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主题：全球变暖对pika是否有坏的影响

1. Air Temperatures

First, rising air temperatures put pikas in danger of overheating. Pikas have a thick coat of fur to insulate them from the cold, and round bodies designed to conserve heat. As a result, they can easily get too hot and die, even in temperatures as mild as 26°C. To escape the heat, many pikas have migrated to higher elevations, where it is cooler. However, scientists point out that this is only a temporary solution. Eventually there will come a time when pikas cannot escape the heat.

1. First, it's not necessarily true that pikas will overheat. You have to realize that the temperature can vary considerably across the pike's habitat. Yes, open spaces do get hot, but pikes spend a great deal of time under rocks and inside openings, where it is shady and temperatures are cooler. Some of the reports claiming that temperatures are too high in pika habitats do not take account of temperatures in those shaded areas. Many scientists believe pika populations will remain stable as long as pikas have cooler places where they can take refuge when it gets too hot.

2. Nourishment

Second, pikas gather and store most of the food they need for the winter during the summer. However, collecting food is a strenuous activity that may lead to overheating if the air temperature is high. If summer temperatures increase, pikas may have to limit their food-collecting activities to avoid overheating. As a result, they may not be able to collect and store enough food for the winter.

2. Second, it should still be possible for pikas to collect enough food. The reading passage forgets to mention one important consequence of warmer weather. In warmer weather, animals don't have to eat as much to keep up their internal temperature. So during these warmer summers pikas eat less, which means they need to collect less food for their immediate consumption. That means they can spend more time collecting food. They will store for later, for the winter. As a result, pikas may actually be able to store more food for the winter than in years when it was cool.

3. Snow Melting

Third, during the winter, pikas depend on a thick layer of snow to insulate them from the cold and shield them from freezing rain and wind. However, global warming is causing snow to melt at a faster rate. Because of the increased rate of snow melting, the thickness of the snow layer in pika habitats during the winter has decreased. Without sufficient protection provided by snow, pikas are more exposed to cold and freezing rain in wintertime.

3. Finally, while increased, snow melting can hurt pikas during the winter by exposing them to cold, A faster rate of snow melting also has a positive effect. You see, the warmer climate and the faster rate of snow belting mean that the winter ends earlier. The spring arrives earlier. Fresh plant food becomes available earlier. And the pika populations that have suffered through the harsh winter conditions. Get a chance to recover and start reproducing. In simple terms, increased snow melting makes the winter shorter. Giving the pikers a better chance to replenish the population that has been lost during the winter.