大规模植树造林可能会减缓气候变化

大规模植树造林可能会减缓气候变化

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.

树木和其他许多超级力量一起，帮助吸收人类最近向地球大气中排放的过量二氧化碳。这是一项有价值的服务，因为我们平均每秒仍在释放约257万磅的二氧化碳，而这种吸热气体可以在天空中停留数百年。

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.

我们知道地球需要更多的树木。尽管我们在总体上对气候变化做得太少，但我们正在植树造林——事实上，植树造林如此之多，据报道，全球树木覆盖率在过去35年里增长了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.

热带森林由于许多原因特别重要，制止这种破坏应是人类的一项高度优先事项。但考虑到气候变化的巨大规模，这仍然不足以避免灾难。除了停止砍伐森林，我们还需要在更多的地方种植更多的树木。

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.

两项新的研究对这个问题进行了更深入的探讨。其中一项研究着眼于在几乎所有可能生长的地方植树造林的可能性，并估计了为应对气候变化而重新造林的最大可能范围。在另一项研究中，研究人员把重点放在了热带地区的再造林机会上，挑出了“恢复热点”，在那里，新种植的森林最有可能获得成功。

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."

气候变化使许多树木的生存越来越困难，特别是在热带地区，因此威胁到它们帮助我们从大气中去除多余二氧化碳的能力。他们写道:“我们估计，如果我们不能偏离目前的轨道，到2050年，全球潜在的林冠覆盖面积可能会减少2.23亿公顷，其中绝大多数损失发生在热带地区。”“我们的研究结果强调了通过全球树木恢复减缓气候变化的机会，也强调了采取行动的迫切需要。”

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.

他们发现了大约8.63亿公顷的可恢复森林面积，大致相当于巴西的面积。他们还为不同的地方分配了“恢复机会评分”(ROS)，并确定大约12%的可恢复面积(约1.01亿公顷)符合他们的“恢复热点”标准。这些热点地区的森林不仅可以储存大量的碳和生物多样性，而且它们比其他地区更有可能茁壮成长。

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.

正如科学作家加布里埃尔•波普金在《蒙加贝》中指出的那样，这两项研究使用了不同的方法，得出了不同的结论，但它们都是一个关键转变的一部分，即从追踪森林的消失，转向规划森林可能的恢复。尽管森林恢复并不是什么灵丹妙药，但正如《科学》杂志的一名作者告诉Vox的那样，这项研究确实表明，这可能是我们为自己争取更多时间的最佳希望。

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."

瑞士苏黎世联邦理工学院的研究人员托马斯•克劳瑟表示:“关键是，(重新造林)比任何人预想的都要强大得多。”“到目前为止，这是碳储存潜力最大的气候变化解决方案。”