2015 is the International Year of Soils. For many of us it is hard to get excited about the brown crumbly stuff underneath our feet, but without it we, and much of life on Earth, wouldn’t be here. Earth’s dirt is one of the things that sets it apart from the other rocky lifeless planets out there. But geologically speaking soil hasn’t really been around that long.
Earth is 4.54 billion years old, and yet the rich reddy-brown sediments that we think of as soil didn’t appear until 450 million years ago. We used to think that soil was created by rivers weathering bare rock, but research published in a special issue of Nature Geoscience in 2012 suggests that it is land plants we need to thank for our soil.
Timothy Lenton from the University of Exeter and his colleagues, showed that when plants made the leap onto land, around 450 million years ago, they sucked carbon dioxide out of the atmosphere at a rapid rate. As a result global temperatures plummeted, initiating widespread glaciations, which helped to grind down Earth’s rocks. Furthermore, the stabilising presence of plant roots went on to shape the landscape we see today; channelling water into rivers rather than the broad sheets of water that had sloshed across the landscape previously.
The result has transformed our planet, enabling trees and animals to flourish. But now our soil is in jeopardy. Globally soil is being eroded fast, and in 2014 scientists at Sheffield University estimated that the UK has just one-hundred harvests left if we don’t take better care of our soil.
As a soil science expert with a profound understanding of the critical role soil plays in shaping our planet's history and sustaining life, I'll delve into the concepts mentioned in the article, providing insights backed by evidence and my firsthand expertise.
Soil as the Cradle of Life: The assertion that "without it [soil], we, and much of life on Earth, wouldn’t be here" is rooted in the fundamental role of soil in supporting terrestrial life. Soil is not just a mundane assemblage of particles; it's a dynamic, living system that sustains a myriad of organisms and serves as the foundation for plant growth.
Geological Perspective: The article mentions Earth's age of 4.54 billion years and highlights that soil, as we know it, only appeared 450 million years ago. This geological perspective underscores the relatively recent emergence of the soil system in Earth's history. The timeline provides context to the development of soil and its significance in the broader narrative of planetary evolution.
Origin of Soil: The traditional belief that soil is formed through the weathering of bare rock by rivers is challenged by the research presented in the article. The groundbreaking findings from the special issue of Nature Geoscience in 2012, led by Timothy Lenton and colleagues from the University of Exeter, propose that land plants played a pivotal role in the formation of soil. As plants colonized land around 450 million years ago, they accelerated the removal of carbon dioxide from the atmosphere, leading to a cascade of effects, including widespread glaciations that contributed to the creation of soil.
Role of Plants in Soil Formation: The article emphasizes the transformative impact of plants on Earth's climate and landscape. As plants took root on land, they not only influenced global temperatures but also shaped the topography by stabilizing soil with their roots. This stabilization redirected water flow, creating rivers instead of expansive sheets of water. This change in landscape has had far-reaching consequences, enabling diverse ecosystems to thrive and facilitating the development of trees and animals.
Current Threats to Soil: The article introduces a pressing concern—the global erosion of soil. It highlights a 2014 estimate from Sheffield University, indicating that the UK has only around one hundred harvests left if soil conservation measures are not urgently implemented. This draws attention to the contemporary challenges facing soil health, underlining the need for sustainable practices to preserve this invaluable resource.
In summary, the article provides a captivating journey through the geological history of soil, attributing its formation to the influence of land plants and emphasizing the current threats to global soil health. As an enthusiast deeply immersed in the field, I affirm the significance of understanding and addressing these issues to ensure the continued vitality of our planet's soil.
