Scientists are amazed at the resurgence in the number of monarch butterflies leaving their winter sanctuaries in Mexico this season, and the hope it is the beginning of a recovery for the species that has been threatened, according to an article on discovery.com.

Officials are not quite ready to lower their concerns about the beautiful orange and black butterflies, but they are saying this could suggest the start of a recovery and they are calling for continued efforts to save the species.

Researchers measure the population by the amount of area the butterflies cover, and this year, the estimators calculate the population to be about 140 million in the mountains of central Mexico.  The monarchs covered 4.01 hectares of pine and fir forests in the 2015-2016 season, more than three time the 1.13 hectares from the previous year’s estimates.  The monarch population hit its all-time low in the 2013-2014 season, at 0.67 hectares.

Experts say the decline in the butterflies was due to illegal logging in the monarchs’ wintering ground in Mexico, and the use of pesticides in the United States and Canada.  Monarchs travel about 2,500 miles from Canada to a mountain reserve in Mexico, where they spend the winter months.  They will normally arrive in their winter grounds in late October and early November and start their return journey to Canada in March.

Dan Ashe, director of the US Fish and Wildlife Service, said he was encouraged by the news and it was an indication that we do have the ability to save the monarchs and along with them, one of the most remarkable wildlife migrations noted on the planet.  The US has restored over 100,000 hectares of fields without pesticides in the effort to save the monarchs, at a cost of about $20 million.  He adds there is still much to do and it will take a coordinated citizen effort on a scale never before seen.

Ashe is encouraging people in the US to plant more milkweed, a plant on which the monarchs feed as an assist to the butterflies.  “A simple stand of native milkweed can make every backyard, school, community center, city park and place of worship a haven for breeding or migrating monarchs, and together we can bring about the greatest citizen conservation victory of our generation,” according to Ashe.

The goal of the Fish and Wildlife Service is to reach a population of 250 million monarchs by the year 2020.