Is there hope for the monarch butterfly?

Wednesday, January 7, 2015, 2:28 PM - Clouds of the iconic butterflies once migrated from Canada and the United States to Mexico each year.

But new findings reveal that the monarch population has decreased by 90 per cent in the past two decades, from roughly 1 billion butterflies in the 1990s to just 35 million last year.

The migratory path of the colourful insects is a feat in and of itself.

Each winter, monarchs head south, traveling from Canada and the U.S. to nesting grounds in western Mexico, often covering a total distance of nearly 5,000 kilometres.

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But the journey isn't even the hardest part.  

There are many factors threatening the survival of the species, including deforestation, logging, increased development, agricultural expansion, livestock raising and forest fires.

Experts were hopeful when vast numbers of monarchs arrived in Mexico City this past November. The balmy climate of the mountains west of the city creates the ideal conditions for the delicate creatures.

But the winter forecast threatens to dash any hope of regenerating their declining numbers.

The threat of an unusually cold winter season could lead to another major decline in the monarch's numbers.

Pesticides have also had a significant effect on the population decline. Certain herbicides kill milkweed, the monarch caterpillar's main food source. Plant numbers have dwindled drastically in the midwestern United States, wiping out monarch habitats collectively equal to the size of Texas.

An official census will be released later this month by the Monarch Butterfly Biosphere Reserve in Mexico.

According to the U.S. Fish and Wildlife Service, the decision to list the the iconic black-and-orange butterflies as endangered or threatened species will be made within the next year.