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This picture is a typical seasonal grassland.
這張圖是典型的季節性草原。
It has just come through four months of rain, and it's now going into eight months of dry season.
剛剛經歷了4個月的雨季，將要進入8個月的旱季。
And watch the change as it goes into this long dry season.
注意看草原進入漫長的旱季后的變化。
Now, all of that grass you see aboveground has to decay biologically before the next growing season,
你們看到的所有地表上的草,在下個生長季節到來之前,都會腐爛掉，
and if it doesn't, the grassland and the soil begin to die.
否則的話，草地和土壤就會開始死亡。
Now, if it does not decay biologically, it shifts to oxidation, which is a very slow process,
如果它不是生物性的腐爛，而是以氧化的形式腐爛，這是一個非常緩慢的過程，
and this smothers and kills grasses, leading to a shift to woody vegetation and bare soil, releasing carbon.
并且會消耗氧氣，殺死草本植物，只有木本的植物才能生存，導致了地表被裸露，碳元素釋放到大氣層。
To prevent that, we have traditionally used fire.
為了防止這種情況，傳統上我們是用火燒。
But fire also leaves the soil bare, releasing carbon, and worse than that, burning one hectare of grassland gives off more,
可是火也會讓地表被裸露，碳元素釋放到大氣層，更糟糕的是，燒掉一公頃的草地所釋放的有害污染物，
and more damaging, pollutants than 6,000 cars.
要比6000輛汽車排放的總和還要多。
And we are burning in Africa, every single year, more than one billion hectares of grasslands, and almost nobody is talking about it.
每年在非洲我們都會燒掉十億公頃以上的草地，幾乎沒人關心過這個。
We justify the burning, as scientists, because it does remove the dead material and it allows the plants to grow.
作為科學家，我們理解燒草可以除掉死植物，允許植物成長。
Now, looking at this grassland of ours that has gone dry, what could we do to keep that healthy?
看看這片草地已經枯干，我們做什么才能保持健康？
And bear in mind, I'm talking of most of the world's land now. Okay?
記住，我講的是世界上大部分的土地。明白么？
We cannot reduce animal numbers to rest it more without causing desertification and climate change.
我們不能用減少動物數量的方式讓植被休養，因為這會引發土地荒漠化和氣候變化。
We cannot burn it without causing desertification and climate change.
我們不能用焚燒的方法，這也會引發荒漠化和氣候變化。
What are we going to do?
那我們能怎么辦？
There is only one option, I'll repeat to you, only one option left to climatologists and scientists,
只有一種方案，我再重復一遍，唯一的一種方法擺在氣候學家和科學家的面前，
and that is to do the unthinkable, and to use livestock, bunched and moving, as a proxy for former herds and predators, and mimic nature.
個方案非常的不可思議，就是使用牲畜，成群結隊地遷移，把它們看作從前的游牧動物和捕食動物，模擬大自然的行為。
There is no other alternative left to mankind.
這這種方法是人類唯一的選擇了。
