发表于 2025年11月5日
In the summer of 2019, ecologist Patrick Sullivan and a Super Cub plane pilot navigated over the narrow valleys of the Brooks Range in northern Alaska, winding toward the remote headwaters of the Salmon River. Sullivan was studying the slow advance of trees into what had been tundra, a sign of the rapidly changing climate, but soon discovered something far more surprising.
Sullivan was expecting a clear, cold river artery with blue-green pools, and had even brought his fishing rod. So he was shocked to see turbid water and banks stained a fluorescent orange. “It looked like sewage,” he recalls. As the research team finished their sampling and paddled downstream in pack rafts, the cloudy, tangerine water persisted. Along the river, they floated past several emaciated bears. At one quiet eddy, a particularly thin bear crept near, its dark eyes fixed on them in a way that made Sullivan uneasy. He wondered if the river’s degraded state was suppressing the fish populations, potentially reducing bears’ food sources. “I started to feel like what we were seeing was an example of ecosystem collapse,” he says.
On a later trip, Sullivan took water samples and found strangely high concentrations of iron and heavy metals like cadmium, aluminum, and in some cases, zinc. By then, Sullivan realized the problem extended far beyond the Salmon: Bush pilots reported the same rusty color in dozens of rivers across the region, spanning an area roughly the size of Nebraska. Researchers around the world have begun to document similar changes in waterways near permafrost.
Environmental scientists have been able to predict some of the many of the changes occurring as the Arctic warms—like species shifting their ranges, tree lines moving north, and animals like beavers and moose appearing in novel places. But rivers rusting, Sullivan says, “has come as a surprise, even to the scientists who are constantly thinking about stuff like this.”
Since his first discovery, Sullivan and colleagues have pieced together a theory for why Arctic rivers are turning orange. Their findings prompt concerns about how this transformation may be affecting the region’s already stressed wildlife, and polluting waterways Alaskan communities depend on. But they also stir a deeper unease — the dread of watching a system come undone.
METALS ARE LEECHING OUT OF THE PERMAFROST
One of Sullivan’s first goals was to discover what contaminants might be causing this change. Across northern Alaska lay rocks that began as shale and sediments on the floor of an ancient ocean. Over time, bacteria formed them into pyrite, often called fool’s gold, a mineral that contains both iron and sulfur. For millennia, these deposits were locked in permafrost, protected from air and water. But as the frozen earth warms, it’s exposing the bedrock, beginning a destructive process that releases sulfuric acid and oxidizes the iron into a toxic orange cocktail that can be carried downstream for miles.
When Timothy Lyons, a biogeochemist at the University of California, Riverside, first saw Sullivan’s work at the University of Anchorage, he was struck by how closely this process resembled acid rock drainage. Common near mines, the reaction occurs when rocks containing sulfide minerals are exposed to water and oxygen, producing acid that leaches heavy metals. At a mine, such contamination is concentrated where it can be monitored or contained. But on wild rivers, “there’s simply nothing that can be done, other than fix climate change,” Lyons explains.
In 2023, Sullivan returned to the Brooks Range with Lyons and a large field team to try to better understand the consequences of the metal-laden runoff. “We could actually see the riverbank just basically dripping iron,” Lyons said, recalling where rusty slime oozed into the water. “It looked like snot.” The amount of dissolved metals in the river approached that of industrial wastewater, their analysis found.
An alarming shift in the Arctic’s waterways is now under way: Over 75 rivers across the Brooks Range have recently turned orange, and the Salmon River’s metal concentrations have reached levels toxic to aquatic life. To make things worse, Sullivan explains, they have also identified over 500 acid seeps in the tundra, where minerals are leaching into the surrounding wetlands. These can lower water pH, increase toxicity, and change microbiomes, disrupting the growth and survival of fish and other invertebrates. In a recent PNAS paper, the researchers found that fish habitat on the river has severely degraded as a result. “Our findings might help explain a recent crash in chum salmon, a really important subsistence food,” Sullivan says — potential evidence for his hunch about the bear he met eye to eye, an image of hunger he couldn’t shake.
THE ARCTIC IS TRANSFORMING IN UNEXPECTED WAYS
Jean-François Boily, a molecular geochemist at Umeå University in Sweden, who was not involved in the study, says the work is an important step in understanding how the Arctic is changing over a short period of time. Scientists may be witnessing a new concerning feedback loop that could continue to accelerate.
It starts with the frozen ground. In a recent paper, Boily’s showed that minerals dissolve more efficiently in ice than liquid water, upending past assumptions. As ice forms, dissolved substances like iron compounds are expelled from the crystalline structure and become condensed into tiny pockets of liquid water trapped between microcrystals. This dramatically increases the acidity. And every time the ground freezes, fresh minerals are reconcentrated.
As climate change accelerates freeze-thaw cycles, that may trigger a feedback loop, further amplifying river acidity. “All of this, by the way, is irreversible,” Boily says. Once these minerals dissolve, the process cannot easily be undone, because the original deposits cannot quickly reform. “Once it starts, it keeps on going.”
This is not just a problem in Alaska: In western Canada, just across the border from the Brooks Range, researchers have documented the familiar orange tint, while corresponding metal concentrations have popped up in permafrost pockets of Colorado, in mountain ponds in the European Alps, and even downstream of melting glaciers in Peru.
Researchers suspect similar processes may be occurring elsewhere, though the full global scope is still unknown. Boily says that across Sweden, scientists are finding an increased mobilization of iron. He explains that across the northern hemisphere, “brownification” of water — a process also associated with iron, which ends up increasing dissolved carbon — is slowing growth, fueling toxic algae blooms, and disrupting ecosystems. “What we cannot see with the naked eye is just as important as those spectacular orange rivers,” Boily said, pointing at the many ways climate change is impacting waterways worldwide.
But so far, researchers are still at the stage of documenting the rusting river problem, and many of the consequences are only beginning to come into focus. For the Alaskan communities who rely on these rivers for drinking water and food, information has been hard to come by. The town of Kivalina, which draws its water from the Wulik River downstream of multiple acid seeps, told National Geographic that the tribal administrator was not yet aware of the problem. Conventional treatment — like that used at large industrial sites, such as the state’s zinc and lead Red Dog Mine — is very expensive, and only effective for a single source.
Just a few hundred miles away, the Salmon watershed has long been celebrated for its intact wilderness. On a journey down it in 1975, New Yorker writer John McPhee described it as having “the clearest, purest water I have ever seen flowing.” As ecologist Alex Huron wrote in academic journal PNAS recently, the river itself has been protected from the oil and gas development on Alaska’s North Slope, but the burning of fossil fuels has still triggered chemical reactions that may ultimately prove far more damaging than a pipeline spill. It’s an omen, he wrote, “of more cryptic and ongoing environmental change yet to be perceived as warming proceeds.”
As Lyons warns, “there’s actually no one protected or immune” from the consequences yet to come.
In the summer of 2019, ecologist Patrick Sullivan and a Super Cub plane pilot navigated over the narrow valleys of the Brooks Range in northern Alaska, winding toward the remote headwaters of the Salmon River. Sullivan was studying the slow advance of trees into what had been tundra, a sign of the rapidly changing climate, but soon discovered something far more surprising.
2019年夏天，生态学家帕特里克·沙利文（Patrick Sullivan）和一位超级幼兽（Super Cub）飞机的飞行员，飞越阿拉斯加北部布鲁克斯山脉（Brooks Range）狭窄的山谷，蜿蜒地飞向萨蒙河（Salmon River）偏远的上游。沙利文当时正在研究树木缓慢地向昔日的苔原（tundra）地带扩张的现象，这一现象是气候快速变化的迹象，但他很快就发现了一个更令人吃惊的现象。
Sullivan was expecting a clear, cold river artery with blue-green pools, and had even brought his fishing rod. So he was shocked to see turbid water and banks stained a fluorescent orange. “It looked like sewage,” he recalls. As the research team finished their sampling and paddled downstream in pack rafts, the cloudy, tangerine water persisted. Along the river, they floated past several emaciated bears. At one quiet eddy, a particularly thin bear crept near, its dark eyes fixed on them in a way that made Sullivan uneasy. He wondered if the river’s degraded state was suppressing the fish populations, potentially reducing bears’ food sources. “I started to feel like what we were seeing was an example of ecosystem collapse,” he says.
萨利文原以为会看到一条清澈冰冷的河道，拥有蓝绿色的深潭，他甚至还带上了鱼竿。然而，他震惊地发现河水浑浊，河岸也被染成了荧光橙色。“看起来就像是污水一样，”他回忆道。当研究团队完成采样，乘坐轻便筏艇顺流而下时，浑浊的橘红色河水依然如故。沿河而下，他们漂过几只瘦骨嶙峋的熊。在一个平静的漩涡处，一只特别瘦弱的熊悄悄靠近，它漆黑的眼睛紧盯着他们，那眼神让萨利文感到不安。他心想，这条河流的退化状况是否正在抑制鱼类数量，从而可能减少了熊的食物来源。“我开始觉得我们所看到的就是生态系统崩溃的一个例子，”他说道。
On a later trip, Sullivan took water samples and found strangely high concentrations of iron and heavy metals like cadmium, aluminum, and in some cases, zinc. By then, Sullivan realized the problem extended far beyond the Salmon: Bush pilots reported the same rusty color in dozens of rivers across the region, spanning an area roughly the size of Nebraska. Researchers around the world have begun to document similar changes in waterways near permafrost.
在后来的考察中，萨利文采集了水样，发现铁以及镉、铝等重金属（有些情况下还有锌）的浓度异常高。那时，萨利文意识到这个问题远不止鲑鱼河（Salmon River）一处：驾驶小型飞机（“丛林飞机”）的飞行员报告说，该地区数十条河流也呈现出同样的铁锈色，覆盖的面积大约相当于美国内布拉斯加州的大小。世界各地的研究人员也已开始记录永久冻土区附近水域发生的类似变化。
Environmental scientists have been able to predict some of the many of the changes occurring as the Arctic warms—like species shifting their ranges, tree lines moving north, and animals like beavers and moose appearing in novel places. But rivers rusting, Sullivan says, “has come as a surprise, even to the scientists who are constantly thinking about stuff like this.”
环保科学家们已经能够预测到北极变暖所带来的一些变化——比如物种活动范围的变化、林线向北推移，以及河狸和驼鹿等动物出现在前所未有的地方。但萨利文表示，河流变成铁锈色，“即使是那些经常思考这类问题的科学家们，也对此感到意外。”
Since his first discovery, Sullivan and colleagues have pieced together a theory for why Arctic rivers are turning orange. Their findings prompt concerns about how this transformation may be affecting the region’s already stressed wildlife, and polluting waterways Alaskan communities depend on. But they also stir a deeper unease — the dread of watching a system come undone.
自从萨利文首次发现这一现象以来，他和同事们逐渐形成了一套理论，解释了北极河流为何会变成橙色。他们的发现令人担忧这种变化可能正在影响该地区本已面临压力的野生动物，并污染阿拉斯加社区赖以生存的水源。然而，这些发现也引发了一种更深层次的不安——那种眼睁睁看着一个（生态）系统走向崩溃的恐惧。
METALS ARE LEECHING OUT OF THE PERMAFROST
金属正从永久冻土中渗出
One of Sullivan’s first goals was to discover what contaminants might be causing this change. Across northern Alaska lay rocks that began as shale and sediments on the floor of an ancient ocean. Over time, bacteria formed them into pyrite, often called fool’s gold, a mineral that contains both iron and sulfur. For millennia, these deposits were locked in permafrost, protected from air and water. But as the frozen earth warms, it’s exposing the bedrock, beginning a destructive process that releases sulfuric acid and oxidizes the iron into a toxic orange cocktail that can be carried downstream for miles.
苏利文最初的目标之一是查明造成这种变化的污染物可能是什么。阿拉斯加北部遍布着岩石，它们最初是古老海洋底部的页岩和沉积物。随着时间的推移，细菌将这些物质转化成了黄铁矿（俗称“愚人金”），这是一种同时含有铁和硫的矿物。数千年来，这些沉积物一直被封存在永久冻土中，免受空气和水的侵蚀。然而，随着冻土变暖，它使得基岩暴露出来，由此引发了一个破坏性过程：硫磺酸被释放，并将铁氧化成一种有毒的橙色混合物（toxic orange cocktail），这种混合物可以随水流向下游传播数英里。
When Timothy Lyons, a biogeochemist at the University of California, Riverside, first saw Sullivan’s work at the University of Anchorage, he was struck by how closely this process resembled acid rock drainage. Common near mines, the reaction occurs when rocks containing sulfide minerals are exposed to water and oxygen, producing acid that leaches heavy metals. At a mine, such contamination is concentrated where it can be monitored or contained. But on wild rivers, “there’s simply nothing that can be done, other than fix climate change,” Lyons explains.
当加州大学河滨分校的生物地球化学家蒂莫西·莱昂斯（Timothy Lyons）第一次看到萨利文在安克雷奇大学的研究工作时，他惊讶于这个过程与酸性岩排水现象如此相似。这种反应常见于矿山附近，当含有硫化物矿物质的岩石暴露在水和氧气中时，会产生酸性物质，从而沥滤出重金属。在矿山，这种污染会集中在可以监测或控制的地方。但莱昂斯解释说，在野外河流中，“除了解决气候变化问题，我们根本无能为力。”
In 2023, Sullivan returned to the Brooks Range with Lyons and a large field team to try to better understand the consequences of the metal-laden runoff. “We could actually see the riverbank just basically dripping iron,” Lyons said, recalling where rusty slime oozed into the water. “It looked like snot.” The amount of dissolved metals in the river approached that of industrial wastewater, their analysis found.
2023年，萨利文（Sullivan）和莱昂斯（Lyons）带着一个大型考察队回到了布鲁克斯山脉（Brooks Range），试图更好地了解富含金属的径流所带来的后果。莱昂斯回忆说：“我们确实能看到河岸基本上都在‘滴’铁。”他描述了生锈的黏液如何渗入水中，并说：“它看起来就像鼻涕一样。”他们的分析发现，河水中溶解的金属含量接近工业废水的水平。
An alarming shift in the Arctic’s waterways is now under way: Over 75 rivers across the Brooks Range have recently turned orange, and the Salmon River’s metal concentrations have reached levels toxic to aquatic life. To make things worse, Sullivan explains, they have also identified over 500 acid seeps in the tundra, where minerals are leaching into the surrounding wetlands. These can lower water pH, increase toxicity, and change microbiomes, disrupting the growth and survival of fish and other invertebrates. In a recent PNAS paper, the researchers found that fish habitat on the river has severely degraded as a result. “Our findings might help explain a recent crash in chum salmon, a really important subsistence food,” Sullivan says — potential evidence for his hunch about the bear he met eye to eye, an image of hunger he couldn’t shake.
北极地区的水道目前正发生着令人担忧的转变：布鲁克斯山脉（Brooks Range）有超过75条河流近期已变成橙色，萨蒙河（Salmon River）的金属浓度已达到对水生生物有毒的水平。萨利文（Sullivan）解释说，更糟糕的是，他们还在苔原中发现了500多处酸性渗水点，那里的矿物质正渗入周围的湿地。这些渗水点会降低水体的pH值，增加毒性，并改变微生物群落，从而扰乱鱼类和其他无脊椎动物的生长和生存。在近期发表于《美国国家科学院院刊》（PNAS）的一篇论文中，研究人员发现该河流的鱼类栖息地因此严重退化。萨利文说：“我们的发现可能有助于解释近期狗鲑（chum salmon）数量的骤降，狗鲑是一种非常重要的维持生计的食物”——这也为他关于那只曾近距离遇到的熊的猜测提供了潜在证据，那是饥饿的景象，让他无法忘怀。
THE ARCTIC IS TRANSFORMING IN UNEXPECTED WAYS
北极正发生意想不到的转变
Jean-François Boily, a molecular geochemist at Umeå University in Sweden, who was not involved in the study, says the work is an important step in understanding how the Arctic is changing over a short period of time. Scientists may be witnessing a new concerning feedback loop that could continue to accelerate.
瑞典于默奥大学的分子地球化学家让-弗朗索瓦·布瓦利（Jean-François Boily）没有参与这项研究，但他表示，这项工作是理解北极在短时间内如何变化的重要一步。科学家们可能正在目睹一个新的、令人担忧的反馈循环，这种循环可能会持续加速。
It starts with the frozen ground. In a recent paper, Boily’s showed that minerals dissolve more efficiently in ice than liquid water, upending past assumptions. As ice forms, dissolved substances like iron compounds are expelled from the crystalline structure and become condensed into tiny pockets of liquid water trapped between microcrystals. This dramatically increases the acidity. And every time the ground freezes, fresh minerals are reconcentrated.
这始于冻土。在最近的一篇论文中，Boily的研究表明，矿物质在冰中的溶解效率比在液态水中更高，这推翻了过去的假设。当冰形成时，像铁化合物这样的溶解物质会被从晶体结构中排出，并凝结成困在微晶之间的微小液态水囊。这显著增加了酸度。而且每次地面结冰时，新的矿物质都会被重新浓缩。
As climate change accelerates freeze-thaw cycles, that may trigger a feedback loop, further amplifying river acidity. “All of this, by the way, is irreversible,” Boily says. Once these minerals dissolve, the process cannot easily be undone, because the original deposits cannot quickly reform. “Once it starts, it keeps on going.”
博伊利说，随着气候变化加速冻融循环，这可能会触发一个反馈循环，进一步加剧河流的酸度。“顺便说一句，所有这一切都是不可逆转的。”一旦这些矿物质溶解，这个过程就很难逆转，因为原始的沉积物无法快速重新形成。“一旦开始，它就会持续下去。”
This is not just a problem in Alaska: In western Canada, just across the border from the Brooks Range, researchers have documented the familiar orange tint, while corresponding metal concentrations have popped up in permafrost pockets of Colorado, in mountain ponds in the European Alps, and even downstream of melting glaciers in Peru.
这不仅仅是阿拉斯加的问题：在加拿大西部，紧邻布鲁克斯山脉的边境地区，研究人员已经记录到了那种熟悉的橙色调；与此同时，科罗拉多州的永久冻土区、欧洲阿尔卑斯山脉的山间池塘，甚至秘鲁融化的冰川下游，也都出现了相应的金属高浓度现象。
Researchers suspect similar processes may be occurring elsewhere, though the full global scope is still unknown. Boily says that across Sweden, scientists are finding an increased mobilization of iron. He explains that across the northern hemisphere, “brownification” of water — a process also associated with iron, which ends up increasing dissolved carbon — is slowing growth, fueling toxic algae blooms, and disrupting ecosystems. “What we cannot see with the naked eye is just as important as those spectacular orange rivers,” Boily said, pointing at the many ways climate change is impacting waterways worldwide.
研究人员怀疑类似的过程可能正在其他地方发生，尽管其全球范围尚不清楚。博利表示，瑞典各地的科学家发现铁的活化量有所增加。他解释说，在整个北半球，水的“褐化”——一个也与铁有关，并最终导致溶解碳增加的过程——正在减缓（生物）生长，助长有毒藻类大量繁殖，并破坏生态系统。博利指出，气候变化正以多种方式影响全球水域，并表示：“我们肉眼看不到的东西，与那些引人注目的橙色河流一样重要。”
But so far, researchers are still at the stage of documenting the rusting river problem, and many of the consequences are only beginning to come into focus. For the Alaskan communities who rely on these rivers for drinking water and food, information has been hard to come by. The town of Kivalina, which draws its water from the Wulik River downstream of multiple acid seeps, told National Geographic that the tribal administrator was not yet aware of the problem. Conventional treatment — like that used at large industrial sites, such as the state’s zinc and lead Red Dog Mine — is very expensive, and only effective for a single source.
但到目前为止，研究人员仍处于记录“河流生锈”问题的阶段，许多后果才刚刚开始显现。对于依赖这些河流获取饮用水和食物的阿拉斯加社区来说，获取相关信息一直很困难。基瓦利纳镇（Kivalina），一个从位于多处酸性渗漏点下游的武利克河（Wulik River）取水的小镇，告诉《国家地理》（National Geographic）杂志，其部落管理者尚未意识到这个问题。传统的处理方法——比如该州大型工业场所，如红狗铅锌矿（Red Dog Mine）所使用的那种——成本非常高昂，而且只对单一污染源有效。
Just a few hundred miles away, the Salmon watershed has long been celebrated for its intact wilderness. On a journey down it in 1975, New Yorker writer John McPhee described it as having “the clearest, purest water I have ever seen flowing.” As ecologist Alex Huron wrote in academic journal PNAS recently, the river itself has been protected from the oil and gas development on Alaska’s North Slope, but the burning of fossil fuels has still triggered chemical reactions that may ultimately prove far more damaging than a pipeline spill. It’s an omen, he wrote, “of more cryptic and ongoing environmental change yet to be perceived as warming proceeds.”
仅仅数百英里之外，萨蒙河流域（Salmon watershed）长期以来一直以其完好无损的荒野生态而闻名。1975年，在一次沿河而下的旅程中，《纽约客》杂志作家约翰·麦克菲（John McPhee）形容这里拥有“我所见过流淌的最清澈、最纯净的水。” 正如生态学家亚历克斯·休伦（Alex Huron）最近在学术期刊《PNAS》（美国国家科学院院刊）上所写，这条河流本身一直受到阿拉斯加北坡（North Slope）石油和天然气开发的保护，但化石燃料的燃烧仍然引发了化学反应，这些反应最终可能比管道泄漏造成更大的破坏。他写道，这是一个预兆，“预示着随着全球变暖的持续，更多隐秘且正在发生的、尚未被察觉的环境变化。”
As Lyons warns, “there’s actually no one protected or immune” from the consequences yet to come.
正如莱昂斯所警告的，没有人能真正幸免于未来将至的后果。