Texas Climate News reports:
Craig Wilson, a senior research associate at [Texas A&M]:
“The severe drought in Texas and much of the Southwest continues to wreak havoc with the number of monarchs, Wilson explains.
“The conditions have been dry both here and in Mexico in recent years. It takes four generations of the insects to make it all of the way up to Canada, and because of lack of milkweed along the way, a lot of them just don’t make it.”
The dry conditions and changing farming practices are hampering the growth of milkweed, the only type of plant the monarch will digest as it makes its trip north. Texas has had dozens of wildfires in the past few years that have hampered milkweed growth, and even though there are more than 30 types of milkweed in the state, the numbers are not there to sustain the Monarchs as they start their 2,000-mile migration trip to Canada. Increased use of pesticides is also adversely affecting milkweed production, he notes.
The latest decrease in monarch butterflies is likely due to a decrease in the milkweed plant (Asclepias) – a primary food for monarchs – from herbicide use in the butterfly’s reproductive and feeding grounds in the U.S., as well as extreme climate variations during the fall and summer affecting butterfly reproduction.
“Extreme climate fluctuations in the U.S. and Canada affect the survival and reproduction of butterflies,” Omar Vidal, director general of WWF-Mexico, said. “The monarch’s lifecycle depends on the climatic conditions in the places where they develop. Eggs, larvae and pupae develop more quickly in milder conditions. Temperatures above 95°F can be lethal for larvae, and eggs dry out in hot, arid conditions, causing a drastic decrease in hatch rate.”