英语听力:自然百科 北极海冰融化 海象上岸(在线收听

 Extreme ice melting led to thousands of walruses making an unusual gathering on the barrier island in Alaska. Biologists with the U.S. geological survey say the situation can be very dangerous, because walruses are easily startled and can't stampede.

 
Some walruses particularly calves and juveniles can get crushed to death by larger walruses moving about. This aerial video recorded for the USGS was taken from an altitude of 4000 feet near Point Lay, Alaska. Because aircraft could prompt stampede, there is no fly zone. The U.S. fishing wildlife service asks aircraft to maintain a lateral distance of a half mile and a minimum altitude of 1500 feet
 
Walruses forage on the sea floor and unusually use sea ice as a resting platform between feedings. This is the first time tens of thousands of walruses have been seen crowded to gather here. Those similar sightings have been recorded in Russia and another area of northwestern Alaska in years past. 
 
The WWF says arctic sea ice is at the third lowest level in recorded history. USGS is conducting more research to better understand the effects of the walruses haul-out and other changes relate to climate change and sea ice melt.
  原文地址:http://www.tingroom.com/lesson/zrbaike/2010/259146.html