Why should we care about nature? Should we care about it for its own sake — or for our sake, because it happens to make us happy or healthy? These might not seem like the brightest questions. Few people need convincing that the destruction of rain forests, the mass extinction of species and the melting of the ice sheets in Greenland would all be very bad things. Do we really need to list the reasons?

We do. After all, in many regards our species has already kissed nature goodbye, and we are better off for it. Technology has come to be more diverse than the biosphere. In 1867, Karl Marx observed that there were 500 types of hammer made in Birmingham, England. In 1988, Donald Norman, a cognitive scientist at the University of California, San Diego, suggested that the average American encounters 20,000 different kinds of artifacts in everyday life, which would be more than the number of animals and plants that we can distinguish. And right now, there are about 1.5 million identified species on Earth — impressive, but nothing compared to the more than 7 million United States patents.

This is mostly good news. No sane person would give up antibi­otics and anesthesia, farming and the written word. Our constructed environments shield us from heat and cold and protect us from predators. We have access to food and drink and drugs that have been devised to stimulate our nervous systems in magnificent ways. We sleep in soft beds and have immediate access to virtual experiences from pornography to classical symphonies. If a family of hunter-gatherers were dropped into this life, they would think of it as a literal heaven.

Or maybe not. There is a considerable mismatch between the world in which our minds evolved and our current existence. Our species has spent almost all of its existence on the African savanna. While there is debate over the details, we know for sure that our minds were not adapted to cope with a world of billions of people. The life of a modern city dweller, surrounded by strangers, is an evolutionary novelty. Thousands of years ago, there was no television or Internet, no McDonald’s, birth-control pills, Viagra, plastic surgery, alarm clocks, artificial lighting or paternity tests. Instead, there was plenty of nature. We lived surrounded by trees and water and animals and sky.

This history has left its mark on our minds. Children are irrepressible taxonomizers, placing the world of distinct individuals into categories based on their appearance, their patterns of movement and their presumed deeper natures, and some psychologists have argued that the hard-wired capacity to organize and structure the world is specially adapted to nature: we are natural-born zoologists and botanists. We may also have evolved to get pleasure from certain aspects of the natural world. About 25 years ago, the Harvard biologist E. O. Wilson popularized the “biophilia” hypothesis: the idea that our evolutionary history has blessed us with an innate affinity for living things. We thrive in the presence of nature and suffer in its absence.

Our hunger for the natural is everywhere. It is reflected in art: the philosopher Denis Dutton, in his book “The Art Instinct,” suggests that popular taste in landscape painting has been shaped by preferences that evolved for the African savanna. The appeal of the natural is also reflected in where we most want to live. People like to be close to oceans, mountains and trees. Even in the most urban environments, it is reflected in real estate prices: if you want a view of the trees of Central Park, it’ll cost you. Office buildings have atriums and plants; we give flowers to the sick and the beloved and return home to watch Animal Planet and the Discovery Channel. We keep pets, which are a weird combination of constructed things (cats and dogs were bred for human companionship), surrogate people and conduits to the natural world. And many of us seek to escape our manufactured environments whenever we can — to hike, camp, canoe or hunt.

Wilson emphasizes the spiritual and moral benefits of an attachment to nature, warning that we “descend farther from heaven’s air if we forget how much the natural world means to us.” But there are more tangible benefits as well. Many studies show that even a limited dose of nature, like a chance to look at the outside world through a window, is good for your health. Hospitalized patients heal more quickly; prisoners get sick less often. Being in the wild re­duces stress; spending time with a pet enhances the lives of everyone from autistic children to Alzheimer’s patients. The author Richard Louv argues that modern children suffer from “nature-deficit disorder” because they have been shut out from the physical and psychic benefits of unstructured physical contact with the natural world.

So the preservation of the natural world should be important to us. But how important? The psycholo­gist Philip Tetlock has pointed out that many people talk about the environment as a “sacred value,” protected from utilitarian trade-offs — when the Exxon Valdez spilled nearly 11 million gallons of crude oil, 80 percent of the respondents in one poll said that we should pursue greater environmental protection “regardless of cost.” But he also points to the need to balance environmental concerns with social and political and personal priorities. (Few of these respondents would be willing to hand over their pensions for a more efficient cleanup of the Alaskan shoreline.) And even if we did value nature above everything else, we would still have to decide which aspects of nature we care about the most. You can see this in the debate over the creation of giant wind farms in the ocean or on hillsides. Proponents are enthusiastic about the cheap, green energy; critics worry about the loss of natural beauty and the yearly filleting of thousands of songbirds and ducks.

In the end, an indiscriminate biophilia makes little sense. Natural selection shaped the human brain to be drawn toward aspects of nature that enhance our survival and reproduction, like verdant landscapes and docile creatures. There is no payoff to getting the warm fuzzies in the presence of rats, snakes, mosquitoes, cockroaches, herpes simplex and the rabies virus. Some of the natural world is appealing, some of it is terrifying and some of it grosses us out. Modern people don’t want to be dropped naked into a swamp. We want to tour Yosemite with our water bottles and G.P.S. devices. The natural world is a source of happiness and fulfillment, but only when prescribed in the right doses.

You might think that technology could provide a simulacrum of nature with all the bad parts scrubbed out. But attempts to do so have turned out to be interesting failures. There is a fortune to be made, for instance, by building a robot that children would respond to as if it were an animal. There have been many attempts, but they don’t evoke anywhere near the same responses as puppies, kittens or even hamsters. They are toys, not companions. Or consider a recent study by the University of Washington psychologist Peter H. Kahn Jr. and his colleagues. They put 50-inch high-definition televisions in the windowless offices of faculty and staff members to provide a live view of a natural scene. People liked this, but in another study that measured heart-rate recovery from stress, the HDTVs were shown to be worthless, no better than staring at a blank wall. What did help with stress was giving people an actual plate-glass window looking out upon actual greenery.

All of this provides a different sort of argument for the preservation of nature. Put aside for the moment practical considerations like the need for clean air and water, and ignore as well spiritual worries about the sanctity of Mother Earth or religious claims that we are the stewards of creation. Look at it from the coldblooded standpoint of the enhancement of the happiness of our everyday lives. Real natural habitats provide significant sources of pleasure for modern humans. We intuitively grasp this, and this knowledge underlies the anxiety that we feel about nature’s loss. It might be that one day we will be able to replace the experience of nature with “Star Trek” holodecks and robotic animals. But until then, this basic fact about human pleasure is an excellent argument for keeping the real thing.

Paul Bloom is a professor of psychology at Yale and the author of “Descartes’ Baby.” He is currently writing a book about pleasure.

為什么我們應該要關注大自然？我們關注它，是為了大自然本身呢，還是出于我們自身的理由，因為大自然恰好令我們快樂和健康？也許還有更巧妙的方式來提出這些問題。大部分的人都相信，熱帶雨林的破壞、物種的大量滅絕以及格陵蘭冰層的融化全部都將是非常糟糕的事情。我們還真的需要舉出其中的原因嗎？

的確如此。畢竟，在許多方面，人類已經告別了大自然，并因此而進步。技術手段已經變得比生物圈更為多樣化。1867年，卡爾馬克思注意到，英格蘭伯明翰出產的錘子有500種之多。1988 年，加州大學圣迭戈分校的認知科學家Donald Norman指出，普通美國人在日常生活中接觸到的人工制品多達2萬種，這一數字將超出我們所能分辨出的動植物種類的數量。目前，地球上存在大約150萬種可識別的物種，這一數字令人印象深刻，但是與超過700萬的美國專利的數量相比就不算什么了。

這些大部分都是好消息。心智正常的人是不會放棄抗生素、麻醉術、種植養殖和書面文字的。我們所建造的環境庇護我們免于嚴寒酷暑，保護我們免于食肉動物的侵害。我們可以獲得食物、飲料和藥物，設計發明它們是為了顯著地刺激我們的神經系統。我們睡于高床軟枕之上，并立即可享受到從色情讀物到古典交響樂的虛擬體驗。要是把一個游牧家族投進這樣的生活當中，他們會認為這是不折不扣的天堂。

或者也許并非如此。在人類大腦進化的世界與我們目前的生存狀態之間存在著非常大的不相匹配。人類幾乎花掉其全部的生存時間在非洲的熱帶大草原上，盡管對其中的細節存有爭議，但是我們確定地知道，人類的大腦還不能適應去面對一個有數十億人的世界。周圍都是陌生人的現代城市居民的生活是進化過程中出現的新事物。幾千年前，沒有電視和互聯網，沒有麥當勞，沒有避孕藥、偉哥、整形手術、鬧鐘、人工照明和親子鑒定。有的是大量的自然物，我們的生活圍繞著樹木、溪流、動物和天空。

這段歷史將它的印記留在了我們的大腦中。孩子們是情不自禁的分類者， 將這個世界多種多樣的個體劃分成類別，按照它們的外形、運動的模式和預設的更深層的特性，一些心理學家曾認為，組織并結構化這個世界的固有本能特別適應于大自然：我們是天生的動物學家和植物學家。我們也可能已經進化到可以從自然界的某些方面獲得快樂。大約在25年前，哈佛大學生物學家E. O. Wilson讓“人類天生熱愛大自然”的假說家喻戶曉：即我們進化的歷史用一種內在的對萬物生靈的親近感保佑著我們的想法。有了大自然，我們就興盛，沒有大自然，我們就受苦。

我們對大自然的渴望隨處可見。反映在藝術上：哲學家Denis Dutton在其著作《藝術本能》中指出，大眾對風景畫的喜愛是由對非洲熱帶大草原的經過進化的偏好所形成的。大自然的魅力還反映在我們最想要生活居住的地方，人們喜歡靠近大海、山脈和樹林，甚至在最城市化的環境中，自然之魅反映到房地產的價格上：如果你想看到中央公園樹林的風景，你就要為此花一大筆錢。商業建筑有中庭和植物，我們給病人和愛人送去鮮花，我們回到家里觀看“動物星球”和“發現”頻道。我們養寵物，這些寵物是一種奇怪的混合產物（人們喂養貓貓狗狗是為了有個伴），它們替代了人的作用，且成為人們通向自然界的管道。許多人一旦有機會就會設法逃離我們工業化的環境，去遠足，去露營，去泛舟，去打獵。

Wilson強調對大自然的依附所產生的心靈上和精神上的收益，警告說，“如果我們忘記自然世界對我們的意義有多重要，我們就會消沉下去而離極樂世界的空氣漸行漸遠。”不過，大自然還有更多看得見的好處。許多研究證實，即便是有限量的大自然，如透過一扇窗戶看到外面世界的機會，對你的健康也是有益的。住院病人康復得更快，囚犯生病較為少見。身處荒郊野外可減輕壓力，與寵物共度時光可改善每個人的生活，從患自閉癥的兒童到患老年癡呆癥的病人。作家Richard Louv認為，現代的兒童嘗受“大自然缺乏病”所帶來的痛苦，因為他們被隔絕于與自然界進行的未經結構化的身體接觸所帶來的身心受益。

因此，保護自然世界對我們而言應該是重要的。不過，有多重要呢？心理學家Philip Tetlock已經指出，許多人談及環境將其作為一種“神圣的價值”，環境得到保護是出于功利主義的權衡，當�？松�石油公司的Valdez號油輪泄漏了將近1100萬加侖的原油時，在一次民意調查中有8成的受訪者表示，我們應該“不計成本”地尋求更大程度的環境保護。不過，他還表明了平衡環境問題與社會、政治及個人優先權的需要。（這些受訪者當中很少有人會愿意拿出他們的養老金用在提高阿拉斯加海岸線清理工作的效率上。）而且，即便是我們的確重視大自然超出其他的任何事物之上，我們仍將不得不決定我們最關注的是大自然的哪些方面。在對建造位于海上或山上的大型風力發電場的爭論中，你能明白這一問題。支持者熱衷于廉價綠色能源；而批評者擔心失去了自然風光的美麗，以及每年數千只歌鳥和野鴨的身體碎片。

最后，不加區分的對大自然的熱愛沒有什么意義。自然選擇塑造了人類的大腦被引導朝著增加我們的繁衍生息的大自然方面而發展，如青山綠水和溫馴的動物。在老鼠、蛇、蚊子、蟑螂、單純皰疹和狂犬病毒出現的時候獲得幸福感是毫無益處的。部分自然界令人向往，部分令人驚恐，部分令人厭惡。現代的人類不想光著身子被扔進一片沼澤地，我們希望帶著我們的水壺和GPS設備游歷 Yosemite國家公園。自然界是一個快樂和滿足的源泉，不過只有在按照指定的要求用以適當的劑量的時候。

你也許會認為，技術手段可以提供一個所有不好的部分均被清除掉的大自然的模擬器�？墒�，嘗試著這么做的結果都已被證明是有趣的失敗。比如說，制造一種機器人，孩子們對著它做出的反應就好像它是一只小動物。出現過許多這樣的嘗試，不過，它們都沒有帶來任何接近于對小狗小貓甚或是倉鼠的同樣反應，它們只是玩具，不是伙伴。或者，看看由華盛頓大學心理學家小Peter H. Kahn及其同事所進行的一項最新的研究，他們將50英寸的高清電視機擺放在教職員工的沒有窗戶的辦公室中，提供自然景色的現場畫面。人們喜歡這種安排，但是，另一項研究測量了從壓力情緒復原的過程中心率的恢復情況，結果顯示高清電視機沒什么用，并不比盯著空白的墻面效果更好。真正有助于減輕壓力的是給人們一塊可向外望到真正的綠色植被的真正的平板玻璃窗。

所有的這些給出的都是保護大自然的另類論據。暫時撇開像需要清潔空氣和水源這樣的實際考慮不談，也不去理會有關神圣地球母親的心靈上的擔憂或者人類看管萬物生靈這一宗教主張。讓我們從提升人類日常生活的快樂這個不帶感情色彩的角度來看待保護大自然的問題。真實的自然環境給現代人類帶來了重要的快樂之源。直覺上，我們完全理解這一點，我們對大自然的破壞所感受到的焦慮正是基于這種認識。也許有一天，我們將能夠用電影《星際迷航》中的全息甲板和動物機器人來替代對大自然的體驗，不過就算到了那時，關于人類快樂的這個基本事實仍是我們保護真實的自然世界的一個極佳的理由。

Paul Bloom是耶魯大學的心理學教授，著有《笛卡爾的孩子》一書。他目前正在寫作一本有關快樂的書。