It was Carl Sagan’s birthday last week as well as a major election in the US that needs some perspective. And it is clear that science will need more advocacy and storytelling than ever on our pale blue dot, the only home we have ever known.
Getting to Green
Aroudn 3.7 billion (3,700,000,000) years ago, the earliest evidence of life exists, a microbial community. By then, or soon after, photosynthesis, the ability to gain energy from light, started, quite likely around the dim light of scalding hot ocean vents, glowing hot, and radiating some light. At least some of the types of photosynthesis that evolved early are still around in various bacteria today. They have strange chemistries to the versions we have today. And it’s been going ever since.
Eventually (perhaps after a billion years later), as life spread in the ocean or in primordial shallow seas photosynthesis got its light from the sun, absorbing red and blue wavelengths, leaving green to pass through. Other forms of photosynthesis rely exist, though the one we care about in this story are ones that would appear green if there had been eyes around to see it.
Solving this requires plant scientists, ecologists, botanists, science communicators, and citizens of Earth all doing their part, lending their ideas, creativity, and effort to this pale blue green-dot is still here long into the future, for us to experience and see.
Then, it kept going. Taking in light, carbon dioxide to make sugar, building their cellular bodies from the air around them and spitting out oxygen. Slowly, the Earth was oxidized. Iron rich seas rusted in this event. Eventually, 2.7 billion years ago, the iron was oxidized and oxygen built up in the atmosphere. It was mostly nitrogen before. Dissolved oxygen in the oceans would also have increased.
Life had to adjust to an oxygenated world as before, it had always been toxic (in fact, oxygen in some forms is not good for life to this day; even humans, it can damage DNA).
At some point, however, most life figured out how to use oxygen, to breathe, as part of their energy generation process (still many bacteria can exist absent oxygen, in fact must do so).
Those original blue-green cyanobacteria ended up being critical the basis for plants we all see today. Oxygen consuming- respiring- cells used oxygen eventually became fungi, animals, and myriad single-celled organisms alive today. At some point, a respiring single cell engulfed a cyanobacteria and it stuck– algae was born. Over an evolutionary time scale, those engulfed green cells became chloroplasts, the basis for future food webs when plants made it to the land, 450 million years ago, ahead of animals.
Like their animal counterparts, life went on, surviving mass extinctions, taking on new forms, expanding, and contracting. The Carboniferous period, 300 million years ago is where the fossil fuels and coal we use today got laid down and it’s mostly plant material- tree-ferns, club mosses that covered huge swaths of land.
Then the Permian extinction wiped out all but 5% species on Earth and it took millions of years to recover.
But recover it did.
This was not just a setback for life, it was a catastrophe. Including for the plants that had to re-colonize, radiate outward and evolve into new forms. Seed ferns, ferns, and conifer forests dominated the landscape. Had humans been around for the Permian extinction, it seems unlikely we’d be in that lucky 5% survivors.
The first flowering plant fossils date to 130 million years ago or so. As dinosaurs ruled the Earth, flowers were slowly diverging, ready to conquer the world. While we don’t know what events took place, eventually, a flowering plant attracted an animal, an insect most likely, to carry its pollen around to make it to the next generation. The flower-animal partnership was a wildly successful one, driving diversification, and speciation. One example can be found in modern Joshua Trees.
Like the Permian Extinction above, after the KT-boundary event, akin to mammals filling the void left by reptiles, flowering plants exploded into the diversity we experience today. Humans have never existed without the flowers, and they dominate the plant world.
More importantly to the eventual humans, 60 million or so years ago, grasses evolved.
Savannas were made possible, with some sparse trees which where we really came into our own. Anatomically modern humans are 200,000 years old, from Africa.
10-20,000 years ago we started farming, grasses being the key to that- rice, millet, maize, oats, barley, and sorghum. Farming enabled some people to not be farmers as the farmers could grow surpluses, allowing others to specialize in other professions. Thus civilization was born.
The story of the green Earth underlies the landscapes we all exist on today, where we build cities, and have our farms in fertile soil layered on the ground over millions of years as continents drifted, mountains rose and eroded. Around 20,000 years ago in the US, people arrived and permanently settled. Native Americans farmed, hunted, shaped the land to make a living.
When Europeans arrived en masse in the 17th century to colonize, it led to the America we see today with all its problems and amazingness. A lot of it green and beautiful still, lots of it farmed, like the bread basket and California’s Central valley.
All of the landscapes we see, that seem so different, are united by the dominance of different and diverse plants. A lot of it is Grasses, staple grains. Maize (a grass) and soy beans are the number one and two crops in the US. Cities have parks and many trees along their streets, community gardens, and urban landscapes devoid of greenery appear to have something missing, while places that do can have special things arise.
Green life has survived and thrived over the history of Earth. It might get knocked back, but plant life came back each time, colonizing the world, making it ready for new animal life to re-populate new niches. None of it is possible without the plants.
In the face of climate change, many plants are under threat – including our agricultural plants that may not fare well – and yet plants will persist. Slowly migrating up mountains, or further North in their range, flowering earlier in the season. They are silent sentinels slowly adjusting themselves in face of human civilization that they help bring about. They’ll outlast most Governments.
That doesn’t mean we’re OK or that all plants that exist now will survive. But we need them more than they need us.
The plant world also demonstrates a principle that we should all take heed of: Diverse ecosystems means more resilience, robustness, and ways out of stresses.
In the face of that, after the US election, the planet needs us to step up as individuals to keep the green world amenable to our civilization, our survival. We rely on plants for so much including air, clean water, shelter, clothing, food, medicine, and culture, that if we want to survive in a climate changed world, we need to save plants as best we can.
Imagine losing your daily cup of coffee. Now imagine worse, being forced to skip eating some days. Food security means addressing climate change. This isn’t really a partisan issue. Science produces answers to questions about how nature works regardless of what anyone believes about it. When scientists are sure, it’s not their opinion, they are reflecting all the data that support an idea, including things we do not yet know.
Solving climate change, securing the future of food for the world, requires plant scienitsts, ecologists, botanists, science communicators, and citizens of Earth working in various areas all doing their part, lending their ideas, creativity, and effort to ensure this pale blue green-dot is still here long into the future for us to experience and see.
11/17/2016: This post has been updated.