Wildfires in Canada have cast a pall of smoke across a swath of the country and the United States, polluting the air for millions of people, forcing hundreds to evacuate in some places and tainting skies with a brick-red haze.

加拿大的野火使浓烟笼罩了加拿大和美国大片地区，导致数百万民众暴露于受到污染的空气中，在一些地方迫使数百人撤离，天空被染成了砖红色。

The fires have darkened skies from Toronto to Detroit and the East Coast of the United States, leaving New York, Toronto and Washington with the worst air quality in the world on Saturday morning.

从多伦多到底特律，再到美国东海岸，野火已使天空变得昏暗。周六上午，纽约、多伦多和华盛顿的空气质量位列全球最差。

Canadian firefighters have sought to bring the wildfires under control, but days of darkened skies and unhealthy air have raised tensions with the United States. A group of Republican lawmakers criticized Ottawa’s handling of the fires, and President Trump threatened to impose tariffs on Canada to pay for harm caused by the smoke.

加拿大的消防人员一直在努力控制火势，但连续数日的阴霾和有害空气已引发与美国的紧张气氛。一些共和党议员批评加拿大政府应对不力，特朗普总统则威胁要对加拿大征收关税，以弥补烟雾给美国造成的损害。

Prime Minister Mark Carney did not directly address the complaints by Republican lawmakers, but he suggested the United States should do more to combat climate change, which scientists say is a significant factor in creating bigger, longer and fiercer wildfires.

加拿大总理卡尼没有直接回应共和党议员的批评，但他表示，美国应该采取更多措施应对气候变化。科学家认为，气候变化是导致野火规模更大、持续时间更长、火势更猛烈的重要因素。

What is the status of the fires?

目前火势如何？

As of Sunday, nearly 200 wildfires were burning in Ontario, including more than 70 raging out of control. Roughly 1.7 million acres have burned in Ontario, according to the Canadian Interagency Forest Fire Center.

截至周日，安大略省共有近200处野火仍在燃烧，其中70余处完全失控。根据加拿大跨部门森林消防中心的数据，安大略省过火面积已达近70万公顷。

Twelve communities have been evacuated, according to the local authorities, many in northwestern Ontario. About 300 people have been rescued from campsites, Premier Doug Ford of Ontario said in a brief address on Saturday. Indigenous communities have been among the worst affected by the fires.

当地政府称，目前已有12个社区实施撤离，它们大多位于安大略省西北部。安大略省省长道格·福特周六在简短讲话中表示，约有300人从露营地获救。原住民是受野火影响最严重的群体之一。

Most of the evacuees have been taken to Thunder Bay, Ontario, a city on Lake Superior, where the air quality index, though still in the high-risk category, had improved on Sunday.

大多数撤离人员已被安置到位于苏必利尔湖畔的安大略省桑德贝市。虽然当地空气质量仍属于高风险水平，但截至周日已有所改善。

What is Canada doing?

加拿大采取了哪些措施？

Mr. Ford said that there were 155 fire crews at work, with 80 water bombers and helicopters active and 40 additional aircraft ready to deploy.

福特表示，目前共有155支消防队、80架灭火飞机和直升机投入灭火作业，另有40架飞机随时待命。

He also urged people not to return to campsites or homes, so that aircraft were not forced to hold off delivering their loads for fear of harming people on the ground. There was little sign on Saturday that the fires would soon wane.

他还呼吁民众不要返回露营地或住所，以免飞机在投水时顾忌地面人员安全而被迫中断作业。截至周六，火势仍没有明显减弱的迹象。

With Thunder Bay rapidly becoming overcrowded with evacuees, some people have been sent on to Toronto and other locations.

随着桑德贝迅速人满为患，部分疏散人员已被转移到多伦多及其他地点。

Officials, including Eleanor Olszewski, Canada’s minister of emergency management, have defended Canada’s forestry practices. “Warmer, drier weather is becoming more common, increasing wildfire risk in Canada and around the world,” Ms. Olszewski said in a statement on Friday evening. “Northern Ontario and Quebec, for example, received less than 40 percent of normal precipitation this June, with temperatures above historical averages.”

加拿大应急管理部长埃莉诺·奥尔谢夫斯基等官员为该国的林业管理做法进行了辩护。“更加炎热、更加干燥的天气正变得越来越普遍，这增加了加拿大乃至全球发生野火的风险，”奥尔谢夫斯基在周五晚的声明中表示。“例如，安大略省北部和魁北克省今年6月的降水量不足正常水平的40%，气温也高于历史平均水平。”

Why is it so hard to control fires in Canada?

为何加拿大的野火如此难以控制？

Most wildfires in Canada spread across such vast, remote areas that they cannot be fought effectively and are often left to burn, experts say.

专家表示，加拿大大多数野火发生在广袤偏远的地区，消防人员很难有效扑救，通常也只能任其燃烧。

Half of Canada’s wildfires, like the blazes in northern Ontario, burn in sparsely populated areas, said Michael Flannigan, an expert on fire management at Thompson Rivers University in British Columbia. They are most often accessible only by plane.

不列颠哥伦比亚省汤普森河大学消防管理专家迈克尔·弗兰尼根指出，加拿大半数野火（如安大略省北部的此次火情）发生在人口稀少的地区，人们通常只能乘飞机抵达。

Even if it were possible to to deploy firefighters to such remote areas, there is rarely enough time to react. Ignited mostly by lightning, wildfires often spread widely in the highly combustible boreal forest before firefighters can respond within the first critical 30 minutes.

即使在如此偏远的地区能够部署消防员，也往往没有足够的时间作出反应。野火多由闪电引发，在消防员能够于关键的前30分钟内作出反应之前，火势就已在高度易燃的北方针叶林中迅速蔓延。

In the long run, wildfires are considered beneficial because they remove the most flammable material in forests, promoting regeneration. Extinguishing every fire increases risk, as Canadian officials have learned in managing national parks.

从长期来看，野火实际上被认为对森林生态有益，因为它能够清除森林中最易燃烧的物质，为植被更新创造条件。加拿大官员在国家公园管理实践中发现，试图扑灭每一场野火反而会增加未来发生更严重火灾的风险。

What is happening with the smoke?

烟雾情况如何？

The plume of smoke far above the Earth’s surface remained on Saturday, but where and when the pollution would spread was hard to predict, as it can shift considerably by the hour. Amid the elusive forecast, air quality warnings and alerts remained in place across many of the affected states and provinces.

弥漫在高空的烟雾周六仍未消散，但污染向何处扩散及何时扩散均难以预测——因为风向可能每小时都发生显著变化。在预报仍存在较大不确定性的情况下，多个受影响的州和省仍维持空气质量预警。

Summer weather, like thunderstorms, can help clear smoke, but the smoke itself complicates the forecast. It can block sunlight, keeping temperatures lower at the surface and preventing storms from rising and intensifying.

夏季天气中的雷暴有助于驱散烟雾，但烟雾本身又会增加天气预报的难度。烟雾能遮挡阳光，使地表温度保持较低水平，并抑制雷暴的生成与增强。

Scientists estimate that wildfire smoke is linked to tens of thousands of deaths a year, and that human-caused climate change is responsible for a growing share of them.

科学家估计，野火产生的烟雾每年与数以万计的死亡病例有关，而其中越来越多的死亡可以归因于人为造成的气候变化。