The passenger pigeon’s extinction has become a poignant symbol of humanity’s shameful over-exploitation of the environment; but its return could signal a new era of environmental change, as humans seek to do the impossible: resurrect species from the dead.
Imagine this: a flock of birds so large it blocks out the sun for many days. Billions of birds migrating through the sky. 19th century pioneers pushing their way through the mighty Appalachian Mountains in the Eastern United States would have been greeted with this majestic sight. It is estimated there were originally 3 to 5 billion of these birds in America, constituting up to 40% of all bird biomass on the continent.
What if I told you that this species of bird is now extinct? It may seem hard to believe that such a numerous bird could disappear forever. It is unlikely to surprise you however, that the culprits of this were us humans.
The species in question was the passenger pigeon (Ectopistes migratorius) which once thrived along the entirety of the Eastern Seaboard of North America. But the bird was easy prey for the influx of Euro-Americans pouring towards the Mississippi River. Ironically, their abundance proved to be their undoing. They were incredibly easy to shoot, shotgun pellets could kill up to fifty birds at a time. Trains would be packed full of pigeon pelts, transporting the bird to be sold in markets daily. In addition, oak and pine forests were cut down to make way for farmland, depriving the birds of their main nesting grounds. This proved to be the last straw. Martha, the last of her kind, died in Cincinnati Zoo in 1914, marking the senseless demise of this species.
They called it the ‘taming of the west’; although on ecological terms it might as well have been called the destruction of the west, as numerous charismatic species such as the American Buffalo and Californian condor were pushed to near extinction.
Back from the dead
Perhaps the tale of the passenger pigeon is not all gloom though. An ambitious collaboration of renowned scientists known as ‘revive and restore’ aims to make amends for humanity’s mistreatment of our world. Their aim is to bring back extinct species (although probably no dinosaurs in the foreseeable future). And their flagship project? Our old friend the passenger pigeon.
This article’s aim isn’t to look at the genetic methods in depth, but I feel a summary could be useful for context. A closely related species, the band-tailed pigeon, will have its genome edited to make it as similar to the passenger pigeon as possible. This can be done since we have DNA extracts from passenger pigeon skins so we can compare the two genomes and edit the band-tailed pigeon’s genomes wherever necessary. After breeding numerous generations, the ‘passenger pigeons’ will be assessed and trained to ensure their behaviour is suitable enough to warrant their release.
Why is it worth it?
You may wonder whether the species is being brought back simply to make amends for a past sin and that the species will have no major effect other than being a pleasant addition to the American countryside. However, this couldn’t be further from the truth!
The return of the passenger pigeon has potential environmental benefits for humans and many other species.
Studies by Ben Novak (of revive and restore) have suggested one of the key ecological roles of the passenger pigeon was that the huge flocks of birds created widespread ‘disturbances’ in the vast oak forests of the Eastern USA. His research also looks at genetic fingerprints of population changes and shows that pigeon populations have been large and stable for the last 21,000 years despite periods of large environmental change (for example transitions between conifer and oak forests).
Pillars of the community
Novak suspects many species of plants in these forests may have relied on these disturbances to spread their seeds and allow growth. In this way the passenger pigeons acted as ‘ecosystem engineers’ and were likely a ‘keystone species’: a species which is important for the healthy functioning of an ecosystem. The study also shows how the pigeons’ jaw shape was optimal for eating certain types of oak seeds, which likely contributed to these trees being able to grow (for once a positive to pigeon droppings!) and establish themselves as a dominant species. In fact, many tree species may have evolved to partially rely on the passenger pigeon for successful growth.
These benefits also affect a multitude of other species. Many bird species reproduce faster in disturbance-linked forest types and these forests, generally, had a higher biodiversity of species ranging from reptiles to amphibians. This also has important implications in modern day forest management. In the past, scientists assumed human-induced forest fires were the main factor affecting the change from oak to maple forest in the Eastern USA, but recent research has challenged this. The return of the passenger pigeon may have large impacts on contemporary forest management by helping them return to more natural states.
So back to my previous question, is it worth it? The answer is probably a strong yes. Bringing back this species of pigeon will likely have a positive effect on the American environment. However, more research will be needed to completely explore the possible impact reintroducing a species could have. Small scale trials will need to be performed to check for any adverse consequences that this species could bring.
De-extinction is either a scary or revolutionary project depending on your mindset. However, one thing which is clear is that we must fully research the ways a species could impact the ecology and the people of an area before trying it. Although a Jurassic Park-level disaster is unlikely, there are some scientists considering bringing the woolly mammoth back…. Imagine seeing one of those in your back garden!
About the author: Tom Wainwright is a third year Natural Sciences student at the University of York. He has never watched the original Jurassic Park but thinks he ought to.