Scientists have recreated a 1985 study of birds in Peru that shows climate change is pushing them from their natural environment.
Thirty years ago, researchers studied more than 400 kinds of birds living on a mountainside in Peru. In 2017, researchers looked again at the bird populations. They found that almost all had moved to higher places in the mountain. Almost all had decreased in size. And, the scientists say at least eight bird groups that started at the higher elevations had died out completely.
John W. Fitzpatrick is director of the Cornell Laboratory of Ornithology and a co-writer of the study. He said, Once you move up as far as you can go, there's nowhere else left.
The researchers say the birds might have moved up the mountain because of temperature changes. Or, they say, changes to food sources may have forced them to go higher.
The findings were published in the Proceedings of the National Academy of Sciences.
Past research has documented birds and other animals moving up in elevation in reaction to warming temperatures. Mark Urban is director of the Center of Biological Risk at the University of Connecticut. He said this recent study was the first to prove that rising temperatures and moving to avoid them can lead to extinction.
In 1985, Fitzpatrick and a team of scientists established a camp alongside a river running down a mountainside in southeastern Peru. He wanted to document where tropical bird groups there lived. His team spent several weeks using nets to catch and release birds. They kept detailed notes of birds they caught, saw or heard.
In 2016, Fitzpatrick passed his notes, photos and other records to Benjamin Freeman. He is with the Biodiversity Research Centre at the University of British Columbia. Freeman has been researching tropical birds for more than 10 years. He set out in August and September of 2017 to copy Fitzpatrick's study. His team used the same methods, searching the same places in the same time of year.
Freeman's team wanted to see how things had changed for the bird groups since 1985. The average temperatures on the mountain had risen 0.42 degrees Celsius.
Freeman's team placed 20 sound recording devices on the mountain to record the sounds of birds that might not easily be seen.
Freeman said that the birds moved an average of 98 meters further up the mountain. He said he believes that temperature is the main cause of the birds' movement.
Fitzpatrick noted that birds used to living in areas with little temperature change may be especially at risk because of climate change. He said, We should expect that what's happening on this mountain top is happening more generally in the Andes, and other tropical mountain ranges.
I'm Jonathan Evans.
1. climate change 气候变化
We are all victims of climate change.
2. in reaction to 随着……
Stock markets across Asia followed U.S. and European shares sharply lower, in reaction to the collapse of the investment company Lehman Brothers.
3. set out 出发，着手
The troops are about to set out.
4. be used to doing sth 习惯于做某事
That must be especially hard in an environment that is so used to doing everything in a way that has already be done.
在 一个一切都习惯于去循规蹈矩的环境里，这样做一定很艰难 。
30年前，多位科学家研究了400多种生活在秘鲁山坡的鸟类 。2017年，科学家回顾了这些鸟类的数据 。他们发现，几乎所有鸟类都迁徙到了山上更高的地方 。几乎鸟类体型都变小了 。此外，该研究的科学家还表示，至少8种鸟类原本生活在更高的海拔上，但现在已经彻底灭绝了 。
约翰是康奈尔鸟类学实验室的负责人，也是该研究的一位署名作者 。他表示，越往上看，越了无生趣 。
研究人员表示，这些鸟类之所以往上迁徙是因为气温变化 。也就是说，食物来源的变化可能迫使它们向上迁徙 。
以前有研究发现鸟类等动物会随着气温的升高而向上迁徙 。马克是康涅狄格大学生物风险中心的负责人 。他表示，最近的这项研究首次证明了气温升高带来的向上迁徙会导致它们死亡 。
1985年，菲茨帕特里克和一组科学家建起了一个营地，营地就在一条小河旁边，河水顺着秘鲁东南部的山坡流下 。菲茨帕特里克向记录那里的热带鸟类在哪儿生活 。他的团队耗时数周，用网来捕捉并释放鸟类 。他们记录了捕捉到的、看到的和听到的鸟类的细节信息 。
2016年，菲茨帕特里克将自己的笔记、照片等记录交给了本杰明·弗里曼 。后者在不列颠哥伦比亚大学生物多样性研究中心任职 。弗里曼研究热带鸟类已有10多年的时间 。他从2017年8月和9月开始做菲茨帕特里克的研究 。弗里曼的团队也用了相同的方法——每年在同一时间搜寻相同的地方 。
弗里曼的团队想知道自1985年以来鸟类族群发生了哪些变化 。山上的平均温度升高了0.42摄氏度 。
弗里曼表示，所有鸟类平均向上迁徙了98米 。他表示自己相信温度是鸟类迁徙的主要原因 。
菲茨帕特里克表示，习惯在温差不大的地区生活的鸟类可能尤其濒临危险，因为全球产生了气候变化 。他表示，我们应该料想到，这座山顶正在发生的一切也在安第斯山脉等热带山脉普遍发生着 。