Mexican authorities are trying hard to crack down on illegal logging in an attempt to protect the Monarch butterfly, but they are fighting a losing battle.

Environmentalists have warned the winter habitat of the butterflies is at risk.

The insects spend their summers in Ontario and the United States. But come fall, they fly 4,000 kilometres south and gather by the millions in the cool, fir forests of Mexico's Michoacan state to spend the winter.

The sight draws about 200,000 people per year to the area. Locals believe the insects are the souls of their departed loved ones.

"They've already destroyed certain areas, and now the illegal loggers are moving into the most pristine forests," said Jordan Honey-Roses of the World Wildlife Fund.

Full canopies are needed to shield the butterflies from rain, cold and sun.

Two years ago, heavy rains and bitter cold killed butterflies by the millions. Scientists blamed the thinning forest canopy for worsening the situation

Deforestation in the region takes place in many forms, from people taking small bundles of wood for cooking fires to truckloads being removed to build things like crates.

The latest crackdown began in November. Authorities have seized more than 400 truckloads of illegal wood so far.

Rogue loggers caught and convicted face jail terms of three to five years. But officials admit the sentences aren't much of a deterrent.

Until the butterfly is worth more economically to locals than the wood, the logging is likely to continue.

As an additional blow to the Monarch, scientists doing climate modeling for the region predict it will get wetter and colder over time. If the butterflies can't adapt or find a new refuge, their risk of extinction increases.