為什么康扎草原的蚱蜢越來(lái)越少

為什么康扎草原的蚱蜢越來(lái)越少

In northeastern Kansas, there's an open-air ecological 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.

在堪薩斯州東北部，有一個(gè)叫做康扎草原的露天生態(tài)實(shí)驗(yàn)室。像埃倫·韋爾蒂這樣的科學(xué)家去那里研究植物、昆蟲(chóng)和大型動(dòng)物。”在春天，它有許多美麗的花朵，有野牛;每個(gè)人都應(yīng)該去參觀，并親自去看看，”韋爾蒂說(shuō)，他目前是俄克拉荷馬大學(xué)的博士后研究員。

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

在這片土地上，蚱蜢扮演著至關(guān)重要的角色。蚱蜢吃草，鳥(niǎo)吃蚱蜢。

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."

韋爾蒂和她的同事們注意到，過(guò)去二十年收集的數(shù)據(jù)顯示，蚱蜢的數(shù)量正在減少。但這并不是因?yàn)槭澄锒倘?。這片草原上的草的數(shù)量實(shí)際上一直在增加，韋爾蒂覺(jué)得這“有點(diǎn)意思”。

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

研究人員想知道，也許關(guān)鍵因素不是可食用的草的數(shù)量，而是它的營(yíng)養(yǎng)成分。“與其他昆蟲(chóng)相比，蚱蜢對(duì)植物質(zhì)量的變化更敏感，”韋爾蒂說(shuō)。

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 nutrients, including nitrogen (which is a measure of protein levels), phosphorus, and potassium.

幸運(yùn)的是，他們可以驗(yàn)證這個(gè)假設(shè)?？茖W(xué)家們收集了過(guò)去20多年來(lái)每年生長(zhǎng)在康扎草原上的草的樣本。那些樣品被儲(chǔ)存在一個(gè)棚子里。當(dāng)科學(xué)家們對(duì)它們進(jìn)行測(cè)試時(shí)，他們發(fā)現(xiàn)，近些年來(lái)，這些草的某些關(guān)鍵營(yíng)養(yǎng)素確是在較低水平，包括氮(一種衡量蛋白質(zhì)水平的指標(biāo))、磷和鉀。

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.

韋爾蒂和她的同事認(rèn)為他們知道這一切的原因，這與氣候變化有關(guān)。現(xiàn)在空氣中有更多的二氧化碳，植物需要這些二氧化碳才能生長(zhǎng)。而且，氣候也變暖了。這兩種物質(zhì)都能使草長(zhǎng)得更快。

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

科學(xué)家們認(rèn)為，這進(jìn)而導(dǎo)致了這些關(guān)鍵營(yíng)養(yǎng)素含量的降低?？茖W(xué)家們觀察到，當(dāng)他們?cè)趯?shí)驗(yàn)室里人工種植二氧化碳含量高的植物時(shí)，觀察到這種“營(yíng)養(yǎng)稀釋”現(xiàn)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 grasshopper declines."

韋爾蒂說(shuō)，康扎大草原的草樣本中營(yíng)養(yǎng)水平的下降“相當(dāng)驚人”。“因此，這似乎是蚱蜢數(shù)量下降的一個(gè)非常合理的解釋。”

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

她的團(tuán)隊(duì)的研究發(fā)表在本周的《美國(guó)國(guó)家科學(xué)院院刊》雜志上。

"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.

“這確實(shí)是一篇有趣的論文，”德州農(nóng)工大學(xué)的昆蟲(chóng)學(xué)家史賓賽·賓莫說(shuō)，他也研究蚱蜢。他說(shuō)，這項(xiàng)新的研究顯示了在像康扎草原這樣的地方進(jìn)行長(zhǎng)期生態(tài)觀察的價(jià)值，在那里，科學(xué)家多年來(lái)收集草地樣本，卻從未知道這些樣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 affected by carbon dioxide levels and climate change — although people have more food options than grasshoppers do.

賓默說(shuō)，這些觀察結(jié)果也可能對(duì)人類營(yíng)養(yǎng)產(chǎn)生影響。人類食用的農(nóng)作物也受到二氧化碳水平和氣候變化的影響，盡管人們比蚱蜢有更多的食物選擇。