高考英语 3500 词・语境速记【152】|城市绿化不只是遮阴 ——24 个高考高频词

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Walk through any city on a hot summer day, and you will feel the difference immediately. A street lined with trees feels several degrees cooler than one without them. The shade they provide is real, but it is only the beginning of what trees do for a city. In recent years, scientists have begun to measure the full value of urban trees, and the numbers are surprising. A single mature tree can absorb more than twenty kilograms of carbon dioxide in a year, while releasing enough oxygen for two people to breathe.

Trees also clean the air in ways that most people do not notice. Their leaves capture dust and smoke from the streets. They absorb pollution such as nitrogen dioxide, a gas that comes mainly from car exhaust and can cause coughing and breathing problems. In cities with heavy traffic, trees placed along busy roads can reduce the amount of pollution reaching pedestrians by a noticeable amount. The bark and branches of a tree act like a natural filter, catching particles that would otherwise float in the air we breathe.

Beyond air quality, trees have a direct effect on public health. Studies have shown that people who live near green spaces report lower levels of stress and visit doctors less often. Children who grow up in neighborhoods with trees are more likely to play outside, which helps them stay fit and build stronger immune systems. Even hospital patients recover faster when their windows look out onto trees rather than concrete walls. The effect is not magical. It is biological: being around greenery lowers blood pressure, reduces anxiety, and improves mood.

Cities are starting to take notice. Many now require that new buildings include a certain amount of green space. Some are planting trees along every major road. Others are creating urban forests on unused land. Of course, trees need care. They need water during droughts, and they need to be trimmed so they do not block power lines. But the cost of caring for a tree is small compared to the benefits it provides over its lifetime. A city is more than buildings and roads. It is a place where people live, work, and raise families. The trees that line its streets are not decorations. They are living infrastructure, as essential as the water pipes under the ground and the electricity lines above it. The next time you walk under a tree on a hot day, take a moment to notice the cool air, the cleaner breeze, and the quiet shade. That tree is working for you, even when you are not looking.

在炎热的夏日走过任何一座城市，你会立刻感受到不同。两旁种满树的街道比没有树的街道感觉低好几度。树提供的遮阴是真实的，但这只是树为城市所做的一切的开始。近年来，科学家开始衡量城市树木的全部价值，数字令人惊讶。一棵成熟的树一年可以吸收超过二十公斤的二氧化碳，同时释放出足够两个人呼吸的氧气。树还以大多数人没有注意到的方式清洁空气。它们的叶子捕获街上的灰尘和烟雾。它们吸收二氧化氮等污染物，这种气体主要来自汽车尾气，会引起咳嗽和呼吸问题。在交通繁忙的城市，种在繁忙道路旁的树可以明显减少到达行人的污染量。树的树皮和树枝就像一个天然过滤器，捕获那些原本会漂浮在我们呼吸的空气中的颗粒物。除了空气质量，树对公共健康有直接影响。研究表明，住在绿地附近的人压力水平更低，看医生的次数更少。在有树的社区长大的孩子更可能在户外玩耍，这有助于他们保持健康并建立更强的免疫系统。即使是医院病人，如果窗外能看到树而不是水泥墙，恢复得也更快。这种效果不是魔法，是生理上的：身处绿色环境中能降低血压、减少焦虑、改善情绪。城市开始注意到这一点。许多城市现在要求新建筑包含一定面积的绿地。有些城市在每条主要道路旁种树。还有些城市在闲置土地上建造城市森林。当然，树需要照顾。干旱时需要浇水，需要修剪以免挡住电线。但照顾一棵树的成本，与它一生中提供的好处相比，微不足道。城市不只是建筑和道路，是人们生活、工作、养育家庭的地方。街道两旁的树不是装饰品，它们是活的基础设施，和地下的水管、地上的电线一样重要。下次你在大热天走在树下时，花一点时间感受凉爽的空气、更清新的微风和安静的树荫。那棵树在为你工作，即使你没有在看它。