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(Irene Tostado / Chicago Park District)

Trees collected through Chicago’s annual holiday tree recycling program are turned into mulch and wood chips for use at Chicago Park District locations. 

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Using the Event Horizon Telescope, scientists obtained an image of the black hole at the center of galaxy M87, outlined by emission from hot gas swirling around it under the influence of strong gravity near its event horizon. (Credits: Event Horizon Telescope collaboration et al.)

From the first-ever image of a black hole to growing concern over climate change, we review some of the year’s top science stories with three of our regular science contributors.

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In this June 15, 2017, file photo, people walk inside the Oculus, the new transit station at the World Trade Center in New York. (AP Photo / Frank Franklin II, File)

The past year’s population growth rate in the United States was the slowest in a century due to declining births, increasing deaths and the slowdown of international migration, according to figures released Monday by the U.S. Census Bureau.

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 In this Dec. 19, 2008, file photo, Jeannie Elias, left, Mary Spencer, and Alison Wagner look for birds in Fayston, Vermont, as they take part in The National Audubon Society’s annual Christmas Bird Count. (AP Photo / Toby Talbot, File)

It’s been 120 years since New York ornithologist Frank Chapman launched his Christmas Bird Count as a bold new alternative to what had been a longtime Christmas tradition of hunting birds.

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Cook County Jail inmate Harris Coteus, standing, fills the biodiesel processor with used vegetable oil from the jail’s officer dining hall. (Evan Garcia / WTTW News)

A small group of detainees are learning how to make biodiesel fuel from reclaimed cooking oil. Hundreds of gallons have so far been produced – and thousands of dollars saved – but officials also touts the program’s rehabilitative value.

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What will the world look like in 20 years if climate change goes unchecked? That’s the premise of “2040 A.D.,” a new collection of short stories that fall under an emerging literary genre known as climate fiction. 

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Prior to its August 2018 launch, NASA’s Parker Solar Probe is packed safely inside the United Launch Alliance Delta IV Heavy rocket payload fairing. (Credit: NASA / Bill Ingalls)

An update on the mission and findings of NASA’s Parker Solar Probe, named after pioneering University of Chicago astrophysicist Eugene Parker, who first proposed the existence of the solar wind in 1958.

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This file photo shows a City of Chicago seal on the side of a salt truck. (t3xt (talk) / Wikimedia Commons)

Two Chicago Park District workers escaped without serious injury after the salt truck they were navigating along an icy lakefront bike path slid into Lake Michigan on Wednesday morning.

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In this May 10, 2019 photo, Brett Adams gestures as he stands where the road to his flooded farm disappears under flood waters, with the farm buildings seen in the background, in Peru, Neb. (AP Photo / Nati Harnik)

This year’s devastating losses are forcing tough decisions about the future of farming in America’s flood plains, even among those skeptical of climate change and humans’ role in it.

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Winter in Chicago, 2013 (David Wilson / Wikimedia Commons)

As winter weather arrives, Chicagoans can seek refuge from the cold at 113 public buildings designated as warming centers. 

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(qimono / Pixabay)

The computer models used to simulate what heat-trapping gases will do to global temperatures have been pretty spot-on in their predictions, a new study found.

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(Maggie Not Margaret / Flickr)

The city’s annual winter overnight parking ban goes into effect early Sunday and continues through April 1, 2020. Here’s what you need to know.

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(Frank McNamara / Flickr)

In 2003, the Illinois Environmental Protection Agency had 1,265 employees. By 2018, that number had fallen to 639, according to a new report that a former IEPA director describes as “both a wake-up call and call to action.”

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In this Nov. 21, 2018, file photo, travelers wait in long lines to pass through a security checkpoint at Denver International Airport in Denver. (AP Photo / David Zalubowski, File)

A storm dumping heavy snow buried highways in Colorado and Wyoming Tuesday. Blizzard and wintry weather warnings extended into the Great Lakes states with the storm expected to bring high winds and snow to Michigan, Minnesota and Wisconsin.

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Scientist Dan Hooper appears on “Chicago Tonight” on Nov. 25, 2019. (WTTW News)

Dan Hooper spends his time contemplating the biggest mystery of all: how the universe came to be. He joins us to discuss his book, “At the Edge of Time: Exploring the Mysteries of our Universe’s First Seconds.”

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In this Monday, Nov. 11, 2019 photo, University of Washington School of Medicine researcher Daniel Promislow, the principal investigator of the Dog Aging Project grant, rubs the head of his elderly dog Frisbee at their home in Seattle. (AP Photo / Elaine Thompson)

Can old dogs teach us new tricks? Scientists are looking for 10,000 pets for the largest-ever study of aging in canines. They hope to shed light on human longevity too.

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