census

There has been a great deal of interest in the plight of monarch butterflies in this country. Monarchs’ population and migratory habits are closely watched, and many people have been planting milkweed in their gardens to help their caterpillars. But other butterfly species have received much less attention despite the fact that many butterfly populations are in decline.

A groundbreaking new study has provided comprehensive answers about the status of butterflies in America. Over the past 20 years, the contiguous US has lost 22 percent of its butterflies.

The study is based on over 12 million individual butteries counted in 77,000 surveys across 35 monitoring programs from 2000 to 2020. Three hundred forty-two butterfly species in total were analyzed. Thirty three percent showed statistically significant declines while less than 3% displayed statistically significant increases. Overall, 13 times as many species decreased as increased.

Why are butterfly populations crashing? Experts point to a combination of factors: habitat loss as land in converted for agriculture or development, climate change, and pesticide use. It is not clear which factor is most important and may well vary by location. Pesticide use – especially neonicotinoids – has been shown to play a particularly lethal role in studies.

Insects including butterflies play a huge role in supporting life on earth. They pollinate plants, feed birds and many other creatures in the food web. Nature collapses without them. And butterflies are clearly in trouble.

**********

Web Links

See How Butterflies Are Surviving, or Not, Near You

Photo, posted August 9, 2016, courtesy of Rachel Larue/Arlington National Cemetery via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

There are countless ways in which humankind has had disproportionate effects on our planet and most of those effects have been negative. A recent study led by the Weizmann Institute of Science in Israel looked at the total combined weight of various groups of mammals on Earth. The results are that human beings and our domesticated mammals are the overwhelming majority of the total mass of mammals.

We think of large land mammals – elephants, bears, bison, wildebeests, and so on – as adding up to a massive amount of animal matter. The study determined that all wild land mammals put together add up to about 22 million metric tons. Wild marine mammals – such as dolphins and whales – add up to about 40 million tons in total. These sound like pretty big numbers until we look at the human and human-created side of the equation.

The study found that humans weigh about 390 million metric tons, while domesticated mammals – like sheep, cows, and pigs as well as dogs and cats – weigh about 630 million metric tons combined.

All told, wild mammals account for only 6% of all mammals by weight. People and their domesticated animals make up the other 94%. This enormous imbalance is an indication of how profoundly humans have reshaped life on Earth. House cats total twice the weight of African elephants and pigs add up to twice the weight of all wild land animals combined.

The conclusion to draw from the big picture here is that wild animals on Earth are not doing very well. We already knew this from many other perspectives, but this census by weight presents a stark picture of the extent to which we have taken over the planet and its ecosystems.

**********

Web Links

Total Weight of Wild Land Mammals Less Than One-Tenth Weight of All Humans

Photo, posted December 27, 2006, courtesy of Nigel Hoult via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

The American butterfly census

Web Links

Humanity Weighs On The World | Earth Wise

Web Links