字幕列表 影片播放 列印英文字幕 [Intro] Every now and then, a story shows up on your Facebook page, your Tumblr dash, your Twitter feed that just doesn't go away, because people keep arguing about it. And arguments are fine, but they often tend not to reveal much in the way of data, or context. So with that in mind, SciShow wanted to weigh in on "The Great Walrus Haulout of 2014". You've seen the pictures, probably, taken last month by a government biologist who counted more than 35,000 Pacific walruses crowded together on Point Lay, a rocky barrier island off Alaska's northern coast. Depending on what online ecosystem you inhabit, you might have seen this picture shared as a grim sign of global warming, or from the opposite perspective, as a normal event that environmentalists have just hyped up. Well, let's start with what we know - walruses can't swim for very long periods like seals can, so they stop between feedings to rest on chunks of land or ice. This is known as "hauling out" and it is a thing that walruses do, especially in late summer and early fall. What's interesting, and kind of weird about the Point Lay haulout, is that there are SO MANY walruses resting together at the same place - it may be the biggest ever recorded. And while it's been described as a walrus "flash mob", it is not nearly as fun as that. Many of these walruses are females with young calves, and having thousands of animals, some weighing more than a ton, in such close quarters can lead to battles over territory, accidental tramplings, and the fast spread of disease. In fact, deaths in these mass haulouts are common. Now many media reports have quoted scientists as saying that haulouts are getting bigger, and therefore more dangerous, because of global warming. As sea ice melts, more walruses have to cluster together on land to rest. But there's also been a backlash among your climate-change-is-not-happening crowd which has pointed out - OFTEN IN ALL CAPS - that these things have been seen before. Well yeah, sort of. Most often the skeptics are citing a University of Alaska study from 1978 that estimated that some 35,000 hauled out en masse that year, but that was an estimate made after the walruses had moved on, gleaned mostly from how much land the walruses had disturbed, and how many dead were left behind. Since then, research into these events has become more regular and rigorous, and results over the past ten years do seem to reveal a pattern. The first large haulout on land was recorded in 2007, when 30,000 walruses were counted on beaches on the Russian side of the Bering Strait. And according to the U.S. National Marine Fisheries Service, this coincided with a loss of sea ice in that part of the Arctic, that at the time, was unprecedented. Then, in 2010, 20,000 walruses hauled out near Point Lay, and the following year, 30,000 appeared in the same place. But these numbers haven't gone up every year - there were no huge haulouts in 2008 and 2012, for example - years when, according to the Feds, there was enough sea ice for all of the animals to rest on. So the likelihood is we're going to be seeing more of these events in the future, but the science behind them is more complicated that you can fit into one hundred and forty characters. Another thing people like to argue about that's also being researched more than ever? Cannabis. By some estimates marijuana is now almost as prevalent as tobacco in many countries, and on Monday, a new study from the University of Queensland laid out all of the research that has been done on marijuana over the past 20 years, listing everything scientists have learned, as well as what patterns they've observed but haven't been connected yet. Among the conclusions, even through it's not chemically addictive like opiates, cannabis has been found to cause what's known as a Dependence Syndrome - a persistent psychological craving that can disrupt a person's thoughts and behavior. This was documented in about one of every ten pot smokers across various studies, but the risk was nearly twice as high - one in six - among adolescents. Also, results show that regular cannabis users have double the risk of experiencing symptoms of psychosis - a disorder often described as a loss of touch with reality, as well as schizophrenia - a condition that causes things like disorganized thinking, delusions, and hallucinations. Now, this doesn't mean that pot causes these conditions, but the data do suggest that people who are genetically predisposed to these disorders are more likely to have symptoms appear if they smoke often. Finally, there are some correlations that scientists have found while studying pot use among teens, but so far they haven't found any direct link between the drug and these observations. Specifically, they found that adolescents who regularly use pot typically attain a lower level of total education, suffer from intellectual impairment, and are more likely to use other illicit drugs. Now, these are all things that could have a number of social causes like poverty, access to education, and family situations, so no causal link has been established at all. But me? We're talking about the health of my brain here, so I'm not taking any chances; it's the only one I got, and I like to think it's working great on its own. Thanks for watching SciShow News, brought to you by Audible - which is giving away a free audio book to SciShow viewers. You can go to audible.com/scishow, and download one of my favorite new science books of the year, "What If? Serious scientific answers to absurd hypothetical questions", narrated by my friend Wil Wheaton, and written by the creator of XKCD, Randall Munroe. Or, you know, practically any other book, for free, so go to audible.com/scishow.