为什么你后院的草坪不能帮助减少大气中的二氧化碳

气候解释：为什么你后院的草坪不能帮助减少大气中的二氧化碳

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.

在新西兰，你的平均碳足迹大约是4吨碳，每年排放(基于16.9吨二氧化碳当量的年人均排放量计算)。一千平方米的草地每年将会吸收一吨左右的碳。所以，如果你不经常坐飞机，住在隔热良好的房子里，骑车上班等等，你可能会把你的总碳足迹降低到每年1吨左右，相当于后院草坪每年所占的碳量。到目前为止一切顺利。

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.

最大的问题(甚至在科学家中引起巨大的困惑)就从这里开始了。在上面，我们讨论的是通量，而不是池。以你的银行账户为例，通量是转移，池是余额。

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.

对于你自己的碳排放，无论它们是每年1吨还是4吨，你每年都要向大气账户支付。这意味着大气中有越来越多的碳。

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).

碳来自化石燃料——一个完全不同的“账户”。不管你有1000平方米还是100000平方米，这就是草做的类比：它每年从大气中吸收碳，但是这些碳会直接回到你修剪草坪时所吸收的地方，生物量会被分解并返回到大气中。换句话说，你的碳足迹是一个通量，它会导致一个池子(大气)的永久变化。这有点像周薪。你不必还钱。然而，你的草坪所做的，是在几周或几个月后(当你修剪草坪时，牛吃了草，或当自然更替发生时)偿还款项。

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(尽管可能很大)不受等价但相反通量的影响。如果你愿意，我们来做这个实验。你每星期在我的账户上付1000美元，我每星期在你的账户上付1000美元。我们没有人会在意——就像大气不会担心你的草坪上短暂锁住的碳一样。

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

所以从长远来看，你的草不会把二氧化碳从大气中锁住。新西兰任何草原都不会。

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.

如果你等的时间足够长，事情可能会变得更复杂，也就是说，如果我给你的还款开始变得少一点或多一点，导致美元或碳在一个账户而不是另一个账户上积累。尽管在一些生态系统中，如农林，新西兰草原不太可能是其中之一。所以你的后院没用，没有办法减少温室气体排放。