Sermon presented at Gloucester UU Church July 13, 2025 by Mern Sibley
“The Living Earth – My Journey through Deep Time”
In the days following the election last November, I found myself feeling discouraged. I imagine many of you felt the same way. So many hourly and daily developments were continually arriving, and they seemed like they had very sinister implications for our country and for the world. We seemed to be at the beginning of a very dark time. I wanted to turn away from this time of news cycles, from the unfolding of events in the US and the world in the twenty-first century. I decided to start learning as much as I could about what happened during the millions and billions of years of the incomprehensible stretch of time our Earth has been forming and changing. I hoped that by learning more about these Earth events far off in time, I could put the current events unfolding into some perspective and learn some lessons about our Earth and the problems we are facing now. So, shortly after the election, I started reading about geology.
Geology, as many of you probably know, is the study of planet Earth and the processes that have shaped it and are shaping it now. By processes I mean things like volcanoes, glaciers, earthquakes, the movement of tectonic plates, the formation of oceans, – all those happenings are events that geologists study.
My personal perspective on geology is that I am a biologist with an interest in plants and how they work, and when I was an undergraduate back in the 1970s, I did take a couple of geology courses. I did that because I wanted to learn something about the rocks that plants grow in (some plants love limestone and others love granite). I was trying to get a sense of why plants are found where they are, and they were very interesting classes at the time. After I took those geology classes, I carried on with my study of plant physiology and I didn’t continue with geological questions.
So it turned out that there were two reasons for my journey back into geology and the millions of years of Earth – first, I wanted to remove myself from the chaos of the second chapter of MAGA domination and get some perspective on Earth as a planet over billions of years. Second, I did wonder how the field of geology had changed since the 1970s when I last studied it.
Geologists have a name for this enormous time of Earth’s developing over billions of years – they call it deep time. The writer John McPhee gave us a good analogy for the scale of deep time in his book, Basin and Range. To appreciate this analogy, you have to first bear in mind that our Earth formed about 4.5 billion years ago. Stretch out your arm sideways, and imagine that the 4.5 billion-year timeline of earth’s history runs from the tip of your nose to the tip of your middle fingernail. One quick swipe of a nail file would wipe out human history. So, a lot happened before we showed up. Continents, oceans, mountains, glaciers, volcanoes, tectonic plates were all surging and changing over vast spans of time – there was even a 300 million year period early on when the Earth was continually bombarded by comets and asteroids. One thing we can confidently say is that Earth has been a living world for more than 80% of its history – the oldest undisputed fossils are about 3.7 billion years old.
Back in the 1970s, when I was taking my geology course, geology and biology were considered two different worlds. Geologists studied the inanimate stuff, and biologists studied the living stuff. Geologists considered living things as incidental to the fundamental physical Earth processes that they were studying; life was just an annoying mushy blanket over the really interesting things that they wanted to look at. Back then, the thinking was that Earth developed and changed over deep time, through all the geological processes, and life finally developed on Earth at some point when conditions were right for it. As an example of the separatist thinking that prevailed back then, as the geologist Robert Hazen tells it, when he was a graduate student at Harvard in the 1970s, “my mineralogy Ph.D. adviser told me – “Don’t take a biology course. You’ll never use it!”
One of the first things I learned in my recent geology readings is that Hazen and many other scientists have experienced a fundamental shift in their viewpoint since that time. Those separate worlds of the 1970s have become linked – geology affects life, and life affects geology. Over the last fifty years, geologists generally have come to appreciate that the events that gave rise to our Earth are much more than these inanimate physical forces of volcanism, glaciers, and plate tectonics. The forces of life have worked to create a place, our Earth, that allows flourishing of MORE life. Life in the past has created the conditions in which we are flourishing now. There is a name for this new branch of science that investigates how biological and geological forces work together – people call it Earth Systems Science.
I’ll provide a couple of quotes that shows how scientists are thinking now:
Earth Systems scientist Tim Lenton said: (We) now think in terms of the coupled evolution of life and the planet, recognizing that the evolution of life has shaped the planet, changes in the planetary environment have shaped life, and together they can be viewed as one process. “
Planetary scientist David Grinspoon has said: Earth is a living planet, which is not the same as a planet with life on it—that’s really the point, simple but profound. Because life is not a minor afterthought on an already functioning Earth, but an integral part of the planet’s evolution and behavior.”
Life is continuous with Earth; we are not inhabitants of the planet. We are not passengers on spaceship Earth.
Going back into deep time, I want to tell you about some important ways that life has changed conditions on Earth. First, if we go back 3 billion years ago, countless tiny organisms called cyanobacteria had already evolved on Earth. Through the process of photosynthesis, they took energy from the Sun and turned it into sugars to power their own bodies, and in doing that they made oxygen as a byproduct. They did that work to such an extent that a significant amount of oxygen built up in Earth’s atmosphere, starting around 2 billion years ago. People call it the Great Oxygenation Event and it was a permanent change to our Earth. You can argue that this oxygen buildup was the most significant event ever to take place on Earth because so much happened because of it, including the evolution of most of the life on Earth today, including us. One consequence of the Great Oxygenation Event was that the rocks on Earth at that time began to change – the rocks reacted with the oxygen, forming many minerals never seen before on Earth, including beautiful copper minerals like malachite and turquoise. Of the 6000 known types of minerals on Earth, it’s estimated that 2/3 of them are a direct consequence of that oxygen produced by photosynthesis.
Then, around 540 million years ago, life itself learned how to make minerals directly in the form of calcium carbonate shells, and over time limestone reefs made of these shells grew gigantic, reaching thousands of feet in thickness. And then, when plate tectonics moved to close up the shallow bodies of water the reefs were in and compressed the sediments, mountain ranges rose up to completely alter Earth’s landscape. The Canadian Rockies, the Dolomites in northern Italy, and even Mount Everest are made of sturdy limestone reefs that once covered shallow ocean floors.
Another important way that life has changed and continues to change Earth is by affecting the endless cycle of water, from ice to rain to water vapor and back again. As our planet has evolved over billions of years, a critical way of regulating its temperature is via that cycle of water. And plants have a central role in the water cycle, and thus in regulating the temperature of the Earth. As plants grow, they move water up through their roots, and that water leaves the plant as water vapor through tiny holes in the leaves (= transpiration). Transpiration is a very effective cooling mechanism, a means of dissipating solar heat. This is because every gram of water that goes from liquid to vapor steals 600 cal of heat from the air. That water vapor coming from the leaves of trees and other plants travels up into the atmosphere and the heat is released 4-5 km above Earth’s surface. You can see that this heat transfer on a large scale could cool the planet. In contrast, air conditioning, our human way of cooling, makes the atmosphere hot on the outside of the building. The water cycle is very important for understanding climate change, just as important as the carbon dioxide that we are all so focused on.
One of the most interesting expressions of the water cycle is something called a flying river. I have just started to learn about flying rivers, and they are amazing. Think of rivers of water vapor traversing the sky. The river is fed by wind, which picks up water vapor given off by the forest through transpiration, and the wind takes the moisture to distant places. Flying rivers are known to happen over several tropical rainforest regions in the world – including the Congo, Indonesia, and the Amazon. I’m going to focus on the Amazon one because that is the most studied of the world’s flying rivers. Over millions of years in the Amazon rainforest, the flying river has been fed by trade winds from the Atlantic. In that rainforest, it’s been estimated that about 250 gallons of water are transpired per tree per day. With the 400 billion trees of the Amazon rainforest, the flying river in the Amazon region moves more water than the Amazon River itself. To really appreciate what the effect of the Amazon flying river is, we need to look at the latitude around 30 degrees South around the world. In most parts of the world, we see significant deserts at this latitude: the Kalahari Desert in Africa, the Altacama Desert in Chile, the Outback of Australia. But if we look at 30 degrees South where the latitude crosses central and southern Brazil, Paraguay, Uruguay, and northern Argentina, we don’t see a desert at all, but rather a very productive agricultural area. The Amazon flying river flows over this region and changes the climate. Today this area of South America is known as “The Lucky Quadrangle” because instead of being a desert, it has the highest population density on the continent and 70% of the continent’s wealth is produced in this area.
As I kept learning, I have found many other examples of how forests and other vegetated areas maintain stable climate through regulating the local and global water cycle. I have come to see that understanding the water cycle is important for coming up with solutions to deal with climate change.
I have been inspired by the words of the late Spanish meteorologist Millan Millan: “Water begets water. Soil is the womb. Vegetation is the midwife.”
This sounds like a poem, but it is a poem based on decades of practical experience and observation by Millan.
Back in 1991, the European Commission asked Millan to work on the question of why the Mediterranean coast in Spain no longer had the regular daily summer afternoon rains that it had had decades ago. This area had become more and more dry over the past eighty years or so. Why was that? Through careful study and modelling, Millan’s team showed that land use alters the water cycle very quickly. When you cut a forest, or when you build a road, you heat the ground but you don’t add moisture. When vegetation is present, you have a certain amount of moisture added from that. Without the vegetation, the breezes heat up but they don’t have enough moisture for rain. Over the 20th century on the Mediterranean coast, forests and marshes were paved over to make way for roads, homes, hotels, water parks, huge oil and gas installations, and on and on. Then the winds blowing from the sea, instead of cooling, picked up heat from concrete and compacted soils. And for every degree Celsius of warming those clouds experienced, they were able to contain 7% more water vapor without making it rain. Day after day the clouds would pile on top of each other, helping make the Mediterranean Sea one of the hottest in the world. These cloud formations could reach 2.5 miles in height. Then, when cold autumn winds came down from Northern Europe, this immense moisture-laden cloud formation sitting over the Mediterranean Sea and eastern Spain could be triggered to produce a super rainstorm, dumping a deluge on a landscape with no forests or marshes. You probably remember that this is exactly what happened in Valencia, Spain, last October, they had a devastating flood there.
Millan believed that there are two legs contributing to climate change – greenhouse gases and land use. For most of the 21st century humanity’s work on climate change has been focusing on greenhouse gases, especially carbon dioxide. We have really neglected the issue of land use.
LAND USE is just as important as greenhouse gases in affecting the climate, and can have climate effects very quickly, much more quickly than greenhouse gases.
So what do we do? There are two important pieces of work to be done. First, of course we must replace fossil fuels with renewable energy as quickly as possible to cut down on greenhouse gases. And second, a complementary effort is EQUALLY important, if not more important, and that is – we must protect and restore Earth’s forests, grasslands, and wetlands. Also, in the ocean we must protect and restore undersea abyssal plains, reefs and meadows. All those planet-stabilizing processes that have developed over eons of time can be sustained by protection and restoration.
I want to tell you about a couple of initiatives that are aimed toward protecting and restoring Earth’s ecosystems that are underway right now.
The first initiative is a large-scale effort. As you probably know, there is an international climate meeting every year, the Conference of the Parties meeting (COP). This year, COP30 will be in Belem, Brazil, on November 10-21, 2025. One important event that will take place at this meeting in Belem is that Brazil intends to launch the Tropical Forests Forever Facility (TFFF) . TFFF is a $125 billion endowment fund that aims to begin payouts to reward forest conservation in tropical countries in 2026 . It’s basically an investment bank for forest conservation. The plan is to get 6 wealthy countries to put up $25B initially (US, Norway, France, UK UAE and Germany) and then attract another $100B from investors for a total of $125B. There is an agreed upon return of 5.5% over 20 years and any money made above that would be paid to tropical rainforest countries to keep their forests standing or restore forested areas. Payments would be made per hectare of land, and advanced satellite monitoring would be used to measure forest loss. One great thing about TFFF is that it is designed and put forward and supported by tropical rainforest countries themselves. There are still a lot of details to be worked out with TFFF, and hopefully those details will be worked out at the COP30 meeting. Certainly TFFF is the best idea the world has right now to preserve those critical tropical forests and keep those flying rivers going.
The other initiative I want to tell you about is a smaller scale effort, coordinated by an organization called Commonland, and this organization focuses on degraded land. Degraded land is land that has been depleted of natural resources, soil fertility, water, biodiversity, trees or native vegetation. As an example, the Mediterranean coast that I mentioned would certainly be described as degraded land. Degraded land is found all over our planet and the UN estimates that 40% of Earth’s land is classified as degraded. Commonland is based in the Netherlands and works in over 20 countries to restore landscapes. The approach of Commonland is that everyone has their own point of view and different ways of perceiving a landscape. This would include farmers, people who live in the landscape, business owners, nature organizations, and many others. When people come together to listen to each other’s experiences and perspectives, they see that they have a shared interest in living and working in healthy ecosystems. Commonland has a rigorous framework that guides stakeholders over time as they collaborate to restore their landscape. The founder of Commonland, Willem Ferwerda, explains what they do – “Integrated land restoration can restore the ecological function of degraded landscapes through making agriculture more regenerative, reviving forests and wetlands to rebuild natural water cycles and stabilize regional climates. However, solving the problem will take time. This is a long-term commitment.” Commonland has ongoing projects in Spain to heal those devastated Mediterranean landscapes I just talked about. As Ferwerda says, “You can’t fix the climate crisis without restoring the land. It’s like trying to rebuild a house on a crumbling foundation. That’s why Commonland is dedicated to supporting local people and organizations to work together. Through restoring the land, we can not only bring back the vital, life-giving summer rains in the Mediterranean basin but also restore a sense of hope and connection for communities living there.”
My learning about the deep time of our Earth has helped me to see that what we do with our land can help restore ecological systems and moderate climate change. The need now is for REPAIR. We can’t turn back the clock and make everything exactly as it was before we humans got here, but we can create a beautiful variation on a theme.
And I want to leave you with the message that there are people diligently doing that restoration work, repairing and preserving, and we should support them in any way that we can.