How Much Time do we have left?
Last semester, I was reading papers with my Conservation Paleobiology class. One paper we discussed included the magnitude of species extinctions since the year 1500. The IUCN Red Lists, which go back to the year 1500, result in calculations of approximately 0.5% loss of species. The paper, by Cowie and others (2022), estimated a much higher extinction level, at 7.5% to 13% since they year 1500.
An opportunity to give a talk at an international conference came up and, with those numbers swirling around in my mind, the opportunity was all it took for me to investigate further. My question was this: given the estimated rates of extinction since 1500, how long do we have left before the present global biodiversity crisis becomes a mass extinction?
That answer heavily depends on how a paleontologist defines a mass extinction - and that was something I didn’t want to dive into; too many definitions spoils the research, to mix metaphors. So instead, I took a pure numbers approach: how long would it take until half of the species presently on Earth became extinct?
As a trained geologist, able to think in thousands to millions of years and realize what that time frame means to the history of life on Earth, the results were sobering. So sobering, in fact, that I had to immediately turn my attention to less depressing research before I could return to the numbers. But I digress; here are my results:
If extinction rate was held constant at 0.5% (one half of one percent) of species per 500 years, Earth will have lost half of its species by 69,000 years from now.
If extinction rate were held constant at 10% of species per 500 years, half of all species will disappear by 3,250 years from now.
Yikes!
Perhaps you are reading this and thinking, “69,000 years? Even 3,250 years? That’s so long from now. 3,000 years ago, humans were just starting to play with iron tools. Look at how much time there is in 3,000 years! That’s no problem.”
But that’s where geological time vs ecological time comes in - we humans tend to think on human time scales, which means years, decades, and lifetimes. Geologists are taught to think in much longer time frames, and we know that the entire time humans have been in existence is essentially an eyeblink, if that, in the history of Earth.
Maybe you aren’t concerned about the time it will take before half of all species go extinct because you think technology will have the solutions. Maybe you think science will fix everything long before then. Or maybe you don’t care, because it’s so far in the future.
But here’s one thing: that’s half of all species. It doesn’t say which species will go extinct when. We could lose critical species that we depend on within decades - we could lose bees and other pollinators; we could lose major fish species. We could pollute the land so badly that even cows have a hard time surviving without major chemical intervention to keep them alive. We may have altered climate and used groundwater so much that our major crops, as they are, can no longer exist.
And here’s another thing: those time frames are only good if extinction rates are kept constant, per 500 years. That’s not realistic. Realistically, extinctions have cascading effects: cause one species to go extinct and others that rely on those species will fall, too. And then more species that depend on those will go extinct. And so on: a cascade. Not a row of Dominoes, a one-after-one toppling, which is what would happen if you could keep extinction rates constant. A cascade: the collapse of a house of cards, if you could balance all those cards on a single card. A cascade: the one little disturbance that sets an avalanche into motion.
As for humanity-important species, I cannot give you a time frame for when they will go extinct. Yes, science is working on the problem - this is my website of solutions, after all. Yes, technology could intervene. But saying things like “science will solve it” or “it’ll be fixed with technology” is ignoring the problem with empty platitudes. The issue is that we have to begin solutions now, before a magical scientific or technological miracle; we have to do our part to, at best, keep the mass extinction from happening, and minimally, to keep it from getting any worse.
My goal is to reduce the magnitude of this next mass extinction for which we, humanity, are the root cause. The more we all work together to reduce our impact on the planet, no matter how small of a change we make in our lives or how unimportant a vote seemingly means - it all adds up. Really; I’m already witnessing, as a scientist, the effects of how many small, individual changes can add up to a great good; we just need to do more, and on more things. Together, through our individual changes - and our voices to direct society - we can create a foundation on which science and technology can apply their solutions. The loss of species is inevitable, given our present global environmental crises. How many species we lose, and how quickly we lose them, is up to all of us.
The reference for the paper:
Cowie, R.H., Bouchet, P., and Fontaine, B., 2022. The sixth mass extinction: fact, fiction, or speculation? Biological Reviews 97, p. 640-663.