Largest Ecosystem
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Earth, the Largest Ecosystem

Climate change threatens food, water, and shelter

Cover Image) Living Earth (Modified by ArcheanWeb) — Original Credit: By NASA images by Reto Stöckli, based on data from NASA and NOAA. Instrument: Terra — MODIS — Earth Observatory: Twin Blue Marbles, Public Domain

The year was 1967, and humankind had ventured into space. As a species, we are perpetual tourists. Photo keepsakes were a must-have once we left our earthbound domain, so in 1967 the first color photos encompassing the whole Earth arrived home courtesy of the Department of Defense Gravitational Experiment (DODGE) satellite. Digital photography was not what it is today, and the color photo was really a composite of three photos taken with red, green, and blue filters. Five years later, the Apollo 17 crew took the iconic “Blue Marble” photograph. For the first time in Earth’s history, the planet could be examined in a single view. The gaian ecosystem we call Earth finally came into focus, and we saw it as our largest ecosystem.

We grapple daily with environmental and climate change issues ranging in scale from microbial changes in soils to vast islands of plastic polluting our seas. Massive forest fires, melting ice sheets, and devastating hurricanes capture the headlines, and it is easy to forget how interconnected our world is. Photos of our planet, taken from afar, remind us of the big picture — life on Earth is a single web of life. At the highest level, Earth’s surface forms a connected, planetary-scale ecosystem — one that has taken over four billion years to evolve.


As a refresher, an ecosystem is a group of interdependent biotic and abiotic components, functioning together as a sustainable unit. Importantly ecosystems are often nested. The Tongass temperate rain forest forms an ecological community that is intimately connected with the marine ecosystems of the Pacific Ocean. Together these two ecosystems form a larger coastal ecosystem. The Cascade Mountains of Oregon are home to temperate rain forests on their western slopes and high deserts on their eastern side. These two distinct ecosystems connect at the hip via a high mountain range, which controls rainfall, keeping one side wet and the other dry.

Our planet’s surface is an interconnected web of life — a master ecosystem with multiple smaller systems nested inside. At the smallest scale, individual ecosystems are the basic units of our environment. Therefore, environmental health in a region is measured by the health of its component ecosystems. At a fundamental level, climate change presents itself as changes in local and regional ecosystems. Higher global temperatures, for example, deplete precious moisture reserves in areas like California and lead to longer, more intense dry seasons. Dryer, hotter conditions then set the stage for larger and more damaging wildfires.

In our efforts to combat climate change, we shouldn’t lose sight of the ultimate goal, which is maintaining a sustainable planetary ecosystem where humans can survive and thrive in balance with the local ecosystems surrounding them.

Life in Flux

Life is always in a state of flux and change, so the goal is not stasis or a return to the past. The objective of tackling climate change is to create a dynamic and sustainable balance between humans and their environments. We depend on healthy ecosystems for our continued survival. Destroy the microbe-laden humus in the farmer’s soil, and crops will fail. Put too many nutrients or toxins into our estuarine hatcheries, and our offshore fisheries will disappear.

The greatest geographic division of ecosystems on our planet is between terrigenous and marine environments. But both of these domains are affected and connected by the single most visible driver of Anthropocene climate change: global warming. The atmosphere provides this connection through its incorporation of carbon dioxide (CO2) from fossil fuel emissions.

The accumulation of greenhouse gases in the atmosphere directly ties to a proven rise in average global temperature over the past 100 years. Temperature is one of the defining environmental conditions affecting ecosystems on land and in the sea. As temperatures change, so do ecosystems.

Our Oceans

But in our oceans, global warming does more than just increase temperatures — it also increases ocean acidity. Oceans cover about 71percent of the surface of our planet. Where the ocean and atmosphere meet, they interact and exchange carbon dioxide (CO2). The Earth’s current CO2 budget dictates that when CO2 enters the atmosphere from burning fossil fuels, only about 45 percent of this CO2 stays in the atmosphere. Land plants use about 25 percent of the emitted CO2, and then the oceans absorb the remaining 30 percent.

Carbonate buffering is the name given to the CO2 exchange process between the atmosphere and the oceans. When CO2 enters the ocean, it reacts with water to form carbonic acid, and this causes ocean acidification.

The effects of ocean acidification start at the bottom of the food chain. Higher acidity decreases the amount of calcium carbonate available for small planktonic creatures to make their shells. Groups like pteropods are an important planktonic component at the base of the food chain. Without the plankton, the ocean ecosystem collapses. If plankton can’t produce viable shells because of increasing acidity, then the species won’t survive, and the ocean’s fish populations dependent on those plankton will decline.

Earth is a single planetary-scale ecosystem, and changes in one part of that system will inevitably affect the whole system to one degree or another. Managing climate change has many aspects, but don’t lose sight of the overall prize: A healthy, sustainable biosphere.

Climate Change and Food

Understanding the impacts of climate change is an integral part of managing a sustainable future. From a geological perspective, Earth is currently in an unnaturally cool period, and a “normal Earth” is much warmer than today. We also know the planet is constantly in flux, and change is the norm. Our planet has experienced between five and seven mass extinction events, depending on how you count them. Historically, these mass extinctions occurred through natural processes that dramatically altered Earth’s ecosystems. Today, however, the Anthropocene extinctions represent rapid environmental changes caused by a single species, Homo sapiens.

The changes wrought by humankind create existential threats to our species, and we fear those changes for good reasons. Understanding the nature of those threats requires an examination of how the relationship between people and ecosystems has evolved over the past 20,000 years.

Rise of agriculture

Approximately 12,000 years ago, Earth exited the last Pleistocene Ice Age, where glaciers covered vast areas of the planet. Climate change was rapid and dramatic, but nomadic hunter-gatherer tribes didn’t ponder climate change as a problem to be solved because they were too busy adapting and surviving. As the ecosystems around them changed, they migrated and adapted their lifestyles to new environmental conditions.

As sea level rose, coastal communities migrated inland, and when food sources disappeared, new food sources were found. Part of the key to this adaptation was a lack of permanence. People moved to where the food source was. Migration was a key component of survival.

The first agricultural revolution changed this dynamic. With the advent of crops and domesticated animals, communities settled into fixed locations for long periods but still maintained adequate food sources. This change gave birth to the age of cities and empires, where adequate food security allowed human creativity to flourish, producing new technologies. The rise and fall of empires didn’t extinguish the true strength of Homo sapiens, the ability to pass knowledge on from generation to generation.

The role of cities

One of the keys to understanding the threats posed by climate change lies in the role cities play in our societies. We take them for granted in places like the USA and forget that 54 percent of the population was rural in 1910; but today, 81 percent of the population is urban. Traditionally, rural populations aligned closely with the ecosystems surrounding them. Food sources were local, and a community’s population-carrying-capacity directly reflected the amount of food an ecosystem could produce.

But the advent of large cities broke this dependence on local ecosystems. It gave rise to agricultural systems where industrialized farms produced food products and shipped them to large urban centers. Readily available food allowed these urban centers to grow into the metropolises we enjoy today. But this process produced a system where most of our population is disconnected from the ecosystems that sustain them.

Food security

Climate change threatens this relationship between rural and urban settings when environmental changes jeopardize major food sources. So, one of the concerns with climate change is food security. But even this threat is nuanced. In wealthy countries, many people were unaware of the 2007–2008 global food crisis when high oil prices, increased biofuel production, weather shocks, and trade restrictions, produced grain shortages and jeopardized food supplies. Food, like other commodities, rises in value when it is in short supply. For those with ample financial resources, the 2007–08 grain shortage translated into household budget tradeoffs as more money went to food and less to other activities. But for the poor, higher prices translated into less food. These shortages triggered social unrest, malnutrition in children, and even starvation.

If climate change causes food production to falter, then rising prices take their toll, with the first to feel the impact being the poorest and most vulnerable. From a global perspective, food scarcity is one of the existential threats posed by climate change. In a world where almost eight billion mouths need feeding each day, changes in the climate, which alter or diminish agricultural output, also threaten social stability and the lives of the poor. Remember, approximately 3.5 billion people, almost half the world’s population, live in poverty, struggling daily to provide food and shelter. Small changes in food availability or costs have life-and-death consequences for half of the people on our planet.

Climate Change and Water

In the framework of climate change, water is a bit of a Goldilocks situation where too much or too little is disruptive, so we want just the right amount in our ecosystems. A farmer might long for the rain to water his parched land, but too much water creates flooding, which washes away his crops. Even in a world where oceans and seas cover 71 percent of the planet’s surface, too much seawater is a threat. Then there is the water in the ground, which supplies the needs of vast agricultural complexes. Both over pumping and drought-reduced recharge currently impact the water supplies for America’s breadbasket and other critical agricultural regions.

The Ogallala

Hidden beneath the high plains of America’s mid-continent is the Ogallala aquifer. It stretches from South Dakota to West Texas and provides water to parts of eight separate states. One-sixth of the world’s grain production, and America’s breadbasket, depend on groundwater from the Ogallala aquifer. However, we ask too much of this natural wonder, which currently supplies 30 percent of all irrigation water in the United States. Because water doesn’t magically appear below the ground, the aquifer must continually recharge from surface water. Unfortunately, the recharge rate for the aquifer is slower than the rate of withdrawal.

The Ogallala aquifer has stored as much water as Lake Huron (29 billion acre-feet) in the past. But sadly, many parts of the aquifer are in decline, thus leading to falling water levels, dry wells, and the aquifer’s failure to meet annual demand. Water volumes in western Kansas, for example, are down by 60 percent from original levels.

The decline of the Ogallala aquifer is only partially due to climate change. Its decline is also driven by insatiable demand and poor water management. This aquifer has historically been the backbone of a vibrant farming economy, and rural farming communities across America’s breadbasket depend on its water. Increasing water demand and shrinking supplies of recharge water are challenging lifestyles and damaging local economies.


One of the manifestations of climate change is a two-decade drought in America’s west, leaving many regions hot, dry, and thirsty. But the situation may get worse before it gets better. Tree ring data tell us megadroughts have occurred four times in the past 1200 years. The current drought started in the year 2000, and the period between 2000 and 2018 was the second driest 19-year period on record since the 800s.

While it is true that natural causes facilitate the occurrence of megadroughts, this does not mean human influences aren’t also at work. Anthropocene climate change and global warming are human-induced changes that amplify the severity of this megadrought.

Global warming has increased the average global temperature by about one degree Celsius over the long-term trend. But this number averages out both larger and smaller regional trends. Average annual temperatures in the American West have increased by 1.2 degrees Celsius over the norm. Higher temperatures result in more moisture loss, so global warming works to amplify the drought severity. Researchers attribute up to 50 percent of the severity of the current drought to human activity. Climate change affects the distribution of water on our continents. There will be winners and losers as water resources become scarce in populated areas that depend on surface and groundwater supplies.

Climate Change and Shelter

Looming climate-change-related water problems on land often play second fiddle to our most significant concern about water — rising sea levels. Under most current, realistic scenarios, the world’s two major ice sheets are engaged in a slow melt into oblivion. The Antarctic and Greenland ice caps are feeling the heat. It is true, a full meltdown is potentially hundreds of years out, but even in the early stages, the impact on coastal cities will be significant.

Our Cities

The threat of sea-level rise is disproportionately large for humans because of the way we have historically sought to settle near the oceans. About a third of the world’s population lives within 100 meters of sea level. But our return to an ice-free planet will submerge the first 66 meters of coastal land. In the USA alone, Houston, Miami, New Orleans, Charleston, New York, Boston, and Washington DC will all disappear beneath the waves.

Much of New Orleans already lies below mean sea level and is susceptible to small rises in the ocean. Other cities like Miami, perched at sea level, are already feeling the pinch from increased tidal and storm flooding. But the cities at highest risk are in Asia, not the Americas. With a 4 degree C global temperature rise, up to three-quarters-of-a-billion Asians will be living below sea level. In Shanghai, China alone, over 22 million people will be displaced by encroaching seas.

We have chosen to locate many of our major cities by the sea. These decisions have their roots in trade, economics, and a traditional reliance on shipping to build wealth and power. Despite the good reasons for locating near the sea, the threat remains. Our habitats have become fixed, and our ability to migrate to happier hunting grounds, as our ancestors did, is limited. When all land is occupied or owned, where do you migrate to? The only viable answer is to either new or existing cities above sea level. Coastal farmers will fare no better. It is not easy to take a 500-acre farming business and quickly relocate somewhere else.

Colorado River

Shelter becomes a priority as climate changes force mass migrations. These changes needn’t be just rising seas. As access to freshwater changes, the fortunes of populated areas will wax and wane. The Colorado River flows 1,450 miles from its headwaters in the Rocky Mountains to the Gulf of California, and it provides water for some 40 million people. Also, it provides irrigation for 5.5 million acres, and 4,200 megawatts of hydroelectric power generation capacity. But the water-usage demands on this river now exceed its annual flow capacity.

The 20th-century annual average discharge for the Colorado River was about 16.5 million acre-feet (MAF), but long-term drought conditions in the 21st century have reduced annual input, leading to lower river flows. However, demand for the Colorado River’s water is increasing and started seriously exceeding supply at the beginning of the 21st century. In 2009, for example, the yearly water recharge supplied via precipitation was about 12 MAF, and demand was just under 15 MAF.

Major cities like Phoenix, Tucson, Las Vegas, and Los Angeles depend on water from the Colorado River. The bottom line is, future aspirations for water use look unrealistic under current plans, because of their projected water demand of between 18 and 20 MAF per year, against a projected annual supply of 14 to 15 MAF. Water insecurity will curtail population growth, but if conditions are severe enough, people may need to move. Such changes are difficult for those with wealth and devastating for those living on the edge of poverty.

The Future

Large human populations have become fixed in areas where climate change may affect their ability to survive. Complex relationships exist between ecosystems, food, water, and our habitats. We are right to be concerned about a future where these relationships change as the climate changes, forcing human migrations and the development of new agricultural strategies. But we shouldn’t fear climate change. Instead, we should concentrate our energy on devising solutions.

What we should fear is inaction and procrastination on the part of governments, both local and federal. A strategy to maintain the status quo is a road to failure. Climate change is not an existential threat unless we collectively decide to let it be.

More from ArcheanWeb:

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ArcheanWeb On Medium:

EarthSphere Publication — Science and the environment

Dropstone Publication — Stories, life observations, art, and more


Reflections on life’s journey and thoughts on the Tao Te Ching — In Search of a Path

A fictional adventure about the origins of life — The Strings of Life

Stories in progress on WattPad


2050 and 2035: Failure and Hope for the Climate Crisis (By William House; Earthsphere on Medium)

The Tongass, Home to Unique and Beautiful Ecosystems (By William House; Climate Conscious on Medium)

The Ogallala Aquifer, Sustaining Life (By William House; Earthsphere on Medium)

Hot and dry in the Western USA, a megadrought in progress (Source: ArcheanWeb)

Ancient analogs show that a hotter planet is the geological norm (By William House; The Startup on Medium)

Mapping Choices: Carbon, Climate, and Rising Seas, Our Global Legacy (By Benjamin Strauss, Scott Kulp, and Anders Levermann)

The Colorado River is running dry (Source: ArcheanWeb)

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.