What Happens When A Species Goes Extinct?

On January 4, George, the reclusive Hawaiian snail and the last of his kind, became the first known species to go extinct in 2019. He was approximately 14 years old.

Does the extinction of George’s species matter?

In short, yes. Putting aside the fact that a unique species was wiped out and its loss is irreversible, the disappearance of one species can affect its entire ecosystem, with knock-on effects that threaten the survival of other species.

Julian Heinen, PhD candidate at the Danish Natural History Museum, studies the consequences of island extinctions.

Her team of collaborators focused on fruit-eating island animals, collecting data on extinct birds, mammals and reptiles on 74 islands within 20 archipelagos worldwide.

“We wanted to get the full picture”, Heinan told ScienceNordic, “so we looked at all of the birds, mammals, and reptiles that eat fruit. We also included animals that have recently become extinct.”

The Spix’s Macaw – a blue parrot – was one of the most publicised extinctions in 2018. The species is believed to be extinct in the wild. Credit: Patrick Pleul Via Getty Images

Their findings revealed that almost half of the islands suffered losses of fruit-eating species and, on average, around one-third of the original community on these islands also disappeared.

Animals are not the only living beings influenced by extinctions. Plants are also greatly affected when one or more species of fruit-eating island animals goes extinct.

“This is because many birds, mammals, and reptiles perform a vital service to the plants by eating their fruits, which contain seeds”, says Heinan. “After a while, these seeds will come out again and land somewhere else. This is how many plants move between different areas to make sure their little seeds can grow up in a good spot”.

When fruit-eating animals disappear, trees, in particular, are deprived of an essential mechanism for relocating their seeds to new areas, so they too, face extinction.

When many large fruit-eating animals have gone extinct on the islands, the remaining small animals cannot swallow and disperse the largest fruits so those plants are now at risk of extinction too. Credit: Julia Heinen

As the saying goes, pulling on a loose thread of yarn can unravel an entire sweater. The same concept applies to how plants and animals depend on each other and how microorganisms, land, water, and climate together keep our entire system healthy.

Our current biodiversity crisis – known to some as the Sixth Extinction – is becoming more pressing than ever, as humans activities wipe out many species at a greater rate than before.

Current extinction rates are a thousand times higher than natural background rates, according to a study in Conservation Biology.

“This reinforces the urgency to conserve what is left and to try to reduce our impacts”, says Jurriaan de Vos, lead author at Duke University. “It was very, very different before humans entered the scene.”

References:

De Vos, Jurriaan, Joppa, Lucas, Gittleman, John, Stephens, Patrick, Pimm, Stuart. “A recent increase in global wave power as a consequence of oceanic warming.” August 2014. Conservation Biology.

Heinen, Julia. “Does it really matter if one species goes extinct?” Science Nordic. October 2018. Natural History Museum of Denmark, University of Copenhagen.

Heinan, Julia H., E. Emiel van Loon, Hansen, Dennis M., Kissling, W. Daniel. “Extinction-driven changes in frugivore communities on oceanic islands”. Ecography. October 2017.

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