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11095 |
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Date: January 06, 2019 at 15:46:08
From: ryan, [DNS_Address]
Subject: Study: Number of monarch butterflies in California declined by 86% |
URL: https://www.sfgate.com/science/article/monarch-butterflies-california-extinct-decline-13507308.php |
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By Michelle Robertson, SFGATE Updated 7:40 am PST, Sunday, January 6, 2019
If you enjoy watching the annual migration of the western monarch along the California coast you have probably already seen the signs of trouble in recent years. Numbers have declined precipitously over the last two decades and extinction looks increasingly likely.
In 1981 the Xerces Society, a nonprofit environmental organization that focuses on invertebrate conservation, counted more than 1 million western monarchs wintering in California.
The group's most recent count, over Thanksgiving weekend, recorded less than 30,000 butterflies — an 86-percent decline since 2017 alone.
Researchers with the group called the number "disturbingly low" and potentially "catastrophic," in a statement.
MORE BAD NEWS FOR MONARCHS: Study shows climate change's devastating effect
The population of western monarchs in California was already low before the most recent count, having declined by an estimated 97 percent since the 1980s. The species will likely go extinct in the next few decades if nothing is done to save them, a 2017 study by Washington State University researchers found.
The Washington State scientists say that 30,000 butterflies is the average quasi-extinction population size — the number of adult butterflies needed to ensure the persistence of the species. A true minimum population size cannot be determined until the seasonal migration of the western monarch collapses.
The Xerces Society, which conducts annual Thanksgiving and New Year's counts, is not certain why the monarch numbers plummeted substantially this year. Beside the overall downward population trend, the scientists suspect the dismal numbers are related to monarchs arriving nearly a month late to breeding areas in 2018, which leaves aging monarchs more exposed to the elements. The species didn't even make it to its northernmost breeding range in Washington state, where it is typically abundant.
ALSO READ: Scientists say monarchs at-risk for extinction
The organization says there is no substantial evidence of a delayed migration, nor are the butterflies being reported in other parts of the country.
Known for coloring the trees along the West Coast in shades of orange and black, the western monarch is threatened by pesticides, herbicides and the destruction of the butterflies' milkweed habitat along their migratory route, scientists say.
A recent study by University of Michigan and Stanford University researchers added climate change to the list. The study found carbon dioxide from car and factory exhaust — which scientists cite as the primary cause for global warming — reduced a natural toxin in milkweed that feeding caterpillars use to fight parasites.
Western monarch butterflies can typically be seen from November to March in over 300 forested groves along the California coast, with large populations in Riverside and Los Angeles counties, Pacific Grove, Monterey and at Natural Bridges State Beach in Santa Cruz.
Peter Fimrite, a San Francisco Chronicle staff writer, contributed to this report.
Read Michelle Robertson's latest stories and send her news tips at mrobertson@sfchronicle.com.
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[11105] [11100] [11096] [11097] |
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11105 |
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Date: January 15, 2019 at 14:17:40
From: Awen, [DNS_Address]
Subject: magnetic pollution? |
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Have they accounted for a shifted migration route.
Reason I ask is that in our area between about the
mid 1990s to last year, the numbers dropped and I
used to see maybe 2-5 per year.
Last year the trees in my hometown were covered with
them.
I'm not saying that as a contradicting or good or
reassuring thing. Altered migration patterns don't
necessarily mean adaptation, if they can't figure
out where to go, they might be dying en route.
Pesticides are a definite problem. I also wonder
about our electronic pollution (34; 4g; 5g etc,
wifi....) Though if we want to speculate on this,
the wandering in our magnetic poles might be a
factor as well....
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11100 |
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Date: January 10, 2019 at 16:35:16
From: georg, [DNS_Address]
Subject: Re: insect populations are plumeting all over the world (NT) |
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11096 |
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Date: January 06, 2019 at 16:40:40
From: Captainj, [DNS_Address]
Subject: Re: Study: Number of monarch butterflies in California declined by... |
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Could it also be linked to the pesticides we are using?
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[11097] |
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11097 |
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Date: January 06, 2019 at 18:47:53
From: ryan, [DNS_Address]
Subject: Re: Study: Number of monarch butterflies in California declined by... |
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Responses:
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