阅读理解Are there any lakes in your hometown? What color are they? Around one-third of the world's lakes are blue according to a study in September 2022. But global warming (全球变暖) may lead them to turn green or even brown.
Yang from Southern Methodist University in the US and his team studied the color of over 85,000 lakes based on satellite photos taken from 2013 to 2020. They found that lakes in places with cooler average summer air temperatures—below 19℃—were more likely to be blue than lakes in places with warmer summers.
According to the research, the color of a lake is in part decided by what's in the water. Water takes in the long wavelengths of sunlight, such as red, orange, and yellow, leaving behind the shorter ones like green and mostly blue. In other words, the cleaner the water is, the bluer it looks. In warmer lakes, phytoplankton (浮游植物) develops easily. It has colors from green to brown and red, giving the lake a different color. If global warming continues, one in ten blue lakes might change color, according to the study.
Lakes serve as an important part of our environment, with their color being one of the oldest ways to decide the health of an ecosystem. Humans get their drinking water from lakes, streams and groundwater. As lakes become greener, people may lose lots of clean water. Because of this, treating the water of such lakes becomes more expensive.
At the same time, blue lakes are also a place for people to relax. Some people, according to Catherine O' Reilly, a scientist from the study, considered blue lakes as a place to set their minds free. As these blue lakes disappear, they may feel sad.
If the temperature keeps rising, the fast growing of phytoplankton in greener lakes will provide lake animals more food. However, an increase in these things may also cause some lake animals to die because there is not enough oxygen for them.