Why are there fewer grasshoppers² in Konza Prairie

为什么康扎草原的蚱蜢越来越少

In northeastern Kansas, there's an open-air ecological³ laboratory called Konza Prairie. Scientists like Ellen Welti go there to study plants, insects, and big animals. "In the spring it has a lot of beautiful flowers, it has bison; everybody should go visit and check it out for themselves," says Welti, who is currently a post-doctoral researcher at the University of Oklahoma.

在堪萨斯州东北部，有一个叫做康扎草原的露天生态实验室。像埃伦·韦尔蒂这样的科学家去那里研究植物、昆虫和大型动物。”在春天，它有许多美丽的花朵，有野牛;每个人都应该去参观，并亲自去看看，”韦尔蒂说，他目前是俄克拉荷马大学的博士后研究员。

In this landscape, grasshoppers play a crucial role. They eat the grass; birds eat them.

在这片土地上，蚱蜢扮演着至关重要的角色。蚱蜢吃草，鸟吃蚱蜢。

为什么康扎草原的蚱蜢越来越少

Welti and her colleagues noticed that data collected over the past two decades showed the number of grasshoppers declining. Yet it wasn't for lack of food. The amount of grass on this prairie actually has been increasing, which Welti found "kind of interesting."

韦尔蒂和她的同事们注意到，过去二十年收集的数据显示，蚱蜢的数量正在减少。但这并不是因为食物短缺。这片草原上的草的数量实际上一直在增加，韦尔蒂觉得这“有点意思”。

The researchers wondered if perhaps the crucial factor wasn't the amount of grass available to eat, but its nutritional⁴ content. "Grasshoppers, even compared to other insects, are more sensitive to changes in plant quality," Welti says.

研究人员想知道，也许关键因素不是可食用的草的数量，而是它的营养成分。“与其他昆虫相比，蚱蜢对植物质量的变化更敏感，”韦尔蒂说。

Fortunately, they could test this hypothesis. Scientists have collected samples of grass that grew at Konza Prairieeach year for the past 20 years or so. Those samples were stored in a shed. When the scientists tested them, they found that, indeed, in more recent years the grass contained lower levels of certain key nutrients⁶, including nitrogen (which is a measure of protein levels), phosphorus, and potassium.

幸运的是，他们可以验证这个假设。科学家们收集了过去20多年来每年生长在康扎草原上的草的样本。那些样品被储存在一个棚子里。当科学家们对它们进行测试时，他们发现，近些年来，这些草的某些关键营养素确是在较低水平，包括氮(一种衡量蛋白质水平的指标)、磷和钾。

Welti and her colleagues think that they know the reason for all this, and it's related to the changing climate. There's more carbon dioxide in the air now, which plants need in order to grow. Also, the climate is warmer. Both things make grass grow faster.

韦尔蒂和她的同事认为他们知道这一切的原因，这与气候变化有关。现在空气中有更多的二氧化碳，植物需要这些二氧化碳才能生长。而且，气候也变暖了。这两种物质都能使草长得更快。

The scientists think that this, in turn, is what led to lower amounts of those crucial nutrients. Scientists have observed this "nutrient⁵ dilution⁷" when they've grown plants in the lab with artificially high levels of carbon dioxide.

科学家们认为，这进而导致了这些关键营养素含量的降低。科学家们观察到，当他们在实验室里人工种植二氧化碳含量高的植物时，观察到这种“营养稀释”现象。

The declines in nutrient levels in the grass samples at Konza Prairie "are pretty striking," Welti says. "So it seems like a pretty logical explanation for grasshopper¹ declines."

韦尔蒂说，康扎大草原的草样本中营养水平的下降“相当惊人”。“因此，这似乎是蚱蜢数量下降的一个非常合理的解释。”

为什么康扎草原的蚱蜢越来越少

Herteam's study was published this week in the journal Proceedings⁸ of the National Academy of Sciences.

她的团队的研究发表在本周的《美国国家科学院院刊》杂志上。

"It's an interesting paper, for sure," says Spencer Behmer, an entomologist at Texas A&M University who also studies grasshoppers. The new study, he says, shows the value of long-term ecological observations at sites like Konza Prairie, where scientists collected samples of grass over many years without ever knowing what those samples might someday reveal.

“这确实是一篇有趣的论文，”德州农工大学的昆虫学家史宾赛·宾莫说，他也研究蚱蜢。他说，这项新的研究显示了在像康扎草原这样的地方进行长期生态观察的价值，在那里，科学家多年来收集草地样本，却从未知道这些样本有朝一日可能揭示什么。

These observations could have implications for human nutrition, too, Behmer says. Crops that humans eat also are affected⁹ by carbon dioxide levels and climate change — although people have more food options than grasshoppers do.

宾默说，这些观察结果也可能对人类营养产生影响。人类食用的农作物也受到二氧化碳水平和气候变化的影响，尽管人们比蚱蜢有更多的食物选择。