Many fir trees in Mexico that provide winter homes for monarch butterflies are being killed by bark beetles.
Authorities who have struggled to stop illegal logging in Mexico's famed monarch butterfly reserve now are cutting down thousands of trees themselves to fight an unprecedented infestation of deadly bark beetles.
Biologists and park workers are racing to fell as many as 9,000 infected fir trees and bury or extract infested wood before the orange-and-black monarchs start arriving in late October to spend the winter bunched together on branches, carpeting the trees.
Environmentalists say the forest canopy of tall firs is essential to shelter the butterflies on their annual migration through Mexico, the United States, and Canada. The journey is tracked by scholars and schoolchildren across North America and draws tens of thousands of tourists to the reserve, a U.N. Heritage site.
But freezing rains and cold night air that can kill the monarchs at the high-altitude reserve, so the insects are threatened by a loss of trees, whether by loggers or the bark beetles.
Because the migration is an inherited trait — no butterfly lives to make the round-trip — it's not clear whether they could find another wintering ground.
Experts say that an insecticide is the best way to control the beetles, but that would endanger the butterflies. Instead, park officials are fighting the plague tree by tree.
"It is obvious that in the medium and long term, if we do not act to adapt to the changes, then there could be a serious risk" to the butterflies' migration, says reserve director Rosendo Caro, a forestry expert. "The forest is not going to disappear, but the conditions that make up the right environment for the wintering phenomenon could disappear."