Category Archives: Climate Change

Fewer White-throated Sparrows?

White-throated sparrow (photo from Wikimedia Commons)

19 May 2016

A study seven years ago of bird population trends predicted that climate change would cause most species to decline while a few would increase. In May 2016 I wrote about two species whose fates would be different.

Did this prediction come true?

The maps below show population trends during the non-breeding season. The white-throated sparrow’s trend map for 2007-2020 indicates their abundance dropped 30% in the lower Mississippi area and on the East Coast from New York to North Carolina.

White-throated sparrow non-breeding season population trends 2007-2020 (map from eBird Status and Trends)

Surprisingly, robins experienced regional decline as well, though not in Pittsburgh.

American robin non-breeding season population trends 2007-2020 (map from eBird Status and Trends)

I’ve noticed the drop in white-throated sparrows during their peak migration in early October and mid-to-late April. American robins seem the same as ever here in Pittsburgh

Have you seen a change in white-throated sparrows? Let me know.

(photo from Wikimedia Commons, maps from Cornell University eBird Status and Trends; click on the captions to see the originals)

Pollen Season Gets Worse Every Year

Oak tree in bloom with dangling pollen flowers (photo by Kate St. John)

25 April 2023

If your pollen allergies have gotten worse there’s a good reason for it. A study of North American pollen trends in the last 30 years, led by William R. L. Anderegg, found that pollen season is starting earlier, lasting longer and has higher pollen counts than in the 1990s because of climate change.

Yale Climate Connections reports “In Anderegg’s research on pollen in North America, he saw pollen seasons starting about 20 days earlier than they did in the 1990s” and pollen concentrations increased by 21%. The higher temperatures and carbon dioxide in today’s atmosphere make plants more productive and allergies worse.

Right now in Pittsburgh we are at the height of pollen season. Recurring hot weather, 15+ degrees above normal, caused the oaks to bloom early and pollen so intense that my car turned yellow while parked at Anderson Playground for just an hour last Friday.

Allergy sufferers get a double whammy here because the pollen is added to Pittsburgh’s poor air quality making it particularly dangerous for children and people with asthma and respiratory illness.

A sneeze! Pollen allergies are in for a bad time (photo from Wikimedia Commons)

So, no, you’re not imagining it. Pollen season in North America is bad and is still getting worse.

Scientists predict that average pollen counts in 2040 will be more than double what they were in 2000.

Allergies and climate Change, Harvard School of Public Health
Shaking a pine bough, releases a cloud of pollen (photo from Wikimedia Commons)

Track the pollen count and get the daily forecast at

screenshot of pollen map on 25 April 2023 from


(photos by Kate St. John and from Wikimedia Commons. Screenshot from

Bird Populations Are Trending North with Curious Exceptions

Blue jay (photo by Steve Gosser)

19 April 2023

Last November eBird enhanced their Status and Trends website with cool interactive maps of overall abundance, weekly abundance, population trends and range for nearly 700 species. The population trends are fascinating for two reasons: northward movement and curious exceptions.

Many eastern species are moving their breeding ranges northward. For some it’s starkly obvious that they’re declining in the Southeastern U.S. and increasing in the northern U.S. and southern Canada. Click HERE to see 12 good examples at Cottonwood Post.

Blue jay (Cyanocitta cristata) trends are doubly fascinating. Jays are definitely moving north but with a curious exception in south Florida (why increasing there?). Check out their trends map. Blue is good, red is bad.

Blue jay breeding season population trends 2007-2021 (map from eBird Status and Trends)

Most of Pennsylvania has no change in blue jay abundance but did you see the tiny red dot near Pittsburgh? Where is that decline? Drill into the map on the eBird website using these step-by-step screenshots to guide you.

First, click to Explore all Status and Trends Species on eBird. When you get there, click on Search all species at top right.

screenshot from eBird Explore all Status and Trends

I searched for Blue Jay and got a global map. Click on the [Trends] button. Still too tiny! Click on the + sign at top left to zoom in.

screenshot from eBird Explore all Status and Trends: blue jay

As I zoomed in it became apparent that nothing has changed (i.e. white dots) for blue jays in our region until I found that red dot in Cranberry Township. I hovered my cursor over it and found that blue jays declined there 7.5% from 2007 to 2021. I wonder why…

screenshot from eBird Explore all Status and Trends: blue jay

Meanwhile wood thrushes (Hylocichla mustelina) are the curious exception. Though declining overall their trends map doesn’t show the predictable north-south pattern.

Wood thrush singing (photo by Steve Gosser)

Wood thrushes are declining in the Northeast but increasing in the Southern Appalachians and Alabama. A line of “No Change” runs from approximately Kingston, Ontario to Charlottesville, Virginia. Again, I wonder why…

Wood thrush breeding season population trends 2007-2021 (map from eBird Status and Trends)

Try this for yourself at Explore all Status and Trends Species at eBird.

(photos by Steve Gosser, maps from Cornell University eBird Status and Trends)

Armadillos Are On Their Way to Pennsylvania

Nine-banded armadillo, Santa Ana National Wildlife Refuge, Texas (photo from Wikimedia Commons)

2 April 2023

Here in Pennsylvania when we see a photo of an armadillo we immediately think “Texas,” but we could just as well think Tennessee. Nine-banded armadillos expanded across Tennessee in less than 50 years and by the end of this century, probably sooner, they’ll walk into Pennsylvania. Their current (2006) and future ranges are shown on the map below.

Current and predicted U.S. range of the nine-banded armadillo as of 2006 (map from Wikimedia Commons)

Northward expansion is nothing new for armadillos. Originally from South America, where there are still 20 species, armadillos are part of the Great American Interchange that began 6.7 million years ago when Panama’s land bridge joined North and South America.

The surprising thing about armadillos, though, is that their expansion in the U.S. is nearly ten times faster than the average rate expected for a mammal. How soon they get to Pennsylvania depends on the speed of climate change.

Armadillos have no fur so they are sensitive to cold weather but not all of it. Yale Climate Connections says, “Researchers now believe that armadillos can thrive as long as average minimum temperatures stay above about 17 degrees Fahrenheit.” Pittsburgh has 12 to 32 days each winter that drop below 17, which are probably too many for an armadillo.

But just wait. They’ll get here. This video explains how and why.

video from Backyard Ecolocy on YouTube

Read more about their range expansion at Yale Climate Connections. Learn about armadillos at “Armadillo Online!

(photos and map from Wikimedia Commons, video from Backyard Ecolocy on YouTube; click on the captions to see the originals)

Fewer Hybrid Golden-Wings Thanks to Climate Change

Golden-winged warbler (photo from Wikimedia Commons)

9 January 2023

Golden-winged warblers (Vermivora chrysoptera) and blue-winged warblers (Vermivora cyanoptera) do not look or sound alike but they are well known to hybridize. Because of this ornithologists used to worried that the more numerous blue-winged warbler would force the golden-winged out of existence. Then a 2016 genetic study showed no need to worry — they are very closely related. Now a 2022 study shows that hybridization will become less likely thanks to climate change.

Blue-winged warbler (photo from Wikimedia Commons)

In 2016 we learned that golden-winged and blue-winged warblers are virtually the same bird — 99.97% genetically alike! No wonder they interbreed.

Put another way, the striking visual differences between Golden- and Blue-winged warblers could be considered akin to the differences between humans with and without freckles. Golden-wings and blue-wings have even less genetic differentiation than two subspecies of the Swainson’s Thrush.

All About Birds: Mixed Wing Warblers: Golden-wings and Blue-wings are 99.97 percent alike genetically

Their colors and songs fooled us so we called them hybrids and even named them Brewster’s and Lawrence’s warblers, but the difference is moot to the birds themselves. This illustration embedded from All About Birds, shows their four color phases governed by a dominant/recessive throat-color gene.

If you’re still worried about hybrids, the newest study should put your mind at ease. Entitled “Change in climatically suitable breeding distributions reduces hybridization potential between Vermivora warblers,” it maps the birds’ past and present breeding ranges and models their future under 6 climate scenarios.

Historically (1932-1997) the warblers’ ranges overlapped a lot but by 2012-2021 it was evident they were moving apart. Climate change has moved the golden-wing’s preferred cooler habitat to the north and higher elevations.

The future will move their ranges even more, shown in six scenarios below. The left column shows climate altering emissions peaking in 2040 and then declining. The right column shows emissions continuing to rise through 2100.

Predicted climate suitability for Golden-winged Warblers (yellow) and Blue-winged Warblers (blue) distributions under future climate scenarios (

Unfortunately climate change may force one or both warblers out of existence. Map (d) is the only happy one for both of them but they will disappear as breeding birds in western Pennsylvania.

Don’t worry about golden-winged warbler hybrids. The real problem is climate change.

* Read more about golden-wing and blue-wing relatedness in All About Birds, Living Bird Magazine: Golden-Winged And Blue-Winged Warblers Are 99.97 Percent Alike Genetically.

* See the breeding range study at Wiley Online: Change in climatically suitable breeding distributions reduces hybridization potential between Vermivora warblers.

(photos from Wikimedia Commons, illustration embedded from All About Birds, maps are open access at Wiley Online Library)

Was The Snow Really Deeper When I Was A Kid?

Snow on sweet gum seed balls, Pittsburgh, 17 December 2020 (photo by Kate St. John)

4 January 2023

Rain. Rain. Rain! For two days it’s been raining in Pittsburgh while the high temperature holds at 61oF. Total rainfall will be 1.4 inches, some of which splashed the Cathedral of Learning falconcam.

Rain distorts the Cathedral of Learning falconcam, 3 January 2023

If the weather had been below freezing we’d be looking at 14 inches of snow! I’m glad it isn’t snowing but heavy rain in January got me thinking … Wasn’t the snow deeper when I was a kid?

I grew up in Pittsburgh so my memories of winter apply to where I live today, but are my memories distorted? Using Pittsburgh’s historical snowfall data I compared my 12 years of growing up in Pittsburgh(*) to the most recent 12 years.

The answer is mixed. There was more snow in winter when I was a kid (maximum winter total and highest minimum), but both the highest and lowest snowfall per month both occurred in the recent past — in fact in the same winter of 2020-21.

DescriptionWhen I Was a KidInchesInchesThe Last 12 Winters
Max Winter TotalWinter 1960-6176.063.4Winter 2013-14
Min Winter TotalWinter 1968-6930.422.4Winter 2019-20
Max Monthly TotalJan 196624.627.5Jan 2021
Min Monthly TotalMar 19611.40.1Mar 2021 (same yr as max)
Snow in May?Up to 3.1 inchesNo snow sticks in May

The wild swings in snowfall nowadays mirror the wild swings in temperature.

Remember how bitter cold it was only 11 days ago? Look at the temperature swing then (Christmas Eve 2022) and now (3 January 2023)!

So the answer is Yes & No. Yes, there was more snow in Pittsburgh when I was a kid. But, No, the snow is deeper today on rare occasions.

Curious about snowfall in Pittsburgh? Check out the historical data at NWS Pittsburgh and the Rain to Snow Calculator here.

(*) The span is 12 years because I moved to Pittsburgh when I was 6 years old.

(photo by Kate St. John, maps and data from the National Weather Service)

Disappearing Islands in Chesapeake Bay

High tide at Tangier Island, Virginia, 16 Sept 2016 (photo from Wikimedia Commons)

7 December 2022

Sea level is rising overall about 3 millimeters (0.1 inches) per year due to climate change but Chesapeake Bay is rising even faster than the ocean — as much as 4.6 millimeters per year — because the area is still subsiding after the last Ice Age. Some Chesapeake Bay islands are disappearing.

NASA’s Landsat images of lower Chesapeake Bay from 1999 and 2019 show how much land has been lost in only 20 years. In 1999 there were white sand beaches on the island edges. By 2019 the beaches are gone and Great Fox Island in the center of the image has almost disappeared.

Satellite imagery from “Great Fox is Disappearing” NASA Landsat Image Gallery

The Chesapeake Bay Foundation used to hold in-residence educational programs on Great Fox (also called Fox Island) but in October 2019, with only 34 island acres left, they declared the end of the program. You can see why in the video below.

Just across the Virginia line (at the bottom of the satellite images) is Tangier Island whose land mass has shrunk 67% since the 1850s. Its population shrank as well. By now Tangier has only 345 acres and a population of about 470.

Residents are routinely flooded during the highest tides, pictured at top and below.

Tide water floods yards on Tangier Island, Virginia, Sept 2016 (photo from Wikimedia Commons)
Tide water floods streets on Tangier Island, Virginia, Sept 2016 (photo from Wikimedia Commons)
Tidewater rising in the yards at Tangier Island, Virginia, Sep 2016 (photo from Wikimedia Commons)

A 2015 analysis by the U.S. Army Corps of Engineers predicted that Tangier Island will become uninhabitable within 25-50 years, about mid-century.

The harbor channel, Tangier Island, Dec 2011 (photo from Wikimedia Commons)

Tangier Island will eventually join Great Fox Island under the bay.

For more information see Great Fox is Disappearing at NASA’s Landsat Image Gallery, Wikipedia’s Tangier Island account and this April 2022 NBC News video about Tangier Island.

(photos from Wikimedia Commons and NASA Landsat Image Gallery; click on the captions to see the originals)

More or Less Drought

Ranking the states by average percentage of land in drought, 2000-to-March-2021 (original map from Wikimedia Commons colored by Kate St. John)

27 November 2022

The western U.S. has always been drier than the east but as climate change heats up the planet, drought has become more prevalent. NOAA’s quarterly weather outlooks now include a 3-month drought prediction along with temperature and precipitation forecasts. Some places are more likely to experience drought than others. Which states are more likely? Which are least?

The graphic above is based on Stacker’s article, States With the Worst Droughts, that ranks states by average percentage of land in drought from 2000 to March 2021. Listing the states in order, I grouped them in 10s with darkest Orange indicating the top ten drought states and darkest Green for the 10 wettest. (White = the middle 10)

  • The top state for drought is Arizona. No surprise; it’s a desert.
  • The state with the least drought is Ohio!
  • Georgia and South Carolina stand alone with a lot more drought than their neighbors. Their drought ranking is like Kansas.
  • Hawaii (dark orange) and Alaska (dark green) are at opposite extremes.
Sign at Georgia Tech during the 2008 drought (photo by Mingaling via Flickr Creative Commons license)

As climate change continues to unfold human populations will migrate from less habitable to more habitable locations. In the U.S. we can expect people to move west to northeast in the coming century — from more drought to less.

Wondering about your state’s ranking? Click here for the Stacker article.

NOAA’s 2022-23 winter weather outlook is here.

(at top, base map from Wikimedia Commons, precipitation outlook from NOAA; click on the captions to see the originals)

8 Billion Of Us!

15 November 2022

Today the global human population has reached 8 billion. Lest we think our current growth rate is normal, this graph shows that human population since 10,000 BCE (the start of agriculture) has had a rapid and unnatural growth spurt in the last 70 years.

World population 100,000 BCE to 2021 from Our World in Data

There are so many humans now that we have changed the surface of the Earth, its atmosphere, and its climate just to supply our own needs.

Satellite image of Amazon basin in Bolivia (photo from Wikimedia Commons)
Smog over Mexico City (photo from Wikimedia Commons)

This rate of growth is unsustainable and somehow our species naturally knows it. Population growth will continue but is slowing to a rate of only 1% by the end of this century. Unfortunately there will be 10.9 billion of us by then!

World population growth from Our World in Data

Asia will lead the world in slowing the rate while North America remains relatively stable. (Note: The dip in 2020 is COVID deaths outperforming births.)

Annual population growth by region from Our World in Data

How will we feed 8 to 10.9 billion people? Where will we live when the sea rises and the deserts expand?

It’s a good thing for humans and the planet that our species will stop reproducing quite so fast.

Read more about the slowing growth rate here at Our World in Data.

(photo/ graph links are in the captions. Slideshow photos from Wikimedia Commons in order: Rush hour in Russia, Beach in the Netherlands, Inauguration Day 2009, Crowded exhibit in India, Crowded street, Sao Paulo station, train surfing in Indonesia, crowded Faire in UK, train in Ecuador)

After the Sixth Mass Extinction, What Next?

Guam kingfisher at Bronx Zoo (photo from Wikimedia Commons)

23 October 2022

The archaeological record shows that life on Earth has experienced five mass extinctions in which 70% to 90% of all species disappeared (*). After each extinction life came back.

The extinction rate today indicates we are now in the midst of a sixth mass extinction. Scientists predict that due to human pressure, habitat loss and climate change as much as 50% of all species will go extinct by 2100. [1] [2] [3] [4]

Interestingly, the IUCN Red List’s extinction ranking shows that birds may not fare as badly as many other organisms. It’s bad news for conifers, frogs and horseshoe crabs, though.

from Wikimedia Commons

In the short term we are helping some species such as the Guam kingfisher (Todiramphus cinnamominus), shown above, already extinct in the wild and in a captive breeding program. In the long term we humans could change our ways to slow or stop species decline. Knowing humans, it doesn’t look good. We can mourn the future but if we take a very long view there is hope.

After the sixth mass extinction, what will happen next?

David Quammen‘s article Planet of Weeds in Harper’s October 1998 described the current mass extinction and asked eminent paleontologist David Jablonski “What next?” The article is quoted below.

Among the last questions I asked Jablonski was, What will happen after this mass extinction, assuming it proceeds to a worst-case scenario?  If we destroy half or two thirds of all living species, how long will it take for evolution to fill the planet back up?  “I don’t know the answer to that,” he said.  “I’d rather not bottom out and see what happens next.”  In the journal paper he had hazarded that, based on fossil evidence in rock laid down atop the K-T event and others, the time required for full recovery might be five or ten million years.  From a paleontological perspective, that’s fast.  “Biotic recoveries after mass extinctions are geologically rapid but immensely prolonged on human time scales,” he wrote.  There was also the proviso, cited from another expert, that recovery might not begin until after the extinction-causing circumstances have disappeared.  But in this case, of course, the circumstances won’t likely disappear until we do.

Still, evolution never rests.  It’s happening right now, in weed patches all over the planet. … So we might reasonably imagine an Earth upon which, ten million years after the extinction (or, alternatively, the drastic transformation) of Homo sapiens, wondrous forests are again filled with wondrous beasts.  That’s the good news.

— from Planet of Weeds, by David Quammen, Harper’s Magazine, October 1998

A 2018 study said the recovery time for mammals may be 3 million years, faster than predicted in Quammen’s article.

The future is a long way away but it looks bright. Earth will again have “wondrous forests filled with wondrous beasts.”

Paradise by Gillis d’Hondecoeter, after 1615 (image from Wikimedia Commons)

p.s. In the comments Liz Spence reminded me of a good book about the current mass extinction: The Sixth Extinction: An Unnatural History by Elizabeth Kolbert. This book won the Pulitzer Prize.

(photos and graph from Wikimedia Commons; click on the captions to see the originals)

(*) The Top Five Extinctions in Earth’s history are paraphrased below from the American Museum of Natural History and Wikipedia:

  • 440 million years ago: Ordovician-Silurian Extinction: Small marine organisms died out at a time when life only existed in the oceans. 85% of all species went extinct.
  • 365 million years ago: Devonian Extinction: Many tropical marine species went extinct. 70% of all species lost.
  • 250 million years ago: Permian-triassic Extinction: The largest mass extinction event in Earth’s history. 90% of all species.
  • 210 million years ago: Triassic-jurassic Extinction: The extinction of other vertebrate species on land allowed dinosaurs to flourish. 70% to 75% of all species went extinct.
  • 65 million years ago: K-Pg (or K-T) Extinction: The event that killed the dinosaurs. 75% of all species lost.