What Is Earth and Environmental Science?

Earth and environmental science is an umbrella field that studies our planet as an interconnected system, from its molten interior to the outer edge of its atmosphere, and investigates how human activity reshapes that system. Rather than belonging to a single discipline, it draws on geology, atmospheric science, oceanography, ecology, chemistry, and increasingly data science to understand processes that no single specialty can explain on its own. The field coalesced in the 1980s out of growing recognition that problems like climate change and biodiversity loss required researchers who could think across traditional boundaries, and it has expanded rapidly since.

How the Field Came Together

For most of modern science’s history, the study of rocks, the study of weather, and the study of living things were separate enterprises with their own journals, departments, and career tracks. That began to change in the mid-twentieth century when researchers realized that the chemistry of the ocean could not be understood without understanding the atmosphere above it, and neither could be understood without accounting for biological activity. Earth System Science emerged as a distinct endeavor in the 1980s, following calls for a unified “science of the Earth” and fueled by perspectives like the Gaia hypothesis, which provocatively framed the planet’s living and nonliving components as a single self-regulating system.¹ The International Geosphere-Biosphere Programme, launched in the late 1980s, pushed that integration forward by organizing global-scale research campaigns that no single country or discipline could have run alone.

The environmental side of the field grew out of different pressures. Industrial pollution, deforestation, and species loss created urgent practical questions that traditional geology or biology could not answer in isolation. Over time, the “Earth” and “environmental” wings merged into departments and degree programs that treat the physical planet and the living, human-affected environment as parts of one story.

Earth’s Interconnected Spheres

A useful way to think about what this field covers is through Earth’s major “spheres.” The lithosphere is the rigid outer shell of rock and soil. The hydrosphere includes all water, from oceans to glaciers to underground aquifers. The atmosphere is the envelope of gases above us. And the biosphere encompasses all life. Earth and environmental science studies each of these, but its real focus is how they interact.

Consider plate tectonics. The movement of the lithosphere’s tectonic plates is driven by convection in the hot, slowly flowing mantle beneath them.² But explaining how rigid plates form, break apart, and slide past each other turns out to require models far more complex than simple fluid flow. Researchers have found that the behavior of the lithosphere demands exotic rock-deformation mechanisms and shear-localizing feedbacks that are still being worked out.³ Density contrasts within the plates themselves, as they cool, thicken, and eventually plunge back into the mantle at subduction zones, provide much of the driving force for plate motion.⁴

None of that stays neatly inside geology. Plate tectonics shapes ocean basins, influences atmospheric circulation by building mountain ranges, and controls volcanic emissions that alter the atmosphere’s chemistry. The biogeosciences, which sit at the intersection of biology and the physical Earth, explicitly study interactions between living systems and the lithosphere, hydrosphere, and atmosphere across scales from a soil microbe’s metabolism to planetary nutrient budgets.⁵

Biogeochemical Cycles and Climate Stability

One of the field’s central concerns is how chemical elements move between Earth’s spheres and, in doing so, regulate conditions at the surface. The carbon cycle is the most high-profile example. Carbon dioxide in the atmosphere traps heat. Volcanoes and mid-ocean ridges release carbon into the atmosphere and oceans. Silicate weathering, the slow chemical breakdown of certain rocks by rain and rivers, draws carbon back out. Over hundreds of millions of years, this cycle has kept Earth’s climate within a range that supports liquid water and life, even as the sun’s output has increased.

Recent work has complicated this classic picture. Marine processes, including the weathering of seafloor sediments and the chemical alteration of underwater basalt, turn out to be major carbon sinks that played a larger role in regulating atmospheric carbon dioxide than researchers traditionally assumed.⁶ Meanwhile, tallying the total carbon going into and coming out of the planet’s interior has proved tricky. A revised calculation of inputs to the ocean-atmosphere system, including volcanic and metamorphic degassing (which account for roughly a quarter of total carbon input), yields a modern organic-carbon burial rate and suggests that overall, Earth’s sedimentary carbon reservoirs are growing rather than staying in a perfect steady state.⁷ The lack of a clean correlation between deep-Earth carbon outgassing and atmospheric carbon dioxide levels over the past 200 million years underscores how much work surface reservoirs, including the silicate weathering feedback, do to buffer climate.⁸

Carbon is not the only cycle that matters. Nitrogen and phosphorus move between land, water, and air in ways that shape ecosystems. Agriculture and fossil-fuel burning have pumped so much reactive nitrogen into the environment that thresholds for drinking-water safety, air quality, freshwater health, biodiversity, and coastal dead zones have all been exceeded.⁹ Phosphorus and nitrogen runoff from farms and cities fuel toxic algal blooms, strip oxygen from water, and kill fish, degrading waterways used for drinking, recreation, and commerce.¹⁰ Tracking these pollutants demands exactly the cross-disciplinary lens Earth and environmental science provides: soil chemistry, hydrology, atmospheric deposition, and ecosystem ecology all at once.

Reading Earth’s Deep Past

Understanding today’s planet also requires understanding its history. Earth and environmental scientists use a toolkit of dating and reconstruction methods that reaches back billions of years. Radiometric dating anchors the geologic timescale. A technique using the rhenium-osmium isotope system in organic-rich black shales, for example, can date the boundaries between geologic periods by directly measuring the age of the sedimentary rock itself, rather than relying on indirect methods like biostratigraphy.¹¹

Ice cores are another window into the past. Oxygen-isotope ratios trapped in ancient ice have long served as a proxy for temperature, but isotope-enabled climate models have revealed that those signals reflect a mix of local and remote climatic influences, not just temperature at the drill site.¹² Antarctic ice cores now cover the last 800,000 years, providing a direct record of glacial and interglacial cycles that serves as one of the most important benchmarks for testing climate models.¹³ Researchers continue to develop new statistical methods to squeeze more reliable climate reconstructions out of these proxy records, including for the Holocene, the roughly 11,700-year warm period we live in.¹⁴

Human Impacts and the Anthropocene Debate

A defining preoccupation of modern Earth and environmental science is the scale of humanity’s footprint. Stratigraphic evidence, the physical record laid down in rock and sediment, shows markers that are unlike anything in earlier geologic layers: aluminum, plastics, concrete, radionuclide fallout from nuclear testing, and soot particles from fossil-fuel combustion. Carbon, nitrogen, and phosphorus cycles have been substantially modified. Rates of sea-level rise exceed what occurred during the late Holocene. Species invasions and accelerating extinction rates compound these signals.¹⁵

Whether to formally declare a new geologic epoch called the Anthropocene remains contentious. Two dates have been proposed as plausible starting points, 1610 and 1964, each marked by distinct global signatures in the stratigraphic record.¹⁶ A formal vote by geologists’ governing bodies has not ratified the term, but the concept has reshaped how researchers frame their work. Earth System Science itself named the Anthropocene as a rupture in planetary history driven by human impact on the Earth System as a whole.¹⁷

A related framework, the planetary boundaries concept, tries to define a “safe operating space” for humanity. A 2023 update found that six of nine planetary boundaries have been transgressed, with ocean acidification close to joining them.¹⁸ On biodiversity specifically, land-use change driven by rising agricultural trade has pushed an additional estimated 1.4 percent of the world’s species toward extinction commitment between 1995 and 2022, with tropical deforestation far outpacing restoration in temperate regions.¹⁹ Between 2000 and 2011, the amount of carbon sequestration lost to agricultural and forestry land use grew by about 6 percent, from 3.2 to 3.4 billion tonnes of carbon per year.²⁰

Pollution cuts across spheres in ways this field is uniquely equipped to track. Microplastics, for instance, accumulate up the oceanic food chain. A study of pelagic and deep-sea species found a clear increase in microplastic concentrations from lower to higher trophic levels, with top predators accumulating the greatest loads.²¹ This kind of finding emerges only when oceanographers, ecologists, and materials scientists collaborate.

Observation Tools and Earth System Models

The field’s ability to answer questions at a planetary scale depends heavily on remote sensing and computational modeling. Over the past two decades, the commercialization of space has generated unprecedented volumes of Earth observation data. The entire planet is now imaged at high frequency by multiple sensor platforms every day, spanning visible light through infrared and radio wavelengths. Visible detections on the order of centimeters and elevation measurements at the millimeter scale are now routine. These data produce everything from land-cover maps to soil-moisture readings to gravity-anomaly surveys.

Raw data, though, is only as useful as the models that interpret it. Earth system models are the main tools for climate projections under different emissions scenarios.²² A growing priority is model-data fusion: combining satellite observations, in-situ sensor networks, and computational models to improve predictions across the atmosphere, oceans, land surface, cryosphere, and atmospheric chemistry, from next-week weather forecasts to century-scale climate projections.²³ The challenge is enormous. Climate feedbacks, from ice-albedo effects to vegetation responses, are nonlinear and operate on wildly different timescales, making the search for a complete, testable Earth system model one of the field’s central ongoing projects.

Practical Applications From Hazards to Energy

Earth and environmental science is not purely academic. Its most visible public-facing work involves natural hazards. Earthquakes, landslides, floods, volcanic eruptions, and wildfires all require understanding of the physical Earth to forecast, monitor, and mitigate. Because hazards rarely occur in isolation (an earthquake can trigger landslides, which dam rivers, which later produce catastrophic floods), researchers have pushed for integrated, multi-hazard risk assessment that cuts across traditional disciplinary lines.²⁴ The science of natural hazards and disaster risk now spans formation mechanisms, early-warning systems, emergency response, and post-disaster reconstruction as a single interlinked research program.²⁵

The energy transition is another area where the field’s expertise is increasingly demanded. Geoscientists contribute to the responsible sourcing of raw materials for low-carbon technologies such as batteries and wind turbines, the development of geothermal heating systems, and the geological capture and storage of carbon dioxide.²⁶ Subsurface knowledge, once associated almost exclusively with oil and gas extraction, is being redirected toward hydrogen storage, compressed-air energy storage, and identifying sites where captured carbon can be safely locked away in rock formations.²⁷

Environmental Justice and Who Gets to Ask the Questions

An increasingly prominent conversation within the field concerns who benefits from environmental research and whose concerns get prioritized. Pollution, flood risk, and heat exposure are not distributed evenly across communities, and the people most affected often have the least say in what gets studied. Researchers in exposure science have proposed frameworks that center affected communities in the research process, from identifying which environmental threats matter most to developing interventions.²⁸ Calls to transform environmental science’s priorities through justice and pluralism, drawing on feminist and anti-colonial scholarship, reflect a growing recognition that the questions scientists choose to ask shape outcomes just as much as the answers they find.²⁹ This is not a fringe argument. It is appearing in mainstream environmental journals and reshaping how funding agencies evaluate research proposals.

Exo-Geoscience and Looking Beyond Earth

One of the field’s more surprising recent expansions is outward, toward other worlds. Exo-geoscience applies Earth science concepts to rocky exoplanets, asking whether processes like plate tectonics, volatile cycling, and magnetic-field generation could support stable climates and habitable surfaces elsewhere. Reviews of this emerging sub-field highlight how comparisons with Earth and other solar-system bodies reveal both the diversity of planetary conditions and the apparent rarity of conditions relevant to life.³⁰ One proposed test of the habitable-zone concept involves surveying water vapor in exoplanet atmospheres across a range of orbital distances. The prediction is that inside the inner edge of the habitable zone, water should be lost to space through a runaway greenhouse process (as likely happened on Venus), while beyond the outer edge it should freeze out.³¹ This kind of work reframes Earth and environmental science not just as the study of our planet, but as the study of what makes any planet work, with our own world as the best-characterized case study we have.