Collaborative Research: The Lost Pastures of Alaska's Last Megafauna

快速的气候变化现在正在影响生活在北极的动植物。了解过去气候变化时发生了什么，有助于预测未来50年可能发生的事情：哪些物种将灭绝，为什么？有什么办法可以保护北极物种免受气候变化的影响吗？这个项目的目标是了解是什么导致了上一次冰河时代结束前后，像猛犸象这样的巨大冰河时代动物的灭绝。一些人认为他们是被人杀死的；另一些人说他们是因为气候的快速变化而死的。没有人确切知道，但每个人都在争论这一点。甚至还不知道这些物种灭绝的确切时间：是12000年前，还是4000年前？该项目旨在查明阿拉斯加最后一头猛犸象、最后一头草原野牛和最后一头冻土带狮子生活的时间。一旦确定它们何时灭绝，就有可能取消一些拟议的解释。例如，可能会发现，4000年前，猛犸象群仍然在阿拉斯加漫步。因为人们已经知道，第一批人大约在1.4万年前到达阿拉斯加，如果这个项目表明猛犸象和人类共存了1万年，那么就不太可能是人类把它们赶到灭绝的。这里提出的这项研究将使用基于保存在冰冻土壤中的DNA的新方法，获得最后一批冰河时代哺乳动物在阿拉斯加生活的更准确的日期。这些动物曾经生活过。所有的动物(包括人类)都不断地通过皮肤碎片、毛发、粪便和尿液将DNA排放到环境中。其中一些组织碎片被埋在地下并保存下来。这在北极尤其如此，那里的腐烂速度因寒冷的气温而减缓。该计划是从地面提取组织碎片(想想毛皮和头皮屑)，然后使用其中包含的DNA来识别它来自哪个动物物种。接下来，含有这种DNA的土层将被测定年代，这些新的日期将被用来测试是什么导致了这种物种的灭绝。通过更好地了解过去灭绝的原因，仍然幸存的北极哺乳动物可以得到更好的保护，如北极熊、麝牛和驯鹿等物种。这项研究的一个主要目标是教育学生和高中教师关于气候变化、DNA和冰河时代生态学的知识。将特别努力让阿拉斯加原住民学生参与进来。所有数据将在每个人都可以免费访问的档案中共享，新发现将通过科学出版物、报纸文章和公开讲座共享。北极生态系统现在处于全球变化的前线。迫切需要更好地了解温度、海冰面积和土地利用的快速变化如何影响大型北极哺乳动物，如麝牛、北极熊和驯鹿。地质记录保存了史前气候迅速变化时动植物发生变化的许多例子。物种灭绝尤其令人感兴趣，因为了解过去是什么原因导致了物种灭绝，可以帮助我们保护地球上剩余的大型动物，其中许多现在已经濒临灭绝。在14,000到10,000年前的上一个冰河时代末期，北极出现了一波灭绝浪潮。就在这个时候，大多数科学家认为，冰河时代的巨型哺乳动物，如猛犸象、草原野牛、冻土带马和冻土带狮子，从西伯利亚和阿拉斯加大陆消失了；然而，没有人确定是什么原因导致了这些灭绝，并提出了许多解释。这场辩论的一个原因是，一个关键的信息仍然缺失，那就是：这些物种实际上是什么时候灭绝的？除非准确地知道物种灭绝发生的时间，否则关于因果关系的各种假说都无法检验。目前对这些物种灭绝发生的时间的理解是基于散布在北部大陆的数百个放射性碳测年数据，而且真正有可能的是，最后一只猛犸象的骨骼永远不会被发现。但现在有了一种新的更好的方法来检测现已灭绝的动物的存在。所有动物都通过皮肤碎片、毛发、粪便和尿液将DNA排放到环境中。其中一些DNA被埋藏并保存在地下，特别是在北极，那里的东西因为寒冷而腐烂得很慢。这个项目的目的是提取灭绝哺乳动物的古代DNA，用它来识别它属于哪个物种，然后确定它来自哪里的土层。然后，这些新的日期可以用来测试是什么导致了这种物种的灭绝。在这项研究中，将重点教育学生和高中教师关于气候变化、DNA和冰河时代生态学的知识。将特别努力让阿拉斯加原住民学生参与进来。我们的所有数据将在每个人都可以免费访问的档案中共享，新发现将通过科学出版物、国际会议、报纸文章和公共讲座共享。这一奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Rapid climate changes are now impacting the animals and plants that live in the Arctic. Learning what happened when climate changed in the past can help predict what could happen over the next 50 years: Which species will become extinct, and why? Is there anything that can be done to protect Arctic species from the impacts of climate change? The goal of this project is to understand what caused the extinctions of giant, ice-age animals like woolly mammoth around the time that the last ice age ended. Some people think they were killed off by people; others say they died because of rapid changes in climate. No one knows for certain, but everyone argues about it. It is not even known when, exactly, these extinctions occurred: Was it 12,000 years ago, or 4000 years ago? This project aims at pin-pointing when the last mammoth, the last steppe bison, and the last tundra lion lived in Alaska. Once it is known for certain when they became extinct, it will be possible to eliminate some of the proposed explanations. For example, it may turn out that herds of mammoths still roamed across Alaska 4000 years ago. Because it is already known that the first people arrived in Alaska around 14,000 years ago, if this project shows that mammoths and people coexisted for 10,000 years, it makes it unlikely that people drove them to extinction. The research proposed here will obtain more precise dates on when the last ice-age mammals lived in Alaska using new methods based on the DNA that is preserved in frozen ground where these animals once lived. All animals (people included) continually shed DNA into the environment in their skin fragments, hair, feces, and urine. Some of these tissue fragments are buried and preserved in the ground. This is especially true in the Arctic where decay is slowed by cold temperatures. The plan is to extract tissue fragments (think: fur and dandruff) from the ground, and then use the DNA it contains to identify which animal species it came from. Next, the soil layer containing this DNA will be dated, and these new dates will be used to test ideas about what caused this species’ extinction. By better understanding the causes of extinctions in the past, the Arctic mammals that still survive can be better protected, species like polar bears, musk oxen, and caribou. A major goal of this study is to educate students and high school teachers about climate change, DNA, and ice-age ecology. A particular effort will be made to involve students who are Alaskan Natives. All data will be shared in archives that everyone has free access to, and new discoveries will be shared through scientific publications, newspaper articles, and public lectures. Arctic ecosystems now lie on the front lines of global change. There is an urgent need to better understand how rapid changes in temperature, sea-ice extent, and land use could impact large-bodied Arctic mammals like musk oxen, polar bears, and caribou. The geological record preserves many examples of what happened to animals and plants when climate changed rapidly during prehistory. Extinctions are of particular interest, because understanding what caused extinctions in the past can help us conserve the planet’s remaining megafauna, many of which are now endangered. A wave of extinctions occurred in the Arctic around the end of the last ice age, 14,000 to 10,000 years ago. This is when most scientists believe that giant ice-age mammals like woolly mammoth, steppe bison, tundra horses, and tundra lions disappeared from mainland Siberia and Alaska; however, no one is sure what caused these extinctions, and many explanations have been proposed. One reason for this debate is that a key piece of information is still missing, namely: When did these species actually go extinct? Unless it is known with precision when an extinction occurred, the various hypotheses about causation cannot be tested. Present understanding of when these extinctions occurred is based on a few hundred radiocarbon dates scattered across the northern continents, and there is a real possibility that the bones of the last woolly mammoth will never be discovered. But now there is a new and better way to detect the presence of now-extinct animals. All animals shed DNA into the environment in their skin fragments, hair, feces, and urine. Some of this DNA is buried and preserved in the ground, especially in the Arctic, where things decay slowly because it is cold. The aim of this project is to extract the ancient DNA of extinct mammals, use it to identify which species it belonged to, and then to date the soil layer where it came from. These new dates can then be used to test ideas about what caused this species’ extinction. In this study, emphasis will be placed on educating students and high school teachers about climate change, DNA, and ice-age ecology. A particular effort will be made to involve students who are Alaskan Natives. All our data will be shared in archives that everyone has free access to, and new discoveries will be shared through scientific publications, international conferences, newspaper articles, and public lectures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.