Left: Muir Glacier Melt, Alaska, 1891 (G.D. Hazard). Right: 2005 (Bruce F. Molnia). Images courtesy of the Glacier Photograph Collection and the National Snow and Ice Data Center
Left: Muir Glacier Melt, Alaska, 1891 (G.D. Hazard). Right: 2005 (Bruce F. Molnia). Images courtesy of the Glacier Photograph Collection and the National Snow and Ice Data Center

NASA Shares Striking Before and After Images of a Changing Earth

Left: Muir Glacier Melt, Alaska, 1891 (G.D. Hazard). Right: 2005 (Bruce F. Molnia). Images courtesy of the Glacier Photograph Collection and the National Snow and Ice Data Center
Left: Muir Glacier Melt, Alaska, 1891 (G.D. Hazard). Right: 2005 (Bruce F. Molnia). Images courtesy of the Glacier Photograph Collection and the National Snow and Ice Data Center

Whether it's a selfie-a-day project or the time machine function on Google Street View, few things are as effective at illustrating change over time as photography. NASA's Images of Change online gallery pairs photos taken of various places on Earth with historical images of the same locations to show how things like climate change, natural disasters, and urban growth have altered the landscape of the planet. Some of the images were taken a century apart, while others show drastic changes over a much shorter period of time.

As NASA notes, the images underscore how mutable Earth's surface really is. There are 309 sets of photos, including shots of growing urban sprawl in Cancun, Mexico, the shrinking ice caps of Iceland, and the damaged marshlands surrounding a post-Katrina New Orleans. Check out a few selections below, and head over to the NASA Global Climate Change website to view the full gallery.

Left: McCarty Glacier Melt, Alaska. 1909. Right: 2004. Images courtesy of Glacier Photograph Collection, National Snow and Ice Data Center/World Data Center for Glaciology.

Left: Urban growth, Mexico, 1979. Right: 2009. Images courtesy of the United Nations Environment Programme (UNEP) 


Left: Drought, California, 2011. Middle: 2013. Right: 2014. Images courtesy of the U.S. Geological Survey (USGS) Landsat Missions Gallery / USGS and NASA.

Left: Drying Lake Urmia, Iran, 2000. Middle: 2010. Right: 2014. Images courtesy of the U.S. Geological Survey (USGS) Landsat Missions Gallery / USGS and NASA.

Left: Shrinking ice cap, Iceland, 1986. Right: 2014. Images courtesy of the NASA Earth Observatory

Left: Agricultural growth, Egypt, 1972. Right: 2003. Images courtesy of Earthshots: Satellite Images of Environmental Change

[h/t Architecture and Design]

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Whale Sharks Can Live for More Than a Century, Study Finds
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Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

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Air Quality in American National Parks and Big Cities Is Roughly the Same
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National parks usually have more vegetation, wildlife, and open spaces than urban areas, but the two don't look much different when it comes to air quality. As City Lab reports, a new study published in Science Advances found that U.S. national parks and the nation's largest cities have comparable ozone levels.

For their research, scientists from Iowa State University and Cornell University looked at air pollution data collected over 24 years from 33 national parks and the 20 most populous metro areas in the U.S. Their results show that average ozone concentrations were "statistically indistinguishable" between the two groups from 1990 to 2014.

On their own, the statistics look grim for America's protected areas, but they're actually a sign that environmental protection measures are working. Prior to the 1990s, major cities had higher ozone concentrations than national parks. At the start of the decade, the federal government passed the Clean Air Act (CAA) Amendments in an effort to fight urban air pollution, and ozone levels have been declining ever since.

The average ozone in national parks did increase in the 1990s, but then in 1999 the EPA enacted the Regional Haze Rule, which specifically aims to improve air quality and visibility in national parks. Ozone levels in national parks are now back to the levels they were at in 1990.

Ground-level ozone doesn't just make America's national parks harder to see: It can also damage plants and make it difficult for human visitors to breathe. Vehicles, especially gas-guzzling trucks and SUVs, are some of the biggest producers of the pollutant.

[h/t City Lab]

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