Nghe TOEFL

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Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a surprising factor in climate change: the role of forests. Most people think trees are simply carbon sinks, absorbing carbon dioxide and storing it. And that's true, but forests also release carbon when they burn or decompose. What's less known is the impact of forest floor, the layer of leaves and branches on the ground. This organic matter releases carbon as it breaks down, especially in warmer temperatures. In fact, a recent study found that in boreal forests, a five-degree Celsius temperature increase could cause the forest floor to release up to 30% more carbon than it currently does. That's a huge amount. This means that as global temperatures rise, forests might shift from being carbon sinks to carbon sources. But here's the catch: the effect depends on the type of tree. For example, pine needles decompose more slowly than broadleaf litter, so forests with pines are less affected. So, in a sense, the very forests we rely on to absorb carbon may release it back, accelerating warming. This feedback loop is something we need to consider in climate models.