How Long Can Plants Survive on Earth?

The plant kingdom has already endured five mass extinctions since plants first colonised dry land around 470 million years ago. How much longer can it survive?

According to a study published in Nature Geoscience in 2023, humanity may already have an expiry date: in 250 million years, the formation of a supercontinent, Pangaea Ultima, will trigger extreme volcanic activity. Temperatures will rise so sharply that researchers estimate just 8% to 16% of land will remain habitable for mammals. Without intensive technological adaptation, such as living underground or air-conditioning entire cities, Homo sapiens and almost all mammals will disappear at that point. But what will happen to plants?

Plants account for roughly 80% of Earth's biomass, yet their survival relies on resources our planet cannot provide indefinitely: sunlight, liquid water, atmospheric carbon dioxide and mineral nutrients. In theory, they cannot persist beyond a certain limit. Two researchers at the Seattle-based independent research institute Blue Marble Space set out to determine where that threshold lies.

Astrobiologist Jacob Haqq-Misra and planetary climatologist Eric Wolf ran a series of simulations to establish when the plant biosphere will vanish. Their calculations, published on 28 May in the Journal of Geophysical Research: Atmospheres, suggest that the final land plant may not die for another 1.87 billion years, when the Sun is 20% brighter than it is today.

How long Earth's plants could survive

Suffocation or heat: the end of the plant kingdom

To reach that estimate, the two scientists created a three-dimensional model of Earth's climate evolution over the next two billion years, incorporating the gradual increase in solar brightness alongside variations in atmospheric CO₂ levels.

This gas is constantly recycled. Rain washes it from the atmosphere into the oceans, where it slowly precipitates into limestone sediments that eventually become rock. At subduction zones, these rocks then descend into the mantle, where heat breaks them down and releases carbon for volcanoes to return to the atmosphere. This loop, known as the carbonate-silicate cycle, is ultimately essential to every organism on Earth that survives through photosynthesis.

Average global surface temperature affects how quickly rainfall weathers rocks, but no research has ever measured the precise scale of that effect. Haqq-Misra and Wolf therefore ran two separate simulations to define two extreme scenarios: one in which chemical weathering of rocks removes large amounts of CO₂, and another in which it removes very little.

Two possible endings for Earth's plant biosphere

In the first scenario, temperatures fluctuate only slightly, but CO₂ levels become depleted. Plants would eventually starve in 1.84 billion years, having lost the carbon needed for growth.

The second outcome is the reverse: CO₂ levels remain stable, but Earth's temperature, driven by the Sun, climbs to an average of 65 °C. No land plant can withstand such conditions, which far exceed the tolerances observed even in the hardiest species from the planet's most unforgiving deserts. This scenario grants plants an additional 30 million years compared with the first, pushing the deadline back to 1.87 billion years.

Whichever timescale proves correct, it lies far beyond estimates from earlier studies on the same subject. “This suggests that Earth's photosynthetic biosphere could persist in some form until the planet begins to lose its water,” Haqq-Misra and Wolf note. In their view, plants will therefore disappear at the same time as the final oceans vanish.

Earth and life: linked until the end?

The authors nevertheless acknowledge that their simulations depend on a methodologically questionable assumption: at no point did they allow for plants to adapt through natural selection. The plants in their models are identical to those alive today, retaining the same physiological limits for almost two billion years. That is four times the period plants needed to emerge from water and spread across the continents.

They readily accept this limitation, and it does not undermine their premise, because they were never trying to forecast the future of life itself. Their primary focus was the habitability of our planet, the only framework within which a prediction remains defensible.

Beyond the model: plants adapting beyond Earth

The next part of their argument more freely moves beyond that rigour. They envisage plants that would regulate their internal temperature and pressure, move to higher altitudes as the Sun grows hotter, establish themselves in the stratosphere, and even spread to low-gravity objects such as the Moon or comets. This is plainly speculative, but they argue for the idea: “We suggest that the default scenario for our planet's future is that life will survive there for at least as long as Earth itself,” they state. From this perspective, plants themselves have no life expectancy: they would endure for as long as Earth retains its water. In effect, this is more a question of geophysics than biology.