Fossils formed today will show how mankind disrupted life on Earth


By Mark Williams, Anthony D. Barnosky, Elizabeth Hadley, Jan Zalasiewicz for The Conversation.

Leicester: When we think of fossils it's usually those of dinosaurs, or perhaps the beautiful spiral shapes of an ammonite picked up on the beach during the summer holidays.

We view fossils as ancient remains of the deep past that allow us to wonder at the history of life on Earth, the history of animals that walked or swam many millions of years ago, the history of giant trees that became buried And were crushed to make coal.

Fossils are an essential record of life on Earth that demonstrate long-term stability, punctuated by episodes of rapid or even catastrophic change. Their value is abstract, as a window into the past and social, enabling us to imagine what might happen to life in the future.

Many textbooks describe how fossils form, but few mention the fossils that are being deposited now, at the bottom of a local lake or river, in a peat bog, or along a beach.

The remains of animals, plants, and other life forms that have begun their path to petrification in such places are sometimes referred to as “subfossils”, as if they are halfway to becoming part of the geological record. Be. However we classify them, they record profound changes already taking place across all life on Earth – the biosphere.

On many river banks in Europe, Himalayan balsam and American ragweed grow, and Asian clams and zebra mussels are also found in the river. You might encounter giant African land snails in the Hawaiian Islands, Amur river snails in San Francisco Bay, and Mediterranean mussels on the Atlantic coast of South Africa – and even hippopotamus in Colombia.

displaced by human actions

All of these species, and thousands of others, have been displaced by human actions – sometimes intentionally, as with the hippopotamus, but often unintentionally, as with the clam. This exchange of species has been occurring on our planet for thousands of years.

But from the 16th century onwards, with the exchange of plants and animals between the Americas and Eurasia and Africa, this pattern became more clearly visible. A field of corn in England represents this, as do cows in America.

Although some patterns of change on land and sea are now apparent, even to a casual glance, fossil patterns that reveal the full scale of these changes require painstaking analysis of recent sedimentary layers.

Some organisms, for example soft-bodied worms, leave no physical fossil traces, although their presence can still be inferred from preserved DNA molecules. Other creatures, such as marine mollusks – or hippopotamus – have a real chance of becoming fossils because they have hard skeletons, and they attach to water bodies where sediment layers are deposited.

A typical step change in Earth's history

Many patterns of recent ecological change can be documented in the modern fossil record. For example, in the Hawaiian Islands, layers of sediment contain shells of native snails – and then the layers above show that these snails are being replaced by non-natives, including giant African snails. The pattern is distinctive, as it records the beginning of global homogenization of fauna and flora often associated with striking changes in the abundance of indigenous organisms.

San Francisco Bay is just one example. There, more than 200 non-native species have been introduced since the American gold rush.

They include Amur River clams from East Asia and tiny Trochaemina hadai – unicellular amoeba-like organisms with a shell – brought from the seas around Japan. T. hadai and clams, and many others, boomed in cross-Pacific trade after the end of World War II.

On land, bones of chickens, domestic cattle, sheep, and pigs far outnumber those of wild animals in nascent geological deposits, indicating a major change in the accumulating vertebrate fossil record. Such examples are part of a pattern that is playing out around the world.

To a paleontologist studying the fossil record being formed today, these patterns identify a distinctive step change in Earth's history, driven by us in our increasingly more interconnected and homogenized world.

New paleontology of the 20th and 21st centuries shows that our actions are significantly disrupting the biosphere, just as massive volcanic eruptions and giant meteorite strikes did in the geological past. It's a disgraceful group to join – and only humans have done so with full awareness of their actions.

What our impact on the biosphere will be in the coming decades will be reflected in this new fossil record, which increasingly resembles those ancient, planet-altering disturbances.

(Mark Williams is Professor of Paleobiology at the University of Leicester, Anthony D. Barnoski is Emeritus Professor in the Department of Integrative Biology at the University of California, Berkeley, Elizabeth Hadley is Professor of Earth System Sciences, and the Paul S. and Billy Achilles Professor of Environmental Sciences at Stanford University) The Chair, Jan Zalasiewicz is Professor of Palaeobiology at the University of Leicester)

published May 13, 2024, 10:56 First


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