Does planting trees actually cool the planet? - Carolyn Beans

譯者: 麗玲 辛 審譯者: Yi-Ping Cho (Marssi)

In the fight to curb climate change,

在遏制氣候變遷的努力中，

there are few solutions more discussed than planting lots and lots of trees.

最受討論的解決方案 莫過於種植大量樹木了。

It sounds simple enough— trees absorb CO2 from the atmosphere to grow,

這聽起來很簡單——樹木從大氣中 吸收二氧化碳來生長，

so planting more of them should help eliminate greenhouse gases.

因此種植更多的樹木 應該有助於消除溫室氣體。

The trouble is, tree planting efforts don't always work as planned.

問題是，植樹行動 並不總是如預期產生效果。

For example, between 1974 and 2012,

例如，1974 年至 2012 年間，

the Chilean government helped fund the planting

智利政府資助

of over a million hectares of new trees.

種植了超過一百萬公頃的新樹木。

Yet a recent analysis suggests this multi-million dollar effort

然而最近的一項分析表明， 這項耗資數百萬美元的努力

resulted in no major carbon storage gains.

並沒有帶來重大的碳儲存效益。

What went wrong?

出了什麼問題呢？

Chile focused on afforestation:

智利主要著眼於造林：

the planting of trees in places long devoid of— or never home to— any forest,

在長期沒有森林 或從未有森林的地方植樹造林，

as opposed to reforestation,

而不是林地復育，

the practice of restoring recently degraded forests.

也就是復原最近退化的森林。

Many governments and international organizations champion afforestation

許多政府和國際組織都倡導植樹造林，

in their efforts to meet lofty tree planting goals

以實現崇高植樹目標， 這需要大量土地。

that require massive amounts of land.

The Bonn Challenge, launched in 2011 by the German government

「波昂挑戰」由德國政府

and the International Union for Conservation of Nature,

和國際自然保護聯盟 於 2011 年發起，

aims to restore 350 million hectares of degraded land

旨在 2030 年前復育 全球 3.5 億公頃的退化土地，

across the globe by 2030,

in part through afforestation.

部分透過植樹造林。

Many companies have also seized on tree planting to offset emissions

許多公司也紛紛抓住 種樹的機會來抵銷排放，

and, in some cases, negative PR from their contributions to the climate emergency.

有的利用對氣候緊急情況的貢獻 來挽救它們的負面公關形象。

A 2021 Oxfam analysis found that the area needed to match the tree planting goals

樂施會 2021 年的一項分析發現，

要滿足四大石油和天然氣生產商 設定的植樹目標，

set by four of the largest oil and gas producers

would require land twice the size of the UK.

所需的土地面積將是英國面積的兩倍。

Here's where things get complicated.

這就是事情變得複雜的地方。

In order to be a long-term carbon sink,

要成為長期的碳匯，

trees need to grow to maturity and stay put.

樹木必須長到成樹並留在原地。

Most of Chile's afforestation funding went to the commercial forestry industry,

智利的大部分造林資金 都流向了商業林業，

which drastically expanded plantations of mostly non-native trees—

該產業主要大幅擴張 非原生樹木的林場——

in some cases even by plowing into native forests.

在某些情況下，甚至破壞了 當地的原生森林。

According to one study, on average,

根據一項研究，平均而言，

natural forests are 40 times better at carbon storage than plantations.

天然林的碳儲存能力 比人工林高 40 倍。

A mature tree can absorb up to 22 kilograms of carbon dioxide each year.

一棵成熟的樹木每年可以吸收 高達 22 公斤的二氧化碳。

But plantation trees are harvested.

但是林場的樹木會被砍伐。

Further, pine and eucalyptus— two commonly grown plantation trees—

此外，松樹和桉樹—— 兩種常見的人工林樹木——

are highly flammable,

非常易燃，

so gains in carbon storage can quickly go up in smoke.

因此碳儲存的效益可能很快化為烏有。

And not all land should be forested.

而且並非所有的土地都應該植樹造林。

In 2019, researchers estimated that, of the 100 million hectares of land

2019 年，研究人員估計，

在非洲的一項植樹倡議中， 預定的一億公頃土地

targeted for a tree planting initiative in Africa,

most is savanna.

大部分是稀樹草原。

Dropping trees into Africa’s savannas threatens wildlife

在非洲的稀樹草原上種樹

that thrive in sunlight and open spaces.

會威脅到在陽光和開放空間中 繁衍生息的野生動物。

And wildfires, not to mention a passing elephant,

野火，更不用說路過的大象，

can quickly stomp out years of tree growth.

可能迅速摧毀多年的樹木生長。

Meanwhile, a savanna’s natural vegetation tucks most of its carbon

同時，稀樹草原的天然植被

將大部分碳安全地儲存在地下，

safely away below ground,

where it’s protected from fire and hungry herbivores.

免受火災和飢餓的草食動物侵害。

Planting trees can also have unintended consequences

在像旱地或雪地等 會自然反射陽光的地方種樹

in places that naturally reflect sunlight

like drylands or snowy terrain.

也可能產生意想不到的後果。

Trees in these regions could absorb more of the Sun’s rays,

這些地區的樹木會吸收更多的太陽光線，

contributing to a warmer planet.

反而讓地球變得更溫暖。

It’s not that we shouldn’t plant more trees.

這並不是說我們不該種更多的樹。

But for the best chance of success,

但為了取得最大程度的進展，

programs should consider which species to plant, which lands to forest,

植樹計畫應考慮種植哪些樹種、 應該在哪些土地造林，

and how to protect the land long-term.

以及如何長期保護土地。

Today, Chile is prioritizing planting native trees

如今，智利優先考慮種植原生樹種，

rather than timber plantations.

而非木材林場。

Some researchers argue that a more efficient way to re-green the planet

一些研究人員認為， 重新綠化地球更有效的方法

is to protect forests and let nature do the work.

是保護森林並讓大自然發揮作用。

On recently deforested land,

在最近砍伐的土地上，

seeds wait in soil and new sprouts grow from old stumps.

種子在土壤中等待， 新芽從舊樹樁上長出來。

As time passes, birds and winds deliver seeds from forests nearby.

隨著時間的推移，鳥類和風 從附近的森林帶來種子。

Others support programs that practice assisted natural regeneration—

其他研究人員則支持進行 輔助自然再生的計畫——

helping nature along by removing grasses that compete with saplings,

透過清除與樹苗競爭的草、防止放牧、

preventing grazing, and even planting trees in small patches.

甚至在小塊土地上種植樹木， 來幫助大自然。

So when is it bad to plant trees?

那麼，什麼時候不適合植樹呢？

When programs put the wrong trees in the wrong places.

當計畫在錯誤的地方 種植錯誤的樹木時。

It’s bad when it’s mistakenly used as a catch-all solution,

很糟的是當植樹被誤用為 包羅萬象的解決方案，

rather than addressing more complex issues like carbon emissions

而沒有去解決碳排放 和定期砍伐等更複雜的問題。

and active deforestation.

It’s also bad to plant trees when it allows companies and governments

植樹也會是錯誤的，如果植樹行動 讓公司和政府得以漂綠，

to practice greenwashing,

throwing money at initiatives that have no real chance of achieving

將錢投入到某些根本無法 實現碳抵銷的倡議。

the carbon offsets they promise.

The best investments in a greener future are to cut carbon emissions,

讓未來更翠綠的最佳投資 是減少碳排放，

while protecting these forests from being destroyed in the first place.

同時首要保護這些森林免受破壞。