Can “trees” grow on terrestrial planets outside the solar system?

With spring in full swing in the northern hemisphere, hikers are once again beckoned by the forest, taking trails through a swath of old-growth trees. Not only do forests have a soothing effect on the human spirit, but there is little doubt that the role they play in the Earth’s ecosystem is also critical to the health of the planet.

But can we expect tree-like life forms to grow on terrestrial planets in star systems outside our solar system?

Can “trees” grow on terrestrial planets outside the solar system?

Erica Etoise, an evolutionary biologist at Yale University, said in an email that living systems orbiting stars similar to the Sun are likely to use some form of photosynthesis, which harnesses light energy and uses storable chemical energy. He said that it is highly likely that the action (generating Photosynthesis emerged from water and onto land about 500 million years ago on Earth, but if the same thing happened on terrestrial exoplanets, it would be expected that some kind of tree-like form would evolve. Etoise says.

Earth without trees

However, for most of Earth’s history, there were no trees on Earth. In fact, trees have only been around for about 400 million years. This is only about one-tenth of Earth’s entire history. There are even shark species that are older than the oldest tree species.

For much of the history of life on Earth, and indeed for most of the history of photosynthesis, there were no trees here on Earth, Edward Schwieterman, an astrobiologist at the University of California, Riverside, said in an email interview. ing. From a geological perspective, the development of trees is relatively recent, appearing during the Devonian period approximately 385 million years ago. Still, planets with trees are more likely to have robust and diverse terrestrial ecosystems.

Can “trees” grow on terrestrial planets outside the solar system?

The Swedish spruce, one of the oldest trees on earth, is over 9,500 years old. Could evolution select such long-lived tree species on terrestrial exoplanets?

Milton Mendonça, an ecologist at Brazil’s Federal University of Rio Grande do Sul, explained in an email that most tree species die early in their lifespans, but it all depends on the stability of the environment. ing. Mendonça points out that on a planet where climate and weather conditions are highly unstable and unpredictable, it may be a good idea to have alternative strategies in place, such as reproducing whenever possible and leaving behind durable spores. . Such a situation, Mendonça continued, could occur in the early stages of the formation of unstable exoplanet systems, or on exoplanet moons with complex orbital dynamics.

Could tree-like life forms that utilize photosynthesis evolve on terrestrial exoplanets? According to Yale’s Etoise, complex ecosystems require primary producers to convert energy into living systems. Etoise points out that because the Earth’s primary producers are photosynthetic organisms, it is difficult to look beyond this preconception.

Trees that change the climate

According to Mendonça of the Federal University of Rio Grande do Sul, individual trees change local temperature, humidity, and wind flow. They also say that when they gather together in forests, they can change the local climate. Mendonça points out that Earth’s vast, ancient rainforests have a very clear impact on Earth’s biosphere.

Forests also serve as an ecological base for other life forms. On Earth, plants, animals of all kinds, fungi and bacteria all depend on the bark, buds, trunks, leaves, roots, flowers and fruits of trees to survive.

How do forests on exoplanets differ from those on Earth?

Can “trees” grow on terrestrial planets outside the solar system?

According to Mendonsa, exoplanets with tree-like life forms would be a world apart from planets without them. While it’s a quieter, less windy place, it’s also likely to be full of life.

Etoise wonders what trees would look like if plants evolved some other system to obtain and distribute water and nutrients throughout their bodies.

Etoise says a number of potential ecological constraints on how trees function will push them back to ancient structures that evolution has created over hundreds of millions of years. Etoise explained that tree height, productivity, and tolerance to drought and cold are all highly dependent on the vascular systems developed by Earth’s plants.

Are trees actually important to halting human-induced climate change?

Trees are carbon sinks because they absorb carbon dioxide and reduce carbon emissions from anthropogenic climate change, Michaela Leon, a planetary astrobiologist at the University of California, Riverside, said in an email. While it plays an important role as a carbon source, the magnitude and timescale of its interaction with the carbon cycle is far smaller than that played by rocks and planetary interiors.

Abiotic “thermostat” processes in rocks and planetary interiors stabilized Earth’s climate long before trees appeared. Therefore, Leon points out that a planet without trees might be able to maintain its climate conditions for long periods of its lifespan.

Many of Earth’s tree species act as environmental filters for the atmosphere. Could trees on exoplanets be evolutionarily selected for the same traits? According to Leon, this characteristic may be similarly manifested to the extent that the tree’s filtration process improves its own environment. Leon pointed out that controlling the local environment through processes such as scavenging may be an important property of life.

Is there a way to determine whether newly discovered exoplanets have trees?

If large plants such as trees did indeed evolve and cover much of the Earth’s surface, they could be detected by observing the surface with telescopes, Leon says. Leon continues that in the future, forests outside the solar system may even be detected.

If in the near future it will be possible to detect forests outside our solar system from Earth, and indeed forests can be found on some distant exoplanets, astronomers on aliens within 1000 light years of the sun could , it is likely that you can do the same thing.

In this way, Leon said, forests help the Earth itself generate signals that can be detected from a distance.

Global impact of exoplanet forests

Can “trees” grow on terrestrial planets outside the solar system?

Mendonça points out that only when forests are sufficiently widespread can they have a profound and lasting impact on the ecology of the planets on which they exist.

The lesson here is that even though trees were late to the evolutionary scene, life on Earth would be unthinkable without the magnificent forests that still exist.

Edwards describes the situation on Earth without forests as bleak. Forests are some of the most species-diverse places on Earth, Edwards continues, and trees facilitate the diversification and coexistence of other biological communities. If plants couldn’t find a way to become trees, Edwards said, the Earth would be a far more sterile place, and we probably wouldn’t be here.


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