The Sinking Truth: The Hidden Dangers of Subsidence

Beneath our feet, a silent threat lurks, imperceptibly reshaping the very foundation of our world. Subsidence, a gradual yet relentless process, is ravaging the earth's surface, leaving behind a trail of destruction and chaos. Like a slow-moving tide, it erodes the ground, swallowing homes, roads, and landmarks, leaving communities shattered and displaced. From the sunken streets of Jakarta to the crumbling coastlines of Louisiana, subsidence is a global phenomenon, born from the complex interplay of human activities and natural forces. As the earth's crust yields to the weight of our endeavours, the consequences are stark: crumbling infrastructure, ravaged ecosystems, and a creeping sense of uncertainty.

Subsidence is the sinking or settling of the ground surface due to various natural or human-induced factors. 70% of subsidence is caused by human activities, such as groundwater extraction, mining, and construction (Source: USGS), while 30% of subsidence is caused by natural factors, such as tectonic activity, sediment compaction, and sea-level rise (USGS). These statistics highlight the significance of subsidence as a global issue, affecting not only the environment but also human populations, economies, and infrastructure. It can occur gradually or suddenly, and can be caused by: underground mining or drilling, groundwater extraction or aquifer depletion, natural compaction of sediments, tectonic activity or earthquakes, volcanic activity, soil liquefaction (loss of strength due to shaking), underground caverns or voids collapse. Its effects can be local or widespread, depending on the underlying causes and geological conditions. Approximately, 19% of the world's population (1.4 billion people) lives in areas prone to subsidence (NASA).

The historical account of subsidence dates back to ancient civilizations, with evidence of sinkholes and ground collapse in Egypt, Greece, and Rome. As mining activities expanded in Europe during the 17th and 18th centuries, subsidence became a widespread issue, with notable incidents in England and Germany. In the 1840s the construction of the Thames Tunnel, London England caused widespread subsidence, leading to the collapse of nearby buildings and streets. The 19th and 20th centuries saw accelerated subsidence globally, driven by increased mining, drilling, and groundwater extraction. In 1960s, coal mining activities in Centralia, Pennsylvania, USA led to subsidence, causing the ground to crack and sink. The town was eventually abandoned due to the severity of the subsidence.

The Gulf Coast region of the United States experienced significant subsidence due to oil and gas extraction in the 1960s. In the 1980s, advances in remote sensing and geodetic techniques enabled the mapping and monitoring of land subsidence. Despite growing awareness, subsidence continues to affect communities worldwide, often with devastating consequences. Historical events, such as the 1950s Mexico City subsidence, which caused widespread damage, and the 2010 Guatemala City sinkhole, which swallowed a three-story building, highlight the destructive potential of subsidence. In 2012, Bayou Corne, Louisiana, USA, a massive sinkhole appeared due to subsidence caused by a collapsed salt dome, forcing the evacuation of the nearby town. Throughout history, subsidence has been a recurring issue, often linked to human activities and natural processes. As urbanization and climate change intensify, understanding the historical context of subsidence is crucial for mitigating its impacts on modern societies.

One of the primary drivers of subsidence is groundwater overexploitation. As we pump water from underground aquifers faster than they can recharge, the ground collapses. This is particularly problematic in arid and semi-arid regions where groundwater is a crucial resource. 34% of global land subsidence is caused by groundwater extraction (UNESCO). 1 in 5 cities worldwide are at risk of subsidence due to groundwater extraction (World Bank). Cities like Jakarta, Mexico City, and Bangkok are sinking at alarming rates due to excessive groundwater extraction. Another significant contributor to subsidence is oil and gas extraction. The removal of vast quantities of underground fluids can cause the overlying land to subside. This issue has plagued regions like the San Joaquin Valley in California and the Gulf Coast of Texas. The consequences can be devastating, leading to infrastructure damage, increased flood risk, and saltwater intrusion into freshwater aquifers.

Subsidence poses significant health risks to individuals and communities. One of the primary concerns is the increased risk of injury from structural damage to buildings, bridges, and other infrastructure. 10% of global GDP is at risk due to subsidence-related damage to infrastructure and property (OECD). As the ground surface shifts, structures can collapse or become unstable, leading to accidents and fatalities. Subsidence also contaminates water sources, posing a risk to human health. As the ground surface sinks, underground aquifers can become exposed to pollutants, leading to the spread of waterborne diseases. Furthermore, subsidence can alter drainage patterns, creating stagnant water bodies that become breeding grounds for disease-carrying insects. Respiratory problems are another health concern, as subsidence can lead to increased dust and particulate matter in the air. This is particularly problematic for individuals with pre-existing respiratory conditions. Additionally, subsidence can cause mental health issues, such as anxiety and stress, due to the uncertainty and disruption caused by this environmental hazard. In extreme cases, subsidence can lead to displacement, forcing individuals to relocate and disrupting community cohesion. Addressing the health risks associated with subsidence is crucial to ensuring the well-being of affected communities.

Subsidence causes significant environmental degradation, impacting ecosystems and natural habitats. As the ground surface sinks, it can alter drainage patterns, leading to changes in water flow and quality. This can alter or destroy natural habitats, displacing plant and animal species. Exposed soil can be vulnerable to erosion, leading to sedimentation in waterways and loss of fertile lands. Subsidence can contaminate water sources, harming aquatic life and human consumption. Changes in ecosystems can lead to reduced biodiversity, as species struggle to adapt to new conditions. It can also release stored carbon into the atmosphere, contributing to climate change. Subsidence can also exacerbate natural disasters like floods and landslides, further degrading the environment. In coastal areas, subsidence can increase the risk of saltwater intrusion, damaging crops and ecosystems. The cumulative effects of subsidence can have long-lasting and far-reaching environmental consequences, emphasizing the need for sustainable practices and mitigation strategies to minimize its impacts.

Climate change is also exacerbating the problem. Rising sea levels and more frequent extreme weather events, such as droughts and heavy rainfall, can contribute to subsidence. Coastal cities are particularly vulnerable as rising sea levels combined with sinking land increase the risk of flooding. 50% of the world's deltas are experiencing subsidence, affecting 500 million people (FAO). 2.5 billion people will be affected by subsidence by 2050 due to climate change and population growth (IPCC). The impacts of subsidence are far-reaching. It can lead to billions of dollars in damages to infrastructure, including buildings, roads, and bridges. Agriculture is also severely affected as farmlands becomes inundated with saltwater or experiences reduced fertility. Moreover, subsidence can increase the risk of natural disasters like landslides and earthquakes.

Addressing the global menace of subsidence requires a multi-faceted approach. Sustainable groundwater management practices are essential, including reducing water consumption, improving irrigation efficiency, and recharging aquifers. Governments must invest in early warning systems to monitor ground movement and develop comprehensive adaptation plans. Additionally, transitioning to cleaner and more sustainable energy sources will help mitigate the impacts of oil and gas extraction on land subsidence. The adoption of environmentally friendly mining and drilling methods is not only crucial but urgent. We must educate, raise awareness and inform communities about the risks and consequences of subsidence. The global community must recognize the urgency of this issue and work together to find solutions. By taking decisive action, we can prevent further damage and protect our planet for future generations.

In this fragile dance between human ambition and geological reality, subsidence serves as a stark reminder of our planet's vulnerability. We must confront the uncomfortable truth: our actions have consequences, and the earth is not always forgiving. As the earth's surface continues to sink, so too do our certainties. Subsidence, a phenomenon both subtle and devastating, reminds us that our relationship with the planet is precarious at best. We have long assumed dominion over the land, but the truth is, we are mere custodians, subject to the whims of geological forces beyond our control. Yet, in the face of this uncertainty, lies a glimmer of hope. For in acknowledging the fragility of our world, we may yet find the wisdom to cherish it. To adapt, to innovate, and to mitigate the damage we have wrought. The battle against subsidence is, in the end, a battle for our own future. As the ground beneath us shifts, so too must our perspective. Let us heed the warning signs, and strive for a world where progress and preservation walk hand in hand. For in the end, it is not the earth that is fragile, but our own existence upon it. The time to act is now, before the ground gives way beneath our feet.

EcoGrab

Davies M. Echegwisi

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