Thewarm coast of California is a place where many western monarch butterflies(帝王-组卷网

阅读理解-阅读单选 0.65 引用8 组卷96

The warm coast of California is a place where many western monarch butterflies(帝王蝶) stay during the cold winter months in the United States. Researchers fear the record low number of monarchs this year could mean the insects are in danger of disappearing in the near future.

Researchers from the Xerces Society said they found fewer than 2,000 orange-and-black butterflies in the yearly count this January. That number showed a big drop from the tens of thousands in recent years. In the 1980s, there were millions of them in trees from Northern California's Marin County to San Diego County near the Mexico border. Last winter, it recorded around 29,000 butterflies in its yearly survey. That was similar to the winter before,when an all-time low of 27,000 monarchs was counted.

Every winter, western monarch butterflies fly south from the northwestern U. S. to California. At the start of November, they arrive in California, often going to the same places and even the same trees. Once warmer weather arrives in March, the monarchs begin their journey back north, stopping somewhere along the route to lay eggs. After egg-laying, the adult butterflies die and the northward migration(迁徙)is continued by their new generations. Thus the monarch butterflies disperse across the country.

Scientists say there are several causes for the extremely low numbers of butterflies in the western states. Homebuilding and chemical use have destroyed milkweed (马利筋) plants along their migratory path. The plants are needed for monarch butterflies to grow and develop, which is the only food monarchs will eat and the only place they will lay their eggs on. Climate change influences the growth of wild plants. And huge wildfires in the west may also have influenced their migration.

Luckily, some public campaigns have encouraged people to plant milkweed in their yards and cities. People can also help scientists collect data, which is critical for developing conservation policies to protect monarchs. Then there are many larger—scale efforts to protect habitats and better manage land for reproduction.

【小题1】How does the author develop paragraph 2?