- Created on Wednesday, 12 February 2014 19:35
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By CATHY McCABE
A Brock professor says the monarch butterfly population that is wintering in Mexico has declined by almost 44 per cent in the last year.
Liette Vasseur, biology professor at Brock University, says, “The decline has been very significant.”
Vasseur says butterflies are counted by the number of hectares of butterflies there are in each tree in Mexico.
Vasseur says the decline is caused by “a combination of many factors.” Habitat loss is one factor and so is the decline of milkweed plants.
“The milkweed plant is one of the most important species for the monarch butterfly.”
She says farmers removed it from their farmland because “it was considered a weed and not useful, not realizing the link between the monarch butterflies and the milkweed.”
Vasseur says pesticide use is also a factor in the population decline of the monarchs.
“Farms, to be able to maintain crops, will spray insecticides. Unfortunately, most insecticides are not perfectly specialized
for one insect.”
She says monarchs are found on farmland about the same time farmers spray their fields for other insects, so the butterflies are killed as well.
Vasseur says one of her master’s students studied monarchs over the summer.
She says her student surveyed many fields and found only four
She says the ones found were given to the Butterfly Conservatory in
“By the end, there were two males and two females, so they were able to produce eggs and the eggs were then given to a school in Fonthill.” Vasseur says classes at the school raised the butterflies and then released them.
Vasseur says the issue of protecting the monarchs is not new.
She was part of the North American Commission for environmental
co-operation. She says when the North American Free Trade Agreement was created, “there were also parallel agreements; one for labour and one for environmental co-operation.”
There was a report from 1997 about monarchs. “It was very clear; you can’t just look at that species on one country, it has to be the whole continent because [its migration] crosses all of the three countries.”
Vasseur says the monarch butterfly is “the canary in the mine.” She says, “We have a lot of other migratory species, especially birds that are having the same fate.”
Vasseur says the number of migratory birds is also in decline due to similar factors such as habitat loss and pesticide use.
Vasseur says people can help the butterfly population by planting butterfly gardens, which have plants that butterflies like, especially milkweed. She says another way is to cut down on pesticide use, but adds she knows that this can be “very difficult” for farmers.
She says one solution being used in the United States is to wait until the butterflies have passed through, before spraying the farmland with pesticide.