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Ecosystems Still Feel the Pain of Ancient Extinctions
物种灭绝对生态系统仍然存在影响
It's not just humans that still feel the effects of a trauma many years later,ecosystems do too.
若干年后，不仅人类仍然会感觉到创伤所带来的影响，生态系统同样也会。
Thousands of years after human hunters wiped out big land animals like giant ground sloths,the ecosystems they lived in are still feeling the effects.
在人类捕猎者消灭了大型陆地动物如巨型地懒的数千年后，人们居住的生态系统仍然能感觉到这些影响。
Many ecosystems rely on big animals to supply them with nutrients, mostly from dung.
许多生态系统都依赖于大型动物来为它们提供营养物质，这些物质主要从粪便中获得。
"If you remove the big animals from an ecosystem, you pretty much stop nutrients moving,"says Chris Doughty of the University of Oxford.
牛津大学的克里斯·道蒂说“如果你从生态系统里消除大型动物，那么你几乎就停止了养分的运送。”
Doughty and colleagues simulated the distribution of phosphorus,a nutrient that plants need to grow in the Amazon basin in South America.
道蒂和他的同事在南美洲亚马逊河流域仿造了磷的分布规律，磷是植物生长所需要的养分。
This area was once home to spectacularly large animals, including the elephant—like gomphotheres and giant ground sloths.
这一地区曾经是很多大型动物的家园，包括与大象类似的嵌齿象科和巨型地懒。
But 12500 years ago, around the time humans moved into South America, these huge animals all died out, hit by a double whammy of being hunted and a changing climate.
但在12500年前，也就是大约在人类搬进南美的时候，这些巨型动物都灭绝了，主要是受到了猎杀和气候变化双重灾难的影响。
Nowadays the Amazon is still home to a huge diversity of animals.
如今，亚马逊仍然是很多不同种类动物的家园。
"But these extinctions cut out all the big animals, "says Doughty.
道蒂说“但这些灭绝已经消灭了所有的大型动物。”
It seems the mass extiction had a profound effect on how phosphorus is spread around the Amazon basin.
似乎看来大量动物灭绝对亚马逊河流域磷的分布有着深远的影响。
Nutrients are released when rocks are eroded, and then get distribute onto floodplains by rivers.
当岩石被侵蚀时，营养物质被释放出来，然后随着河流分布到冲积平原。
In South America, the most phosphorus rich soils are found near the Andes mountain chain in the west.
在南美洲，西部的安第斯山脉被发现拥有富含磷最多的土壤。
If Doughty is right, the Amazon is still changing in response to the extinction.
如果道蒂的观点是正确的，为了回应这种灭绝，亚马逊仍然在改变着。
He estimates the spread of nutrients will keep getting patchier for another 17 000 years,
他估计，再过17000年，营养的传播将会变得更加不规则，
although the effect will likely be dwarfed by the impacts of deforestation and climate change in the short term.
虽然这种影响相对于短期内的森林砍伐和气候变化所带来的后果会显得相形见绌。
