Threats to Monarch Butterflies
Less than 20 years ago, the number of Monarch butterflies migrating from Canada to central Mexico to overwinter in trees was estimated to be about 682,000,000 butterflies. Last year, in the winter of 2016, this number was reduced to about 150,000,000 butterflies. The population of Monarch butterflies decreased by 532,000000 butterflies. Why?
Monarchs and Milkweed
The only plant on which the Monarch butterfly lays eggs is the milkweed plant. It is because the caterpillars only feed on the leaves of this plant, which has a toxic chemical that protects Monarchs from predators. Since Monarch caterpillars eat this toxic plant, the taste and color of the adult butterfly is also toxic. So, predators do not eat them.
Milkweed is hard to find in the grasslands and other areas of North America. Less milkweed has caused Monarch butterfly populations to decrease. There are many reasons why milkweed plants are hard to find. One reason is that chemicals are used in farming and planting foods in large fields. Pesticides are chemicals that kill all weeds including milkweed plants, but don't kill corn or soy crops. Another reason is that towns and cities were built where grasslands once were. Instead of milkweed plants, there are now buildings. In cities and towns where there are green areas, like backyards and gardens, people mow (cut) their lawns and plant flowers. Also, people don't like to have weeds in their gardens, so they pull out weeds and use pesticides.
Milkweed is hard to find in the grasslands and other areas of North America. Less milkweed has caused Monarch butterfly populations to decrease. There are many reasons why milkweed plants are hard to find. One reason is that chemicals are used in farming and planting foods in large fields. Pesticides are chemicals that kill all weeds including milkweed plants, but don't kill corn or soy crops. Another reason is that towns and cities were built where grasslands once were. Instead of milkweed plants, there are now buildings. In cities and towns where there are green areas, like backyards and gardens, people mow (cut) their lawns and plant flowers. Also, people don't like to have weeds in their gardens, so they pull out weeds and use pesticides.
Videos
Video from National Geographic Kids:
http://kids.nationalgeographic.com/videos?videoGuid=7a8977e9-a09e-41f9-8c08-498f3c53945b
http://kids.nationalgeographic.com/videos?videoGuid=7a8977e9-a09e-41f9-8c08-498f3c53945b