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Focus to save monarch butterflies

22 June 2007

Threats to the survival of the extraordinary North American monarch butterfly migration will be highlighted next week in a lecture at the Natural History Museum.

Monarch butterflies migrate from northern USA and southern Canada to warmer climes in Mexico each autumn, some travelling more than 2000 miles to reach their destination.

Millions of monarchs make the two- to three-month journey and are a spectacular sight for anyone lucky enough to see it.

In the spring the survivors fly north again, to breed in central and eastern USA and around the Great Lakes in Canada.

Monarch butterflies congregate on a tree trunk. © Lincoln Brower

Monarch butterflies congregate on a tree trunk. © Lincoln Brower

Leading expert

Dr Lincoln Brower has spent over 50 years studying the monarch butterfly and is giving his lecture about this unique biological phenomenon at the Museum on Wednesday 27 June.

Dick Vane-Wright, author of the Natural History Museum's book Butterflies, says 'Lincoln Brower has done far more to understand the biology and conservation needs of the monarch than anyone else, and it will be a great privilege to hear him talk about his life's work.'

Major threats

Brower warns that the mass migration and over-wintering behaviour of the monarch is under threat.

The major threats are large-scale farming, forest degradation and human encroachment.

The large-scale farming using genetically engineered crops in North America eliminates the natural plants and weeds that produce nectar for the adults and food for the larvae.

Illegal logging in the highlands of central Mexico destroys or degrades their winter habitat.

And, humans moving into the coastal areas of California have an impact on the winter habitat used by monarchs in the far west.

Returning home
Lincoln Brower has studied the monarch butterflies for more than 50 years. © Lincoln Brower

Lincoln Brower has studied the monarch butterflies for more than 50 years. © Lincoln Brower

The survival of the monarch butterfly is made more precarious because they over-winter in the same area of forest their great grandparents came from each year.

Brower reports that in his surveys of hundreds of thousands of square kilometres of land, he has not found any new areas where the butterflies have wintered.

When butterflies arrive at badly damaged forests, they seem to stay rather than move on and Brower describes a report of a massive kill-off.

Microclimate protection
Monarch butterflies in the sky. © Lincoln Brower

Monarch butterflies in the sky. © Lincoln Brower

When a forest is thinned rather than totally destroyed, the impact on the butterflies can still be great.

Brower explains how the canopy in undamaged forests produces a microclimate that protects the butterflies from freezing rain and low temperatures. This favourable microclimate is destroyed when a forest is thinned out.

Free lecture

The annual Frederick W. Edwards Lecture on Insect Natural History is organised by the Department of Entomology at the Natural History Museum. On this occasion it has been co-sponsored by The British Enological Society, The Linnean Society of London and the Royal Entomological Society. 

You can still book tickets for this free event by telephoning Esther Murphy on +44 (0)20 7942 5738.

Further Information

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