers put black plastic to warm the soil and plastic tents to accelerate plant growth early in the season. Was the warmer city helping plant growth such a big surprise?
Where is the common sense here.?
Let’s put 2 miles of ice back on top of Central Park…
Gee, I wonder what that would do to the trees…
I know, they’d have to fund another study for that…

crosspatch

Could it also be the care such as fertilizing, watering, etc. that goes on in the park and not just the temperature? My guess a tree growing in a forest in the wild is living most of the time right on the edge of existence. It is facing competition from surrounding trees where it is a “dog eat dog” world and everyone is straining to out-compete their neighbors. I would guess a tree in a park may not suffer those hardships. It might find its soild amended from time to time with compost. Neighboring brush and other trees cut back, lawns around it watered.
Sounds too simplistic of an explanation to me. I think there is more difference between living in a park and living in a forest than just the temperature.

Patrick

“City streets can be mean, but somewhere near Brooklyn, a tree grows far better than its country cousins, due to chronically elevated city heat levels, says a new study.”
Last time I was in New York and Long Island the heat was so elevated that 2 feet of snow fell on the first night.

Paul Westhaver

If you have never been to Columbia University, you may not enjoy the amusing appropriateness of this study to that institution.
It seems a surprise to me that this is true. Not when you think it through logically. When you think it through, it makes a lot of sense. I guess I was guilty of thinking urban=antilife. I don’t know when I assumed that posture?
Well, thanks to the article I sense my mind has changed in THAT assumption now. Thank-you to Watts, Griffen and Searle. I feel dislodged from yet another green axiom.

John B

I believe it is a common misconception that the urban heat island effect is caused by the heating of pavement and buildings. The surfaces of cities do heat up but no more than a desert would. The countryside is cooler than a desert because it contains plants that transpire, The energy that might be used to increase temperature goes to evaporate water. A city is somewhere between a desert and the countryside. It is the reduction of cooling due to evapotranspiration that should be looked at when considering the large number of long term temperature records from airport sites.

Graeme No.3

4 degrees F during the day, and 8 at night. That’s 2.2 ºC and 4.4 ºC respectively.
Now lets see; AGW “science” says that
1. The first sign of global warming is the increase in night time temperatures will be more than the rise in daytime.
2. The UHI effect is only 0.05 ºC, therefore cannot be an explanation for recent temperature rises.
3. The recent (1975-1995) temperature rise of 0.55 ºC (refer to UEA and James Hansen for latest estimates) can only be explained by global warming.
I had better not join these up, or people will think that I am a denier.

Brian H

dp says:
April 24, 2012 at 10:49 pm
Regarding park trees within the city I would not misunderestimate the power of irrigation, frequent fertilization, and the nurturing hand of the local arborists.
The trees in my suburban Seattle back yard, far from UHI effects, are doing far better than their country cousins for the reasons I’ve mentioned. Never attribute to UHI that which can be lain at the foot of nurturing care and preventative maintenance. The primal forest is a harsh world for all living things.
I’m skeptical.

Not relevant.
The study just used seedlings in controlled patches that the researchers watered and fertilized identically themselves. They also replicated the study in lab enclosures.

DavidB

I’ve noticed that plane trees in central London parks and squares have put out their leaves at least 2 weeks before those in the suburbs. I don’t think this is due to any difference in management, which is minimal anyway.

Sera

“; massive die-offs are underway in the U.S. West and interior Alaska.”
What massive die-offs?

Sera

Wait a second- the “massive die-offs” were caused by drought and pests. Not one word of temperatures or CO2.
http://www.todaysgardencenter.com/article/25335/massive-tree-die-offs-making-the-news

ntesdorf

Graeme No.3 says:
April 24, 2012 at 11:32 pm
” None so blind as those who will not see”.

ferdberple

Graeme No.3 says:
April 24, 2012 at 11:32 pm
4 degrees F during the day, and 8 at night. That’s 2.2 ºC and 4.4 ºC respectively.
Now lets see; AGW “science” says that:
The IPCC says that all warming is BAD. A warming of 2C will result in catastrophic global warming and exterminate life as we know it. Warming is especially bad because mostly it will take place in cold places, which is a threat to nature because the earth would then be able to support even more people and there are too many people already and people are not natural. Nature is everything except people.

Scottish Sceptic

dp says: April 24, 2012 at 10:49 pm
Regarding park trees within the city I would not misunderestimate the power of irrigation, frequent fertilization, and the nurturing hand of the local arborists.
Well said!
As the climategate emails said about one tree that “proved” global warming … “did some reindeer crap on it?”

Robertvdl

Near big highways plants also grow better. Besides heat a plant also needs food (CO2). Stop man made CO2 production in the city (cars etc)1 year and let’s see if they still grow that much better.

Scottish Sceptic

kbray in california says: April 24, 2012 at 11:10 pm
Let’s put 2 miles of ice back on top of Central Park…
Gee, I wonder what that would do to the trees…
I know, they’d have to fund another study for that…

That really don’t think that is an appropriate comment when we get research which appears to have accurately reported its findings and contributed to the understanding of the Urban heat island and climatic effects on plants.
It is not because we’ve had too much research that we are in the mess we are now. It is because we have had too little good quality research and e.g. that the climategate scamsters, were so cavaliar with their equipment an readings that the world is heading toward a $trillion exenditure. We couldn’t even be bothered to spend 0.1% of that on a network of sensors capable of answering the question “is the climate changing”!
If we had just spent $10billion on good instrumentation first on the breath and depth of science & good climatic measuring instrumentation and sites instead of penny pinching, we would not have wasted $trillion on a solution to a problem that didn’t exist.
It’s not because of too much good science like this, its because there are idiots who would not spend the money on decent science that we got the 5th rate dolts and charlatans who … who are so stupid, they do nothing to get money for good science …. instead they spend all their effort attempting to destroy the economy that funds them and suck the public purse to give to wind & carbon trading scamsters.

Cassio

“Due to air pollution, the city also has higher fallout of airborne nitrogen—a fertilizer—which could have helped the trees as well, said Searle, but temperature seemed to be the main factor.”
What value is there in a study which is so shamefully vague ?

Ashby Manson

Southern California is proof that almost anything will grow in a hot environment if you give it enough water. The most interesting thing about this study is the support and quantification it provides for the existence of an urban heat island effect.

Looking at the city planners of the late 1600’s to the 1800’s; they deliberately included avenues and parks in order to temper UHI as well as to provide the city with “lungs” and people in the city with shade from the sun. City trees have long been observed to grow better than those of the countryside; and it wasn’t only because of the higher availability of manure. vis:comment image
Architects of large buildings designed slightly-curved wallls so that they would heat differentially; and not the whole face at once, intending to promote convection from hot to cold along the same surface.

8 times …
The scale of this type is very misleading. Unfortunately some of this material is written with a dream vacation. Not very scientific. Nobody does it take for such a case. Green space within urban areas is a luxury. With this arrangement is best recommended to farmers to come to the cities and 8 times more to produce.

Jimbo

Not only are they doing better in the heat they are also doing it under all that extra carbon dioxide dome. Sounds like a large scale greenhouse to me.
http://wattsupwiththat.com/2010/03/16/stanford-urban-co2-domes-mean-more-death/
Domes of death but what about the poor office workers? 😉

If indoor carbon dioxide levels are more than 1,000 ppm, there is probably inadequate ventilation; and complaints such as headaches, fatigue, and eye and throat irritation may be prevalent.
Carbon dioxide itself is not responsible for the complaints; however, a high level of carbon dioxide may indicate that other contaminants in the building also may be present at elevated levels and could be responsible for occupant complaints…………………………………..
Therefore, 1,000 ppm should be used as a guideline for improving ventilation. If a building exceeds this guideline, it should NOT be interpreted as a hazardous or life-threatening situation. An elevated carbon dioxide level is only an indication of an inadequate amount of outside air being brought into a building.

federico

…and don’t forget possibly higher CO2 (nutrient) concentrations in cities as additional growth accelerator.

Philip Bradley

There will be far less competition for CO2 in a city versus a forest, and I’d say this could be at least as important as temperature.
I recall a recent study, reported here at WUWT, that strongly indicated trees grow taller to access more CO2 rather than to access more sunlight as commonly believed.
Do trees grow more leaves if more CO2 is available?

Dave in Delaware

A lot of people walk their dogs in Central Park …. lol … just sayin’

prjindigo

The growth pattern is consistent with increased CO2 availability and fertilization alone… it has very little to do with heat.

polistra

As usual, the saddest part of this idiocy is the total neglect of real pollution. Heavy metal pollution unquestionably kills plants; that’s why trees used to have trouble in cities. Now that autos no longer put out tons of lead, trees have returned to happily enjoying the warmth and CO2 of cities.
The more we switch to wind power (= coal power) to ‘solve’ the ‘warming crisis’, the more we bring back old-fashioned pollution that truly kills plants and animals.

Warmintim

I was astonished in London at the weekend to see Ceonothus bushes (lovely deep blue flower clusters) in full bloom. Back home in the country mine are weeks away from this. Urban heating is real, and should not be dismissed by supposedly unbiased studies that set out to prove that UHI is not significant.

John

Regarding the effects of pollution on tree growth, such as nitrogen oxide emissions from vehicles, which are high in cities: the effects of another pollutant, ozone, might also be important, because ozone harms plant growth (not in a major way, but in a measurable way).
A possible added beneficial effect for trees in big cities vs. in rural areas or suburban areas 75 or more miles downwind is that ozone levels are low in the center of large cities, but higher outside of the cities. The reason is that oxides of nitrogen, high in cities because of so many cars, actually scavenge ozone by reacting with it. Downwind, atmospheric chemistry with oxides of nitrogen causes ozone levels to increase.
A study was done a few years ago comparing tree grown in NYC with growth in downwind Connecticut, and suggested that the lower growth in Connecticut reflected the higher ozone levels.
There probably isn’t one answer here. Nitrogen oxide levels, and perhaps CO2 levels (marginally) are higher in the city, ozone levels lower. They might all work together.

Latitude

Cutting edge science: “Trees grow faster with a longer growing season”

Hell_Is_Like_Newark

CO2 has to be a factor as well. When evaluating building for demand control ventilation, urban areas like NYC can be tricky because the natural background CO2 levels are typically in the 600 to 700 ppm range. The max indoor CO2 levels are normally kept at 700 ppm to 1000 ppm.

Didn’t notice mention of control for higher CO2 levels.

mikerossander

To anyone who has studied the concept of Growing Degree Days, this is utterly unsurprising. An average six degree-day/day boost is the equivalent of an extra month or more to the growing season.
The “eight-times” growth rate is suspicious but that could be an artifact of their data collection method or timing.

Alan Watt

Seems only fair: UHI affects trees. What is also true is trees affect (moderate) UHI. Before WWII in many US cities once you got away from downtown the streets and avenues were shaded by lines of elm trees, which were particularly well adapted to the urban environment of the time. The branches from opposite sides of the street would form an arch shading much of the pavement. You can see this in many photographs of pre-war city neighborhoods; New Haven, CT was known as “the Elm City”. In the 1940’s Dutch Elm disease took hold and by the late 1960’s had wiped out virtually the entire elm population in US cities. That plus the post-war automobile boom resulted in more and wider streets, all completely exposed to the sun.
I have wondered how much of the warming in the 2nd half of the 20th century attributed to CO2 is really due to Dutch Elm disease and its effect on virtually all Northern and Midwestern US Cities in a fairly short period of time. It had the same effect through much of Europe a few decades later. I don’t know if elm trees were as significant a factor in urban shade in Europe as they were in the US. See here.
I remember S. Hyde Park Blvd in Chicago (near the Museum of Science & Industry) in 1972; it was completely denuded of trees, as were most all of the streets in the neighborhood. But new trees including resistant strains of elm have come back and if you look at the streets there today they are well populated with trees and branches again form an arch shading much of the pavement.
I hope this HTML will work, otherwise go to Google Maps and look for the intersection of South Hyde Park Blvd & E 55th Street in Chicago, IL. Go to street view looking North on S. Hyde Park Blvd and move North. These pictures are from the winter, so there are no leaves, but you can clearly see the canopy of branches and appreciate the amount of shade they would provide. This street was completely bare 40 years ago.
Hyde Park, Chicago

RockyRoad

Again, (even though not mentioned or monitored), CO2 is king of the forest. (Ok, it has to share rent with temperature, sunlight, water, nutrients…)

MarkW

How much of that extra growth is from the higher CO2 levels that can usually be found in big cities?

MarkW

Speaking of growing season. If I remember my basic biology correctly, trees use the amount of light received every day to determine when to drop their leaves, and the temperature of the roots to determine when to start budding.
In addition to UHI causing plants to bud earlier in the year, the city lights might encourage them to keep the leaves on until later in the year. (With UHI protecting those late season leaves from early frost.)

John

Did some research, found a published paper which says that central city CO2 levels in Phoenix are around 30% higher in the central city than in the surrounding countryside — the authors call their finding a “CO2 dome” over Phoenix:
http://www.atmos.berkeley.edu/~inez/MSRI-NCAR_CarbonDA/papers/barnet_refs/01_idso_domes.pdf
These are based on actual measurements, transects.
I had no idea that CO2 would be THAT enhanced at ground level in a central city.
So now we have several reasons for trees growing better in Central Park than in surrounding countryside:
1. Higher CO2
2. Heat island effect
3. Higher nitrogen compounds
4. Lower ozone levels
Which are the most important?

Juice

So you’re saying that trees are a good temperature proxy?

“it is the result of solar energy being absorbed by pavement, buildings and other infrastructure, then radiated back into the air.”
Thats the tradition “Mosher” UHI.
But in fact, satellite measured UHI is stronger in the daytime because of things like vast quantities of hot moist air coming out of A/C units.
http://hockeyschtick.blogspot.ca/2012/04/new-paper-finds-urban-heat-island.html
http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-11-00509.1
“Furthermore, the skin-level UHI is stronger during the day and summer than during nighttime and winter, respectively. “

Gail Combs

J. Philip Peterson says:
April 24, 2012 at 10:36 pm
Anything in the study as to how high the CO2 concentration was in relation to the other sites? Are they only studying temp variations? What about nitrogen, ozone, CO2 and oxygen concentrations etc.?
____________________________
You beat me to it. The limiting factor in growth esp. for C3 plants (Trees) is CO2.
Growth Response to CO2 (Forests): http://www.co2science.org/subject/f/forests.php
Summary: http://www.co2science.org/subject/f/summaries/forests.php
Effects of Temperature on Forests: http://www.co2science.org/subject/f/foresttemp.php

kbray in california

Scottish Sceptic says:
April 25, 2012 at 1:36 am
My point is that warmer being good for growth is already acknowledged and is also intuitively obvious. Farmers already use this principle.
The effect of 2 miles of ice on top of trees is also intuitively obvious.
It’s not a bad study, it just confirms the obvious.

Bill Wood

How does energy focusing relate to the UHI effect? In addition to “The “urban heat island” is a well-known phenomenon that makes large cities hotter than surrounding countryside; it is the result of solar energy being absorbed by pavement, buildings and other infrastructure, then radiated back into the air” we import the energy of the flow of the Niagra, petrochemicals from aroud the world, fission energy from nearby nuclear plants, and huge amounts of biomass which is converted to heat by 98.6F degree heat generators. This is all focused in a few square miles. The heat generated inside the buildings by people imported daily from New Jersey and Connecticut is transferred to the outside environment by a variety of expensive and power using machinery. I wonder how much this contributes in addition to the paving, etc.
If someone estimates this effect, please remember to include the population of Columbia U..

Jimbo

And for those who are convinced that Co2 and warmth are bad for plants take a peek.

“There is no evidence for enhanced aridity in the northern Neotropics. The tropical rainforest was able to persist under elevated temperatures and high levels of atmospheric carbon dioxide, in contrast to speculations that tropical ecosystems were severely compromised by heat stress. ”
http://dx.doi.org/10.1126/science.1193833

Co2 is cooking the streets.

“2005: Global levels of CO2 have reached 380 ppm compared with preindustrial levels of 280 ppm. Studies have found concentrations ranging up to 600 ppm in cities such as Phoenix, New York City, and Baltimore. Paris sometimes reached as high as 950 ppm (Widory and Javoy, 2003); Rome averaged 505 ppm on weekdays (Gratani and Varone, 2005).”
http://colli239.fts.educ.msu.edu/2005/05/17/city-levels-2005/
http://ff.org/centers/csspp/library/co2weekly/20061117a/20061117a_04.html

Parisians must be absolute gluttons. 😉

Food fight: CO2 makes us fatter
http://wattsupwiththat.com/2012/03/13/food-fight-co2-makes-us-fatter/

The overselling of AGW is an absolute scandal. Warmists just won’t listen to reason and evidence.

Resourceguy

Sush, thou shalt not speak of CO2 in this context until the ministry of truth and enviro justice says so (or comes up with a story line).