Environmental Hazards: Natural and Man-Induced

Environmental hazards are extreme events or processes in the physical environment that pose a threat to human life, property, and the ecosystem. These hazards are classified into two broad categories: Natural Hazards (caused by biophysical processes beyond human control) and Man-induced (Anthropogenic) Hazards (triggered or accelerated by human activities).

1. Natural Hazards

A. Earthquakes

An earthquake is the sudden shaking of the Earth's surface caused by the release of seismic energy along fault lines in the crust. The point of origin underground is the focus (hypocentre), while the point directly above it on the surface is the epicentre.

• Causes: Tectonic plate movements (convergent, divergent, and transform boundaries).
• Measurement: Magnitude is measured using the Richter Scale (quantitative), while intensity/damage is measured using the Modified Mercalli Scale (qualitative). Both utilize data from a seismograph.
• Common Areas: The Pacific Rim (the "Ring of Fire"), Mid-Atlantic Ridge, and the Mediterranean-Himalayan belt.
• Effects: Destruction of infrastructure, tsunamis, landslides, loss of life, and soil liquefaction.

B. Volcanic Eruptions

Volcanic eruptions occur when molten rock (magma), gases, and pyroclastic debris escape from the Earth's interior through a vent to the surface, where it becomes known as lava.

• Causes: High pressure from sub-crustal magma seeking outlets along tectonic plate margins or hotspots.
• Common Areas: Mount Vesuvius (Italy), Mount Fuji (Japan), Mount Nyiragongo (DR Congo), and Cameroon Mountain (Cameroon).
• Effects: Destruction of habitats by lava flows, toxic gas emissions (sulfur dioxide), pyroclastic flows (fast-moving hot ash and gas), mudflows (lahars), and temporary global cooling due to atmospheric ash.

C. Droughts

Drought is a prolonged period of abnormally low rainfall, leading to a severe water shortage.

• Causes: Shift in atmospheric circulation patterns (like El Niño), high rates of evapotranspiration, and global warming.
• Common Areas: The Sahel region of Africa (including Northern Nigeria), Horn of Africa, and parts of Central Australia.
• Effects: Crop failure, famine, death of livestock, drop in water tables, and initiation of desertification.

D. Flooding (Natural)

Natural flooding occurs when water bodies overflow their banks due to natural physical processes.

• Causes: Prolonged, heavy rainfall, rapid snowmelt, or storm surges from tropical cyclones.
• Common Areas: Monsoon regions of Southern Asia (e.g., Bangladesh) and major river basins (e.g., the Mississippi and River Niger basins).
• Effects: Drowning, displacement of populations, destruction of farmlands, and outbreak of waterborne diseases (cholera, typhoid).

2. Man-Induced (Anthropogenic) Hazards

A. Soil Erosion

Soil erosion is the wearing away of topsoil by natural agents (water and wind), heavily accelerated by human activities.

• Causes: Deforestation, overgrazing, poor farming methods (like farming along slopes), and intensive mining.
• Common Areas: Gully erosion is highly prevalent in Southeastern Nigeria (e.g., Agulu-Nanka in Anambra State), while wind erosion is common in Northern Nigeria.
• Effects: Loss of arable land, silting of rivers and reservoirs, landslide triggers, and destruction of transport infrastructure.

B. Deforestation

Deforestation is the permanent clearance of forests to make land available for other uses.

• Causes: Commercial logging, agricultural expansion, urbanization, and fuel-wood collection.
• Common Areas: The Amazon rainforest (South America), Congo Basin, and the southern rainforest belt of Nigeria.
• Effects: Loss of biodiversity, disruption of the water cycle, increased carbon dioxide in the atmosphere (accelerating global warming), and increased soil vulnerability to erosion.

C. Pollution

Pollution is the introduction of harmful contaminants into the natural environment.

• Types and Causes:
  • Air Pollution: Burning fossil fuels, industrial emissions, and gas flaring (very common in the Niger Delta).
  • Water Pollution: Industrial effluents, domestic sewage, agricultural runoff containing chemical fertilizers, and oil spills (Niger Delta).
  • Land Pollution: Open dumping of non-biodegradable municipal solid waste.
• Effects: Respiratory diseases, eutrophication in water bodies, destruction of aquatic life, acid rain, and loss of soil fertility.

D. Desertification

Desertification is the degradation of land in arid, semi-arid, and dry sub-humid areas, resulting from various factors, including climatic variations and human activities.

• Causes: Overgrazing, over-cultivation, deforestation, and poor irrigation systems combined with prolonged droughts.
• Common Areas: The Sahelian states of Northern Nigeria (Sokoto, Katsina, Jigawa, Yobe, Borno).
• Effects: Loss of productive rangelands, dust storms, forced migration of pastoralists (herder-farmer conflicts), and extreme poverty.

3. Prevention, Mitigation, and Control of Hazards

Addressing environmental hazards requires active, sustainable policies, engineering controls, and community-based practices:

• Earthquake and Volcanic Mitigation: Building earthquake-resistant structures (using flexible steel frames), installing early warning systems, mapping risk zones, and establishing evacuation protocols.
• Flood Control: Constructing dykes, levees, and dams; implementing strict zoning laws that prohibit building on floodplains; maintaining proper urban drainage systems; and preserving wetlands.
• Erosion Control: Practicing contour ploughing, terracing on hillsides, cover-cropping, afforestation, and construction of retaining walls or gabions.
• Combating Desertification and Drought: Establishing shelterbelts (lines of trees planted to block wind), implementing sustainable grazing practices, adopting water-harvesting techniques, and participating in the "Great Green Wall" initiative.
• Pollution Mitigation: Enforcing strict environmental protection laws (such as NESREA regulations in Nigeria), treatment of industrial effluents before discharge, promoting recycling, and transitioning to clean energy sources.