隨著城市的發(fā)展，對(duì)城市樹(shù)木的需求也在增長(zhǎng)

隨著城市的發(fā)展，對(duì)城市樹(shù)木的需求也在增長(zhǎng)

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(shù)木在城市地區(qū)所執(zhí)行的必要且廣泛的任務(wù)。它們毋庸置疑的無(wú)價(jià)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(shù)木是空氣洗滌、降溫、改善情緒、緩解洪水的機(jī)器。發(fā)表在《柳葉刀行星健康》雜志上的一項(xiàng)新研究指出，它們甚至可以拯救生命。看看費(fèi)城，研究人員計(jì)算出，僅在該市就可以避免403例過(guò)早死亡，只要達(dá)到該市提高30%城市冠層的目標(biāo)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(shù)木顯然價(jià)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(jù)美國(guó)林務(wù)局北方研究站的一項(xiàng)綜合研究，美國(guó)城市估計(jì)有55億棵樹(shù)，每年通過(guò)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(huì)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(jù)林務(wù)局的調(diào)查結(jié)果，當(dāng)提到與城市樹(shù)木相關(guān)的經(jīng)濟(jì)福利時(shí)，五個(gè)州尤其值得投資。佛羅里達(dá)州以每年大約20億美元的儲(chǔ)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(chǔ)蓄。然而，這并不意味著這些州一定擁有最多的城市樹(shù)木。例如，佐治亞州的城市樹(shù)木(3.72億棵)比加利福尼亞州(3.43億棵)多，而北卡羅來(lái)納州(3.2億棵)和得克薩斯州(3.09億棵)的城市樹(shù)木都比賓夕法尼亞州、紐約州和俄亥俄州多。佛羅里達(dá)擁有最多的城市樹(shù)木，估計(jì)有4.07億棵樹(shù)葉，仍然是最有價(jià)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(dá)州的城市樹(shù)木比其他任何一個(gè)州都多。事實(shí)上，塔拉哈西是美國(guó)樹(shù)木覆蓋率最高的城市之一，樹(shù)木覆蓋率達(dá)55%，是所有可比城市中最高的。(有趣的是，塔拉哈西在樹(shù)下的成名源于一場(chǎng)悲劇:1843年，一場(chǎng)災(zāi)難性的大火將佛羅里達(dá)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(wù)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(gè)陽(yáng)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(wù)局的研究還強(qiáng)調(diào)了在城市土地面積預(yù)計(jì)將呈指數(shù)增長(zhǎng)的州，保護(hù)、保護(hù)和種植城市樹(shù)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(guó)人口密度最大、面積最小的幾個(gè)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(wù)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(duì)較大，當(dāng)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(nèi)進(jìn)行的研究發(fā)現(xiàn)，城市土地面積從2.6%(5790萬(wàn)英畝)躍升至3%(6800萬(wàn)英畝)。在這段時(shí)間內(nèi)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(shù)木價(jià)值最低的州是那些城市規(guī)模小或距離遠(yuǎn)，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(dá)科他州、南達(dá)科他州、懷俄明州、蒙大拿州和愛(ài)達(dá)荷州。例如，北達(dá)科他州的城市樹(shù)木在吸收碳、消除污染、控制排放和減少能源使用方面的價(jià)值是每年730萬(wàn)美元，而排名前五的州每年的價(jià)值超過(guò)10億美元。盡管如此，對(duì)于人口稀少的州來(lái)說(shuō)，最大的城市法戈(Fargo)不算太破舊，它的人口只有10萬(wàn)多一點(diǎn)。

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(rèn)為是“森林”的州，其城市樹(shù)木每年提供的效益分別為3.28億美元、1.36億美元和4000萬(wàn)美元。(我本以為這些州的數(shù)字會(huì)更高。)