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This is Scientific American — 60-Second Science. I'm Marissa Shieh.

这里是科学美国人——60秒科学。我是玛丽莎·谢赫。

One of the delights of summer is to see monarch¹ butterflies dancing through the air. But it's becoming harder to see them in certain locales—in some places the population has dropped by as much as 90 percent. And climate change may make life even more challenging for these charismatic insects. That's because higher carbon dioxide levels can lower the amount of toxins² in milkweed—the monarch caterpillar's food. The caterpillars³ use those toxins to protect themselves from a deadly parasite⁴ that produces spores⁵.

夏天的一大乐趣就是看着黑脉金斑蝶（俗称帝王蝶）在空中翩翩起舞。但是在某些地方，人们却越来越难以看到它们的身影，因为一些地方的帝王蝶数量已经减少了90%。而气候变化甚至会使这些魅力十足的昆虫的生活变得更加艰难。这是因为较高的二氧化碳水平会降低马利筋（俗名乳草）的毒素含量，马利筋是帝王蝶的食物。毛虫利用这些毒素来保护自己免受会产生孢子的致命寄生虫的伤害。

"When the caterpillars are really small...those spores get into the monarch's gut⁶ and they break apart and they start drilling holes in the gut lining⁷ and reproducing and just doing nasty parasite things that are bad for the monarchs⁸."

“当毛虫很小的时候，这些孢子就会进入帝王蝶的肠道，然后分裂并开始在肠道里钻洞、繁殖，做些令人厌恶的寄生虫会做的事情，而这对帝王蝶有害。

Leslie Decker, an ecologist at Stanford University. Decker and her colleagues raised hundreds of monarchs. They fed half of the caterpillars milkweed grown at current CO2 levels. The other half got milkweed grown at nearly double those CO2 levels.

斯坦福大学的生态学家莱斯利·德克尔说到。德克尔和同事养育了数百只帝王蝶。他们给其中一半的毛虫喂食了当前二氧化碳水平下的马利筋。另一半毛虫吃的则是在现有二氧化碳水平近两倍浓度的环境中生长的马利筋。

"What we found is that elevated CO2 changes the medicinal quality of the milkweed in a way that makes monarchs sicker. They're less able to tolerate their pathogen, so the parasite becomes more hurtful...to them. And it also reduces their overall lifespan when they're infected in comparison to uninfected monarchs."

“我们发现，高浓度的二氧化碳会在某种程度上改变马利筋的药用质量，这会使帝王蝶更不舒服。它们对病原体的耐受性会变差，继而会加大寄生虫对它们造成的伤害。与未受感染的帝王蝶相比，感染寄生虫的帝王蝶的整体寿命也会缩短。”

The caterpillars that ate milkweed grown with more carbon dioxide grew into butterflies that died as much as a week earlier than the normal life span.

食用二氧化碳浓度更高的马利筋的毛虫，在变成蝴蝶后，其寿命会比正常帝王蝶的寿命要短一周。

"As a human, you think, oh, well that's not that meaningful. But then as an insect, or as an insect that needs to reproduce within a week, it's pretty important." The study is in the journal Ecology Letters.

“作为人类，你可能会想，哦，那不算什么。但是作为昆虫，或者说作为需要在一周内繁殖的昆虫，这是相当重要的事情。”这项研究发表在《生态学快报》期刊上。

Decker say these findings are not just about butterflies and milkweed.

德克尔表示，这些发现不仅仅与蝴蝶和马利筋有关。

"Many of our medicines come from plants...and so what this study is highlighting to us, or at least creating a red flag for, is the fact that the medicinal contents in those plants could be changing under elevated CO2. They could be going up or down, but it could mean that we lose the medicinal efficacy, the protective ability of that green pharmacy⁹ around us."

“我们的许多药物都来自植物，因此这项研究向我们强调的，或者说至少向我们发出的危险信号是，这些植物中的药物成分可能会在二氧化碳浓度升高的情况下发生变化。它们可能会上升或下降，但这可能意味着，我们会失去药物功效，失去我们身边的绿色药房的保护能力。”

Thanks for listening for Scientific American — 60-Second Science. I'm Marissa Shieh.

谢谢大家收听科学美国人——60秒科学。我是玛丽莎·谢赫。