Whole branches on the Tree of Life are dying, scientists warn: ScienceAlert | Brasarr

Whole branches on the Tree of Life are dying, scientists warn: ScienceAlert

Like the comet that hit the dinosaurs—slower-moving but just as deadly—human activity is chipping away at entire branches of the tree of life, a new study confirms.

“It changes the trajectory of evolution globally and destroys the conditions that make human life possible,” ecologists warn in their new newspaper.

“It is an irreversible threat to the persistence of civilization and the viability of future environments Homo sapiens.”

Over the past few months, the sixth mass extinction has become devastatingly visible.

We have witnessed mass death of seabirds, shores have been littered with shoals of dead fish, and sea lions poisoned by heat-induced algal blooms. Last year, entire populations of penguins failed to breed, and for years now scientists have been studying an alarming reduction in insect life.

So ecologist Gerardo Ceballos of the National Autonomous University of Mexico and Stanford University conservation biologist Paul Ehrlich assessed species extinctions since 1500 CE and compared them over the past 500 million years. They found that we have driven 73 genera of vertebrates to extinction over the past 500 years.

Kindred is the taxonomic classification just above species that brings together the most closely related organisms, like siblings, in a family tree.

This rate is 35 times higher than previous extinctions at the genus level.

Simple schematic representation of the mutilation of the tree of life due to generic extinctions and extinction risks. The lower half of the tree depicted as dead branches shows examples of the extinct genera, and the upper half shows examples of genera at risk of extinction. (Ceballosa & Ehrlich, PNAS2023)

Without human influence, it would have taken 18,000 years for the same number of lineages to have reached their end. Other studies have also found similarly high extinction rates for plants, fungi and invertebrates.

“(The sixth mass extinction) causes rapid mutilation of the tree of life, with entire branches (collections of species, genera, families, and so on) and the functions they perform being lost.” explain the researchers.

The biosphere we live in is extremely interconnected, so the loss of groups of species that play particular functions within their interconnected living tissues can have serious cascading effects.

“We and all other species have evolved together and thrive in a stable tree of life,” Ceballos and Ehrlich sayso the loss of entire ecological functions performed by groups of species also affects us directly.

E.g loss of mosquito-eating frogs has occurred alongside increasing malaria infections in Central America.

What’s more, this gene loss is set to increase, Ceballos and Ehrlich calculate. If we continue on our current trajectory and all currently threatened genera are removed from existence by 2100, the equivalent 300-year loss since 1800 would have taken 106,000 years at normal background levels of extinction.

The most vulnerable species are usually the most unique yet overlooked on the planet. Along with them, we will lose millions of years of evolutionary history that can never be repeated, as well as the loss of critical functions they performed that helped keep all the surrounding biological cycles running like a well-oiled machine.

“(It) required millions of years for evolution to generate functional replacements for the extinct organisms,” Ceballos and Ehrlich Note.

Climate change alone is creating massive destabilization across these systems, spreading critical timing of ecosystem services like pollination, reducing species and allowing new ones to invade more easily.

Another new study have documented these exact processes in an Arizona dryland stream between 1985 and 2019.

“Our study provides evidence of climate change-induced alterations of mechanisms that support long-term community stability, resulting in an overall destabilizing effect,” Junna Wang and team write.

Yet the sixth mass extinction is far greater than the massive cluster catastrophe of climate change alone.

From plastic, to pesticides, habitat loss and poaching, we don’t allow the life around us to take a break.

“Immediate political, economic and social efforts of an unprecedented scale are essential if we are to prevent these extinctions and their societal consequences.” say Ceballos and Ehrlich.

Unlike the comet that eliminated the non-avian dinosaurs, we are conscious of our actions and have the ability to change course.

“What happens in the next two decades will most likely define the future of biodiversity and H. sapiens,” the team finishes.

This research was published in PNAS.

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