The fact that we’re losing biodiversity at an alarming rate turned from ‘news’ into ‘common knowledge’ decades ago. There is not one major animal or plant group that does not contain critically endangered species, or in some way threatened and soon to become critically endangered and this is due to the negative impact our dominant species has on the planet.
“But surely species disappear even without human interference, right?” sceptics will ask, arguing that Earth’s biosphere is able of vast levels of self-preservation and can withstand external pressures far more destructive that the human activity. They’re right until a certain point.
Life evolves, diversifies, expands across space and specialises according to what resources are available, but every now and then, for various reasons, a species may decline until it becomes extinct with no dramatic effects on the environment. This is a natural process known as a background extinction and the most recent estimate is around 0.1 species out of a million species per year. That is, every year one species in ten million dies out. Coupled with a higher diversification rate, it explains why the Earth is not devoid of life: because more species arise than go extinct. This equation does not include the human impact, which, when taken into account, significantly changes the result.
Earlier this year, an international team of researchers led by Gerardo Ceballos from the National Autonomous University of Mexico has compared the conventional background extinction rate to the rate at which biodiversity is being lost at present. The findings, published in Science Advances, are depressing and terrifying. If the background extinction rate had persisted, nine vertebrate species were expected to disappear since 1900 but, in reality, 468 species (including fish, reptiles, amphibians, birds and mammals) have been lost. And this is still an underestimate, since only the best studied species have been included in the calculation. There is a high chance that some of the organisms that are now gone have never been encountered, let alone studied.
“But species have gone extinct in vast numbers before in Earth’s history and biodiversity recovered. Surely the current situation it’s not too much to worry about?” sceptics will ask again, claiming the impact of the human activity is exaggerated. Of course mass extinctions have happened before, five times during the Earth’s convoluted history spanning 4.5 billion years.
There is a recurring series of events: a natural disaster takes place that drastically changes the environment, species have no time to adapt and die in mass, the conditions stabilise and species richness returns to its initial level. “Mass extinction” is indeed a very strong term and it might induce the wrong impression that species are being lost over night, but in reality each of these steps stretched over hundreds of thousands to millions of years. What we are witnessing now is a dramatic change of trend that, if left to continue, will leave behind a hardly recognizable Earth.
The idea of an anthropogenically-induced extinction is not newly emerged. From Richard Leakey’s and Roger Lewin’s book The Sixth Extinction: Patterns of Life and the Future of Humankind, published in 1995, to Elizabeth Kolbert’s The Sixth Extinction: An Unnatural History published in 2014, entire libraries have been written on the subject and so many authors have proved it loud and clear: we are in the middle of a sixth mass extinction. It is no longer a remote risk, but the reality we live in. According to the same study by Ceballos and colleagues, we are currently losing species between eight and 100 times faster than they would naturally disappear. It can’t be emphasised enough how serious this is. Pollination, nitrogen and phosphorus regulation, water purification and so many other ecosystem services that the humankind depends on would stop functioning within three generations if species keep disappearing at this rate.
While it is hard to predict which species are more threatened than others, the general rule is that the easier it is for an organism to adapt to new conditions, whether brought about by climate change or habitat alteration, the higher the likelihood that it would survive. Endemic species (that are only naturally found in a certain place on Earth, such as Madagascar or the Arctic region) are more endangered, because they are highly specialised for their environment and those specialisations would not work anywhere else. Migratory species might be disadvantaged, since they require separate feeding and breeding grounds and the destruction of any of the two would disrupt their life cycle. Also, the higher the resource demand of a certain species, the more affected it would be; so large animals that need more food and territory are more vulnerable.
Extinction is irreversible, no matter what Jurassic World would have us believe. The species that we have lost so far are gone forever, so protecting the ones that are still around is crucial. With the risk of repeating what has already been said hundreds of times, greatly intensified conservation efforts are needed before the window of opportunity closes. However, this is not a job for the specialists in the field only, but every human inhabitant of Earth needs to take part. Everyone can reduce their waste of resources (or, ideally, stop it altogether), recycle more and get involved in local conservation projects. And of course, maybe most importantly, learn about the natural world, as much as you can. The more you know about the intricately wonderful web that is life on Earth, the more likely you are to be fascinated by its beauty and to play an active role in preserving it.
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