When most people imagine the end of life on Earth, the scene usually resembles some cosmic disaster Hollywood movie: our sun turning into a big, fat red giant and swallowing up all the inner planets! Very dramatic, yes.
But if you look far enough ahead, that fiery end isn’t the first thing to end life on Earth. For a long time, scientists thought that plants would disappear rapidly, becoming extinct as the planet became less and less welcoming. Turns out, the story may not be that serious. However, a recent study is convincing us of that dire ending.
What does science say about the existence of plants on this planet?
The study, published in the Journal of Geophysical Research: Atmospheres and written by Jacob Haq-Mishra and Eric Wolf of Blue Marble Space, paints a bright future for Earth’s green life, thanks to some serious number crunching (and some high-powered computers, of course).
Using new climate and biosphere models, researchers believe plants could survive for 1.8 to 2 billion years, much longer than previously predicted. This means that forests and grasslands, and all the other photosynthetic wonders, may continue for millions of years longer than we thought, forcing scientists to rethink how and when Earth’s chapter of life will actually end.
In other words, vegetarians (or, really, anyone else) have no need to worry about running out of salad anytime soon. Plants have time – just not an endless amount of it. Ultimately, the sun decides.
Its energy output, or luminosity, increases by about 10% every billion years, constantly raising the thermostat on our planet. This process is slow but continuous, and it will continue for ages to come.
What about global warming and the greenhouse effect?
After sunlight, greenhouse gases, especially carbon dioxide (CO₂), have the greatest impact on Earth’s surface temperature. However, the future of CO₂ is unclear, and it may matter how long the plants hang on to it. For those unaware, CO₂ does not stay in the air forever. The planet has a mechanism for expelling it: silicate weathering.
This is a slow reaction where rocks, rain and CO₂ are transformed into new chemicals, eventually making their way into the oceans and settling as calcium carbonate.
Thanks to volcanoes, this carbon eventually comes back up. Currently, silicate weathering removes about 130 million tonnes of carbon from the atmosphere annually. Unfortunately, humans are extracting about ninety times that amount of water every year. The study raised the question: How much time do plants really have?
The researchers ran detailed climate and CO₂ models, testing how things worked under strong versus weak silicate weathering. He also divided plants into three main types, classified based on the way they photosynthesise: C3 plants, C4 plants, and CAM plants.
C3 plants constitute about 95% of the species, C4 about 3%, and CAM makes up the last 2%. Each group has its own CO₂ “starvation threshold.” Below about 50 parts per million CO₂, C₃ plants are phased out.
C4 plants make it up to about 10 ppm, and CAM plants can make even less. So, the key question is: how fast do CO₂ levels fall as the planet warms and the climate changes?
What about the possible consequences?
Let’s look at two main scenarios here: Weak Silicate Weathering: Here, as the sun shines and the earth warms, the weather doesn’t do much to reduce atmospheric CO₂.
. Instead, CO₂ levels remain about the same as today, allowing plant life to last longer and longer. Surface habitability lasts for perhaps 1.5 billion years, then gradually declines until you’re down to microbes surviving the last summer. Strong silicate weathering: Consider the opposite extreme.
The planet’s surface temperature remains the same as today’s, but intense weather continues to strip CO₂ from the air. This ultimately reduces greenhouse warming so much that the Earth becomes too cool for complex plants long before extreme heat arrives.
For the study, Haq-Mishra and Wolf used a state-of-the-art 3D climate model (Exo-CAM) to take all these factors into account. Their decision? Plants can keep it up for at least another 1.35 to 1.86 billion years, depending on what “weathered” world we get.
Life on this planet is hard; in fact, it’s even harder than most people thought. But as the sun rises, as long as CO₂ sticks around, plants can find ways to adapt. However, ultimately, nothing fools physics forever.
When ocean water boils and CO₂ disappears, plants also disappear. Then it’s just the microbes hanging around. And who knows? Maybe by then, some life (Earth or something else) will find its way to the stars. Or at least apply enough sunscreen to last a while.
