Nature

• 1. Introduction

  ›

  Nature borrows its name from a word that, in ancient times, literally meant birth. The Latin natura carried the sense of essential qualities and innate disposition. It served as the translation of the Greek physis, which first described the intrinsic character of plants, animals, and the features of the world that develop of their own accord. From those roots grew an idea vast enough to mean the laws, elements, and phenomena of the entire physical world, including life itself. Yet the same word also draws a line. Humans are part of nature, but human activity is often described as at odds with it, or even superior to it. So what, exactly, gets to count as natural? Why does a manufactured object fall outside the category while a forest falls inside? And how did one Earth, third in line from its Sun, come to be the only known place where any of this lives?

• 2. A Word That Divides

  ›

  Manufactured objects and human interaction generally are not considered part of nature, unless qualified as something like human nature or the whole of nature. This is the older, traditional concept still in use today. It implies a distinction between the natural and the artificial, where the artificial is whatever has been brought into being by a human mind. Depending on context, the natural might also be set against the unnatural or the supernatural. The history of the idea shifted with the rise of the modern scientific method over the last several centuries. Nature became a passive reality, organized and moved by divine laws. With the Industrial Revolution, it increasingly meant the part of reality not subject to deliberate human intervention. Some traditions treated it as sacred, including Rousseau and American transcendentalism. Others, such as Hegel and Marx, saw it as mere decorum for divine providence or human history. A competing vision survived too. A vitalist picture of nature, closer to the pre-Socratic one, was reborn around the same time, especially after Charles Darwin. Today the everyday use of the word often narrows to geology and wildlife, or to the natural environment and wilderness, those things not substantially altered by human hands.

• 3. The Living Planet

  ›

  Earth is the only planet known to support life. Within the Solar System it sits third closest to the Sun, the largest of the rocky terrestrial planets and the fifth largest overall. Its climate is marked by two large polar regions, two narrow temperate zones, and a wide tropical-to-subtropical belt at the equator. Precipitation swings enormously, from several metres of water a year to less than a millimetre. Salt-water oceans cover 71 percent of the surface, with most inhabited land in the Northern Hemisphere. Beneath that surface, the planet is far from still. The outer shell is divided into gradually migrating tectonic plates. The interior stays active, with a thick layer of plastic mantle and an iron-filled core that has a solid inner phase and a fluid outer phase. Convective motion in that outer core drives electric currents through dynamo action, and those currents generate the geomagnetic field. Life itself has reshaped the air. The atmosphere was significantly altered from its original state by life-forms, which create an ecological balance that steadies surface conditions. That balance is delicate. A shift of only a degree or two in average global temperature has historically produced major effects on ecology and even on the geography of the Earth.

• 4. Deep Time

  ›

  Earth is estimated to have formed 4.54 billion years ago from the solar nebula, alongside the Sun and the other planets. The Moon followed roughly 20 million years later. The molten outer layer cooled into a solid crust, while outgassing and volcanic activity produced the primordial atmosphere. The oceans came from condensing water vapor, most or all of it delivered as ice by comets. From that energetic chemistry, a self-replicating molecule is believed to have appeared around 4 billion years ago. The continents have never held still. They formed, broke apart, and recombined over hundreds of millions of years, sometimes merging into a supercontinent. Rodinia, the earliest known supercontinent, began breaking apart roughly 750 million years ago. Pannotia followed and split about 540 million years ago, then Pangaea broke apart about 180 million years ago. During the Neoproterozoic era, freezing temperatures buried much of the planet under glaciers and ice sheets, a state nicknamed Snowball Earth. It preceded the Cambrian explosion, when multicellular life began to proliferate about 530 to 540 million years ago. Since then there have been five distinct mass extinctions. The last struck some 66 million years ago, when a meteorite collision probably killed off the non-avian dinosaurs and other large reptiles while sparing small animals such as mammals. The present era is itself classed as a mass extinction, the Holocene extinction event, the fastest ever to occur. E. O. Wilson of Harvard University has predicted that human destruction of the biosphere could wipe out half of all species within the next 100 years.

• 5. Where Water Lives

  ›

  Water covers 71 percent of the Earth's surface, yet its distribution is lopsided in surprising ways. Oceans hold 96.5 percent of surface water. Glaciers and polar ice caps hold 2.4 percent, and other land surface water, including rivers, lakes, ponds, and groundwater, accounts for 1 percent. The smallest freshwater reserve is the 0.1 percent held in the atmosphere as vapor, clouds, and precipitation. Through subduction in the Earth's crust, an equivalent mass of the planet's surface water has been buried in the upper mantle. The ocean is best understood as one thing, not many. Though customarily divided into the Pacific, Atlantic, Indian, Southern, and Arctic, in descending order of size, these waters form one global, interconnected body often called the World Ocean. It spans some 361 million square kilometers, more than half of it over 3000 metres deep, with average salinity around 35 parts per thousand. Lakes tell a quieter story. A lake sits inland in the bottom of a basin, larger and deeper than a pond, fed by a river, and moving slowly if at all. The only world besides Earth known to harbor lakes is Titan, Saturn's largest moon, whose lakes are made of ethane most likely mixed with methane. Rivers keep the whole system circulating. They collect water from precipitation, groundwater, springs, and melting glaciers, and they serve as corridors for fish and wildlife migration. Given the ongoing Holocene extinction, streams play an important role in linking fragmented habitats and conserving biodiversity.

• 6. The Web Of Life

  ›

  Eugene Odum, a founder of ecology, defined the ecosystem as any unit that includes all the organisms in a given area interacting with the physical environment, so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles. Within that unit, species are connected and dependent on one another in the food chain, exchanging energy and matter among themselves and with their surroundings. The scale can shrink to a microecosystem, such as a stone and all the life beneath it, or expand to a whole ecoregion. The biosphere is the outer shell of Earth where life occurs, spanning land, surface rocks, water, and air. It holds over 75 billion tons of biomass. More than nine-tenths of that total is plant life, on which animal life depends heavily. Life itself resists a single definition, though scientists generally accept that it shows organization, metabolism, growth, adaptation, response to stimuli, and reproduction. Its origin on Earth is not well understood, but it is known to have occurred at least 3.5 billion years ago. Once life appeared, evolution by natural selection produced ever more diverse forms. When plants developed photosynthesis, the resulting oxygen accumulated and gave rise to the ozone layer. With that layer absorbing harmful ultraviolet radiation, life was finally able to colonize the land surface of the Earth. More than 2 million species of plant and animal life have been identified so far, with estimates of the true number ranging from several million to well over 50 million.

• 7. The Human Hand

  ›

  Anthropogenic mass now outweighs all living biomass on Earth, according to a 2020 study published in the journal Nature, with plastic alone exceeding the combined mass of all land and marine animals. Humans make up a minuscule share of living biomass, yet their effect on nature is disproportionately large. A 2021 study in Frontiers in Forests and Global Change found that only about 3 percent of the planet's terrestrial surface remains ecologically and faunally intact. Philip Cafaro, a professor of philosophy at Colorado State University, wrote in 2022 that the cause of global biodiversity loss is clear: other species are being displaced by a rapidly growing human economy. The numbers around that loss are stark. Roughly 1 million species are threatened with extinction within decades. The annual global cost of public subsidies that damage nature is conservatively estimated at 4 to 6 trillion dollars. Part of the problem is pricing. Natural resources carry extraction costs but are typically available free of charge, which distorts their market value and leads to underinvestment in natural assets. Agriculture, first adopted around the 9th millennium BCE, remains the dominant way humans use plants. Clearing large tracts of land for crops has sharply reduced forestation and wetlands, taking habitat from many species and increasing erosion. Even the line between native and introduced blurs here, since some species brought in centuries ago by migrating people have become part of the natural flora of their new homes.

• 8. Beauty And The Cosmos

  ›

  David Rothenburg writes that the beautiful is the root of science and the goal of art, the highest possibility that humanity can ever hope to see. The link between nature and beauty has filled large sections of libraries with art, photography, and poetry, and the study of why that link exists belongs to the branch of philosophy called aesthetics. An early tradition of landscape art began in China during the Tang Dynasty, from 618 to 907, and shaped the aims of Chinese painting. In the West, wilderness became a prevalent subject in art during the 1800s, especially among the Romantic movement. The British artists John Constable and J. M. W. Turner turned to capturing the natural world, and William Wordsworth's poetry described its wonder, a place formerly viewed as threatening. One classical idea of beautiful art is mimesis, the imitation of nature. Beyond Earth, the same matter and energy that compose a painting compose the universe, bound together by mass-energy equivalence. The visible components of the cosmos are now believed to make up only 4.9 percent of its total mass. The rest is unknown, thought to consist of 26.8 percent cold dark matter and 68.3 percent dark energy. Stars form in galaxies that can span up to 100,000 light years, which gather into clusters, superclusters, and the galaxy filaments that are the largest known structures. The question of life elsewhere remains open. Mars once held bodies of liquid water and may have briefly been capable of forming life, while Europa, the fourth-largest moon of Jupiter, may hide a sub-surface ocean that could potentially host life of its own.