Anthropogenic Biomes

On a planet increasingly shaped by human hands, the traditional concept of natural biomes—vast expanses governed by climate—is becoming insufficient. We now live in the Anthropocene, an era where human activity is the dominant force of planetary change. This new reality demands a new framework for understanding our world, one that recognizes our cities, farms, and managed forests not as exceptions to nature, but as its new, prevailing forms. This article confronts this paradigm shift by introducing the concept of anthropogenic biomes, or anthromes: ecosystems defined and sustained by humanity.

This shift in perspective addresses a critical knowledge gap: how do these human-built worlds actually work? To answer this, we will embark on a two-part exploration. The first chapter, ​​Principles and Mechanisms​​, will lay the foundation by defining anthromes and dissecting the energetic, chemical, and evolutionary rules that govern them. Following this, the chapter on ​​Applications and Interdisciplinary Connections​​ will explore the far-reaching consequences of this global re-engineering. We will examine how anthromes serve as new arenas for rapid evolution, restructure ecological communities, and force us to rethink fundamental challenges from conservation to global environmental stability. Through this journey, we will gain a deeper understanding of our role as the architects of a new planetary ecology.

For centuries, we have mapped our world using the grand patterns of nature. We speak of biomes—the sprawling tundra, the dense rainforest, the arid desert—each a masterpiece sculpted by the patient hand of climate over millennia. These were the fundamental units of life on Earth, large-scale communities of plants and animals living in equilibrium with the sun, soil, and rain. But if you were to step outside today, into a city, a suburb, or even a modern farm, you would quickly realize that this map is becoming a historical document. A new cartographer is at work, redrawing the lines with unprecedented speed and power: humanity itself. To understand our planet now, we must first understand the principles and mechanisms of these new, human-dominated worlds: the ​​anthropogenic biomes​​, or ​​anthromes​​.

Let’s begin our journey with a simple thought experiment, a comparison of three landscapes that you might find somewhere on a continent today. Imagine first a remote patch of savanna, untouched by roads or development. Lightning sparks natural fires, native herds graze the grasses, and the entire rhythm of life pulses in time with the seasonal rains. This is a classic picture of a natural biome, a system where the rules are set by the climate and the local cast of evolved characters. We can call this an ​​intact ecosystem​​.

Now, picture a park in a bustling city. The lawns are a brilliant, uniform green, sustained not by rain but by sprinklers. The soil is enriched with fertilizers, pests are kept at bay with chemicals, and the trees are a curated collection of ornamental species from around the world. Mowers impose a constant, artificial "grazing" pressure. Here, the regional climate is almost an afterthought. The ecosystem's structure and function—its water, its nutrients, its very inhabitants—are dictated by continuous, direct human management. This is the essence of an ​​anthrome​​: a system where sustained human inputs and design-choices are the primary organizing forces. The suburban lawn, the city park, and the intensively managed farm are all examples; they are ecosystems that we actively build and maintain.

Finally, consider a third landscape: an old, abandoned farm field. Decades ago, humans irrigated this land, which gradually made the soil salty. The farming has stopped, and no one manages it now. But the salt remains. A new, self-sustaining community of salt-tolerant native plants and hardy weeds has taken root. The ecosystem is on its own, but it cannot return to the original prairie that existed before the farm. The legacy of human action has locked it into a new and persistent state. This is what ecologists call a ​​novel ecosystem​​—a self-organizing system with a historically unprecedented mix of species and abiotic conditions, born from theghost of human influence.

These distinctions are not just academic. They reveal a fundamental truth about the Anthropocene: we are no longer merely living within ecosystems; we are the principal architects of them. Our world is no longer a mosaic of natural biomes dotted with human settlements. It is a continuum of anthromes and novel ecosystems, with only relicts of the old world remaining.

What does it take to run these new worlds? What is the "horsepower" behind an anthrome? Natural ecosystems are solar-powered. They run on the steady stream of energy from the sun, captured by plants through photosynthesis. Anthromes, however, are different. They are powered by sunlight, yes, but also by a massive infusion of energy from another source: our industrial civilization.

Think again about that manicured urban park. The energy to produce and transport the 2,000 kg of fertilizer, the energy to pump 25,000 cubic meters of water for irrigation, even the metabolizable energy from the waste left by visiting pets—all of this is what we call an ​​anthropogenic energy subsidy​​. When you add it all up, this hidden energy can be a substantial fraction of, or in some cases even exceed, the total energy the park's plants capture from the sun. Our farms and cities are vast, open systems, gulping down energy from fossil fuels to maintain their structure and productivity.

This altered flow of energy has direct, physical consequences you can feel on a hot summer day. Why is a city's downtown core almost always hotter than a leafy suburb? The answer lies in the physics of the surface energy balance. Imagine the ground surface has an energy budget. Its "income" is the net radiation it absorbs from the sun ($Q^*$) plus any heat we release from cars, buildings, and industry ($Q_F$, the anthropogenic heat flux). It "spends" this energy in three main ways:

1. ​​Sensible Heat ($Q_H$):​​ Heating the air directly, like a hot plate.
2. ​​Latent Heat ($Q_E$):​​ Using the energy to evaporate water, which has a powerful cooling effect—the ecosystem's version of sweating.
3. ​​Storage ($\Delta Q_S$):​​ Soaking up heat into the mass of buildings and asphalt, like a brick left in the sun.

The budget must balance: $Q^* + Q_F = Q_H + Q_E + \Delta Q_S$.

A vegetated suburban landscape with plenty of trees and lawns can "spend" a large portion of its energy income on latent heat ($Q_E$). It sweats efficiently, staying cool. A dense urban core, made of concrete and asphalt, has very little water to evaporate. Its ability to sweat is crippled. It is forced to dispose of its massive energy income—both from the sun and our own activities—primarily by jacking up the air temperature ($Q_H$) and storing heat in its concrete mass ($\Delta Q_S$), which it then radiates back out long into the night. The ​​Urban Heat Island​​ is not a mysterious phenomenon; it is a direct and predictable consequence of building landscapes that have forgotten how to sweat.

If energy is the engine of our human-built world, then elements like nitrogen and phosphorus are its bricks and mortar. Life depends on the constant cycling of these nutrients through the environment. For eons, these cycles were governed by a delicate balance of geology and biology. In the 20th century, we seized control of the planet's plumbing.

The story of nitrogen is perhaps the most dramatic. Most of the nitrogen on Earth exists as inert dinitrogen gas ($N_2$) in the atmosphere, which is unusable by most life. For life to flourish, this gas must be "fixed"—converted into reactive forms like ammonia ($\text{NH}_3$). Historically, this was done by lightning and, more importantly, by specialized microbes. Then, in the early 1900s, the ​​Haber-Bosch process​​ was invented, a feat of industrial chemistry that could synthesize ammonia from air and natural gas. Its primary use? Agricultural fertilizer.

The consequences have been staggering. Today, humanity's industrial and agricultural activities fix an amount of nitrogen ($R_{anthro} \approx 150$ teragrams per year) that is greater than all natural terrestrial fixation combined ($R_{nat} \approx 110$ Tg/yr). We have, in a single century, more than doubled the entire planet's supply of life-giving, reactive nitrogen. This incredible act of planetary engineering has allowed us to feed a population of billions, but it has also pushed us far outside the ​​planetary boundary​​—the scientifically-defined "safe operating space" for the nitrogen cycle.

A similar, though less dramatic, story has unfolded for phosphorus. Unlike nitrogen, phosphorus has no major atmospheric pool. It is mined from a few phosphate-rich rock deposits around the world and spread across our farmlands. This represents another massive new flow of a key nutrient. According to the simple law of mass conservation, this added phosphorus doesn't just disappear. It inevitably accumulates, cascading through a series of reservoirs. On decadal timescales, it builds up in our soils and gets buried in the sediments of our lakes and reservoirs. Over centuries, it flows out to fertilize the coastal oceans, with the ultimate sink being slow burial on the continental shelves. We have hijacked the nutrient cycles, creating a one-way firehose of life-sustaining elements from mines and factories to our fields and, eventually, to the sea.

This global re-plumbing has profound local consequences. What happens when a natural ecosystem, like a temperate forest, is continuously showered with this excess nitrogen from atmospheric deposition? Ecologists have a term for it: ​​nitrogen saturation​​.

Imagine a forest ecosystem's growth is limited by the availability of nitrogen, just as a baker is limited by the amount of flour they have. If we suddenly start air-dropping a huge supply of nitrogen "flour," the forest's growth will soon become limited by something else—perhaps phosphorus "sugar" or calcium "eggs," following ​​Liebig’s Law of the Minimum​​. The system is now phosphorus-limited, but the nitrogen rain continues. The surplus nitrogen has to go somewhere. It leaches out of the soil as nitrate ($\text{NO}_3^-$), polluting streams and rivers. Worse, as the negatively-charged nitrate ions wash out, they pull positively-charged nutrient ions, like calcium ($\text{Ca}^{2+}$), out with them, depleting the soil of essential minerals and making it acidic.

This process is compounded by the chemistry of air pollution. Emissions from power plants ($\text{SO}_2$) and vehicles ($\text{NO}_x$) form sulfuric and nitric acid in the atmosphere—the classic "acid rain." But there is a twist in the tale. Ammonia ($\text{NH}_3$), released in massive quantities from agricultural operations, is a base and actually neutralizes these acids in the atmosphere, forming ammonium salts. This seems like good news, but it creates a kind of "delayed-action" acid. When this ammonium ($\text{NH}_4^+$) is deposited on the forest floor, soil microbes can convert it back to nitrate in a process called ​​nitrification​​. This microbial process releases two protons for every ammonium ion it consumes, resulting in significant soil acidification long after the initial pollution was released and far from its source. The anthrome's reach is long, carried on the wind and transformed by the hidden work of microbes.

We have defined new landscapes, fueled them with novel energy sources, and flooded them with a deluge of nutrients and chemicals. This brings us to a final, profound question: What does this mean for the evolution of life itself? Are these anthromes simply degraded, impoverished versions of the "real" nature they replaced? Or are they something more?

The evidence is mounting that these human-shaped worlds are powerful new arenas for evolution, acting as intense ​​selective landscapes​​ that are driving rapid adaptation in the species living among us. Consider the common songbird that has made a home in our cities. It faces a completely new set of challenges to its survival and reproduction.

• ​​A World of Noise:​​ The urban environment is filled with the low-frequency roar of traffic. To be heard by mates and rivals, many city birds have adapted by shifting their songs to a higher pitch, finding a clearer channel in the acoustic chaos.

• ​​A World of Light:​​ Our cities never truly get dark. This ​​Artificial Light at Night (ALAN)​​ can disrupt the natural light cues that govern daily rhythms. In response, many birds have adapted to this artificial dawn, starting their morning songs and foraging activities earlier than their rural cousins.

• ​​A World of Fear (or Lack Thereof):​​ Cities can be safer for a small bird. Many traditional predators are rare, while the most common large animal—the human—is generally harmless. Birds that are excessively wary, wasting energy by flying away from every passing person, are at a disadvantage. As a result, city birds have evolved to be bolder, showing a reduced ​​flight initiation distance​​. They have learned, in an evolutionary sense, to tolerate us.

This is not a story of degradation, but of resilience and adaptation. We are not just paving over nature; we are, entirely by accident, creating evolutionary hotspots where life is responding to our presence in real-time. We have not ended evolution; we have simply become its most potent and unpredictable force. In building our world, we are redirecting the future of life on Earth.

Now that we have sketched the principles of anthropogenic biomes—the ways in which humanity has become the dominant force shaping the patterns of life on Earth—we arrive at the most thrilling part of our journey. It is one thing to draw new maps of the world, labeling forests as “managed” and grasslands as “rangelands.” It is another thing entirely to ask: what happens inside these human-dominated landscapes? What are the new rules of the game for the creatures and processes that inhabit them?

The answer, you will see, is that the emergence of anthromes is not merely a geographic reshuffling. It is a catalyst for profound changes, sparking new evolutionary trajectories, re-wiring ecological networks, and forcing us to confront the deepest questions about our stewardship of the planet. These are not abstract academic curiosities; they have far-reaching consequences that touch everything from the song of a bird outside your window to the stability of the global climate.

Perhaps the most startling consequence of our remade world is that evolution itself has been kicked into high gear. Natural selection, far from being a slow, geological-time process, is visibly at work in our cities, farms, and waterways, responding with astonishing speed to the new pressures and opportunities we create. Anthropogenic biomes are, in effect, giant, unplanned evolutionary experiments.

Imagine a songbird living in a bustling city. For millennia, the complexity of its song was a masterful advertisement of fitness, a delicate symphony broadcast through the quiet woods to woo a mate. But in the urban anthrome, that symphony is drowned out by the low-frequency roar of traffic and construction. A signal, no matter how beautiful, is useless if it cannot be heard. In this new acoustic environment, selection favors a different strategy. Instead of nuance, the premium is on punch. Birds that sing simpler, but louder and higher-pitched, songs are the ones that successfully find mates. And as the males adapt, so do the females, their preferences co-evolving to favor the new, more effective broadcast. We are, without intending to, rewriting the love songs of the natural world.

This evolutionary screenplay is not limited to communication. Consider the diet of an urban omnivore, like a raccoon or a coyote. Our cities offer a feast of high-calorie, easily accessible anthropogenic foods—a trophic subsidy that flows from our world into theirs. But this bounty comes with a trade-off. To exploit it, an animal must possess a certain behavioral boldness to venture near humans and their structures. It also benefits from a digestive system adapted to process our carbohydrate-rich, processed leftovers, a starkly different diet from the varied foods of a forest. Evolution in the city thus becomes a balancing act. It favors individuals who are bold, but not reckless; it pushes their digestive physiology toward specializing on our junk food, sometimes at the cost of being less efficient on their ancestral diet. Our trash, in a very real sense, becomes an agent of natural selection, sculpting the behavior and the very bodies of the animals who share our cities.

The story gets even more intricate when we consider our explicit attempts to manage wildlife. Our actions and policies become direct selective pressures. When we set traps to cull "nuisance" animals, we are not randomly sampling the population. We are preferentially removing the boldest and often most innovative individuals, those who are not wary enough to avoid us. This imposes a strong selection for wariness and perhaps against the kind of problem-solving that gets them into trouble in the first place. Conversely, if we use non-lethal deterrents like complex fencing, we may inadvertently select for problem-solving, rewarding the clever few who can figure out a way around our defenses. And when residents provide food, they create powerful selection against wariness, rewarding animals that tolerate human presence. Each management strategy pushes the evolution of animal behavior in a different direction, often with unintended consequences.

As species evolve in response to anthromes, so too do the connections between them. The intricate web of life is being rewired, with some threads weakened and others forged anew.

Think of the vast pelagic biomes of our oceans, which we have transformed through global shipping. For an echolocating whale or dolphin, the world is a symphony of sound. It "sees" an object—a fish, a mate, a predator—by interpreting the echoes of its own calls. The chronic, low-frequency noise from shipping traffic is like a dense fog, masking these vital acoustic signals. This isn't just an annoyance; it's a fundamental disruption of the predator-prey relationship. When a predator cannot effectively find its food, its attack rate plummets. In a simplified model of such an ecosystem, this disruption can lead to a surprising outcome: the prey population may actually increase as predation pressure is artificially relaxed. Our noise pollution is inadvertently restructuring the marine food web, with consequences that ripple through the entire community.

This rewiring also happens at the boundaries we create. The "edge" of a forest fragment, where the woods meet a farm or a suburb, is not just a line on a map. It is a unique environment with more sun, higher temperatures, and drier soil than the cool, damp interior. This acts as an environmental filter. In the stable interior, the soil microbial community might be dominated by species adapted to cool, moist conditions. But at the harsh, fluctuating edge, selection favors a different cast of characters: microbes that can tolerate heat and resist drying out, perhaps by forming hardy spores or surrounding themselves in protective slime. The very act of carving up a landscape changes the rules for even the unseen microbial world, altering the fundamental processes of decomposition and nutrient cycling.

These edges have consequences for our own health. They are often hotspots of activity for species like deer and mice, which thrive in fragmented landscapes. Ticks, which feed on these hosts, also flourish. This creates a "perfect storm" for the transmission of zoonotic diseases like Lyme disease. By increasing the amount of edge habitat, we are inadvertently increasing the contact rates between wildlife hosts, disease vectors, and humans. A model of disease transmission shows that such landscape changes can dramatically increase the basic reproduction number ($R_0$) of a pathogen, magnifying the risk of spillover into human populations. The way we shape our environment directly influences our own vulnerability to disease.

Understanding anthromes forces a radical rethinking of conservation. The old dream of preserving a pristine wilderness untouched by human hands is no longer viable on a planet where no place is truly untouched. Conservation must now operate within human-modified landscapes.

This new reality presents bizarre and dangerous new threats. Consider a species poached for its rarity, like a pangolin. Classical ecological models would suggest that as the population dwindles, it should become harder and more expensive to find, giving the species a natural refuge at low numbers. But human economics can pervert this logic. For certain luxury goods, rarity increases value and demand. This creates a perverse incentive for poachers to intensify their efforts as the species becomes rarer. The result is a deadly feedback loop called an "anthropogenic Allee effect." The constant poaching pressure acts as a fixed "tax" on the population that becomes proportionally more devastating as the population shrinks, creating a tipping point below which recovery is impossible. A population that seems stable could be pushed over this cliff by a single bad year or a sudden disease outbreak, spiraling into extinction because of a dynamic born from human desire.

The effects of anthromes are not just local; they aggregate to influence the entire Earth system. The world's biomes are interconnected through the great biogeochemical cycles of carbon, water, and nutrients. Our modifications of these biomes have global consequences.

For instance, nitrogen, a key building block of life, is naturally scarce in many ecosystems. Through industrial fertilizer production and fossil fuel combustion, we have more than doubled the amount of reactive nitrogen cycling through the biosphere. This excess nitrogen gets deposited on land and sea, in a sense "fertilizing" the globe. In a temperate or boreal forest, this anthropogenic nitrogen can alleviate natural limitations on growth. The trees grow faster and larger, and more carbon gets locked away in their wood and in the soil. This creates a fascinating and complex link: our nitrogen pollution, a major environmental problem in its own right, is simultaneously causing some of the world’s forests to absorb more carbon dioxide from the atmosphere, acting as a partial brake on climate change. A calculation based on a simple stoichiometric model shows this effect is significant, amounting to a substantial fraction of a petagram of carbon per year globally. This reveals the law of unintended consequences on a planetary scale.

This planetary scale of our influence is the ultimate challenge. Scientists have proposed the concept of "Planetary Boundaries" to define a "safe operating space for humanity" with respect to crucial Earth system processes like climate change, biodiversity loss, and nutrient cycles. But how does one translate a global limit, like the maximum sustainable amount of nitrogen we can fix each year, into meaningful guidance for a single country or individual? One approach is to use consumption-based accounting, like an ecological footprint, which traces the resources consumed by a nation, regardless of where they were produced. By allocating a "fair share" of the planetary boundary to each nation (for example, on an equal per-capita basis), we can create a powerful diagnostic tool. We can calculate whether a nation's consumption "footprint" for nitrogen or fresh water overshoots its share of the safe operating space. This framework links individual and national consumption choices directly to the stability of the Earth system, providing a scientific basis for navigating the Anthropocene.

Finally, there is a subtle but profound way in which our remaking of the planet affects not just its future, but our understanding of its past. Evolutionary biologists rely on the geographic distribution of genetic variation to reconstruct the history of life—to learn how species colonized new islands, adapted, and speciated over millions of years. These genetic patterns are the living echoes of history.

But in the Anthropocene, we have become the world’s greatest dispersal agent. We move species around the globe, intentionally and accidentally, at a rate and scale that dwarfs natural processes. A plant or insect that naturally would have taken millennia to cross an ocean can now do so in a day in the cargo hold of an airplane. When these species establish themselves in new lands, they inject a new, very recent genetic signal. This human-mediated dispersal scrambles the ancient record, erasing the subtle patterns of isolation by distance and creating deep confusion. Is a species found on a remote archipelago a natural, ancient colonist or a recent, human-vectored arrival? Disentangling these signals requires a multi-pronged forensic approach, combining genetic data on divergence times with archaeological evidence and comparisons across many species. Our actions are not only writing a new, dramatic chapter of Earth’s history; we are also smudging the ink on all the preceding pages, making them harder for us, and our descendants, to read.

The study of anthropogenic biomes, then, is more than just a new branch of ecology. It is a lens through which we can see the full, intricate, and often surprising tapestry of our relationship with the planet—a relationship that is perpetually remaking the world, and ourselves.