The use of pesticides and habitat destruction have lead to the decline of the monarch butterfly population by almost a billion butterflies since 1990. People are starting to see this as a sentinel environmental issue (i.e., when bad things are happening to monarchs they are happening to us too). Do you want to help stop the decline by planting milkweed? The story below details how people can help. The monarch massacre: Nearly a billion butterflies have vanished - The Washington Post
Interesting article David, I seam to recall that deforestation in Mexico is also a major factor in the decline, as the thinning of the trees around roosting sites allowed cold air and frosts into the center of the forest areas the insects roost in, killing the outer ring of butterflies. And of course the less that survive the winter the more likely the decline in the next generation.
