The numbers behind the critical zone are striking. The layer ranges from just a few tens of meters to perhaps a few hundred meters in thickness, yet it supports a global population of 8 billion people along with virtually all terrestrial wildlife, many marine organisms, and the encompassing ecosystems on which they depend. Doss likens the zone to a human organ to make its scale and vulnerability vivid. “It envelops the Earth as a very thin layer…much like a human’s skin,” he says. “Our skin is our body’s largest organ, so a comparison is reasonable. We as humans don’t always walk around thinking about our skin as an organ like our heart or lungs—I think the Earth’s critical zone gets the same neglect.” The analogy is technically apt: like skin, the critical zone mediates exchanges of energy, water, gases, and nutrients between the deeper planet and the atmosphere, and like skin, it can be wounded faster than it can heal.

Nearly every process essential to the sustenance of life occurs within this narrow band. Weathering of bedrock releases the mineral nutrients—calcium, potassium, phosphorus, magnesium—that anchor food webs. Soils store and filter water, regulate carbon, and host microbial communities that drive biogeochemical cycles. Groundwater feeds streams, wetlands, and wells. Vegetation anchors the surface, moderates temperature, and photosynthesizes the base of nearly every terrestrial food chain. Remove or degrade any one of these linked components and the others feel the consequences, often in ways that take decades to become obvious. Doss has spent much of his career making exactly this point, from his early work in the Indiana Dunes to fieldwork in Yellowstone National Park, the Everglades, and the Manistee National Forest in Michigan. Across those radically different landscapes, he says, the inherent connection between geology and ecosystems has been consistently apparent.

What has also been consistent, in his experience, is the neglect of that geological foundation in ecological conversations. “In Yellowstone National Park, the absolute control of the biotic by the abiotic (geology) is on remarkable display, from microbial communities to the apex predators,” Doss states. The park makes the point almost nowhere else can match. Its hydrothermal basins, fed by volcanic heat and fractured rock, host microbial mats whose chemistry is dictated entirely by water temperature, pH, and dissolved minerals. Its wolf and elk populations move across landscapes shaped by lava flows, glacial deposits, and river-cut valleys that determine where soil, water, and forage accumulate. Yet, Doss observes, “I don’t always see the same recognition by life scientists. Importantly, when I’ve shared my thoughts about this with whoever will listen, ecologists have uniformly agreed that the abiotic is often neglected in their conceptual framework.”

That admission matters because the critical zone is not merely underappreciated—it is actively degrading. Doss attributes the decline to two main forces: human transformation of the Earth’s surface and climate change. The first is staggering in its magnitude. Humans now move more sediment, soil, and rock across the planet’s surface than wind, water, ice, and gravity combined. In effect, humanity has become the single largest geomorphic agent on Earth, outstripping every natural process of erosion and deposition. As a result, more than half of the planet’s arable land has been altered, habitats have been fragmented, and the hydrologic connections that ecosystems depend on—how water moves from ridge to valley, from aquifer to stream—have been reshaped, severed, or rerouted.

Climate change compounds the damage by altering the fundamental processes that govern the critical zone. Precipitation patterns are shifting, with consequences for soil moisture, groundwater recharge, and streamflow. Changes in the timing and intensity of rainfall affect erosion rates, nutrient transport, and the frequency of droughts and floods. Because the critical zone is a coupled system, a change in one input cascades through the whole: altered streamflow changes sediment delivery, which changes channel form, which changes habitat, which changes the biota. Together, Doss notes, these forces are driving extinctions, degrading habitats, eroding biodiversity, and changing the availability of the resources on which human societies depend.

One of the conceptual challenges, Doss suggests, is that these impacts unfold on geological time scales spanning years, decades, and centuries—slower than the news cycle, but not slower than the pace of human consequence. Soil that took millennia to form can be lost in a single storm on an unprotected field. An aquifer drawn down over decades may not recharge for generations. A fragmented habitat corridor, once severed, may take centuries of natural succession to reestablish—if it reestablishes at all. The critical zone operates on a budget: inputs of weathered rock, organic matter, and infiltrating water against outputs of erosion, extraction, and runoff. When human activity pushes outputs above inputs, the deficit accumulates silently, and the ledger is inherited by future generations.

Doss hopes to help illuminate what these changes mean right now, not just in the abstract future. “The earth sciences define, describe, and provide an understanding of how our planet works,” he states. “We’ve only got one of those, and it seems kind of important that humans have that understanding…particularly when we are so obviously capable of altering, damaging, and manipulating global-scale processes upon which life depends.” His argument is, at its core, a call for integration: for ecologists to treat geology, hydrology, and soil science as foundational rather than peripheral, and for geologists to engage more directly with biological and conservation questions. The critical zone is, by definition, where the abiotic and biotic worlds are inseparable, and any framework that studies one without the other is, in his view, incomplete.

The stakes extend well beyond academia. The critical zone is where food is grown, where drinking water is stored and filtered, where carbon is exchanged with the atmosphere, and where the raw materials of civilization are extracted. Its degradation is therefore not a niche scientific concern but a question of resource security, public health, and intergenerational equity. “We ALL need the critical zone. And so do our children and future generations,” Doss says. “We better understand it, advocate for it, and care for it.” Framing the ground beneath our feet as an organ—one that can be monitored, injured, and healed—offers a powerful rhetorical tool for communicating that urgency to audiences who may never think about weathering rates or water tables but who understand instinctively what it means when a vital organ begins to fail.

Doss will develop these arguments in his Michel T. Halbouty Distinguished Lecture, “Geologists in the Critical Zone…in a Critical Time,” delivered at GSA Connects 2026 on Wednesday, 14 October, from 12:15 to 1:15 p.m. in room Bluebird 1AB of the Colorado Convention Center in Denver, Colorado. The lecture platform is fitting: the Geological Society of America, a global professional society with more than 18,000 members across over 100 countries, has long championed the integration of Earth science into broader scientific and public conversations. Whether the critical zone gains the recognition Doss seeks will depend on whether researchers, educators, and communicators can persuade the public that the thin, living skin of the planet is not scenery but infrastructure—as essential, and as vulnerable, as any organ that keeps a body alive.

Subject of Research: The degradation of Earth's critical zone and the role of geology in ecosystem science

Article Title: Geologist makes the case for Earth’s most overlooked organ: the ground beneath our feet

Article References: Geologist makes the case for Earth’s most overlooked organ: the ground beneath our feet. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: critical zone, geology, soil, groundwater, ecosystems, climate change, biodiversity, Yellowstone, land degradation, Geological Society of America, hydrology, Earth science