Things are not looking great for the Monarch butterfly. This winter has seen the smallest recorded population of over-wintering Monarchs in Mexico since the records began in 1975. This number is down 59% from the population last year. This graph from Monarch Watch is a chart of recorded over wintering populations in Mexico from the winter of 1994-1995 to present.
So, what is causing this decline? Chip Taylor of Monarch Watch had this to say about the causes of this decline on the Monarch Watch Blog:
"At issue is the cause of the decline and there are a number of factors involved:
1) The loss of milkweeds in row crops (corn and soybeans) due to the adoption of seed varieties genetically modified to tolerate treatment with herbicides. The utilization of these herbicide tolerant crops has all but eliminated milkweeds from these fields.
2) The push for the production of biofuels, which has resulted in the planting of 25.5 million more acres of corn and soybeans than were planted as recently as 2006. This increase has been at the expense of milkweed-containing Conservation Reserve Program land, grassland, and rangeland (as well as other crops).
3) Development, which consumes 6000 acres at day or 2.2 million acres a year.
4) Intensive farming that reduces the area from the edge of the road to the field and management of our roadsides with the use of herbicides (and excessive mowing) which also eliminates milkweeds.
5) Deforestation of the oyamel fir forests – although this has declined over the last few years, the condition of these forests is less than optimal for the survival of overwintering monarchs.
6) Unusual weather – and we had plenty of that during the 2012 monarch breeding season. March was the warmest recorded since nationwide record keeping began in 1895. Warm weather tends allow returning monarchs to spread north rapidly and arrivals of monarchs in areas north of Oklahoma in April are often followed by low temperatures that delay development of the population. In 2012, first generation monarchs moving north-northeast out of Texas arrived much earlier in the northern breeding areas than previously recorded. Historically, low overwintering numbers have followed the early arrival of monarchs. These early establishments were followed by one of the hottest and driest summers in recent decades. Hot and dry conditions probably have the effect of reducing adult lifespan and therefore the number of eggs laid per female over their lifetime."
"Bring Back The Monarchs" created by Monarch Watch and funded by Monarch Watch and the Monarch Joint Venture. |
- Jonathan Neal's Living With Insects Blog has a rather concise look at Monarch Population Decline.
- National Geographic has a similar article entitled Monarch Butterflies Hit New Low.
How to help Monarch populations in your area:
No comments:
Post a Comment
We welcome your participation! Please note that while lively discussion and strong opinions are encouraged, the MOSI BioWorks Butterfly Garden reserves the right to delete comments that it deems inappropriate for any reason. Comments are moderated and publication times may vary.