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The Plight Of Monarch Butterflies | Earth Wise

April 20, 2022 By EarthWise Leave a Comment

The monarch butterfly is one of the world’s best-known butterflies and has become the symbol for a whole class of imperiled pollinators. Populations of the iconic orange-and-black insects have declined dramatically in recent decades.

According to the U.S. Fish and Wildlife Service, the eastern monarch population has dropped 88% between 1996 and 2020. Habitat loss, pesticide use, and global climate change are some of the factors driving monarch butterfly population declines.

According to a new study led by scientists at Emory University, monarch butterflies are also increasingly plagued by a debilitating parasite. The study, which was recently published in The Journal of Animal Ecology, reviewed 50 years of data on the infection rate of wild monarch butterflies by the protozoan Ophryocystis elektrosirrha (or O.E.). The research team found that the O.E. infection rate had increased from less than 1% of the eastern monarch population in 1968 to as much as 10% today.

The O.E. parasite invades the gut of monarch caterpillars. If the adult butterfly leaves the pupal stage with a severe parasitic infection, it begins oozing fluids from its body and dies. If the infection is lighter and the butterfly survives, it will not fly as well or live as long as uninfected butterflies.

The study found that one of the contributors to the rise in parasitism is the increased density of monarchs in places where they lay their eggs. The increased density may be due to several factors, including the loss of habitat, the widespread planting of non-native milkweed, and by people raising large numbers of monarchs in confined spaces.

If the infection rate continues to increase, monarch butterfly populations will likely continue to plummet.

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Monarch butterflies increasingly plagued by parasites

Plight of the Monarch

Saving The Monarch Butterfly

Photo, posted September 18, 2008, courtesy of Roy Niswanger via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

More Trouble For Monarchs | Earth Wise

April 14, 2020 By EarthWise Leave a Comment

Monarch butterflies have been in trouble for quite a while and now it seems like their prospects are worse than ever. Multiple surveys of butterfly populations are reporting plummeting numbers.

Western monarch butterflies spend their winters on the central California coast. Months later, they breed in California’s Central Valley and as far north and east as Idaho. But in recent years, it has become harder and harder to find them in their breeding sites.

The Western monarch population was in the millions in the 1980s. In 2017, an annual survey found 200,000 butterflies. In 2018 and 2019, only about 30,000 butterflies were tallied. The loss of Western butterflies in general has come about from a variety of factors, including development, climate change, farming practices and the widespread use of pesticides by farmers and on home and business lawns.

Scientists use the area of land that migrating Monarchs occupy in Mexico to gauge populations. This year, they covered about 7 acres, down from 15 acres in 2019.

Meanwhile, there are also far fewer Eastern monarch butterflies on the opposite side of the country. According to a new population survey, the Eastern monarch has passed the extinction threshold. Its population in 2020 dropped 53% from its already low 2019 numbers. Scientists were expecting lower numbers this year, but they were staggered by their findings.

Butterfly populations are quite variable, so it is possible that the drastic declines this year are not necessarily irreversible, but the news is not good. Researchers and environmental advocates continue to point out that mitigating the climate crisis, reducing pesticide use and planting pollinator gardens could help the butterflies to recover.

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Monarch Butterfly Populations Are Plummeting

Photo, posted September 7, 2017, courtesy of C. Watts via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

2018 Was A Wet Year

March 20, 2019 By EarthWise Leave a Comment

Recent news reports noted that 2018 was the fourth hottest year on record. But the changing climate is not just about temperature. 2018 was also the third-wettest year since 1895, when steady record-keeping began.

Overall, the U.S. recorded 4.68 inches more precipitation in 2018 than the 20th century average. But all that rain and snow was nothing like evenly distributed. The eastern half of the country – especially in places like North Carolina and Virginia – saw record amounts of precipitation, while most of the West remained stuck in drought.

The warming climate leads to precipitation extremes at both ends, meaning that wet places are likely to get wetter and dry places drier. There has been a marked upward trend in short-duration extreme events. For example, Cyclone Mekunu dumped almost 13 inches of rain on Salalah, Oman in 36 hours, more than double its annual average rainfall.

In the southeast and eastern U.S., the trend toward stronger storm events is mostly driven by strong warming of the oceans that fringe their shores. Warm oceans evaporate more water into the air and warm air holds more water than cooler air. Warmer, moisture-laden air acts like a blanket over the land, keeping heat trapped near the ground. Many of the states that had their wettest-ever years also set records for high minimum temperatures – their coldest temperatures were less cold than in the past.

Air temperatures are projected to warm up even further in the coming years and, as a result, many scientists are anticipating that extreme precipitation events will only get more extreme. The pattern of drought in the west and wetness in the east is likely to stay.

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2018 was the U.S.’s third-wettest year on record—here’s why

Photo, posted August 18, 2018, courtesy of Jim Lukach via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.