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Danger For North American Biomes | Earth Wise

October 8, 2020 By EarthWise Leave a Comment

Biomes are large, naturally occurring communities of flora and fauna that occupy a major habitat. Examples include several different kinds of forests, grasslands, deserts, and tundra. According to a new study published in the journal Global Change Biology, the resilience of North America’s plant biomes is declining, which means that they are in danger of succumbing to a major extinction event.

The research analyzed over 14,000 fossil pollen samples from 358 sites across North America for the purpose of reconstructing their “landscape resilience”, meaning the ability of the habitats to persist or quickly rebound in response to disturbances.

Some 13,000 years ago, North American ecosystems were destabilized by the one-two punch of the retreat of glaciers at the end of the last ice age along with the arrival of humans. That combination resulted in the extinction of large terrestrial mammals on the continent.

Today, there is a comparable one-two punch created by the rapidly changing climate combined with the dramatic expansion of the footprint of human civilization. The result could again be the demise of some of North America’s biomes. In past eras, forests persisted longer than grasslands, but also took longer to reestablish after disruptions. Overall, only 64% of historic biomes regained their original ecosystem type.

The scientists said that strategic conservation effects could help counteract or slow down the impacts of climate change in the coming decades. In particular, efforts focusing on improving landscape and ecosystem resilience by increasing local connectivity and concentrating on regions with high richness and diversity could have the greatest positive effect.

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North American Biomes Are Losing Their Resilience, With Risks for Mass Extinctions

Photo, posted January 9, 2020, courtesy of Tony Webster via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Fresh Water Under The Sea

July 18, 2019 By EarthWise Leave a Comment

A new survey of the sub-seafloor off the U.S. Northeast coast has revealed the existence of a gigantic aquifer of relatively fresh water trapped in porous sediments lying beneath the salty ocean. This appears to be the largest such formation ever found.

The newly-discovered aquifer stretches from the shore at least from Massachusetts to New Jersey and extends more-or-less continuously out about 50 miles to the edge of the continental shelf. The deposits begin at around 600 feet below the ocean floor and bottom out at about 1,200 feet. If all that water was found on the surface, it could create a lake some 15,000 miles in area. The researchers estimate that the region holds at least 670 cubic miles of fresh water.

Researchers made use of innovative measurements of electromagnetic waves to map the water, which had not been detected by other technologies. It was already known that fresh water existed in places under the sea bottom as a result of oil drilling as far back as the 1970s. But there was previously no hint of the extent of the undersea aquifer.

The water probably was trapped by sediments deposited during the last ice age when sea levels were much lower. But modern subterranean runoff from land sources might also be a contributor.

If water from the aquifer was to be withdrawn, it would still have to be desalinated for most uses, but the cost would be much less than processing ordinary seawater. There is probably no need to do this in the Northeastern US, but the discovery suggests that such aquifers probably lie off many other coasts worldwide and could provide desperately needed water in places like southern California, Australia, the Mideast or Saharan Africa.

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Scientists Map Huge Undersea Fresh-Water Aquifer Off U.S. Northeast

Photo, courtesy of August 1, 2015, courtesy of Michael Vadon via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Examining Sea Level Rise

January 17, 2019 By EarthWise Leave a Comment

It’s no secret that sea levels along the East Coast of the United States are rising. But what’s less known is that the water isn’t rising at the same rate everywhere. As the climate continues to change, some cities may remain dry while others struggle to keep water out.

During the 20th century, sea levels rose about 18 inches near Cape Hatteras in North Carolina and along the Chesapeake Bay in Virginia. During that same time period, New York City and Miami experienced a 12 inch sea level rise, while the waters near Portland, Maine only rose 6 inches. According to a study recently published in the journal Nature, there’s an explanation for this.

The variation is a result of a phenomenon called “post-glacial rebound.” During the last ice age, huge sheets of ice once covered land areas in the Northern Hemisphere, including parts of the Northeast U.S. The weight of the ice weighted down the land like a boulder on a trampoline. At the same time, peripheral lands such as the U.S. mid-Atlantic coast rose up. As the ice melted, the previously weighted-down regions rebounded while the peripheral lands began to sink. While these ice sheets disappeared some 7,000 years ago, this see-sawing of post-glacial rebound continues to this day.

Researchers combined data from GPS satellites, tide gauges, and fossils in sediment with complex geophysical models to produce this comprehensive view of sea level change since 1900. While post-glacial rebound accounts for most of the sea level variation along the East Coast, researchers noted that when that factor is stripped away, “sea level trends increased steadily from Maine all the way down to Florida.”

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Why is sea level rising faster in some places along the US East Coast than others?

Photo, posted August 24, 2014, courtesy of Bill Dickinson via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Carbon Dioxide Marches On

June 21, 2017 By EarthWise

The end of 2013 marked the first occasional observations of carbon dioxide levels in the atmosphere of 400 parts per million. There is nothing magical about that value, but we do tend to focus on round numbers.

Wildlife Corridors

December 28, 2016 By EarthWise

It is widely thought that we are in the midst of the 6th great mass extinction of species on Earth and, unlike the previous ones that were caused by things like asteroid impacts or ice ages, this one is caused by us. Our impact on the climate, on natural resources, on landscapes and habitats, and more, has wreaked havoc on ecosystems across the globe.

[Read more…] about Wildlife Corridors

Carbon Dioxide Continues To Rise

November 7, 2016 By WAMC WEB

Back in December of 2013, a little less than three years ago, Earth Wise reported that the observatory on Mauna Loa in Hawaii had briefly measured carbon dioxide levels greater than 400 parts per million for the first time ever. During the following year, readings above the 400 level started to pop up occasionally elsewhere as well.