Why Earth’s critical zone is so very critical

It’s called “the critical zone” and it refers to the section of Earth that is most crucial to human survival. The critical zone exists between the tops of the tallest trees and stretches down into soil and rock. The bottom of the critical zone is marked by the start of the weathering zone, which is the area where soil is made.

The critical zone truly is everything for humans. It’s where we grow our food and what we build our homes on top of. It holds our water and supports all life forms.

Pennsylvania State University professor Henry Lin recently published a review on research about the critical zone in the Vandose Zone Journal. Lin argues that the critical zone is more than just a physical space, that it’s also a research approach that can shed new light on understand Earth’s layers from a macro perspective.

“The critical zone approach provides a framework for combining below ground and above ground, nonliving and living, and space and time in our ecosystems,” said Lin. “To truly understand this zone, research from many areas must be mixed into one framework. It includes perspectives on time, depth, and coupling.”

All three concepts affect the critical zone in different ways. Time is an important framework in order to understand soil changes over time and how this has affected waterflow and vegetation growth. Depth is significant because of how much of the zone exists underground where we processes occur that we cannot see. And a coupling framework allows for the study of how the zone impacts the larger ecosystem and our natural resources.

Human activity has caused both intentional and unintentional changes to the critical zone. Lin argues that further study of how the critical zone has changed overtime can allow us to more accurately predict what will happen in the future.

“With our ongoing development, the critical zone is under ever-increasing pressures from humans, such as rapid growth of human and livestock population, land use increases, and global environmental changes,” said Lin. “Possible negative effects include degraded soil health and water quality. It’s important to continue closely studying this area.”

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By Olivia Harvey, Earth.com Staff Writer