San Mateo Almomoloa, Mexico: After a staggering decline over the past two decades, the population of the iconic monarch butterfly is expected to recover following coordinated efforts across North American governments, Mexico's environment minister said on Thursday.

The monarchs, unique among butterflies for the length of their annual migration, are a major tourist draw to the temperate forests of central Mexico, where millions hunker down for the winter.

A guide holds up a damaged and dying butterfly at the monarch butterfly reserve in Piedra Herrada, Mexico. Credit:AP

The black-and-orange insects have been damaged by illegal logging and pesticide use that have destroyed the milkweed plants they depend on for food and to lay their eggs.

As a result, monarch populations plunged almost 90 per cent to a record low of about 35 million two years ago, compared with a peak of roughly 1 billion in the 1990s.