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

快速的气候变化正在影响着生活在北极的动植物。了解过去气候变化时发生的情况有助于预测未来50年可能发生的事情：哪些物种会灭绝，为什么会灭绝？有没有什么可以保护北极物种免受气候变化的影响？这个项目的目标是了解是什么导致了冰河时代的巨型动物灭绝，比如长毛象，在最后一个冰河时代结束的时候。有些人认为它们是被人类杀死的；还有人说，它们的死亡是因为气候的快速变化。没有人知道确切的答案，但每个人都在争论。我们甚至不知道这些灭绝发生的确切时间：是12000年前，还是4000年前？这个项目旨在确定最后的猛犸象、最后的草原野牛和最后的苔原狮子是什么时候生活在阿拉斯加的。一旦确定了它们是何时灭绝的，就有可能消除一些提出的解释。例如，事实可能证明，猛犸象群在4000年前仍在阿拉斯加漫游。因为我们已经知道，第一批人类大约在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，那么人类就不太可能导致它们灭绝。这里提出的研究将利用保存在这些动物曾经生活过的冻土中的DNA的新方法，获得更精确的冰河时期哺乳动物在阿拉斯加生活的时间。所有动物（包括人类）都会通过皮肤碎片、毛发、粪便和尿液不断地将DNA释放到环境中。其中一些组织碎片被埋在地下并保存下来。在北极尤其如此，因为那里的低温减缓了腐烂的速度。该计划是从地面上提取组织碎片（比如：皮毛和头皮屑），然后利用其中包含的DNA来识别它来自哪个动物物种。接下来，将测定含有这种DNA的土层的年代，这些新的日期将被用来检验导致这种物种灭绝的原因。通过更好地了解过去物种灭绝的原因，可以更好地保护那些幸存下来的北极哺乳动物，比如北极熊、麝牛和驯鹿。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土著学生参与进来。所有的数据都将在档案中共享，每个人都可以免费访问，新的发现将通过科学出版物、报纸文章和公共讲座分享。北极生态系统现在处于全球变化的前沿。我们迫切需要更好地了解温度、海冰范围和土地利用的快速变化对麝牛、北极熊和驯鹿等大型北极哺乳动物的影响。地质记录保存了许多史前史时期气候迅速变化时动植物所发生变化的例子。灭绝是一个特别有趣的问题，因为了解过去导致灭绝的原因可以帮助我们保护地球上现存的巨型动物，其中许多现在濒临灭绝。在1.4万到1万年前的最后一个冰河时代末期，北极发生了一波物种灭绝。大多数科学家认为，就在这个时候，像长毛象、草原野牛、苔原马和苔原狮子这样的冰河时代的巨型哺乳动物从西伯利亚和阿拉斯加大陆消失了；然而，没有人确定是什么导致了这些物种的灭绝，人们提出了许多解释。这场争论的一个原因是一个关键的信息仍然缺失，即：这些物种到底是什么时候灭绝的？除非精确地知道灭绝发生的时间，否则各种关于因果关系的假设是无法检验的。目前对这些灭绝发生时间的了解是基于散布在北部大陆上的几百个放射性碳年代，而且很有可能永远不会发现最后一头长毛象的骨头。但是现在有一种新的更好的方法来检测已经灭绝的动物的存在。所有动物的皮肤碎片、毛发、粪便和尿液都会将DNA释放到环境中。其中一些DNA被埋在地下并保存下来，特别是在北极，那里的东西因为寒冷而腐烂得很慢。该项目的目的是提取已灭绝哺乳动物的古代DNA，用它来确定它属于哪个物种，然后确定它来自的土层的年代。这些新的日期可以用来测试导致这个物种灭绝的原因。在这项研究中，重点将放在教育学生和高中教师关于气候变化，DNA和冰河时代生态学。将特别努力让阿拉斯加土著学生参与进来。我们所有的数据都将在档案中共享，每个人都可以免费访问，新的发现将通过科学出版物、国际会议、报纸文章和公共讲座分享。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识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.