By Larissa Walker, Policy & Campaign Coordinator
January 29th, 2014
We hate to be the bearer of bad news, again, but the 2013-2014 overwintering population numbers for Monarch butterflies in Mexico werejust released this morning, confirming our bleak predictions from a few months ago: the situation is worsening. Last year’s overwintering numbers were an all-time low, with monarchs occupying 1.19 hectares. The area occupied by monarchs this year is a frightening 0.67 hectares – a 44% decline in just the past year. So what does that number actually mean for the population size of monarchs? An average estimate of about 50 million butterflies per hectare would mean there are roughly 33.5 million monarchs – a huge drop from just one year ago. Another way to visualize this downward spiral is to look at the trend of declining overwintering numbers in Mexico throughout the past two decades:
Total annual area occupied by overwintering butterflies from 1994 through 2013, with linear (upper line) and exponential (lower line) regression analyses. The significant decline charted by Brower and colleagues (Brower et al. 2011[i], Fig. 1) through 2011-12 continues through 2013-14.
Etiquetas: Center for Food Safety, en, Monarch butterflies