Latest Study: Decline in Monarch Butterfly due to Loss of Milkweed

According to a latest study, there has been a significant decline in the population of monarch butterfly in the eastern part of North America. The decline has been attributed to the loss of milkweed in the breeding grounds of U.S.

The milkweed plant is important since it is the only group of plants on which the monarch butterflies feed. These butterflies also lay their eggs on milkweed and their generations migrate up north from Mexico after laying eggs. When the breeding season ends, they head back thousands of kilometres in order to start the cycle again.

In the recent past, their population in Mexico has been dwindling, the month of December having the lowest recorded numbers.

There is evidence that due to major cultivation in the US corn belt of corn and soybean crops that are genetically modified, a major side effect on the milkweed crops has been observed.

Whenever any genetically modified crops are planted in a field, herbicides are sprayed to wipe out any wild plants. Due to this, the milkweed which grows adjacent to the crops is damaged.

A new study which has been published in the Animal Ecology Journal draws on all the information regarding the logging in Mexico, change in the climatic conditions, prevalence of milkweed and the timing of migration of monarchs. All this data is analysed and the researchers then study the yearly cycle of butterflies.

The findings of this study are also based on the mathematical model which includes many factors which are linked to the decline of butterfly populations and changed the beliefs that were long-held that the drop in population was because of degradation of the Mexican wintering grounds.

US, Canada and Mexico formed a working group in February for the conservation of monarch butterflies. This group also holds discussions on the restoration of milkweeds.