Massive Monarch Butterfly Die-Off
Butterfly population down a record-breaking 59%.
The number of Monarch butterflies wintering in Mexico is down 59% over last year -- the third straight consecutive year of decline and the lowest number since scientists started keeping track over 20 years ago.
Scientists cannot count individual butterflies so they measure the size of the butterfly colonies instead. The area the butterflies occupied was less than 3 acres -- down from a one-time peak of nearly 50.
Scientists have blamed the standard culprits for the demise -- global warming, air pollution, the expansion of farmland -- but no clear cause has been attributed to the steep drop off.