This is Scientific American's 60-second Science. I'm Jason Goldman.
Large mammals can be lost from a particular place, from being hunted or by the destruction of their habitat. And the loss of these big animals can greatly affect the rest of the ecosystem. Take elephants: They can leave deep footprints in soil. After it rains, each footprint becomes a tiny pond, which becomes a home to a variety of invertebrates. No elephants means no homes for those critters. So while it's well known that the loss of large mammals can mean bad news, just how pervasive those impacts can be still remains unclear.
"I spent a lot of time when I was there in these heavily hunted forests. And in these pristine forests — well, relatively pristine forests — they were hunted, they were pretty protected, remember. Just walking around, I was noticing that there's a visual difference in the amount of understory vegetation in these areas where the elephants and other large animals like forest buffalo are hunted out. There was a lot more vegetation in the understory, compared to deep within the park, where it was more protected and remote. It was a lot easier to walk around."
Rice University biologist Therese Lamperty, who conducted fieldwork in Gabon in West Central Africa.
"If overhunting is allowing this vegetation to be released from herbivory and trampling, I was imagining that would probably do a lot to the understory environment and the microclimates invertebrates are exposed to."
So Lamperty and her team compared the understory vegetation and biodiversity within hunted and protected areas in northeastern Gabon. They discovered that areas with fewer larger mammals indeed had a thicker understory, as Lamperty suspected. And there were fewer termites—which is not good.
Termites help decompose plants and, as a result, are vital for storing carbon underground. They are also food for a variety of predators. The researchers suspect that the lack of elephant dung and trampled brush removed two important sources of nutrition for the social insects. And that led to a huge decline in termite populations, down by more than 99 percent.
The results are in the journal Biological Conservation.
But with termites gone, other organisms picked up the slack.
"The termites and invertebrates on the forest floor that we had been sampling were contributing less to decomposition in the hunted forest. But the overall rate didn't change, so maybe fungus or something else is able to pick up the slack."
In other words, while the community of organisms that break down dead plants is different in hunted versus intact ecosystems, the overall work that they do remained fairly constant. According to Lamperty, that means that these ecosystems are equipped to deal with these human-caused changes, at least to a point.
"Invertebrates contribute a lot to nutrient cycling, so that's going to influence how healthy a forest is and its own regeneration processes, which means how much carbon it can store. So that directly affects climate change."
Our planet has been losing large mammals for a long time, and if current trends continue, some researchers believe the largest terrestrial mammal in 200 years could well be the domestic cow. And we need to understand what that world might look like.
Thanks for the minute for Scientific American's 60-second Science. I'm Jason Goldman.
大型哺乳动物可能会因为被猎杀或栖息地遭破坏而从特定的地方消失 。大型动物的减少会极大地影响生态系统的其他部分 。以大象为例：它们能在土壤中留下深深的足印 。下雨后，每个足印都会形成一个小池塘，成为各种无脊椎动物的家园 。没有大象，这些生物就会失去家园 。因此，虽然众所周知大型哺乳动物减少可能是件坏事，但其影响的普遍程度仍不得而知 。
“我花了很多时间待在被大量捕猎的森林里 。在原始森林里，实际上是相对原始的森林里，人们在捕猎受到了很好的保护 。在森林里四处走动时我注意到，在大象和森林水牛等大型动物被猎杀的地区，林下植被的数量存在视觉差异 。这些地区的林下植被比公园深处的多得多，而公园深处的受保护程度更高，也更偏僻 。在这里四处走动要容易得多 。”
因此，兰佩蒂及其团队比较了加蓬东北部狩猎区和保护区内的林下植被和生物多样性 。他们发现，大型哺乳动物较少的地区确实有较厚的林下植被，这与兰佩蒂所猜想的一样 。而且白蚁数量更少，这可不是件好事 。
白蚁有助于分解植物，因此对地下碳储存至关重要 。而且许多动物以白蚁为食 。研究人员猜测，大象排便和遭踩踏灌木的减少，会导致这种群居昆虫缺乏两种重要的营养来源 。这会导致白蚁数量大幅下降，降幅达99%以上 。
这项研究结果发表在《生物保护》期刊 上 。
“我们在捕猎森林中采样的地表白蚁和无脊椎动物，它们的分解作用正在减少 。但整体效率没有变化，因此真菌等生物体也许可以弥补这一空缺 。”
换言之，虽然分解死亡植物的有机体群落在捕猎生态系统和完整生态系统中的效率不同，但它们的整体工作仍然相当稳定 。兰佩蒂表示，这意味着这些生态系统至少在一定程度上具备处理这些人为变化的能力 。
“无脊椎动物对养分循环有很大贡献，因此这会影响森林及其自身再生过程的健康程度，而这会决定森林的碳储存量 。所以这会直接对气候变化产生影响 。”
长期以来，我们的地球一直在失去大型哺乳动物，如果目前的趋势继续下去，一些研究人员认为200年后最大的陆生哺乳动物很可能就是家畜 。我们需要了解这个世界会变成什么样子 。
谢谢大家收听科学美国人——60秒科学 。我是杰森·古德曼 。
1. a variety of 各式各样；多种多样；
People change their mind for a variety of reasons.
2. be exposed to 使接触；
It is a closed society in the sense that they've not been exposed to many things.
3. pick up the slack 接手他人不再做的工作；补位提供；
As major airlines give up less-traveled routes, smaller planes are picking up the slack.
4. break down （使）（物质）分解；
Sugar and starch are broken down in the stomach.