Record low migrations of the widely-recognized monarch butterflies from the northern United States and Canada to the California coast and Mexico have environmentalists worried the orange-colored insects are on the verge of disappearing.

The monarch migration has been documented in books and movies and attracts thousands of tourists to a nature preserve about 100 miles west of Mexico City, as well as a long list of locations in California where tens of thousands of butterflies gather from late fall through winter.

Over the two decades researchers have kept detailed observations of the monarch's winter habitats, the butterflies have at times covered upwards of 45 acres of forest in the Mexican state of Michoacan.

However, last December, it was discovered only 1.6 acres of the forest was occupied by the monarchs during the latest migration study.

"I am deeply saddened by the terrible news," said Karen Oberhauser, a professor at the University of Minnesota who studies the monarchs, during a news conference that marked the release of a report on the monarch migration by the World Wildlife Fund, Mexico's Environment Department and the National Commission for Protected Areas.

"To preserve the monarch migration," Oberhauser implored, we need a groundswell of conservation."

Phil Schappert, a monarch expert in Halifax, Nova Scotia, said "it's past time for Canada and the United States to enact measures to protect the breeding range of the monarchs, or I fear the spiral of decline will continue," according to a story published by the Washington Post.

The monarch population faces a number of challenges along its transcontinental route.

Illegal logging has significantly reduced the butterflies' winter habitat among the oyamel fir trees in Michoacan and in the U.S. and Canada, herbicides used in industrial-scale farming have destroyed many of the the milkweed plants where they lay their eggs.

Monarch counts dipped during the drought years of the 1930s, when the population then was "probably as low or lower than they are right now, and they recovered," said Oberhauser, noting one female monarch can lay between 500 and 1,000 eggs in her lifetime.

Yet, "the problem is that now a lot of the habitat that they had in the past is gone, due to increasing use of this land for agriculture," she said.

Omar Vidal, director of the World Wildlife Fund's Mexico office, said he wants North American leaders to agree on a plan to protect the monarch, which he believes "symbolically unites our three countries."