隨著城市的發(fā)展，對城市樹木的需求也在增長

隨著城市的發(fā)展，對城市樹木的需求也在增長

It's easy to rattle off the necessary and wide-ranging tasks that trees perform in urban areas. They're unarguably invaluable.

我們很容易就能脫口而出樹木在城市地區(qū)所執(zhí)行的必要且廣泛的任務。它們毋庸置疑的無價的。

Trees are air-scrubbing, temperature-cooling, mood-improving, flood-mitigating machines. And as a new study published in Lancet Planetary Health points out, they can even save lives. Just look at Philadelphia, where researchers calculated that 403 premature deaths could be prevented in that city alone, simply by meeting the city's goal to improve its urban canopy by 30%.

樹木是空氣洗滌、降溫、改善情緒、緩解洪水的機器。發(fā)表在《柳葉刀行星健康》雜志上的一項新研究指出，它們甚至可以拯救生命?？纯促M城，研究人員計算出，僅在該市就可以避免403例過早死亡，只要達到該市提高30%城市冠層的目標即可。

Tallahassee is the most heavily forested urban area, and it's the capital of the state with largest number of urban trees. This gorgeous specimen is at Lake Jackson Mounds Archeological Site inside the city limits. (Photo: Benevolent Medley/Shutterstock.com)

Urban trees are obviously worth a lot. But how much?

城市樹木顯然價值不菲，但到底值多少錢呢?

According to a comprehensive study from U.S. Forest Service's Northern Research Station, the nation's urban canopies, which are home to an estimated 5.5 billion trees, provide roughly $18 billion in annual benefits to society through the removal of pollution from the air ($5.4 billion), carbon sequestration ($4.8 billion), reduced emissions ($2.7 billion) and improved energy efficiency in buildings ($5.4 billion).

根據美國林務局北方研究站的一項綜合研究，美國城市估計有55億棵樹，每年通過消除空氣污染(54億美元)、碳封存(48億美元)、減少排放(27億美元)和提高建筑能效(54億美元)為社會提供大約180億美元的效益。

Five states are particularly bankable when it comes to the economic perks associated with urban trees, per the Forest Service's findings. Florida leads the way with roughly $2 billion in annual savings while California, Pennsylvania, New York and Ohio follow in the ballpark of $1 billion of value per year. This doesn't mean, however, that these states necessarily have the most urban trees. Georgia, for example, has more urban trees (372 million) than California (343 million) while North Carolina (320 million) and Texas (309 million) both have more urban trees than Pennsylvania, New York and Ohio. Florida, which indeed has the most urban trees with an estimated 407 million leafy specimens, remains the most valuable.

根據林務局的調查結果，當提到與城市樹木相關的經濟福利時，五個州尤其值得投資。佛羅里達州以每年大約20億美元的儲蓄而居首位，而加利福尼亞州、賓夕法尼亞州、紐約州和俄亥俄州緊隨其后，每年大約有10億美元的儲蓄。然而，這并不意味著這些州一定擁有最多的城市樹木。例如，佐治亞州的城市樹木(3.72億棵)比加利福尼亞州(3.43億棵)多，而北卡羅來納州(3.2億棵)和得克薩斯州(3.09億棵)的城市樹木都比賓夕法尼亞州、紐約州和俄亥俄州多。佛羅里達擁有最多的城市樹木，估計有4.07億棵樹葉，仍然是最有價值的。

Trees have long played a prominent role in the landscape of Florida's capital city. (Photo: Boston Public Library [CC BY 2.0]/Flickr)

It's true. Florida has more urban trees than any other state. In fact, Tallahassee is among America's most tree-blessed cities with 55 percent total tree coverage — that's the highest percentage of any comparable city. (Interestingly, Tallahassee's arboreal claim to fame sprung from tragedy: In 1843, a catastrophic fire leveled large swaths of Florida's capital city. In addition to fire safety, one of the top imperatives when rebuilding Tallahassee was not only replacing the urban canopy that was lost but adding to it.)

這是真的。佛羅里達州的城市樹木比其他任何一個州都多。事實上，塔拉哈西是美國樹木覆蓋率最高的城市之一，樹木覆蓋率達55%，是所有可比城市中最高的。(有趣的是，塔拉哈西在樹下的成名源于一場悲劇:1843年，一場災難性的大火將佛羅里達州首府的大片地區(qū)夷為平地。除了消防安全之外，重建塔拉哈西的首要任務之一，不僅是替換掉失去的城市天篷，而且還要增加天篷。)

The Sunshine State's hugely beneficial — not to mention somewhat surprising — urban lushness aside, the Forest Service study stresses the importance of preserving, protecting and planting city-dwelling trees in states where the amount of urban land area is expected to grow exponentially.

除了這個陽光之州的巨大好處——更不要提它的一些令人驚訝之處——城市繁茂之外，林務局的研究還強調了在城市土地面積預計將呈指數(shù)增長的州，保護、保護和種植城市樹木的重要性。

Pennsylvania is home to some seriously high-value urban trees, like these on a Pittsburgh street. The Keystone State set to experience some of the highest urban land growth in the coming decades. (Photo: Nick Amoscato [CC BY 2.0]/Flickr)

States with the highest percentage of urban land overall consist of the nation's densest and most diminutive states, all of them located in the Mid-Atlantic and Northeast: Rhode Island (35 percent), Delaware (29 percent), Connecticut (28 percent), Massachusetts (23 percent) and New Jersey (23 percent). It's in these highly urbanized locales where the Forest Service notes that the "impact of current urban forests is likely greatest due to the relatively large proportion of urban land."

城市用地比例最高的州包括美國人口密度最大、面積最小的幾個州，它們都位于大西洋中部和東北部:羅德島(35%)、特拉華州(29%)、康涅狄格州(28%)、馬薩諸塞州(23%)和新澤西州(23%)。森林服務指出，正是在這些高度城市化的地區(qū)，“由于城市土地的比例相對較大，當前城市森林的影響可能最大。”

Previous studies conducted within a 10-year period (2000 to 2010) found that the amount of urban land jumped from 2.6 percent (57.9 million acres) to 3 percent (68 million acres). States that experienced the highest amount of urbanization during this time were largely limited to the South and Southeast.

此前在10年(2000年至2010年)內進行的研究發(fā)現(xiàn)，城市土地面積從2.6%(5790萬英畝)躍升至3%(6800萬英畝)。在這段時間內城市化程度最高的州主要集中在南部和東南部。

When it comes to urban tree value, typically woodsy states like Oregon (pictured here in Portland) aren't as high-ranking as you might think. (Photo: Jonathan Miske [CC BY-SA 2.0]/Flickr)

Not surprisingly, the states with the lowest value of urban trees are the ones where cities are small or far and few between, even though the states in question might be impressively forested: North Dakota, South Dakota, Wyoming, Montana and Idaho. For example, the value of North Dakota's urban trees when it comes to sequestering carbon, removing pollution, curbing emissions and reducing energy use was $7.3 million annually compared to the $1 billion-plus figures claimed by the top five states. Still, not too shabby for a sparsely populated state that's largest city, Fargo, boasts a population just north of 100,000.

毫不奇怪，城市樹木價值最低的州是那些城市規(guī)模小或距離遠，城市之間很少的州，盡管這些州可能是令人印象深刻的森林覆蓋州:北達科他州、南達科他州、懷俄明州、蒙大拿州和愛達荷州。例如，北達科他州的城市樹木在吸收碳、消除污染、控制排放和減少能源使用方面的價值是每年730萬美元，而排名前五的州每年的價值超過10億美元。盡管如此，對于人口稀少的州來說，最大的城市法戈(Fargo)不算太破舊，它的人口只有10萬多一點。

States with large and heavily urbanized metro areas that are often thought of as being "woodsy" like Washington, Oregon and Colorado have urban trees that provide annual benefits amounting to $328 million, $136 million and $40 million, respectively. (I would have figured the amounts to be higher for these states.)

像華盛頓州、俄勒岡州和科羅拉多州這樣大都市區(qū)面積大、城市化程度高、通常被認為是“森林”的州，其城市樹木每年提供的效益分別為3.28億美元、1.36億美元和4000萬美元。(我本以為這些州的數(shù)字會更高。)