When all plants on Earth have disappeared

New modelling has shown that plant life could persist on the planet for longer than many previous estimates suggested: approximately 1.35 to 1.86 billion years, depending on how the Earth’s climate and carbon cycle evolve.

The study has been published in the *Journal of Geophysical Research: Atmospheres*.

Details

The authors, Jacob Haqq-Misra and Eric Wolf, used a three-dimensional climate model to investigate how much longer plants could survive on Earth as solar energy increases and CO₂ levels change. Unlike simpler models, this approach takes a more comprehensive view of the atmosphere and the planet’s surface, rather than reducing the Earth to a single averaged point.

The main question was this: which would first render the Earth uninhabitable for plants – a fall in CO₂ levels or overheating?

Plants need CO₂ for photosynthesis. But over very long time scales, it can be removed from the atmosphere through silicate weathering: a process in which rocks, water and carbon dioxide undergo chemical reactions, with the carbon ultimately being sequestered and deposited in ocean sediments.

Two scenarios for the future

In the first scenario, weathering is intense. The Earth effectively ‘pulls’ CO₂ out of the atmosphere. Temperatures may remain more moderate, but plants begin to suffer from carbon starvation.

According to the authors’ calculations, the typical threshold for C4 plants — around 10 ppm CO₂ — could be reached in approximately 1.35 billion years. However, some forms of photosynthesis, such as CAM plants, as well as aquatic plants capable of utilising dissolved bicarbonate, may survive for longer. If a lower CO₂ threshold – around 1 ppm – is assumed, the plant biosphere could persist for approximately 1.84 billion years.

In the second scenario, weathering is weak. In this case, CO₂ levels do not fall as sharply, but the Sun continues to heat the planet. Here, plants die not from a lack of carbon dioxide, but from the heat.

According to the model, the Earth will become too hot for most terrestrial plants in about 1.68 billion years, and for all terrestrial plants in about 1.87 billion years.

In simple terms

Plants will face two dire scenarios in the distant future.

The first: the Earth isn’t too hot yet, but there is becoming too little CO₂ in the atmosphere. Plants have nothing to ‘feed’ photosynthesis with.

The second: there is still enough CO₂, but the planet is heating up so much that terrestrial plants can no longer withstand the temperatures.

In both cases, the end of the green era will not come tomorrow, nor in a million years, but in billions of years.

Why this matters

The study shows that Earth may remain habitable for some plant life almost until the planet begins to approach the limits of the wet or runaway greenhouse— that is, the stage at which the oceans will evaporate rapidly and be lost to space.

This is important not only for the future of Earth. Such models help astrobiologists understand how long planets orbiting other stars might remain habitable for complex life. If a planet has plants or their equivalents, their lifespan depends not only on the distance from the star, but also on the atmosphere, the carbon cycle and the ability of life to adapt.

What will disappear first

It is unlikely that ‘all plants’ will disappear at the same time. The most sensitive groups will be the first to suffer. More resilient forms of photosynthesis may outlive them by hundreds of millions of years.

C3 plants, which include most modern species, are more dependent on CO₂. C4 plants function better in low CO₂ conditions and in the heat. CAM plants, such as many succulents, are even more economical in their use of water and carbon dioxide. Therefore, the end of the plant world will not be an abrupt shutdown, but a long-term contraction of the green biosphere.

Background

Plants form the basis of complex life on Earth. They produce organic matter, sustain food webs and help regulate the atmosphere. Consequently, the question of when the plant biosphere will disappear is, in effect, a question about the lifespan of complex life on the planet.

This new study is distinctive in that it considers not just a single future scenario, but several extreme scenarios: one in which CO₂ levels fall sharply, and another in which they remain almost constant, but the Earth overheats.

Source

Study: Jacob Haqq-Misra, Eric Wolf — “Maximum Lifetime of the Vegetative Biosphere”, Journal of Geophysical Research: Atmospheres, 2026.