Monarch butterfly: Courtesy Matt Stratton
Monarch butterfly: Courtesy Matt Stratton

The number of butterflies migrating through California has dropped to a forty year low, according to researchers at the University of California, Davis. One-half of the usual species of butterflies have not appeared this season, and other species have been observed in very low numbers. Climate change related to global warming and habitat destruction may be the cause.

Global warming is the increase in the Earth’s average temperature over recent decades primarily attributable to human activities.

Habitat destruction is a change in land use in which one habitat is replaced with another. The plants and animals which previously used the site are destroyed or displaced in the process.

A mild winter in Northern California has caused many species to not end their winter dormancy at the right time. This means that many butterflies emerged too late in the season. The proper climate for breeding was disrupted by a wet spring.

In Southern California, an unusually dry desert left little food for caterpillars of some species to feed on. A late snow in the Sierra Nevada may have killed many insects used for food.

Some species of butterflies that breed several times a year may rebound from these events, but for other species the effects may be devastating for up to a decade.

Read the original press release here.

Your Comments, Thoughts, Questions, Ideas

Anonymous's picture
Anonymous says:

Are these the butterflies that eventually wind up in Mexico? I heard there was a problem in Mexico too a while back. Might the problem go back to last year's crop in Mexico?\r\n\r\nButterfly lover...

posted on Thu, 05/18/2006 - 9:18am
Anonymous's picture
Anonymous says:

How do they know how many butterflies there are? Do they sample the population? Could they have chosen different migration routes?

posted on Thu, 05/18/2006 - 11:12am
Anonymous's picture
Anonymous says:

What dangers are there in losing butterflies? Of course, other than they are pretty to look at. I guess I want to know why we should be concerned with butterfly populations being devestated.

posted on Fri, 05/19/2006 - 10:01am
Anonymous's picture
Anonymous says:

Butterflies are important because they are food for birds, right? And no butterflies means no birds, which means insects will overpopulate and destroy crops, and that means no food for us!

posted on Fri, 12/29/2006 - 1:49pm
Anonymous's picture
Anonymous says:

I didn't know that half of the butterflies did not appear in Mexico.

posted on Fri, 07/07/2006 - 12:44pm
KT's picture
KT says:

My favorite butterfly is the monarch butterfly because it is really pretty and cool...

posted on Sun, 07/23/2006 - 4:13pm
andrea's picture
andrea says:

ilike them to

posted on Thu, 09/13/2007 - 2:14pm
Anonymous's picture
Anonymous says:


posted on Sun, 07/23/2006 - 6:36pm
Anonymous's picture
Anonymous says:

I disagree with that cause they just leave for the winter and then and why wouldnt they not like humans...we can feed them.... come on

posted on Mon, 07/24/2006 - 10:42am
Allison's picture
Allison says:

hey, I think you are both really nuts! its got nothing to do with if butterflies like or dislike humans. its because we keep killing them with pollution and the front of our cars.

posted on Sun, 07/30/2006 - 3:27pm
bianca's picture
bianca says:

all i know is that when it to hot or cold they go somewhere where its perfect.

posted on Sun, 07/30/2006 - 4:26pm
Anonymous's picture
Anonymous says:

Interestingly, I did an internet search on "Where have all the butterflies gone?" which led me to this page. I asked the question because this year in Ontario there has been a significant INCREASE of butterflies! I grew up in West Africa where spotting large and gorgeous butterflies drifting through the forest is one of life's most spectacular experiences! When I came to Canada in the 1970's, my "homesickness" for butterflies was soothed by the presence of the Monarachs. But in the past ten years they have dwindled down to almost nothing! In fact, recently, several summers have gone by without a single one coming to my notice! But this year they are here in groups! I've even seen them drifting in the "air" over the congested 401 highway! There is also a noticeable increase in the presence of some of the other smaller and perhaps more common butterflies.

posted on Wed, 08/09/2006 - 2:57pm
Vicky Phillips's picture

all i know is that when it to hot or cold they go somewhere where its perfect.

posted on Thu, 11/05/2009 - 6:29am
bella451001's picture

the butterflies are navigating now due to human activitis one way or the other warming causes the habitat destruction ov these monarchs butterflies. there is a possibility in most of the places where there number have decreased is due to lack of food thats flowers due to lack of rains .........

posted on Sat, 05/01/2010 - 4:55am
Anon's picture
Anon says:

Last year our buddlia bush in worcestershire England was full of butterflies all summer and gave my wife hrs of entertainment and joy . But alass this year the bush is bare with only the occasional visitor. So now she wants to go shopping instead . I wish the butterflies would come back they save me a fortune !!

posted on Sat, 08/07/2010 - 8:55am
Zdenek's picture
Zdenek says:

Dear Sir, unfortunately, there is a simillar situation with butterflies in Central Europe. We are mapping the distribution of btfls, and over 50% of species are declined.
Cause: destruction of biotopes, succession on meadows, extensive management, extensive forestry, european endowment for 100% mowing of meadows and unifictaion of biotops with sharp barrier (wood, field, town, meadow).
Some pictures of lepidoptera, biotopes and protected areas you can see on my website.

posted on Tue, 08/17/2010 - 11:07am
Sandrin's picture
Sandrin says:

Sorry to hear this. I love butterflies. Here is the video of their migration: . But unfortunately not only butterflies face this problem. A lot of animals extinct. Because of people's activity and climate change this appears to be inevitable.

posted on Thu, 01/06/2011 - 7:11am

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