60秒科学:Do Rainforests Create Rain?

Rainforests exist because it rains a lot and that makes the forests grow, right? Well, not so fast. What if it’s not the rain that makes the forests—what if it’s the forests that actually generate the rain? That’s the contention¹ of a paper in BioScience Magazine called How Forests Attract Rain.

The article discusses a mostly overlooked hypothesis that, if right, would explain how big rainforests—like the Amazon—actually drive the entire global water cycle.

Here’s the idea. Forests pull in large amounts of water vapor² from surrounding regions and from nearby bodies of water. As the vapor condenses into rain, the local atmospheric³ pressure drops. Which sucks in more water vapor from outside the forest. Which repeats the process. Creating a positive feedback loop. The whole rainforest-water vapor system is called a biotic pump, because the living forest matter is what’s moving the water.

If proven, the biotic-pump hypothesis could explain how big rainforests far from oceans stay so moist. The info would help climate models. And highlight the potential dangers of deforesting large parts of the pump.

—Steve Mirsky

 

1 contention   

n.争论，争辩，论战；论点，主张

参考例句：

• The pay increase is the key point of contention. 加薪是争论的焦点。
• The real bone of contention,as you know,is money.你知道，争论的真正焦点是钱的问题。

2 vapor   

n.蒸汽，雾气

参考例句：

• The cold wind condenses vapor into rain.冷风使水蒸气凝结成雨。
• This new machine sometimes transpires a lot of hot vapor.这部机器有时排出大量的热气。

3 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。