為什么你后院的草坪不能幫助減少大氣中的二氧化碳

氣候解釋：為什么你后院的草坪不能幫助減少大氣中的二氧化碳

In New Zealand, your average carbon footprint will be around four tonnes of carbon, emitted per year (based on the carbon contained in16.9 tonnes of carbon dioxide equivalent annual per-capita emissions ). A 1,000-square-metre area of grass will take up around one tonne of carbon per year. So if you didn't fly much, lived in a well insulated home, cycled to work etc, you might bring your overall footprint down to around one tonne of carbon per year, the equivalent of what a backyard lawn may take up per year. So far so good.

在新西蘭，你的平均碳足跡大約是4噸碳，每年排放(基于16.9噸二氧化碳當(dāng)量的年人均排放量計(jì)算)。一千平方米的草地每年將會(huì)吸收一噸左右的碳。所以，如果你不經(jīng)常坐飛機(jī)，住在隔熱良好的房子里，騎車上班等等，你可能會(huì)把你的總碳足跡降低到每年1噸左右，相當(dāng)于后院草坪每年所占的碳量。到目前為止一切順利。

The big problem (causing tremendous confusion even among scientists) begins right here. In the above, we talk about fluxes, not pools. Using your bank account as an analogy, fluxes are transfers, pools are balances.

最大的問題(甚至在科學(xué)家中引起巨大的困惑)就從這里開始了。在上面，我們討論的是通量，而不是池。以你的銀行賬戶為例，通量是轉(zhuǎn)移，池是余額。

With your own carbon emissions, regardless whether they are one or four tonnes per year, you pay into the atmosphere's account every year. This means that there is more and more carbon in the atmosphere.

對(duì)于你自己的碳排放，無論它們是每年1噸還是4噸，你每年都要向大氣賬戶支付。這意味著大氣中有越來越多的碳。

That carbon comes from fossil fuels – an entirely different 'account'. Regardless of whether you have 1,000 or 100,000 square metres, this is what grass is doing in this analogy: it takes carbon from the atmosphere every year, but that carbon is going straight back to where it was taken from when you mow the lawn and the biomass is broken down and returned to the atmosphere. In other words, your carbon footprint is a flux that leads to a permanent change in a pool (the atmosphere). This is a bit like a weekly salary. You don't have to pay it back. What your lawn is doing however, is making payments that are returned a few weeks or months later (when you mow the lawn, a cow eats the grass, or when natural turnover takes place).

碳來自化石燃料——一個(gè)完全不同的“賬戶”。不管你有1000平方米還是100000平方米，這就是草做的類比：它每年從大氣中吸收碳，但是這些碳會(huì)直接回到你修剪草坪時(shí)所吸收的地方，生物量會(huì)被分解并返回到大氣中。換句話說，你的碳足跡是一個(gè)通量，它會(huì)導(dǎo)致一個(gè)池子(大氣)的永久變化。這有點(diǎn)像周薪。你不必還錢。然而，你的草坪所做的，是在幾周或幾個(gè)月后(當(dāng)你修剪草坪時(shí)，牛吃了草，或當(dāng)自然更替發(fā)生時(shí))償還款項(xiàng)。

The bottom line is that short-term fluxes (as large as they might be) don't matter if they are reciprocated by an equivalent but opposite flux. If you want, let's do the experiment. You pay $1,000 onto my account ever odd week, and I pay $1,000 onto yours every even week. None of us will care – as little as the atmosphere will worry about the carbon that your grass patch briefly locks away from it.

最重要的是，短期通量(盡管可能很大)不受等價(jià)但相反通量的影響。如果你愿意，我們來做這個(gè)實(shí)驗(yàn)。你每星期在我的賬戶上付1000美元，我每星期在你的賬戶上付1000美元。我們沒有人會(huì)在意——就像大氣不會(huì)擔(dān)心你的草坪上短暫鎖住的碳一樣。

So your grass won't lock away carbon dioxide from the atmosphere in the long run. Neither will any grassland in New Zealand.

所以從長(zhǎng)遠(yuǎn)來看，你的草不會(huì)把二氧化碳從大氣中鎖住。新西蘭任何草原都不會(huì)。

If you wait long enough, things can become a bit more complicated, namely if my payments back to you start to become a little less or a little more, causing dollars or carbon to accumulate on one account rather than the other. While this is the case in some ecosystems, such as agrowing forest , New Zealand grassland is unlikely one of them. So your backyard isn't helping, there is no way around reducing our greenhouse gas emissions.

如果你等的時(shí)間足夠長(zhǎng)，事情可能會(huì)變得更復(fù)雜，也就是說，如果我給你的還款開始變得少一點(diǎn)或多一點(diǎn)，導(dǎo)致美元或碳在一個(gè)賬戶而不是另一個(gè)賬戶上積累。盡管在一些生態(tài)系統(tǒng)中，如農(nóng)林，新西蘭草原不太可能是其中之一。所以你的后院沒用，沒有辦法減少溫室氣體排放。