Each winter, an army of ice, fishermen move onto frozen (结冰的) lakes. After digging a hole, through the ice, they all hope to land a tasty dinner. But within just a decade, many dozens of northern lakes are no longer frozen all winter long. That number may jump to thousands within 70 years.
When lakes warm too much, things then worsen in summer. “At sea and on land,many species respond to warming environments by moving to cooler ones,” says R. Iestyn Woolway. He’s a scientist. He says, “In lakes, the only place is deeper, cooler water. However, deeper water is often oxygen-poor.” Soon, he worries, lakes may warm to a situation where there is nowhere for the fish to go.
To find out when this is likely to happen, his team used a computer to model the likely influences of summer heat on 702 lakes throughout a 200-year span, starting from 1901. According to the model, the average (平均的) temperature of lake heatwaves (酷热期) will increase about 3.7 to 5.4 degrees Celsius. And such lake heatwaves will last more than three months by 2099. In 1901, the average was only one week.
That may make the water more comfortable for people to swim in, but many fish and other creatures won’t like it. As water temperatures rise, the number of species will decrease greatly, Woolway says. Weather patterns also will change. That will lead to increased rainfall in some regions and changes of local air temperatures in others, he adds.
Gretchen Hansen is a fisheries ecologist. She points out that each study is important in under-standing how warming lakes are likely to affect fish and other water creatures. “We should be working hard to protect lakes for fish communities and drinking water,” she says. To achieve that, she argues, “We should do everything we can to move towards a CO2-free economy within the next decade.”
12. What will happen to northern lakes in the near future?
A.They will be polluted by garbage. |
B.They will become ice-free in winter. |
C.They will dry up due to climate change. |
D.They will be covered with thick ice and snow. |
13. Why is R. Iestyn Woolway concerned about the warming of lakes?
A.It may cause species to fight with each other. |
B.It can lead to overfishing in northern lakes. |
C.It will change summer into a hotter season. |
D.It may make fish unable to survive. |
14. What does the author use the data to show in Paragraph 3?
A.Lake heatwaves are likely to be more serious. |
B.Global lakes will be influenced by summer heat. |
C.Lake heatwaves can only be noticed during a long time. |
D.Human activities play a role in increasing lake temperatures. |
15. What is Paragraph 4 mainly about?
A.The difficulty in dealing with climate change. |
B.The ways of reducing water temperatures. |
C.The influences of warming water. |
D.The causes of natural disasters. |