大規(guī)模植樹造林可能會(huì)減緩氣候變化

大規(guī)模植樹造林可能會(huì)減緩氣候變化

Trees, among their many other superpowers, help absorb some of the excess carbon dioxide humans have been adding to Earth's atmosphere lately. That's a valuable service, considering we still release about 2.57 million pounds of CO2 every second, on average, and the heat-trapping gas can linger in the sky for centuries.

樹木和其他許多超級(jí)力量一起，幫助吸收人類最近向地球大氣中排放的過量二氧化碳。這是一項(xiàng)有價(jià)值的服務(wù)，因?yàn)槲覀兤骄棵肴栽卺尫偶s257萬磅的二氧化碳，而這種吸熱氣體可以在天空中停留數(shù)百年。

We know Earth needs more trees. And although we are doing far too little about climate change in general, we are planting trees — so many, in fact, that global tree cover has reportedly increased by about 7% in the last 35 years.

我們知道地球需要更多的樹木。盡管我們?cè)诳傮w上對(duì)氣候變化做得太少，但我們正在植樹造林——事實(shí)上，植樹造林如此之多，據(jù)報(bào)道，全球樹木覆蓋率在過去35年里增長了7%左右。

Morning fog hangs over a tropical forest at Kaeng Krachan National Park in Thailand. (Photo: Stephane Bidouze/Shutterstock)

Tropical forests are especially important for many reasons, and stopping this destruction should be a high priority for humanity. But given the huge scale of climate change, that still won't be nearly enough to avert disaster. On top of stopping deforestation, we'll need to add a lot more trees in a lot more places.

熱帶森林由于許多原因特別重要，制止這種破壞應(yīng)是人類的一項(xiàng)高度優(yōu)先事項(xiàng)。但考慮到氣候變化的巨大規(guī)模，這仍然不足以避免災(zāi)難。除了停止砍伐森林，我們還需要在更多的地方種植更多的樹木。

Dead trees stand in a recently deforested section of the Brazilian Amazon in 2017. (Photo: Mario Tama/Getty Images)

Two new studies take a closer look at this issue. One looks at the possibility of planting trees virtually everywhere they could grow, estimating the maximum possible scope of reforestation in response to climate change. In the other, researchers focused on reforestation opportunities in the tropics, singling out "restoration hotspots" where newly planted forests are most likely to succeed.

兩項(xiàng)新的研究對(duì)這個(gè)問題進(jìn)行了更深入的探討。其中一項(xiàng)研究著眼于在幾乎所有可能生長的地方植樹造林的可能性，并估計(jì)了為應(yīng)對(duì)氣候變化而重新造林的最大可能范圍。在另一項(xiàng)研究中，研究人員把重點(diǎn)放在了熱帶地區(qū)的再造林機(jī)會(huì)上，挑出了“恢復(fù)熱點(diǎn)”，在那里，新種植的森林最有可能獲得成功。

This map shows areas that could support new forests, excluding existing forests as well as urban and agricultural areas. (Map: Bastin et. al./Science)

Climate change is making life harder and harder for many trees, especially in the tropics, and thus threatening their ability to help us remove our excess CO2 from the atmosphere. "We estimate that if we cannot deviate from the current trajectory, the global potential canopy cover may shrink by 223 million hectares by 2050, with the vast majority of losses occurring in the tropics," they write. "Our results highlight the opportunity of climate change mitigation through global tree restoration but also the urgent need for action."

氣候變化使許多樹木的生存越來越困難，特別是在熱帶地區(qū)，因此威脅到它們幫助我們從大氣中去除多余二氧化碳的能力。他們寫道:“我們估計(jì)，如果我們不能偏離目前的軌道，到2050年，全球潛在的林冠覆蓋面積可能會(huì)減少2.23億公頃，其中絕大多數(shù)損失發(fā)生在熱帶地區(qū)。”“我們的研究結(jié)果強(qiáng)調(diào)了通過全球樹木恢復(fù)減緩氣候變化的機(jī)會(huì)，也強(qiáng)調(diào)了采取行動(dòng)的迫切需要。”

The sun sets over Bwindi Impenetrable Forest in Uganda. (Photo: Dietmar Rauscher/Shutterstock)

They found about 863 million hectares of restorable area for forests overall, an area roughly the size of Brazil. They also assigned a "restoration opportunity score" (ROS) to various places, and determined that about 12% of the restorable area — about 101 million hectares — meets their criteria as a "restoration hotspot." Forests in these hotspots can not only hold lots of carbon and biodiversity, but they're also more likely to thrive than in other areas.

他們發(fā)現(xiàn)了大約8.63億公頃的可恢復(fù)森林面積，大致相當(dāng)于巴西的面積。他們還為不同的地方分配了“恢復(fù)機(jī)會(huì)評(píng)分”(ROS)，并確定大約12%的可恢復(fù)面積(約1.01億公頃)符合他們的“恢復(fù)熱點(diǎn)”標(biāo)準(zhǔn)。這些熱點(diǎn)地區(qū)的森林不僅可以儲(chǔ)存大量的碳和生物多樣性，而且它們比其他地區(qū)更有可能茁壯成長。

The two studies used different approaches and reached different conclusions, as science writer Gabriel Popkin points out in Mongabay, but both are part of a key shift from tracking the loss of forests to mapping out their potential comeback. And while forest restoration isn't a silver bullet, this research does suggest it may be our best hope for buying ourselves more time, as an author of the Science study tells Vox.

正如科學(xué)作家加布里埃爾•波普金在《蒙加貝》中指出的那樣，這兩項(xiàng)研究使用了不同的方法，得出了不同的結(jié)論，但它們都是一個(gè)關(guān)鍵轉(zhuǎn)變的一部分，即從追蹤森林的消失，轉(zhuǎn)向規(guī)劃森林可能的恢復(fù)。盡管森林恢復(fù)并不是什么靈丹妙藥，但正如《科學(xué)》雜志的一名作者告訴Vox的那樣，這項(xiàng)研究確實(shí)表明，這可能是我們?yōu)樽约籂幦「鄷r(shí)間的最佳希望。

A rainforest stream flows through Masoala National Park in Madagascar. (Photo: Dennis van de Water/Shutterstock)

"The point is that [reforestation is] so much more vastly powerful than anyone ever expected," says Thomas Crowther, a researcher at the Swiss university ETH Zurich. "By far, it's the top climate change solution in terms of carbon storage potential."

瑞士蘇黎世聯(lián)邦理工學(xué)院的研究人員托馬斯•克勞瑟表示:“關(guān)鍵是，(重新造林)比任何人預(yù)想的都要強(qiáng)大得多。”“到目前為止，這是碳儲(chǔ)存潛力最大的氣候變化解決方案。”