城市和乡村哪个更宜居？

Whether you’re worried about pollution or stress, you may wonder if leaving your town or city for the countryside may boost not only your happiness, but your health.

不管你是担心污染还是压力，你可能想知道，离开你的城镇或城市去农村，是否不仅能增进你的幸福感，还能促进你的健康。

But evidence-based research that can help us identify the healthiest environments to live is surprisingly scant. As scientists begin to tease apart the links between well-being and the environment, they are finding that many nuances contribute to and detract from the benefits offered by a certain environment – whether it be a metropolis of millions or a deserted beach.

但是，能帮助我们找到最健康的生存环境的实证研究少得令人吃惊。当科学家们开始梳理健康与环境之间的联系时，他们发现，许多细微的差别既可以让某一特定环境带来的益处有所增加，也可以使其有所减损。无论是拥有数百万人口的大都市，还是荒芜的海滩，都是如此。

“What we’re trying to do as a group of researchers around the world is not to promote these things willy-nilly, but to find pro and con evidence on how natural environments – and our increasing detachment from them – might be affecting health and well-being,” says Mathew White, an environmental psychologist at the University of Exeter Medical School.

埃克塞特大学医学院（University of Exeter Medical School）的环境心理学家怀特（Mathew White）说， “我们这群来自世界各地的研究人员不是在毫无章法地倡导什么，而是就自然环境如何影响健康和幸福这个问题，在寻找正反面的证据；人类对环境的态度日益冷漠。”

White and other researchers are revealing that a seemingly countless number of factors determine how our surroundings influence us. These can include a person’s background and life circumstances, the quality and duration of exposure and the activities performed in it.

怀特和其他研究人员发现，似乎有无数的因素决定着我们周围的环境如何对我们产生影响。这包括一个人的背景和生活环境，在该环境中生活质量、持续时间以及在其中进行何种活动等等。

Generally speaking, evidence suggests that green spaces are good for those of us who live in urban areas. Those who reside near parks or trees tend to enjoy lower levels of ambient air pollution, reduced manmade noise pollution and more cooling effects (something that will become increasingly useful as the planet warms).

一般来说，证据表明绿色空间（green space）对我们这些生活在城市的人是有好处的。居住在公园或树林附近的人往往受益于较少的空气污染、更低的人为噪音和更好的凉爽效应 （随着地球变暖，它会越来越有用）。

Natural spaces are conducive to physical and social activities – both of which are associated with myriad benefits of their own.

自然空间有益于体育和社会活动，这两项活动又会带来相当多的益处。

Time in nature has been linked to reduced physical markers of stress. When we are out for a stroll or just sitting beneath the trees, our heart rate and blood pressure both tend to go down. We also release more natural ‘killer cells’: lymphocytes that roam throughout the body, hunting down cancerous and virus-infected cells.

长时间身处大自然中，能够减轻压力造成的身体不适。当我们外出散步或只是坐在树下时，我们的心率和血压都会下降。我们还释放出更多的天然“杀手细胞”（killer cells）：即在身体各处游走的淋巴细胞，可以随时捕捉癌细胞和受病毒感染的细胞。

Researchers are still trying to determine why this is so, although they do have a number of hypotheses. “One predominate theory is that natural spaces act as a calming backdrop to the busy stimuli of the city,” says Amber Pearson, a health geographer at Michigan State University. “From an evolutionary perspective, we also associate natural things as key resources for survival, so we favour them.”

研究人员已有一些假设，但他们仍在试图确定这是为什么。“一个占主导地位的理论是，自然空间可让城市的繁忙刺激平静下来”。 密歇根州立大学（Michigan State University）的健康地理学家皮尔森（Amber Pearson）说。“从进化论的观点来看，我们也认为自然界是我们赖以生存的重要资源，所以我们喜欢它们”。

This does not necessarily mean that urban denizens should all move to the countryside, however.

然而，这并不一定意味着城市居民都应该搬到农村去。

City residents tend to suffer from higher levels of asthma, allergies and depression. But they also tend to be less obese, at a lower risk of suicide and are less likely to get killed in an accident. They lead happier lives as seniors and live longer in general.

城市居民往往患哮喘、过敏和抑郁的程度更高。但他们的肥胖程度、自杀风险和事故死亡率都较低。他们在老年时生活更幸福，总体上寿命更长。

Although we tend to associate cities with pollution, crime and stress, living in rural locales may entail certain costs as well. Disease-carrying insects and arachnids can detract from the health factor of that otherwise idyllic cabin in Maine, for example.

尽管我们总是把城市与污染、犯罪和压力联系在一起，但生活在农村地区也可能需要付出一定的代价。例如，携带疾病的昆虫和蛛形纲动物会影响健康，让缅因州（Maine）那种田园诗般的小屋生活没那么浪漫。

In other cases, rural pollution poses a major threat. In India, air pollution contributed to the deaths of 1.1 million citizens in 2015 – with rural residents rather than urban ones accounting for 75% of the victims. This is primarily because countryside dwellers are at greater risk of breathing air that is polluted by burning of agricultural fields, wood or cow dung (used for cooking fuel and heat).

在其它案例中，农村污染构成重大威胁。在印度，2015年空气污染造成了110万印度人死亡——其中75%的受害者是农村居民，而不是城市居民。这主要是因为农村居民更容易吸入因焚烧农田、树木或牛粪（用于做饭燃料和取暖）而受到污染的空气。

Indonesia’s slash and burn-style land clearing likewise causes a blanket of toxic haze that lasts for months and sometimes affects neighbouring countries, including Singapore, Malaysia and Thailand. Meanwhile, smoke pollution from fires lit in South America and southern Africa has been known to make its way around the entire southern hemisphere. (That said, the air in the southern hemisphere is generally cleaner than in the northern hemisphere – simply because there are fewer people living there).

印度尼西亚刀耕火种式的土地清理同样会造成持续数月的有毒雾霾，有时会影响到邻国，包括新加坡、马来西亚和泰国。与此同时，南美和非洲南部火灾产生的烟尘污染已经在整个南半球蔓延开来。（即便如此，南半球的空气通常比北半球的空气要干净——仅仅是因为那里的人更少）。