Day: July 28, 2021

Circular economics and the $57B e-waste opportunity

Read the full story at GreenBiz.

There is a huge market in being able to divert these materials from landfills, and in being able to extend the asset life of products or the individual components within.

Sharks that hunted near Antarctica millions of years ago recorded Earth’s climate history in their teeth

Sharks’ teeth carry clues about the oceans they swam in. Christina Spence Morgan

This story is part of Oceans 21
The Conversation’s series on the global ocean opened with five in depth profiles. Look out for new articles on the state of oceans in the lead up to the UN’s next climate conference, COP26. The series is brought to you by The Conversation’s international network.

by Sora Kim (University of California, Merced)

Tens of million years ago, sand tiger sharks hunted in the waters off the Antarctic Peninsula, gliding over a thriving marine ecosystem on the seafloor below.

All that remains of them today is their sharp pointed teeth, but those teeth tell a story.

They’re helping solve the mystery of why the Earth, some 50 million years ago, began shifting from a “greenhouse” climate that was warmer than today toward cooler “icehouse” conditions.

Many theories about this climate shift focus on Antarctica. There is geologic evidence that both the Drake Passage, which is the water between South America and the Antarctic Peninsula, and the Tasman Gateway, between Australia and East Antarctica, widened and deepened during this time as Earth’s tectonic plates moved. The wider, deeper passages would have been necessary for the waters of the major oceans to come together and the Antarctic Circumpolar Current to form. That current, which flows around Antarctica today, traps cold waters in the Southern Ocean, keeping Antarctica cold and frozen.

Map showing temperature differences from very cold around Antarctica to warming beyond the current.
A map of the ocean surface temperature as measured by satellites shows the Antarctic Circumpolar Current, marked by dark lines. Antarctica’s sea ice appears in light blue. Copernicus Marine Services/European Union

The now-extinct sand tiger shark species Striatolamia macrota was once a constant in the waters around the Antarctic Peninsula, and it left exquisitely preserved fossil teeth on what is now Seymour Island near the tip of the peninsula.

By studying the chemistry preserved in these shark teeth, my colleagues and I found evidence of when the Drake Passage opened, which allowed the waters of the Pacific and Atlantic oceans to mix, and what the water felt like at the time. The temperatures recorded in shark teeth are some of the warmest for Antarctic waters and verify climate simulations with high atmospheric carbon dioxide concentrations.

Oxygen captured in very sharp teeth

Sand tiger sharks have sharp teeth that protrude from their jaw to grasp prey. A single shark has hundreds of teeth in multiple rows. Over a lifetime, it sheds thousands of teeth as new ones grow.

Important environmental information is encoded within the chemistry of each tooth and preserved there over millions of years.

For example, the outer layer of a shark’s tooth is composed of an enameloid hydroxyapatite, similar to enamel in human teeth. It contains oxygen atoms from the water the shark lived in. By analyzing the oxygen, we can determine the temperature and salinity of the surrounding water during the shark’s life.

The teeth from Seymour Island show that the Antarctic waters – at least where the sharks lived – stayed warmer longer than scientists had estimated.

Five sizes of shark teeth
Illustrations of sand tiger shark teeth used by the scientists. Christina Spence Morgan

Another clue comes from the element neodymium, which adsorbs and replaces other elements in the outer enameloid of the tooth during early fossilization. Each ocean basin has a distinct ratio of two different neodymium isotopes based on the age of its rocks. Looking at the ratio in the shark teeth allows us to detect the sources of the water where the shark died.

If conditions are stable, the neodymium composition would not change. However, if neodymium composition does change in fossil teeth over time, that indicates changes in oceanography.

Big sharks, warm water

We studied 400 teeth from Seymour Island, from all ages of shark, juvenile to adult, from individuals living between 45 million to 37 million years ago. The combination of tooth size and chemistry yielded some surprising clues to the past.

Some of the teeth were extremely large, suggesting these ancient Antarctic sand tigers were larger than today’s sand tiger shark, Carcharias taurus, which can grow to about 10 feet long.

In addition, water temperatures the sharks lived in were warmer than previous studies involving Antarctic clam shells suggested. It’s possible the difference was between waters closer to the surface and deeper on the sea floor, or the sharks whose teeth we found may have spent part of their lives in South America. Today’s sand tiger sharks track warm waters. They spend summer and early fall between coastal Massachusetts and Delaware, but when waters cool off, they migrate to coastal North Carolina and Florida. Because their teeth continuously form and move forward almost like a conveyor belt, there are some teeth within the jaw that represent a different habitat than where a shark is living. It is possible that the ancient sand tiger sharks also migrated, and when Antarctic waters cooled off, they headed north to warmer waters at lower latitudes.

A shark showing its teeth
A modern sand tiger shark, also known as a grey nurse shark, shows its rows of teeth. Jlencion/Wikimedia, CC BY-SA

The teeth suggested that the sharks’ water temperature then was similar to the water temperatures where modern sand tiger sharks can be found today. Carbon dioxide concentrations were also three to six times higher than today, so scientists would expect amplified temperatures in the regions.

Finally, the neodymium in the fossil sand tiger shark teeth provides the earliest chemical evidence of water flowing through the Drake Passage that aligns with tectonic evidence. The early timing of the Drake Passage opening, but the delayed cooling effect, indicates there are complex interactions between Earth’s systems that affect climate change.

What about their northern cousins?

Sand tiger sharks were found around the world during the Eocene, suggesting they survived in a wide range of environments. In the Arctic Ocean, for example, they lived in brackish waters that are less salty than the open ocean 53 million to 38 million years ago and were much smaller than their southern cousins off Antarctica.

Differences in the saltiness of the tiger sharks’ habitat and size of the sharks also show up in the Gulf of Mexico during this time. That range of environmental tolerance bodes well for the modern sand tiger sharks’ survival as the planet warms once again. Unfortunately, the pace of warming today is faster and may be beyond the sand tiger shark’s ability to adapt.

Sora Kim, Assistant Professor of Paleoecology, University of California, Merced

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Los Reales Landfill to become a zero waste ‘sustainability campus’

Read the full story in the Arizona Daily Star.

Tucson plans to change Los Reales’ landscape while diverting as much waste as possible away from the landfill, which currently takes in about 2,300 tons of solid waste a day.

More power lines or rooftop solar panels: The fight over energy’s future

Read the full story in the New York Times.

The president and energy companies want new transmission lines to carry electricity from solar and wind farms. Some environmentalists and homeowners are pushing for smaller, more local systems.

Coastal ecosystems worldwide: Billion-dollar carbon reservoirs

Read the full story from the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig.

Australia’s coastal ecosystems alone save the rest of the world costs of around 23 billion US dollar a year by absorbing CO2 from the atmosphere. Coastal ecosystems such as seagrass meadows, salt marshes and mangrove forests make an important contribution to mitigating climate change.

A microgrid powered only by solar and batteries points the way to bigger all-renewable grids

Read the full story at Canary Media.

Australia’s Horizon Power and partner PXiSE showed they could power a town without generators. The implications for expanding renewable energy are massive.

Male dragonflies get less flashy in hotter climates

Read the full post at Treehugger.

When temperatures rise, male dragonflies have come up with a decidedly drab but clever way to stay cool. They lose some of the showy pigmentation on their wings, a new study finds. Shedding the dark patches helps regulate their body temperature, but it could make it harder to attract mates and fend off rivals.

Returned merchandise stockpiles as waste: One company’s solution

Read the full story at Waste360.

Each year about five billion pounds of returned merchandise ends up landfilled, according to goTRG’s data.

The Miami, Fla-based organization is among businesses working to keep these materials in circulation. It recovers and manages returns, distressed inventory, and overstock. And it processes these materials to prepare them for resale (and occasionally for first-time sales).

E-waste recycling boost ‘needed to enable transition to net-zero’

Read the full story at edie.

The UK alone is losing at least £13.6m worth of critical raw materials for the net-zero transition, such as lithium, to the linear economy each year, due to a lack of capacity for recycling used electricals and electronics.

Pandemic garbage boom ignites debate over waste as energy

Read the full story from the Associated Press.

America remains awash in refuse as new cases of the coronavirus decline — and that has reignited a debate about the sustainability of burning more trash to create energy.

Waste-to-energy plants, which produce most of their power by incinerating trash, make up only about half a percent of the electricity generation in the U.S. But the plants have long aroused considerable opposition from environmentalists and local residents who decry the facilities as polluters, eyesores and generators of foul odor.

The industry has been in retreat mode in the U.S., with dozens of plants closing since 2000 amid local opposition and emissions concerns. But members of the industry said they see the increase in garbage production in the U.S. in recent months as a chance to play a bigger role in creating energy and fighting climate change by keeping waste out of methane-creating landfills.

%d bloggers like this: