17. In the last 25 years, the populations of monarch butterflies have reduced by hundreds of millions, according to the Wildlife Services Species report. The black and orange butterflies face insecticides (杀虫剂), loss of milkweed — the plant monarchs lay eggs on and the caterpillars only food source, and habitat(栖息地) loss.
City people making a difference
The smaller population led Field Museum researchers in Chicago to ask:What makes a successful city monarch garden? Hasle, an ecologist at the Field Museum, and Karen Klinger, a geographer, are working to answer that question. Many stops along the monarchs migratory (迁徙) route are taking an all-hands-on-deck way to help out the butterfly, looking for more places where milkweed might grow. "We think, in one way, cities are providing an important place for a lot of insects, "Hasle said. Although the project is still fairly new, there are already some findings. Unlike some other field work
derailed by the COVID-19, the monarch project worked well with more people staying home to watch over their gardens.
According to the weekly reports participants (参与者) sent, more successful gardens had more milkweed and blooming plants or much larger fields. But Klinger said one participant with a single plant watched eggs change all the way to a chrysalis. So, she said, "You just need one plant."
(3) In 2020, during the second season of the study, the number of caterpillars dropped, even though the number of participants more than doubled.
Chicago saw a hot, dry summer in 2020, which may have affected the health of the milkweed plants. In 2021, the reports out of Mexico noted illegal logging (非法砍伐), as well as trees hit by wind and drought. But they also said spring and summer weather conditions were hard for milkweed blossoms (开花) and egg development in the southern U. S. , which limited reproduction.
Not giving up
Now is the perfect time to start planning to plant some milkweed, Hasle and Klinger said.
"The best thing to do is what you can do," Hasle said. " One milkweed plant in a pot on your window board is doing something." "Probably it gives you something to look forward to during the boring winter in Chicago."